budibase/packages/core/dist/budibase-core.umd.js

(function (global, factory) {
  typeof exports === 'object' && typeof module !== 'undefined' ? factory(exports, require('lodash/fp'), require('shortid'), require('lodash'), require('@nx-js/compiler-util'), require('lunr'), require('safe-buffer')) :
  typeof define === 'function' && define.amd ? define(['exports', 'lodash/fp', 'shortid', 'lodash', '@nx-js/compiler-util', 'lunr', 'safe-buffer'], factory) :
  (global = global || self, factory(global['@budibase/core'] = {}, global.fp, global.shortid, global._, global.compiler_util, global.lunr, global.safe_buffer));
}(this, function (exports, fp, shortid, _, compilerUtil, lunr, safeBuffer) { 'use strict';

  var ___default = 'default' in _ ? _['default'] : _;
  lunr = lunr && lunr.hasOwnProperty('default') ? lunr['default'] : lunr;

  const commonPlus = extra => fp.union(['onBegin', 'onComplete', 'onError'])(extra);

  const common = () => commonPlus([]);

  const _events = {
    recordApi: {
      save: commonPlus([
        'onInvalid',
        'onRecordUpdated',
        'onRecordCreated']),
      delete: common(),
      getContext: common(),
      getNew: common(),
      load: common(),
      validate: common(),
      uploadFile: common(),
      downloadFile: common(),
    },
    indexApi: {
      buildIndex: common(),
      listItems: common(),
      delete: common(),
      aggregates: common(),
    },
    collectionApi: {
      getAllowedRecordTypes: common(),
      initialise: common(),
      delete: common(),
    },
    authApi: {
      authenticate: common(),
      authenticateTemporaryAccess: common(),
      createTemporaryAccess: common(),
      createUser: common(),
      enableUser: common(),
      disableUser: common(),
      loadAccessLevels: common(),
      getNewAccessLevel: common(),
      getNewUser: common(),
      getNewUserAuth: common(),
      getUsers: common(),
      saveAccessLevels: common(),
      isAuthorized: common(),
      changeMyPassword: common(),
      setPasswordFromTemporaryCode: common(),
      scorePassword: common(),
      isValidPassword: common(),
      validateUser: common(),
      validateAccessLevels: common(),
      setUserAccessLevels: common(),
    },
    templateApi: {
      saveApplicationHierarchy: common(),
      saveActionsAndTriggers: common(),
    },
    actionsApi: {
      execute: common(),
    },
  };

  const _eventsList = [];

  const makeEvent = (area, method, name) => `${area}:${method}:${name}`;

  for (const areaKey in _events) {
    for (const methodKey in _events[areaKey]) {
      _events[areaKey][methodKey] = fp.reduce((obj, s) => {
        obj[s] = makeEvent(areaKey, methodKey, s);
        return obj;
      },
      {})(_events[areaKey][methodKey]);
    }
  }


  for (const areaKey in _events) {
    for (const methodKey in _events[areaKey]) {
      for (const name in _events[areaKey][methodKey]) {
        _eventsList.push(
          _events[areaKey][methodKey][name],
        );
      }
    }
  }


  const events = _events;

  const eventsList = _eventsList;

  class BadRequestError extends Error {
      constructor(message) {
          super(message);
          this.httpStatusCode = 400;
      }
  }

  class UnauthorisedError extends Error {
      constructor(message) {
          super(message);
          this.httpStatusCode = 401;
      }
  }

  class ForbiddenError extends Error {
      constructor(message) {
          super(message);
          this.httpStatusCode = 403;
      }
  }

  class NotFoundError extends Error {
      constructor(message) {
          super(message);
          this.httpStatusCode = 404;
      }
  }

  const apiWrapper = async (app, eventNamespace, isAuthorized, eventContext, func, ...params) => {
    pushCallStack(app, eventNamespace);

    if (!isAuthorized(app)) {
      handleNotAuthorized(app, eventContext, eventNamespace);
      return;
    }

    const startDate = Date.now();
    const elapsed = () => (Date.now() - startDate);

    try {
      await app.publish(
        eventNamespace.onBegin,
        eventContext,
      );

      const result = await func(...params);

      await publishComplete(app, eventContext, eventNamespace, elapsed, result);
      return result;
    } catch (error) {
      await publishError(app, eventContext, eventNamespace, elapsed, error);
      throw error;
    }
  };

  const apiWrapperSync = (app, eventNamespace, isAuthorized, eventContext, func, ...params) => {
    pushCallStack(app, eventNamespace);

    if (!isAuthorized(app)) {
      handleNotAuthorized(app, eventContext, eventNamespace);
      return;
    }

    const startDate = Date.now();
    const elapsed = () => (Date.now() - startDate);

    try {
      app.publish(
        eventNamespace.onBegin,
        eventContext,
      );

      const result = func(...params);

      publishComplete(app, eventContext, eventNamespace, elapsed, result);
      return result;
    } catch (error) {
      publishError(app, eventContext, eventNamespace, elapsed, error);
      throw error;
    }
  };

  const handleNotAuthorized = (app, eventContext, eventNamespace) => {
    const err = new UnauthorisedError(`Unauthorized: ${eventNamespace}`);
    publishError(app, eventContext, eventNamespace, () => 0, err);
    throw err;
  };

  const pushCallStack = (app, eventNamespace, seedCallId) => {
    const callId = shortid.generate();

    const createCallStack = () => ({
      seedCallId: !fp.isUndefined(seedCallId)
        ? seedCallId
        : callId,
      threadCallId: callId,
      stack: [],
    });

    if (fp.isUndefined(app.calls)) {
      app.calls = createCallStack();
    }

    app.calls.stack.push({
      namespace: eventNamespace,
      callId,
    });
  };

  const popCallStack = (app) => {
    app.calls.stack.pop();
    if (app.calls.stack.length === 0) {
      delete app.calls;
    }
  };

  const publishError = async (app, eventContext, eventNamespace, elapsed, err) => {
    const ctx = fp.cloneDeep(eventContext);
    ctx.error = err;
    ctx.elapsed = elapsed();
    await app.publish(
      eventNamespace.onError,
      ctx,
    );
    popCallStack(app);
  };

  const publishComplete = async (app, eventContext, eventNamespace, elapsed, result) => {
    const endcontext = fp.cloneDeep(eventContext);
    endcontext.result = result;
    endcontext.elapsed = elapsed();
    await app.publish(
      eventNamespace.onComplete,
      endcontext,
    );
    popCallStack(app);
    return result;
  };

  const lockOverlapMilliseconds = 10;

  const getLock = async (app, lockFile, timeoutMilliseconds, maxLockRetries, retryCount = 0) => {
    try {
      const timeout = (await app.getEpochTime())
              + timeoutMilliseconds;

      const lock = {
        timeout,
        key: lockFile,
        totalTimeout: timeoutMilliseconds,
      };

      await app.datastore.createFile(
        lockFile,
        getLockFileContent(
          lock.totalTimeout,
          lock.timeout,
        ),
      );

      return lock;
    } catch (e) {
      if (retryCount == maxLockRetries) { return NO_LOCK; }

      const lock = parseLockFileContent(
        lockFile,
        await app.datastore.loadFile(lockFile),
      );

      const currentEpochTime = await app.getEpochTime();

      if (currentEpochTime < lock.timeout) {
        return NO_LOCK;
      }

      try {
        await app.datastore.deleteFile(lockFile);
      } catch (_) {
        //empty
      }

      await sleepForRetry();

      return await getLock(
        app, lockFile, timeoutMilliseconds,
        maxLockRetries, retryCount + 1,
      );
    }
  };

  const getLockFileContent = (totalTimeout, epochTime) => `${totalTimeout}:${epochTime.toString()}`;

  const parseLockFileContent = (key, content) => $(content, [
    fp.split(':'),
    parts => ({
      totalTimeout: new Number(parts[0]),
      timeout: new Number(parts[1]),
      key,
    }),
  ]);

  const releaseLock = async (app, lock) => {
    const currentEpochTime = await app.getEpochTime();
    // only release if not timedout
    if (currentEpochTime < (lock.timeout - lockOverlapMilliseconds)) {
      try {
        await app.datastore.deleteFile(lock.key);
      } catch (_) {
        //empty
      }
    }
  };

  const NO_LOCK = 'no lock';
  const isNolock = id => id === NO_LOCK;

  const sleepForRetry = () => new Promise(resolve => setTimeout(resolve, lockOverlapMilliseconds));

  // this is the combinator function
  const $$ = (...funcs) => arg => _.flow(funcs)(arg);

  // this is the pipe function
  const $ = (arg, funcs) => $$(...funcs)(arg);

  const keySep = '/';
  const trimKeySep = str => _.trim(str, keySep);
  const splitByKeySep = str => _.split(str, keySep);
  const safeKey = key => _.replace(`${keySep}${trimKeySep(key)}`, `${keySep}${keySep}`, keySep);
  const joinKey = (...strs) => {
    const paramsOrArray = strs.length === 1 & _.isArray(strs[0])
      ? strs[0] : strs;
    return safeKey(_.join(paramsOrArray, keySep));
  };
  const splitKey = $$(trimKeySep, splitByKeySep);
  const getDirFomKey = $$(splitKey, _.dropRight, p => joinKey(...p));
  const getFileFromKey = $$(splitKey, _.takeRight, _.head);

  const configFolder = `${keySep}.config`;
  const fieldDefinitions = joinKey(configFolder, 'fields.json');
  const templateDefinitions = joinKey(configFolder, 'templates.json');
  const appDefinitionFile = joinKey(configFolder, 'appDefinition.json');
  const dirIndex = folderPath => joinKey(configFolder, 'dir', ...splitKey(folderPath), 'dir.idx');
  const getIndexKeyFromFileKey = $$(getDirFomKey, dirIndex);

  const ifExists = (val, exists, notExists) => (_.isUndefined(val)
    ? _.isUndefined(notExists) ? (() => { })() : notExists()
    : exists());

  const getOrDefault = (val, defaultVal) => ifExists(val, () => val, () => defaultVal);

  const not = func => val => !func(val);
  const isDefined = not(_.isUndefined);
  const isNonNull = not(_.isNull);
  const isNotNaN = not(_.isNaN);

  const allTrue = (...funcArgs) => val => _.reduce(funcArgs,
    (result, conditionFunc) => (_.isNull(result) || result == true) && conditionFunc(val),
    null);

  const anyTrue = (...funcArgs) => val => _.reduce(funcArgs,
    (result, conditionFunc) => result == true || conditionFunc(val),
    null);

  const insensitiveEquals = (str1, str2) => str1.trim().toLowerCase() === str2.trim().toLowerCase();

  const isSomething = allTrue(isDefined, isNonNull, isNotNaN);
  const isNothing = not(isSomething);
  const isNothingOrEmpty = v => isNothing(v) || _.isEmpty(v);
  const somethingOrGetDefault = getDefaultFunc => val => (isSomething(val) ? val : getDefaultFunc());
  const somethingOrDefault = (val, defaultVal) => somethingOrGetDefault(_.constant(defaultVal))(val);

  const mapIfSomethingOrDefault = (mapFunc, defaultVal) => val => (isSomething(val) ? mapFunc(val) : defaultVal);

  const mapIfSomethingOrBlank = mapFunc => mapIfSomethingOrDefault(mapFunc, '');

  const none = predicate => collection => !fp.some(predicate)(collection);

  const all = predicate => collection => none(v => !predicate(v))(collection);

  const isNotEmpty = ob => !_.isEmpty(ob);
  const isNonEmptyArray = allTrue(_.isArray, isNotEmpty);
  const isNonEmptyString = allTrue(_.isString, isNotEmpty);
  const tryOr = failFunc => (func, ...args) => {
    try {
      return func.apply(null, ...args);
    } catch (_) {
      return failFunc();
    }
  };

  const tryAwaitOr = failFunc => async (func, ...args) => {
    try {
      return await func.apply(null, ...args);
    } catch (_) {
      return await failFunc();
    }
  };

  const defineError = (func, errorPrefix) => {
    try {
      return func();
    } catch (err) {
      err.message = `${errorPrefix} : ${err.message}`;
      throw err;
    }
  };

  const tryOrIgnore = tryOr(() => { });
  const tryAwaitOrIgnore = tryAwaitOr(async () => { });
  const causesException = (func) => {
    try {
      func();
      return false;
    } catch (e) {
      return true;
    }
  };

  const executesWithoutException = func => !causesException(func);

  const handleErrorWith = returnValInError => tryOr(_.constant(returnValInError));

  const handleErrorWithUndefined = handleErrorWith(undefined);

  const switchCase = (...cases) => (value) => {
    const nextCase = () => _.head(cases)[0](value);
    const nextResult = () => _.head(cases)[1](value);

    if (_.isEmpty(cases)) return; // undefined
    if (nextCase() === true) return nextResult();
    return switchCase(..._.tail(cases))(value);
  };

  const isValue = val1 => val2 => (val1 === val2);
  const isOneOf = (...vals) => val => _.includes(vals, val);
  const defaultCase = _.constant(true);
  const memberMatches = (member, match) => obj => match(obj[member]);


  const StartsWith = searchFor => searchIn => _.startsWith(searchIn, searchFor);

  const contains = val => array => (_.findIndex(array, v => v === val) > -1);

  const getHashCode = (s) => {
    let hash = 0; let i; let char; let
      l;
    if (s.length == 0) return hash;
    for (i = 0, l = s.length; i < l; i++) {
      char = s.charCodeAt(i);
      hash = ((hash << 5) - hash) + char;
      hash |= 0; // Convert to 32bit integer
    }

    // converting to string, but dont want a "-" prefixed
    if (hash < 0) { return `n${(hash * -1).toString()}`; }
    return hash.toString();
  };

  // thanks to https://blog.grossman.io/how-to-write-async-await-without-try-catch-blocks-in-javascript/
  const awEx = async (promise) => {
    try {
      const result = await promise;
      return [undefined, result];
    } catch (error) {
      return [error, undefined];
    }
  };

  const isSafeInteger = n => _.isInteger(n)
      && n <= Number.MAX_SAFE_INTEGER
      && n >= 0 - Number.MAX_SAFE_INTEGER;

  const toDateOrNull = s => (_.isNull(s) ? null
    : _.isDate(s) ? s : new Date(s));
  const toBoolOrNull = s => (_.isNull(s) ? null
    : s === 'true' || s === true);
  const toNumberOrNull = s => (_.isNull(s) ? null
    : _.toNumber(s));

  const isArrayOfString = opts => _.isArray(opts) && all(_.isString)(opts);

  const pause = async duration => new Promise(res => setTimeout(res, duration));

  const retry = async (fn, retries, delay, ...args) => {
    try {
      return await fn(...args);
    } catch (err) {
      if (retries > 1) {
        return await pause(delay).then(async () => await retry(fn, (retries - 1), delay, ...args));
      }
      throw err;
    }
  };

  var index = {
    ifExists,
    getOrDefault,
    isDefined,
    isNonNull,
    isNotNaN,
    allTrue,
    isSomething,
    mapIfSomethingOrDefault,
    mapIfSomethingOrBlank,
    configFolder,
    fieldDefinitions,
    isNothing,
    not,
    switchCase,
    defaultCase,
    StartsWith,
    contains,
    templateDefinitions,
    handleErrorWith,
    handleErrorWithUndefined,
    tryOr,
    tryOrIgnore,
    tryAwaitOr,
    tryAwaitOrIgnore,
    dirIndex,
    keySep,
    $,
    $$,
    getDirFomKey,
    getFileFromKey,
    splitKey,
    somethingOrDefault,
    getIndexKeyFromFileKey,
    joinKey,
    somethingOrGetDefault,
    appDefinitionFile,
    isValue,
    all,
    isOneOf,
    memberMatches,
    defineError,
    anyTrue,
    isNonEmptyArray,
    causesException,
    executesWithoutException,
    none,
    getHashCode,
    awEx,
    apiWrapper,
    events,
    eventsList,
    isNothingOrEmpty,
    isSafeInteger,
    toNumber: _.toNumber,
    toDate: toDateOrNull,
    toBool: toBoolOrNull,
    isArrayOfString,
    getLock,
    NO_LOCK,
    isNolock,
    insensitiveEquals,
    pause,
    retry,
  };

  const stringNotEmpty = s => isSomething(s) && s.trim().length > 0;

  const makerule = (field, error, isValid) => ({ field, error, isValid });

  const validationError = (rule, item) => ({ ...rule, item });

  const applyRuleSet = ruleSet => itemToValidate => $(ruleSet, [
    fp.map(applyRule(itemToValidate)),
    fp.filter(isSomething),
  ]);

  const applyRule = itemTovalidate => rule => (rule.isValid(itemTovalidate)
    ? null
    : validationError(rule, itemTovalidate));

  const filterEval = 'FILTER_EVALUATE';
  const filterCompile = 'FILTER_COMPILE';
  const mapEval = 'MAP_EVALUATE';
  const mapCompile = 'MAP_COMPILE';


  const getEvaluateResult = () => ({
    isError: false,
    passedFilter: true,
    result: null,
  });

  const compileFilter = index => compilerUtil.compileExpression(index.filter);

  const compileMap = index => compilerUtil.compileCode(index.map);

  const passesFilter = (record, index) => {
    const context = { record };
    if (!index.filter) return true;

    const compiledFilter = defineError(
      () => compileFilter(index),
      filterCompile,
    );

    return defineError(
      () => compiledFilter(context),
      filterEval,
    );
  };

  const mapRecord = (record, index) => {
    const recordClone = _.cloneDeep(record);
    const context = { record: recordClone };

    const map = index.map ? index.map : 'return {...record};';

    const compiledMap = defineError(
      () => compilerUtil.compileCode(map),
      mapCompile,
    );

    const mapped = defineError(
      () => compiledMap(context),
      mapEval,
    );

    const mappedKeys = _.keys(mapped);
    for (let i = 0; i < mappedKeys.length; i++) {
      const key = mappedKeys[i];
      mapped[key] = _.isUndefined(mapped[key]) ? null : mapped[key];
      if (_.isFunction(mapped[key])) {
        delete mapped[key];
      }
    }

    mapped.key = record.key;
    mapped.sortKey = index.getSortKey
      ? compilerUtil.compileCode(index.getSortKey)(context)
      : record.id;

    return mapped;
  };

  const evaluate = record => (index) => {
    const result = getEvaluateResult();

    try {
      result.passedFilter = passesFilter(record, index);
    } catch (err) {
      result.isError = true;
      result.passedFilter = false;
      result.result = err.message;
    }

    if (!result.passedFilter) return result;

    try {
      result.result = mapRecord(record, index);
    } catch (err) {
      result.isError = true;
      result.result = err.message;
    }

    return result;
  };

  const indexTypes = { reference: 'reference', ancestor: 'ancestor' };

  const indexRuleSet = [
    makerule('map', 'index has no map function',
      index => isNonEmptyString(index.map)),
    makerule('map', "index's map function does not compile",
      index => !isNonEmptyString(index.map)
                  || executesWithoutException(() => compileMap(index))),
    makerule('filter', "index's filter function does not compile",
      index => !isNonEmptyString(index.filter)
                  || executesWithoutException(() => compileFilter(index))),
    makerule('name', 'must declare a name for index',
      index => isNonEmptyString(index.name)),
    makerule('name', 'there is a duplicate named index on this node',
      index => fp.isEmpty(index.name)
                  || fp.countBy('name')(index.parent().indexes)[index.name] === 1),
    makerule('indexType', 'reference index may only exist on a record node',
      index => isRecord(index.parent())
                    || index.indexType !== indexTypes.reference),
    makerule('indexType', `index type must be one of: ${_.join(', ', _.keys(indexTypes))}`,
      index => fp.includes(index.indexType)(_.keys(indexTypes))),
  ];

  const getFlattenedHierarchy = (appHierarchy, useCached = true) => {
    if (isSomething(appHierarchy.getFlattenedHierarchy) && useCached) { return appHierarchy.getFlattenedHierarchy(); }

    const flattenHierarchy = (currentNode, flattened) => {
      flattened.push(currentNode);
      if ((!currentNode.children
              || currentNode.children.length === 0)
              && (!currentNode.indexes
              || currentNode.indexes.length === 0)
              && (!currentNode.aggregateGroups
              || currentNode.aggregateGroups.length === 0)) {
        return flattened;
      }

      const unionIfAny = l2 => l1 => fp.union(l1)(!l2 ? [] : l2);

      const children = $([], [
        unionIfAny(currentNode.children),
        unionIfAny(currentNode.indexes),
        unionIfAny(currentNode.aggregateGroups),
      ]);

      for (const child of children) {
        flattenHierarchy(child, flattened);
      }
      return flattened;
    };

    appHierarchy.getFlattenedHierarchy = () => flattenHierarchy(appHierarchy, []);
    return appHierarchy.getFlattenedHierarchy();
  };

  const getLastPartInKey = key => fp.last(splitKey(key));

  const getNodesInPath = appHierarchy => key => $(appHierarchy, [
    getFlattenedHierarchy,
    fp.filter(n => new RegExp(`${n.pathRegx()}`).test(key)),
  ]);

  const getExactNodeForPath = appHierarchy => key => $(appHierarchy, [
    getFlattenedHierarchy,
    fp.find(n => new RegExp(`${n.pathRegx()}$`).test(key)),
  ]);

  const getNodeForCollectionPath = appHierarchy => collectionKey => $(appHierarchy, [
    getFlattenedHierarchy,
    fp.find(n => (isCollectionRecord(n)
                     && new RegExp(`${n.collectionPathRegx()}$`).test(collectionKey))),
  ]);

  const hasMatchingAncestor = ancestorPredicate => decendantNode => switchCase(

    [node => isNothing(node.parent()),
      fp.constant(false)],

    [node => ancestorPredicate(node.parent()),
      fp.constant(true)],

    [defaultCase,
      node => hasMatchingAncestor(ancestorPredicate)(node.parent())],

  )(decendantNode);

  const getNode = (appHierarchy, nodeKey) => $(appHierarchy, [
    getFlattenedHierarchy,
    fp.find(n => n.nodeKey() === nodeKey
                    || (isCollectionRecord(n)
                        && n.collectionNodeKey() === nodeKey)),
  ]);

  const getCollectionNode = (appHierarchy, nodeKey) => $(appHierarchy, [
    getFlattenedHierarchy,
    fp.find(n => (isCollectionRecord(n)
                      && n.collectionNodeKey() === nodeKey)),
  ]);

  const getNodeByKeyOrNodeKey = (appHierarchy, keyOrNodeKey) => {
    const nodeByKey = getExactNodeForPath(appHierarchy)(keyOrNodeKey);
    return isNothing(nodeByKey)
      ? getNode(appHierarchy, keyOrNodeKey)
      : nodeByKey;
  };

  const getCollectionNodeByKeyOrNodeKey = (appHierarchy, keyOrNodeKey) => {
    const nodeByKey = getNodeForCollectionPath(appHierarchy)(keyOrNodeKey);
    return isNothing(nodeByKey)
      ? getCollectionNode(appHierarchy, keyOrNodeKey)
      : nodeByKey;
  };

  const isNode = (appHierarchy, key) => isSomething(getExactNodeForPath(appHierarchy)(key));

  const getActualKeyOfParent = (parentNodeKey, actualChildKey) => $(actualChildKey, [
    splitKey,
    fp.take(splitKey(parentNodeKey).length),
    ks => joinKey(...ks),
  ]);

  const getParentKey = (key) => {
    return $(key, [
      splitKey,
      fp.take(splitKey(key).length - 1),
      joinKey,
    ]);
  };

  const isKeyAncestorOf = ancestorKey => decendantNode => hasMatchingAncestor(p => p.nodeKey() === ancestorKey)(decendantNode);

  const hasNoMatchingAncestors = parentPredicate => node => !hasMatchingAncestor(parentPredicate)(node);

  const findField = (recordNode, fieldName) => fp.find(f => f.name == fieldName)(recordNode.fields);

  const isAncestor = decendant => ancestor => isKeyAncestorOf(ancestor.nodeKey())(decendant);

  const isDecendant = ancestor => decendant => isAncestor(decendant)(ancestor);

  const getRecordNodeId = recordKey => $(recordKey, [
    splitKey,
    fp.last,
    getRecordNodeIdFromId,
  ]);

  const getRecordNodeIdFromId = recordId => $(recordId, [fp.split('-'), fp.first, parseInt]);

  const getRecordNodeById = (hierarchy, recordId) => $(hierarchy, [
    getFlattenedHierarchy,
    fp.find(n => isRecord(n)
                      && n.nodeId === getRecordNodeIdFromId(recordId)),
  ]);

  const recordNodeIdIsAllowed = indexNode => nodeId => indexNode.allowedRecordNodeIds.length === 0
      || fp.includes(nodeId)(indexNode.allowedRecordNodeIds);

  const recordNodeIsAllowed = indexNode => recordNode => recordNodeIdIsAllowed(indexNode)(recordNode.nodeId);

  const getAllowedRecordNodesForIndex = (appHierarchy, indexNode) => {
    const recordNodes = $(appHierarchy, [
      getFlattenedHierarchy,
      fp.filter(isRecord),
    ]);

    if (isGlobalIndex(indexNode)) {
      return $(recordNodes, [
        fp.filter(recordNodeIsAllowed(indexNode)),
      ]);
    }

    if (isAncestorIndex(indexNode)) {
      return $(recordNodes, [
        fp.filter(isDecendant(indexNode.parent())),
        fp.filter(recordNodeIsAllowed(indexNode)),
      ]);
    }

    if (isReferenceIndex(indexNode)) {
      return $(recordNodes, [
        fp.filter(n => fp.some(fieldReversesReferenceToIndex(indexNode))(n.fields)),
      ]);
    }
  };

  const getNodeFromNodeKeyHash = hierarchy => hash => $(hierarchy, [
    getFlattenedHierarchy,
    fp.find(n => getHashCode(n.nodeKey()) === hash),
  ]);

  const isRecord = node => isSomething(node) && node.type === 'record';
  const isSingleRecord = node => isRecord(node) && node.isSingle;
  const isCollectionRecord = node => isRecord(node) && !node.isSingle;
  const isIndex = node => isSomething(node) && node.type === 'index';
  const isaggregateGroup = node => isSomething(node) && node.type === 'aggregateGroup';
  const isShardedIndex = node => isIndex(node) && isNonEmptyString(node.getShardName);
  const isRoot = node => isSomething(node) && node.isRoot();
  const isDecendantOfARecord = hasMatchingAncestor(isRecord);
  const isGlobalIndex = node => isIndex(node) && isRoot(node.parent());
  const isReferenceIndex = node => isIndex(node) && node.indexType === indexTypes.reference;
  const isAncestorIndex = node => isIndex(node) && node.indexType === indexTypes.ancestor;

  const fieldReversesReferenceToNode = node => field => field.type === 'reference'
      && fp.intersection(field.typeOptions.reverseIndexNodeKeys)(fp.map(i => i.nodeKey())(node.indexes))
        .length > 0;

  const fieldReversesReferenceToIndex = indexNode => field => field.type === 'reference'
      && fp.intersection(field.typeOptions.reverseIndexNodeKeys)([indexNode.nodeKey()])
        .length > 0;

  var hierarchy = {
    getLastPartInKey,
    getNodesInPath,
    getExactNodeForPath,
    hasMatchingAncestor,
    getNode,
    getNodeByKeyOrNodeKey,
    isNode,
    getActualKeyOfParent,
    getParentKey,
    isKeyAncestorOf,
    hasNoMatchingAncestors,
    findField,
    isAncestor,
    isDecendant,
    getRecordNodeId,
    getRecordNodeIdFromId,
    getRecordNodeById,
    recordNodeIdIsAllowed,
    recordNodeIsAllowed,
    getAllowedRecordNodesForIndex,
    getNodeFromNodeKeyHash,
    isRecord,
    isCollectionRecord,
    isIndex,
    isaggregateGroup,
    isShardedIndex,
    isRoot,
    isDecendantOfARecord,
    isGlobalIndex,
    isReferenceIndex,
    isAncestorIndex,
    fieldReversesReferenceToNode,
    fieldReversesReferenceToIndex,
    getFlattenedHierarchy,
  };

  const getSafeFieldParser = (tryParse, defaultValueFunctions) => (field, record) => {
    if (_.has(record, field.name)) {
      return getSafeValueParser(tryParse, defaultValueFunctions)(record[field.name]);
    }
    return defaultValueFunctions[field.getUndefinedValue]();
  };

  const getSafeValueParser = (tryParse, defaultValueFunctions) => (value) => {
    const parsed = tryParse(value);
    if (parsed.success) {
      return parsed.value;
    }
    return defaultValueFunctions.default();
  };

  const getNewValue = (tryParse, defaultValueFunctions) => (field) => {
    const getInitialValue = fp.isUndefined(field) || fp.isUndefined(field.getInitialValue)
      ? 'default'
      : field.getInitialValue;

    return _.has(defaultValueFunctions, getInitialValue)
      ? defaultValueFunctions[getInitialValue]()
      : getSafeValueParser(tryParse, defaultValueFunctions)(getInitialValue);
  };

  const typeFunctions = specificFunctions => _.merge({
    value: fp.constant,
    null: fp.constant(null),
  }, specificFunctions);

  const validateTypeConstraints = validationRules => async (field, record, context) => {
    const fieldValue = record[field.name];
    const validateRule = async r => (!await r.isValid(fieldValue, field.typeOptions, context)
      ? r.getMessage(fieldValue, field.typeOptions)
      : '');

    const errors = [];
    for (const r of validationRules) {
      const err = await validateRule(r);
      if (isNotEmpty(err)) errors.push(err);
    }

    return errors;
  };

  const getDefaultOptions = fp.mapValues(v => v.defaultValue);

  const makerule$1 = (isValid, getMessage) => ({ isValid, getMessage });
  const parsedFailed = val => ({ success: false, value: val });
  const parsedSuccess = val => ({ success: true, value: val });
  const getDefaultExport = (name, tryParse, functions, options, validationRules, sampleValue, stringify) => ({
    getNew: getNewValue(tryParse, functions),
    safeParseField: getSafeFieldParser(tryParse, functions),
    safeParseValue: getSafeValueParser(tryParse, functions),
    tryParse,
    name,
    getDefaultOptions: () => getDefaultOptions(fp.cloneDeep(options)),
    optionDefinitions: options,
    validateTypeConstraints: validateTypeConstraints(validationRules),
    sampleValue,
    stringify: val => (val === null || val === undefined
      ? '' : stringify(val)),
    getDefaultValue: functions.default,
  });

  const stringFunctions = typeFunctions({
    default: _.constant(null),
  });

  const stringTryParse = switchCase(
    [_.isString, parsedSuccess],
    [_.isNull, parsedSuccess],
    [defaultCase, v => parsedSuccess(v.toString())],
  );

  const options = {
    maxLength: {
      defaultValue: null,
      isValid: n => n === null || isSafeInteger(n) && n > 0,
      requirementDescription: 'max length must be null (no limit) or a greater than zero integer',
      parse: toNumberOrNull,
    },
    values: {
      defaultValue: null,
      isValid: v => v === null || (isArrayOfString(v) && v.length > 0 && v.length < 10000),
      requirementDescription: "'values' must be null (no values) or an arry of at least one string",
      parse: s => s,
    },
    allowDeclaredValuesOnly: {
      defaultValue: false,
      isValid: _.isBoolean,
      requirementDescription: 'allowDeclaredValuesOnly must be true or false',
      parse: toBoolOrNull,
    },
  };

  const typeConstraints = [
    makerule$1(async (val, opts) => val === null || opts.maxLength === null || val.length <= opts.maxLength,
      (val, opts) => `value exceeds maximum length of ${opts.maxLength}`),
    makerule$1(async (val, opts) => val === null
                             || opts.allowDeclaredValuesOnly === false
                             || _.includes(opts.values, val),
    (val) => `"${val}" does not exist in the list of allowed values`),
  ];

  var string = getDefaultExport(
    'string',
    stringTryParse,
    stringFunctions,
    options,
    typeConstraints,
    'abcde',
    str => str,
  );

  const boolFunctions = typeFunctions({
    default: _.constant(null),
  });

  const boolTryParse = switchCase(
    [_.isBoolean, parsedSuccess],
    [_.isNull, parsedSuccess],
    [isOneOf('true', '1', 'yes', 'on'), () => parsedSuccess(true)],
    [isOneOf('false', '0', 'no', 'off'), () => parsedSuccess(false)],
    [defaultCase, parsedFailed],
  );

  const options$1 = {
    allowNulls: {
      defaultValue: true,
      isValid: _.isBoolean,
      requirementDescription: 'must be a true or false',
      parse: toBoolOrNull,
    },
  };

  const typeConstraints$1 = [
    makerule$1(async (val, opts) => opts.allowNulls === true || val !== null,
      () => 'field cannot be null'),
  ];

  var bool = getDefaultExport(
    'bool', boolTryParse, boolFunctions,
    options$1, typeConstraints$1, true, JSON.stringify,
  );

  const numberFunctions = typeFunctions({
    default: _.constant(null),
  });

  const parseStringtoNumberOrNull = (s) => {
    const num = Number(s);
    return isNaN(num) ? parsedFailed(s) : parsedSuccess(num);
  };

  const numberTryParse = switchCase(
    [_.isNumber, parsedSuccess],
    [_.isString, parseStringtoNumberOrNull],
    [_.isNull, parsedSuccess],
    [defaultCase, parsedFailed],
  );

  const options$2 = {
    maxValue: {
      defaultValue: Number.MAX_SAFE_INTEGER,
      isValid: isSafeInteger,
      requirementDescription: 'must be a valid integer',
      parse: toNumberOrNull,
    },
    minValue: {
      defaultValue: 0 - Number.MAX_SAFE_INTEGER,
      isValid: isSafeInteger,
      requirementDescription: 'must be a valid integer',
      parse: toNumberOrNull,
    },
    decimalPlaces: {
      defaultValue: 0,
      isValid: n => isSafeInteger(n) && n >= 0,
      requirementDescription: 'must be a positive integer',
      parse: toNumberOrNull,
    },
  };

  const getDecimalPlaces = (val) => {
    const splitDecimal = val.toString().split('.');
    if (splitDecimal.length === 1) return 0;
    return splitDecimal[1].length;
  };

  const typeConstraints$2 = [
    makerule$1(async (val, opts) => val === null || opts.minValue === null || val >= opts.minValue,
      (val, opts) => `value (${val.toString()}) must be greater than or equal to ${opts.minValue}`),
    makerule$1(async (val, opts) => val === null || opts.maxValue === null || val <= opts.maxValue,
      (val, opts) => `value (${val.toString()}) must be less than or equal to ${opts.minValue} options`),
    makerule$1(async (val, opts) => val === null || opts.decimalPlaces >= getDecimalPlaces(val),
      (val, opts) => `value (${val.toString()}) must have ${opts.decimalPlaces} decimal places or less`),
  ];

  var number = getDefaultExport(
    'number',
    numberTryParse,
    numberFunctions,
    options$2,
    typeConstraints$2,
    1,
    num => num.toString(),
  );

  const dateFunctions = typeFunctions({
    default: _.constant(null),
    now: () => new Date(),
  });

  const isValidDate = d => d instanceof Date && !isNaN(d);

  const parseStringToDate = s => switchCase(
    [isValidDate, parsedSuccess],
    [defaultCase, parsedFailed],
  )(new Date(s));


  const dateTryParse = switchCase(
    [_.isDate, parsedSuccess],
    [_.isString, parseStringToDate],
    [_.isNull, parsedSuccess],
    [defaultCase, parsedFailed],
  );

  const options$3 = {
    maxValue: {
      defaultValue: new Date(32503680000000),
      isValid: _.isDate,
      requirementDescription: 'must be a valid date',
      parse: toDateOrNull,
    },
    minValue: {
      defaultValue: new Date(-8520336000000),
      isValid: _.isDate,
      requirementDescription: 'must be a valid date',
      parse: toDateOrNull,
    },
  };

  const typeConstraints$3 = [
    makerule$1(async (val, opts) => val === null || opts.minValue === null || val >= opts.minValue,
      (val, opts) => `value (${val.toString()}) must be greater than or equal to ${opts.minValue}`),
    makerule$1(async (val, opts) => val === null || opts.maxValue === null || val <= opts.maxValue,
      (val, opts) => `value (${val.toString()}) must be less than or equal to ${opts.minValue} options`),
  ];

  var datetime = getDefaultExport(
    'datetime',
    dateTryParse,
    dateFunctions,
    options$3,
    typeConstraints$3,
    new Date(1984, 4, 1),
    date => JSON.stringify(date).replace(new RegExp('"', 'g'), ''),
  );

  const arrayFunctions = () => typeFunctions({
    default: _.constant([]),
  });

  const mapToParsedArrary = type => $$(
    fp.map(i => type.safeParseValue(i)),
    parsedSuccess,
  );

  const arrayTryParse = type => switchCase(
    [_.isArray, mapToParsedArrary(type)],
    [defaultCase, parsedFailed],
  );

  const typeName = type => `array<${type}>`;


  const options$4 = {
    maxLength: {
      defaultValue: 10000,
      isValid: isSafeInteger,
      requirementDescription: 'must be a positive integer',
      parse: toNumberOrNull,
    },
    minLength: {
      defaultValue: 0,
      isValid: n => isSafeInteger(n) && n >= 0,
      requirementDescription: 'must be a positive integer',
      parse: toNumberOrNull,
    },
  };

  const typeConstraints$4 = [
    makerule$1(async (val, opts) => val === null || val.length >= opts.minLength,
      (val, opts) => `must choose ${opts.minLength} or more options`),
    makerule$1(async (val, opts) => val === null || val.length <= opts.maxLength,
      (val, opts) => `cannot choose more than ${opts.maxLength} options`),
  ];

  var array = type => getDefaultExport(
    typeName(type.name),
    arrayTryParse(type),
    arrayFunctions(),
    options$4,
    typeConstraints$4,
    [type.sampleValue],
    JSON.stringify,
  );

  const referenceNothing = () => ({ key: '' });

  const referenceFunctions = typeFunctions({
    default: referenceNothing,
  });

  const hasStringValue = (ob, path) => _.has(ob, path)
      && _.isString(ob[path]);

  const isObjectWithKey = v => _.isObjectLike(v)
      && hasStringValue(v, 'key');

  const tryParseFromString = s => {

    try {
      const asObj = JSON.parse(s);
      if(isObjectWithKey) {
        return parsedSuccess(asObj);
      }
    }
    catch(_) {
      // EMPTY
    }

    return parsedFailed(s);
  };

  const referenceTryParse = v => switchCase(
    [isObjectWithKey, parsedSuccess],
    [_.isString, tryParseFromString],
    [_.isNull, () => parsedSuccess(referenceNothing())],
    [defaultCase, parsedFailed],
  )(v);

  const options$5 = {
    indexNodeKey: {
      defaultValue: null,
      isValid: isNonEmptyString,
      requirementDescription: 'must be a non-empty string',
      parse: s => s,
    },
    displayValue: {
      defaultValue: '',
      isValid: isNonEmptyString,
      requirementDescription: 'must be a non-empty string',
      parse: s => s,
    },
    reverseIndexNodeKeys: {
      defaultValue: null,
      isValid: v => isArrayOfString(v) && v.length > 0,
      requirementDescription: 'must be a non-empty array of strings',
      parse: s => s,
    },
  };

  const isEmptyString = s => _.isString(s) && _.isEmpty(s);

  const ensureReferenceExists = async (val, opts, context) => isEmptyString(val.key)
      || await context.referenceExists(opts, val.key);

  const typeConstraints$5 = [
    makerule$1(
      ensureReferenceExists,
      (val, opts) => `"${val[opts.displayValue]}" does not exist in options list (key: ${val.key})`,
    ),
  ];

  var reference = getDefaultExport(
    'reference',
    referenceTryParse,
    referenceFunctions,
    options$5,
    typeConstraints$5,
    { key: 'key', value: 'value' },
    JSON.stringify,
  );

  const illegalCharacters = '*?\\/:<>|\0\b\f\v';

  const isLegalFilename = (filePath) => {
    const fn = fileName(filePath);
    return fn.length <= 255
      && fp.intersection(fn.split(''))(illegalCharacters.split('')).length === 0
      && none(f => f === '..')(splitKey(filePath));
  };

  const fileNothing = () => ({ relativePath: '', size: 0 });

  const fileFunctions = typeFunctions({
    default: fileNothing,
  });

  const fileTryParse = v => switchCase(
    [isValidFile, parsedSuccess],
    [fp.isNull, () => parsedSuccess(fileNothing())],
    [defaultCase, parsedFailed],
  )(v);

  const fileName = filePath => $(filePath, [
    splitKey,
    fp.last,
  ]);

  const isValidFile = f => !fp.isNull(f)
      && fp.has('relativePath')(f) && fp.has('size')(f)
      && fp.isNumber(f.size)
      && fp.isString(f.relativePath)
      && isLegalFilename(f.relativePath);

  const options$6 = {};

  const typeConstraints$6 = [];

  var file = getDefaultExport(
    'file',
    fileTryParse,
    fileFunctions,
    options$6,
    typeConstraints$6,
    { relativePath: 'some_file.jpg', size: 1000 },
    JSON.stringify,
  );

  const allTypes = () => {
    const basicTypes = {
      string, number, datetime, bool, reference, file,
    };

    const arrays = $(basicTypes, [
      _.keys,
      fp.map((k) => {
        const kvType = {};
        const concreteArray = array(basicTypes[k]);
        kvType[concreteArray.name] = concreteArray;
        return kvType;
      }),
      types => _.assign({}, ...types),
    ]);

    return _.merge({}, basicTypes, arrays);
  };


  const all$1 = allTypes();

  const getType = (typeName) => {
    if (!_.has(all$1, typeName)) throw new BadRequestError(`Do not recognise type ${typeName}`);
    return all$1[typeName];
  };

  const getSampleFieldValue = field => getType(field.type).sampleValue;

  const getNewFieldValue = field => getType(field.type).getNew(field);

  const safeParseField = (field, record) => getType(field.type).safeParseField(field, record);

  const validateFieldParse = (field, record) => (_.has(record, field.name)
    ? getType(field.type).tryParse(record[field.name])
    : parsedSuccess(undefined)); // fields may be undefined by default

  const getDefaultOptions$1 = type => getType(type).getDefaultOptions();

  const validateTypeConstraints$1 = async (field, record, context) => await getType(field.type).validateTypeConstraints(field, record, context);

  const detectType = (value) => {
    if (fp.isString(value)) return string;
    if (fp.isBoolean(value)) return bool;
    if (fp.isNumber(value)) return number;
    if (fp.isDate(value)) return datetime;
    if (fp.isArray(value)) return array(detectType(value[0]));
    if (fp.isObject(value)
         && _.has(value, 'key')
         && _.has(value, 'value')) return reference;
    if (fp.isObject(value)
          && _.has(value, 'relativePath')
          && _.has(value, 'size')) return file;

    throw new BadRequestError(`cannot determine type: ${JSON.stringify(value)}`);
  };

  // 5 minutes
  const tempCodeExpiryLength = 5 * 60 * 1000;

  const AUTH_FOLDER = '/.auth';
  const USERS_LIST_FILE = joinKey(AUTH_FOLDER, 'users.json');
  const userAuthFile = username => joinKey(AUTH_FOLDER, `auth_${username}.json`);
  const USERS_LOCK_FILE = joinKey(AUTH_FOLDER, 'users_lock');
  const ACCESS_LEVELS_FILE = joinKey(AUTH_FOLDER, 'access_levels.json');
  const ACCESS_LEVELS_LOCK_FILE = joinKey(AUTH_FOLDER, 'access_levels_lock');

  const permissionTypes = {
    CREATE_RECORD: 'create record',
    UPDATE_RECORD: 'update record',
    READ_RECORD: 'read record',
    DELETE_RECORD: 'delete record',
    READ_INDEX: 'read index',
    MANAGE_INDEX: 'manage index',
    MANAGE_COLLECTION: 'manage collection',
    WRITE_TEMPLATES: 'write templates',
    CREATE_USER: 'create user',
    SET_PASSWORD: 'set password',
    CREATE_TEMPORARY_ACCESS: 'create temporary access',
    ENABLE_DISABLE_USER: 'enable or disable user',
    WRITE_ACCESS_LEVELS: 'write access levels',
    LIST_USERS: 'list users',
    LIST_ACCESS_LEVELS: 'list access levels',
    EXECUTE_ACTION: 'execute action',
    SET_USER_ACCESS_LEVELS: 'set user access levels',
  };

  const getUserByName = (users, name) => $(users, [
    fp.find(u => u.name.toLowerCase() === name.toLowerCase()),
  ]);

  const stripUserOfSensitiveStuff = (user) => {
    const stripped = fp.clone(user);
    delete stripped.tempCode;
    return stripped;
  };

  const parseTemporaryCode = fullCode => $(fullCode, [
    fp.split(':'),
    parts => ({
      id: parts[1],
      code: parts[2],
    }),
  ]);

  const isAuthorized = app => (permissionType, resourceKey) => apiWrapperSync(
    app,
    events.authApi.isAuthorized,
    alwaysAuthorized,
    { resourceKey, permissionType },
    _isAuthorized, app, permissionType, resourceKey,
  );

  const _isAuthorized = (app, permissionType, resourceKey) => {
    if (!app.user) {
      return false;
    }

    const validType = $(permissionTypes, [
      fp.values,
      fp.includes(permissionType),
    ]);

    if (!validType) {
      return false;
    }

    const permMatchesResource = (userperm) => {
      const nodeKey = isNothing(resourceKey)
        ? null
        : isNode(app.hierarchy, resourceKey)
          ? getNodeByKeyOrNodeKey(
            app.hierarchy, resourceKey,
          ).nodeKey()
          : resourceKey;

      return (userperm.type === permissionType)
          && (
            isNothing(resourceKey)
              || nodeKey === userperm.nodeKey
          );
    };

    return $(app.user.permissions, [
      fp.some(permMatchesResource),
    ]);
  };

  const nodePermission = type => ({
    add: (nodeKey, accessLevel) => accessLevel.permissions.push({ type, nodeKey }),
    isAuthorized: resourceKey => app => isAuthorized(app)(type, resourceKey),
    isNode: true,
    get: nodeKey => ({ type, nodeKey }),
  });

  const staticPermission = type => ({
    add: accessLevel => accessLevel.permissions.push({ type }),
    isAuthorized: app => isAuthorized(app)(type),
    isNode: false,
    get: () => ({ type }),
  });

  const createRecord = nodePermission(permissionTypes.CREATE_RECORD);

  const updateRecord = nodePermission(permissionTypes.UPDATE_RECORD);

  const deleteRecord = nodePermission(permissionTypes.DELETE_RECORD);

  const readRecord = nodePermission(permissionTypes.READ_RECORD);

  const writeTemplates = staticPermission(permissionTypes.WRITE_TEMPLATES);

  const createUser = staticPermission(permissionTypes.CREATE_USER);

  const setPassword = staticPermission(permissionTypes.SET_PASSWORD);

  const readIndex = nodePermission(permissionTypes.READ_INDEX);

  const manageIndex = staticPermission(permissionTypes.MANAGE_INDEX);

  const manageCollection = staticPermission(permissionTypes.MANAGE_COLLECTION);

  const createTemporaryAccess = staticPermission(permissionTypes.CREATE_TEMPORARY_ACCESS);

  const enableDisableUser = staticPermission(permissionTypes.ENABLE_DISABLE_USER);

  const writeAccessLevels = staticPermission(permissionTypes.WRITE_ACCESS_LEVELS);

  const listUsers = staticPermission(permissionTypes.LIST_USERS);

  const listAccessLevels = staticPermission(permissionTypes.LIST_ACCESS_LEVELS);

  const setUserAccessLevels = staticPermission(permissionTypes.SET_USER_ACCESS_LEVELS);

  const executeAction = nodePermission(permissionTypes.EXECUTE_ACTION);

  const alwaysAuthorized = () => true;

  const permission = {
    createRecord,
    updateRecord,
    deleteRecord,
    readRecord,
    writeTemplates,
    createUser,
    setPassword,
    readIndex,
    createTemporaryAccess,
    enableDisableUser,
    writeAccessLevels,
    listUsers,
    listAccessLevels,
    manageIndex,
    manageCollection,
    executeAction,
    setUserAccessLevels,
  };

  const getNew = app => (collectionKey, recordTypeName) => {
    const recordNode = getRecordNode(app, collectionKey);
    return apiWrapperSync(
      app,
      events.recordApi.getNew,
      permission.createRecord.isAuthorized(recordNode.nodeKey()),
      { collectionKey, recordTypeName },
      _getNew, recordNode, collectionKey,
    );
  };

  const _getNew = (recordNode, collectionKey) => constructRecord(recordNode, getNewFieldValue, collectionKey);

  const getRecordNode = (app, collectionKey) => {
    collectionKey = safeKey(collectionKey);
    return getNodeForCollectionPath(app.hierarchy)(collectionKey);
  };

  const getNewChild = app => (recordKey, collectionName, recordTypeName) => 
    getNew(app)(joinKey(recordKey, collectionName), recordTypeName);

  const constructRecord = (recordNode, getFieldValue, collectionKey) => {
    const record = $(recordNode.fields, [
      fp.keyBy('name'),
      fp.mapValues(getFieldValue),
    ]);

    record.id = `${recordNode.nodeId}-${shortid.generate()}`;
    record.key = joinKey(collectionKey, record.id);
    record.isNew = true;
    record.type = recordNode.name;
    return record;
  };

  const getRecordFileName = key => joinKey(key, 'record.json');

  const load = app => async key => apiWrapper(
    app,
    events.recordApi.load,
    permission.readRecord.isAuthorized(key),
    { key },
    _load, app, key,
  );

  const _load = async (app, key, keyStack = []) => {
    key = safeKey(key);
    const recordNode = getExactNodeForPath(app.hierarchy)(key);
    const storedData = await app.datastore.loadJson(
      getRecordFileName(key),
    );

    const loadedRecord = $(recordNode.fields, [
      fp.keyBy('name'),
      fp.mapValues(f => safeParseField(f, storedData)),
    ]);

    const newKeyStack = [...keyStack, key];

    const references = $(recordNode.fields, [
      fp.filter(f => f.type === 'reference'
                      && isNonEmptyString(loadedRecord[f.name].key)
                      && !fp.includes(loadedRecord[f.name].key)(newKeyStack)),
      fp.map(f => ({
        promise: _load(app, loadedRecord[f.name].key, newKeyStack),
        index: getNode(app.hierarchy, f.typeOptions.indexNodeKey),
        field: f,
      })),
    ]);

    if (references.length > 0) {
      const refRecords = await Promise.all(
        fp.map(p => p.promise)(references),
      );

      for (const ref of references) {
        loadedRecord[ref.field.name] = mapRecord(
          refRecords[references.indexOf(ref)],
          ref.index,
        );
      }
    }

    loadedRecord.transactionId = storedData.transactionId;
    loadedRecord.isNew = false;
    loadedRecord.key = key;
    loadedRecord.id = $(key, [splitKey, fp.last]);
    loadedRecord.type = recordNode.name;
    return loadedRecord;
  };

  // adapted from https://github.com/dex4er/js-promise-readable
  // thanks :)
    
  const promiseReadableStream = stream => {
     
      let _errored;

      const _errorHandler = err => {
          _errored = err;
      };

      stream.on("error", _errorHandler);
    
      const read = (size) => {
    
        return new Promise((resolve, reject) => {
          if (_errored) {
            const err = _errored;
            _errored = undefined;
            return reject(err)
          }
    
          if (!stream.readable || stream.closed || stream.destroyed) {
            return resolve();
          }
    
          const readableHandler = () => {
            const chunk = stream.read(size);
    
            if (chunk) {
              removeListeners();
              resolve(chunk);
            }
          };
    
          const closeHandler = () => {
            removeListeners();
            resolve();
          };
    
          const endHandler = () => {
            removeListeners();
            resolve();
          };
    
          const errorHandler = (err) => {
            _errored = undefined;
            removeListeners();
            reject(err);
          };
    
          const removeListeners = () => {
            stream.removeListener("close", closeHandler);
            stream.removeListener("error", errorHandler);
            stream.removeListener("end", endHandler);
            stream.removeListener("readable", readableHandler);
          };
    
          stream.on("close", closeHandler);
          stream.on("end", endHandler);
          stream.on("error", errorHandler);
          stream.on("readable", readableHandler);
    
          readableHandler();
        });
      };
    
    
      const destroy = () => {
        if (stream) {
          if (_errorHandler) {
            stream.removeListener("error", _errorHandler);
          }
          if (typeof stream.destroy === "function") {
            stream.destroy();
          }
        }
      };
    
      return {read, destroy, stream};
    };

  const getIndexedDataKey = (indexNode, indexKey, record) => {
    const getShardName = (indexNode, record) => {
      const shardNameFunc = compilerUtil.compileCode(indexNode.getShardName);
      try {
        return shardNameFunc({ record });
      } catch(e) {
        const errorDetails = `shardCode: ${indexNode.getShardName} :: record: ${JSON.stringify(record)} :: `;
        e.message = "Error running index shardname func: " + errorDetails + e.message;
        throw e;
      }
    };

    const shardName = isNonEmptyString(indexNode.getShardName)
      ? `${getShardName(indexNode, record)}.csv`
      : 'index.csv';

    return joinKey(indexKey, shardName);
  };

  const getShardKeysInRange = async (app, indexKey, startRecord = null, endRecord = null) => {
    const indexNode = getExactNodeForPath(app.hierarchy)(indexKey);

    const startShardName = !startRecord
      ? null
      : shardNameFromKey(
        getIndexedDataKey(
          indexNode,
          indexKey,
          startRecord,
        ),
      );

    const endShardName = !endRecord
      ? null
      : shardNameFromKey(
        getIndexedDataKey(
          indexNode,
          indexKey,
          endRecord,
        ),
      );

    return $(await getShardMap(app.datastore, indexKey), [
      fp.filter(k => (startRecord === null || k >= startShardName)
                      && (endRecord === null || k <= endShardName)),
      fp.map(k => joinKey(indexKey, `${k}.csv`)),
    ]);
  };

  const ensureShardNameIsInShardMap = async (store, indexKey, indexedDataKey) => {
    const map = await getShardMap(store, indexKey);
    const shardName = shardNameFromKey(indexedDataKey);
    if (!fp.includes(shardName)(map)) {
      map.push(shardName);
      await writeShardMap(store, indexKey, map);
    }
  };

  const getShardMap = async (datastore, indexKey) => {
    const shardMapKey = getShardMapKey(indexKey);
    try {
      return await datastore.loadJson(shardMapKey);
    } catch (_) {
      await datastore.createJson(shardMapKey, []);
      return [];
    }
  };

  const writeShardMap = async (datastore, indexKey, shardMap) => await datastore.updateJson(
    getShardMapKey(indexKey),
    shardMap,
  );

  const getAllShardKeys = async (app, indexKey) => await getShardKeysInRange(app, indexKey);

  const getShardMapKey = indexKey => joinKey(indexKey, 'shardMap.json');

  const getUnshardedIndexDataKey = indexKey => joinKey(indexKey, 'index.csv');

  const createIndexFile = async (datastore, indexedDataKey, index) => {
    if (isShardedIndex(index)) {
      const indexKey = getParentKey(indexedDataKey);
      const shardMap = await getShardMap(datastore, indexKey);
      shardMap.push(
        shardNameFromKey(indexedDataKey),
      );
      await writeShardMap(datastore, indexKey, shardMap);
    }
    await datastore.createFile(indexedDataKey, '');
  };

  const shardNameFromKey = key => $(key, [
    splitKey,
    fp.last,
  ]).replace('.csv', '');

  const getIndexKey_BasedOnDecendant = (decendantKey, indexNode) => {
    if (isGlobalIndex(indexNode)) { return `${indexNode.nodeKey()}`; }

    const indexedDataParentKey = getActualKeyOfParent(
      indexNode.parent().nodeKey(),
      decendantKey,
    );

    return joinKey(
      indexedDataParentKey,
      indexNode.name,
    );
  };

  const generateSchema = (hierarchy, indexNode) => {
    const recordNodes = getAllowedRecordNodesForIndex(hierarchy, indexNode);
    const mappedRecords = $(recordNodes, [
      fp.map(n => mapRecord(createSampleRecord(n), indexNode)),
    ]);

    // always has record key and sort key
    const schema = {
      sortKey: all$1.string,
      key: all$1.string,
    };

    const fieldsHas = fp.has(schema);
    const setField = (fieldName, value) => {
      if (value === null || value === undefined) { return; }

      const thisType = detectType(value);
      if (fieldsHas(fieldName)) {
        if (schema[fieldName] !== thisType) {
          schema[fieldName] = all$1.string;
        }
      } else {
        schema[fieldName] = thisType;
      }
    };

    for (const mappedRec of mappedRecords) {
      for (const f in mappedRec) {
        setField(f, mappedRec[f]);
      }
    }

    // returing an array of {name, type}
    return $(schema, [
      fp.keys,
      fp.map(k => ({ name: k, type: schema[k].name })),
      fp.filter(s => s.name !== 'sortKey'),
      fp.orderBy('name', ['desc']), // reverse aplha
      fp.concat([{ name: 'sortKey', type: all$1.string.name }]), // sortKey on end
      fp.reverse, // sortKey first, then rest are alphabetical
    ]);
  };

  const createSampleRecord = recordNode => constructRecord(
    recordNode,
    getSampleFieldValue,
    recordNode.parent().nodeKey(),
  );

  var global$1 = (typeof global !== "undefined" ? global :
              typeof self !== "undefined" ? self :
              typeof window !== "undefined" ? window : {});

  var lookup = [];
  var revLookup = [];
  var Arr = typeof Uint8Array !== 'undefined' ? Uint8Array : Array;
  var inited = false;
  function init () {
    inited = true;
    var code = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';
    for (var i = 0, len = code.length; i < len; ++i) {
      lookup[i] = code[i];
      revLookup[code.charCodeAt(i)] = i;
    }

    revLookup['-'.charCodeAt(0)] = 62;
    revLookup['_'.charCodeAt(0)] = 63;
  }

  function toByteArray (b64) {
    if (!inited) {
      init();
    }
    var i, j, l, tmp, placeHolders, arr;
    var len = b64.length;

    if (len % 4 > 0) {
      throw new Error('Invalid string. Length must be a multiple of 4')
    }

    // the number of equal signs (place holders)
    // if there are two placeholders, than the two characters before it
    // represent one byte
    // if there is only one, then the three characters before it represent 2 bytes
    // this is just a cheap hack to not do indexOf twice
    placeHolders = b64[len - 2] === '=' ? 2 : b64[len - 1] === '=' ? 1 : 0;

    // base64 is 4/3 + up to two characters of the original data
    arr = new Arr(len * 3 / 4 - placeHolders);

    // if there are placeholders, only get up to the last complete 4 chars
    l = placeHolders > 0 ? len - 4 : len;

    var L = 0;

    for (i = 0, j = 0; i < l; i += 4, j += 3) {
      tmp = (revLookup[b64.charCodeAt(i)] << 18) | (revLookup[b64.charCodeAt(i + 1)] << 12) | (revLookup[b64.charCodeAt(i + 2)] << 6) | revLookup[b64.charCodeAt(i + 3)];
      arr[L++] = (tmp >> 16) & 0xFF;
      arr[L++] = (tmp >> 8) & 0xFF;
      arr[L++] = tmp & 0xFF;
    }

    if (placeHolders === 2) {
      tmp = (revLookup[b64.charCodeAt(i)] << 2) | (revLookup[b64.charCodeAt(i + 1)] >> 4);
      arr[L++] = tmp & 0xFF;
    } else if (placeHolders === 1) {
      tmp = (revLookup[b64.charCodeAt(i)] << 10) | (revLookup[b64.charCodeAt(i + 1)] << 4) | (revLookup[b64.charCodeAt(i + 2)] >> 2);
      arr[L++] = (tmp >> 8) & 0xFF;
      arr[L++] = tmp & 0xFF;
    }

    return arr
  }

  function tripletToBase64 (num) {
    return lookup[num >> 18 & 0x3F] + lookup[num >> 12 & 0x3F] + lookup[num >> 6 & 0x3F] + lookup[num & 0x3F]
  }

  function encodeChunk (uint8, start, end) {
    var tmp;
    var output = [];
    for (var i = start; i < end; i += 3) {
      tmp = (uint8[i] << 16) + (uint8[i + 1] << 8) + (uint8[i + 2]);
      output.push(tripletToBase64(tmp));
    }
    return output.join('')
  }

  function fromByteArray (uint8) {
    if (!inited) {
      init();
    }
    var tmp;
    var len = uint8.length;
    var extraBytes = len % 3; // if we have 1 byte left, pad 2 bytes
    var output = '';
    var parts = [];
    var maxChunkLength = 16383; // must be multiple of 3

    // go through the array every three bytes, we'll deal with trailing stuff later
    for (var i = 0, len2 = len - extraBytes; i < len2; i += maxChunkLength) {
      parts.push(encodeChunk(uint8, i, (i + maxChunkLength) > len2 ? len2 : (i + maxChunkLength)));
    }

    // pad the end with zeros, but make sure to not forget the extra bytes
    if (extraBytes === 1) {
      tmp = uint8[len - 1];
      output += lookup[tmp >> 2];
      output += lookup[(tmp << 4) & 0x3F];
      output += '==';
    } else if (extraBytes === 2) {
      tmp = (uint8[len - 2] << 8) + (uint8[len - 1]);
      output += lookup[tmp >> 10];
      output += lookup[(tmp >> 4) & 0x3F];
      output += lookup[(tmp << 2) & 0x3F];
      output += '=';
    }

    parts.push(output);

    return parts.join('')
  }

  function read (buffer, offset, isLE, mLen, nBytes) {
    var e, m;
    var eLen = nBytes * 8 - mLen - 1;
    var eMax = (1 << eLen) - 1;
    var eBias = eMax >> 1;
    var nBits = -7;
    var i = isLE ? (nBytes - 1) : 0;
    var d = isLE ? -1 : 1;
    var s = buffer[offset + i];

    i += d;

    e = s & ((1 << (-nBits)) - 1);
    s >>= (-nBits);
    nBits += eLen;
    for (; nBits > 0; e = e * 256 + buffer[offset + i], i += d, nBits -= 8) {}

    m = e & ((1 << (-nBits)) - 1);
    e >>= (-nBits);
    nBits += mLen;
    for (; nBits > 0; m = m * 256 + buffer[offset + i], i += d, nBits -= 8) {}

    if (e === 0) {
      e = 1 - eBias;
    } else if (e === eMax) {
      return m ? NaN : ((s ? -1 : 1) * Infinity)
    } else {
      m = m + Math.pow(2, mLen);
      e = e - eBias;
    }
    return (s ? -1 : 1) * m * Math.pow(2, e - mLen)
  }

  function write (buffer, value, offset, isLE, mLen, nBytes) {
    var e, m, c;
    var eLen = nBytes * 8 - mLen - 1;
    var eMax = (1 << eLen) - 1;
    var eBias = eMax >> 1;
    var rt = (mLen === 23 ? Math.pow(2, -24) - Math.pow(2, -77) : 0);
    var i = isLE ? 0 : (nBytes - 1);
    var d = isLE ? 1 : -1;
    var s = value < 0 || (value === 0 && 1 / value < 0) ? 1 : 0;

    value = Math.abs(value);

    if (isNaN(value) || value === Infinity) {
      m = isNaN(value) ? 1 : 0;
      e = eMax;
    } else {
      e = Math.floor(Math.log(value) / Math.LN2);
      if (value * (c = Math.pow(2, -e)) < 1) {
        e--;
        c *= 2;
      }
      if (e + eBias >= 1) {
        value += rt / c;
      } else {
        value += rt * Math.pow(2, 1 - eBias);
      }
      if (value * c >= 2) {
        e++;
        c /= 2;
      }

      if (e + eBias >= eMax) {
        m = 0;
        e = eMax;
      } else if (e + eBias >= 1) {
        m = (value * c - 1) * Math.pow(2, mLen);
        e = e + eBias;
      } else {
        m = value * Math.pow(2, eBias - 1) * Math.pow(2, mLen);
        e = 0;
      }
    }

    for (; mLen >= 8; buffer[offset + i] = m & 0xff, i += d, m /= 256, mLen -= 8) {}

    e = (e << mLen) | m;
    eLen += mLen;
    for (; eLen > 0; buffer[offset + i] = e & 0xff, i += d, e /= 256, eLen -= 8) {}

    buffer[offset + i - d] |= s * 128;
  }

  var toString = {}.toString;

  var isArray = Array.isArray || function (arr) {
    return toString.call(arr) == '[object Array]';
  };

  var INSPECT_MAX_BYTES = 50;

  /**
   * If `Buffer.TYPED_ARRAY_SUPPORT`:
   *   === true    Use Uint8Array implementation (fastest)
   *   === false   Use Object implementation (most compatible, even IE6)
   *
   * Browsers that support typed arrays are IE 10+, Firefox 4+, Chrome 7+, Safari 5.1+,
   * Opera 11.6+, iOS 4.2+.
   *
   * Due to various browser bugs, sometimes the Object implementation will be used even
   * when the browser supports typed arrays.
   *
   * Note:
   *
   *   - Firefox 4-29 lacks support for adding new properties to `Uint8Array` instances,
   *     See: https://bugzilla.mozilla.org/show_bug.cgi?id=695438.
   *
   *   - Chrome 9-10 is missing the `TypedArray.prototype.subarray` function.
   *
   *   - IE10 has a broken `TypedArray.prototype.subarray` function which returns arrays of
   *     incorrect length in some situations.

   * We detect these buggy browsers and set `Buffer.TYPED_ARRAY_SUPPORT` to `false` so they
   * get the Object implementation, which is slower but behaves correctly.
   */
  Buffer.TYPED_ARRAY_SUPPORT = global$1.TYPED_ARRAY_SUPPORT !== undefined
    ? global$1.TYPED_ARRAY_SUPPORT
    : true;

  function kMaxLength () {
    return Buffer.TYPED_ARRAY_SUPPORT
      ? 0x7fffffff
      : 0x3fffffff
  }

  function createBuffer (that, length) {
    if (kMaxLength() < length) {
      throw new RangeError('Invalid typed array length')
    }
    if (Buffer.TYPED_ARRAY_SUPPORT) {
      // Return an augmented `Uint8Array` instance, for best performance
      that = new Uint8Array(length);
      that.__proto__ = Buffer.prototype;
    } else {
      // Fallback: Return an object instance of the Buffer class
      if (that === null) {
        that = new Buffer(length);
      }
      that.length = length;
    }

    return that
  }

  /**
   * The Buffer constructor returns instances of `Uint8Array` that have their
   * prototype changed to `Buffer.prototype`. Furthermore, `Buffer` is a subclass of
   * `Uint8Array`, so the returned instances will have all the node `Buffer` methods
   * and the `Uint8Array` methods. Square bracket notation works as expected -- it
   * returns a single octet.
   *
   * The `Uint8Array` prototype remains unmodified.
   */

  function Buffer (arg, encodingOrOffset, length) {
    if (!Buffer.TYPED_ARRAY_SUPPORT && !(this instanceof Buffer)) {
      return new Buffer(arg, encodingOrOffset, length)
    }

    // Common case.
    if (typeof arg === 'number') {
      if (typeof encodingOrOffset === 'string') {
        throw new Error(
          'If encoding is specified then the first argument must be a string'
        )
      }
      return allocUnsafe(this, arg)
    }
    return from(this, arg, encodingOrOffset, length)
  }

  Buffer.poolSize = 8192; // not used by this implementation

  // TODO: Legacy, not needed anymore. Remove in next major version.
  Buffer._augment = function (arr) {
    arr.__proto__ = Buffer.prototype;
    return arr
  };

  function from (that, value, encodingOrOffset, length) {
    if (typeof value === 'number') {
      throw new TypeError('"value" argument must not be a number')
    }

    if (typeof ArrayBuffer !== 'undefined' && value instanceof ArrayBuffer) {
      return fromArrayBuffer(that, value, encodingOrOffset, length)
    }

    if (typeof value === 'string') {
      return fromString(that, value, encodingOrOffset)
    }

    return fromObject(that, value)
  }

  /**
   * Functionally equivalent to Buffer(arg, encoding) but throws a TypeError
   * if value is a number.
   * Buffer.from(str[, encoding])
   * Buffer.from(array)
   * Buffer.from(buffer)
   * Buffer.from(arrayBuffer[, byteOffset[, length]])
   **/
  Buffer.from = function (value, encodingOrOffset, length) {
    return from(null, value, encodingOrOffset, length)
  };

  if (Buffer.TYPED_ARRAY_SUPPORT) {
    Buffer.prototype.__proto__ = Uint8Array.prototype;
    Buffer.__proto__ = Uint8Array;
  }

  function assertSize (size) {
    if (typeof size !== 'number') {
      throw new TypeError('"size" argument must be a number')
    } else if (size < 0) {
      throw new RangeError('"size" argument must not be negative')
    }
  }

  function alloc (that, size, fill, encoding) {
    assertSize(size);
    if (size <= 0) {
      return createBuffer(that, size)
    }
    if (fill !== undefined) {
      // Only pay attention to encoding if it's a string. This
      // prevents accidentally sending in a number that would
      // be interpretted as a start offset.
      return typeof encoding === 'string'
        ? createBuffer(that, size).fill(fill, encoding)
        : createBuffer(that, size).fill(fill)
    }
    return createBuffer(that, size)
  }

  /**
   * Creates a new filled Buffer instance.
   * alloc(size[, fill[, encoding]])
   **/
  Buffer.alloc = function (size, fill, encoding) {
    return alloc(null, size, fill, encoding)
  };

  function allocUnsafe (that, size) {
    assertSize(size);
    that = createBuffer(that, size < 0 ? 0 : checked(size) | 0);
    if (!Buffer.TYPED_ARRAY_SUPPORT) {
      for (var i = 0; i < size; ++i) {
        that[i] = 0;
      }
    }
    return that
  }

  /**
   * Equivalent to Buffer(num), by default creates a non-zero-filled Buffer instance.
   * */
  Buffer.allocUnsafe = function (size) {
    return allocUnsafe(null, size)
  };
  /**
   * Equivalent to SlowBuffer(num), by default creates a non-zero-filled Buffer instance.
   */
  Buffer.allocUnsafeSlow = function (size) {
    return allocUnsafe(null, size)
  };

  function fromString (that, string, encoding) {
    if (typeof encoding !== 'string' || encoding === '') {
      encoding = 'utf8';
    }

    if (!Buffer.isEncoding(encoding)) {
      throw new TypeError('"encoding" must be a valid string encoding')
    }

    var length = byteLength(string, encoding) | 0;
    that = createBuffer(that, length);

    var actual = that.write(string, encoding);

    if (actual !== length) {
      // Writing a hex string, for example, that contains invalid characters will
      // cause everything after the first invalid character to be ignored. (e.g.
      // 'abxxcd' will be treated as 'ab')
      that = that.slice(0, actual);
    }

    return that
  }

  function fromArrayLike (that, array) {
    var length = array.length < 0 ? 0 : checked(array.length) | 0;
    that = createBuffer(that, length);
    for (var i = 0; i < length; i += 1) {
      that[i] = array[i] & 255;
    }
    return that
  }

  function fromArrayBuffer (that, array, byteOffset, length) {
    array.byteLength; // this throws if `array` is not a valid ArrayBuffer

    if (byteOffset < 0 || array.byteLength < byteOffset) {
      throw new RangeError('\'offset\' is out of bounds')
    }

    if (array.byteLength < byteOffset + (length || 0)) {
      throw new RangeError('\'length\' is out of bounds')
    }

    if (byteOffset === undefined && length === undefined) {
      array = new Uint8Array(array);
    } else if (length === undefined) {
      array = new Uint8Array(array, byteOffset);
    } else {
      array = new Uint8Array(array, byteOffset, length);
    }

    if (Buffer.TYPED_ARRAY_SUPPORT) {
      // Return an augmented `Uint8Array` instance, for best performance
      that = array;
      that.__proto__ = Buffer.prototype;
    } else {
      // Fallback: Return an object instance of the Buffer class
      that = fromArrayLike(that, array);
    }
    return that
  }

  function fromObject (that, obj) {
    if (internalIsBuffer(obj)) {
      var len = checked(obj.length) | 0;
      that = createBuffer(that, len);

      if (that.length === 0) {
        return that
      }

      obj.copy(that, 0, 0, len);
      return that
    }

    if (obj) {
      if ((typeof ArrayBuffer !== 'undefined' &&
          obj.buffer instanceof ArrayBuffer) || 'length' in obj) {
        if (typeof obj.length !== 'number' || isnan(obj.length)) {
          return createBuffer(that, 0)
        }
        return fromArrayLike(that, obj)
      }

      if (obj.type === 'Buffer' && isArray(obj.data)) {
        return fromArrayLike(that, obj.data)
      }
    }

    throw new TypeError('First argument must be a string, Buffer, ArrayBuffer, Array, or array-like object.')
  }

  function checked (length) {
    // Note: cannot use `length < kMaxLength()` here because that fails when
    // length is NaN (which is otherwise coerced to zero.)
    if (length >= kMaxLength()) {
      throw new RangeError('Attempt to allocate Buffer larger than maximum ' +
                           'size: 0x' + kMaxLength().toString(16) + ' bytes')
    }
    return length | 0
  }
  Buffer.isBuffer = isBuffer;
  function internalIsBuffer (b) {
    return !!(b != null && b._isBuffer)
  }

  Buffer.compare = function compare (a, b) {
    if (!internalIsBuffer(a) || !internalIsBuffer(b)) {
      throw new TypeError('Arguments must be Buffers')
    }

    if (a === b) return 0

    var x = a.length;
    var y = b.length;

    for (var i = 0, len = Math.min(x, y); i < len; ++i) {
      if (a[i] !== b[i]) {
        x = a[i];
        y = b[i];
        break
      }
    }

    if (x < y) return -1
    if (y < x) return 1
    return 0
  };

  Buffer.isEncoding = function isEncoding (encoding) {
    switch (String(encoding).toLowerCase()) {
      case 'hex':
      case 'utf8':
      case 'utf-8':
      case 'ascii':
      case 'latin1':
      case 'binary':
      case 'base64':
      case 'ucs2':
      case 'ucs-2':
      case 'utf16le':
      case 'utf-16le':
        return true
      default:
        return false
    }
  };

  Buffer.concat = function concat (list, length) {
    if (!isArray(list)) {
      throw new TypeError('"list" argument must be an Array of Buffers')
    }

    if (list.length === 0) {
      return Buffer.alloc(0)
    }

    var i;
    if (length === undefined) {
      length = 0;
      for (i = 0; i < list.length; ++i) {
        length += list[i].length;
      }
    }

    var buffer = Buffer.allocUnsafe(length);
    var pos = 0;
    for (i = 0; i < list.length; ++i) {
      var buf = list[i];
      if (!internalIsBuffer(buf)) {
        throw new TypeError('"list" argument must be an Array of Buffers')
      }
      buf.copy(buffer, pos);
      pos += buf.length;
    }
    return buffer
  };

  function byteLength (string, encoding) {
    if (internalIsBuffer(string)) {
      return string.length
    }
    if (typeof ArrayBuffer !== 'undefined' && typeof ArrayBuffer.isView === 'function' &&
        (ArrayBuffer.isView(string) || string instanceof ArrayBuffer)) {
      return string.byteLength
    }
    if (typeof string !== 'string') {
      string = '' + string;
    }

    var len = string.length;
    if (len === 0) return 0

    // Use a for loop to avoid recursion
    var loweredCase = false;
    for (;;) {
      switch (encoding) {
        case 'ascii':
        case 'latin1':
        case 'binary':
          return len
        case 'utf8':
        case 'utf-8':
        case undefined:
          return utf8ToBytes(string).length
        case 'ucs2':
        case 'ucs-2':
        case 'utf16le':
        case 'utf-16le':
          return len * 2
        case 'hex':
          return len >>> 1
        case 'base64':
          return base64ToBytes(string).length
        default:
          if (loweredCase) return utf8ToBytes(string).length // assume utf8
          encoding = ('' + encoding).toLowerCase();
          loweredCase = true;
      }
    }
  }
  Buffer.byteLength = byteLength;

  function slowToString (encoding, start, end) {
    var loweredCase = false;

    // No need to verify that "this.length <= MAX_UINT32" since it's a read-only
    // property of a typed array.

    // This behaves neither like String nor Uint8Array in that we set start/end
    // to their upper/lower bounds if the value passed is out of range.
    // undefined is handled specially as per ECMA-262 6th Edition,
    // Section 13.3.3.7 Runtime Semantics: KeyedBindingInitialization.
    if (start === undefined || start < 0) {
      start = 0;
    }
    // Return early if start > this.length. Done here to prevent potential uint32
    // coercion fail below.
    if (start > this.length) {
      return ''
    }

    if (end === undefined || end > this.length) {
      end = this.length;
    }

    if (end <= 0) {
      return ''
    }

    // Force coersion to uint32. This will also coerce falsey/NaN values to 0.
    end >>>= 0;
    start >>>= 0;

    if (end <= start) {
      return ''
    }

    if (!encoding) encoding = 'utf8';

    while (true) {
      switch (encoding) {
        case 'hex':
          return hexSlice(this, start, end)

        case 'utf8':
        case 'utf-8':
          return utf8Slice(this, start, end)

        case 'ascii':
          return asciiSlice(this, start, end)

        case 'latin1':
        case 'binary':
          return latin1Slice(this, start, end)

        case 'base64':
          return base64Slice(this, start, end)

        case 'ucs2':
        case 'ucs-2':
        case 'utf16le':
        case 'utf-16le':
          return utf16leSlice(this, start, end)

        default:
          if (loweredCase) throw new TypeError('Unknown encoding: ' + encoding)
          encoding = (encoding + '').toLowerCase();
          loweredCase = true;
      }
    }
  }

  // The property is used by `Buffer.isBuffer` and `is-buffer` (in Safari 5-7) to detect
  // Buffer instances.
  Buffer.prototype._isBuffer = true;

  function swap (b, n, m) {
    var i = b[n];
    b[n] = b[m];
    b[m] = i;
  }

  Buffer.prototype.swap16 = function swap16 () {
    var len = this.length;
    if (len % 2 !== 0) {
      throw new RangeError('Buffer size must be a multiple of 16-bits')
    }
    for (var i = 0; i < len; i += 2) {
      swap(this, i, i + 1);
    }
    return this
  };

  Buffer.prototype.swap32 = function swap32 () {
    var len = this.length;
    if (len % 4 !== 0) {
      throw new RangeError('Buffer size must be a multiple of 32-bits')
    }
    for (var i = 0; i < len; i += 4) {
      swap(this, i, i + 3);
      swap(this, i + 1, i + 2);
    }
    return this
  };

  Buffer.prototype.swap64 = function swap64 () {
    var len = this.length;
    if (len % 8 !== 0) {
      throw new RangeError('Buffer size must be a multiple of 64-bits')
    }
    for (var i = 0; i < len; i += 8) {
      swap(this, i, i + 7);
      swap(this, i + 1, i + 6);
      swap(this, i + 2, i + 5);
      swap(this, i + 3, i + 4);
    }
    return this
  };

  Buffer.prototype.toString = function toString () {
    var length = this.length | 0;
    if (length === 0) return ''
    if (arguments.length === 0) return utf8Slice(this, 0, length)
    return slowToString.apply(this, arguments)
  };

  Buffer.prototype.equals = function equals (b) {
    if (!internalIsBuffer(b)) throw new TypeError('Argument must be a Buffer')
    if (this === b) return true
    return Buffer.compare(this, b) === 0
  };

  Buffer.prototype.inspect = function inspect () {
    var str = '';
    var max = INSPECT_MAX_BYTES;
    if (this.length > 0) {
      str = this.toString('hex', 0, max).match(/.{2}/g).join(' ');
      if (this.length > max) str += ' ... ';
    }
    return '<Buffer ' + str + '>'
  };

  Buffer.prototype.compare = function compare (target, start, end, thisStart, thisEnd) {
    if (!internalIsBuffer(target)) {
      throw new TypeError('Argument must be a Buffer')
    }

    if (start === undefined) {
      start = 0;
    }
    if (end === undefined) {
      end = target ? target.length : 0;
    }
    if (thisStart === undefined) {
      thisStart = 0;
    }
    if (thisEnd === undefined) {
      thisEnd = this.length;
    }

    if (start < 0 || end > target.length || thisStart < 0 || thisEnd > this.length) {
      throw new RangeError('out of range index')
    }

    if (thisStart >= thisEnd && start >= end) {
      return 0
    }
    if (thisStart >= thisEnd) {
      return -1
    }
    if (start >= end) {
      return 1
    }

    start >>>= 0;
    end >>>= 0;
    thisStart >>>= 0;
    thisEnd >>>= 0;

    if (this === target) return 0

    var x = thisEnd - thisStart;
    var y = end - start;
    var len = Math.min(x, y);

    var thisCopy = this.slice(thisStart, thisEnd);
    var targetCopy = target.slice(start, end);

    for (var i = 0; i < len; ++i) {
      if (thisCopy[i] !== targetCopy[i]) {
        x = thisCopy[i];
        y = targetCopy[i];
        break
      }
    }

    if (x < y) return -1
    if (y < x) return 1
    return 0
  };

  // Finds either the first index of `val` in `buffer` at offset >= `byteOffset`,
  // OR the last index of `val` in `buffer` at offset <= `byteOffset`.
  //
  // Arguments:
  // - buffer - a Buffer to search
  // - val - a string, Buffer, or number
  // - byteOffset - an index into `buffer`; will be clamped to an int32
  // - encoding - an optional encoding, relevant is val is a string
  // - dir - true for indexOf, false for lastIndexOf
  function bidirectionalIndexOf (buffer, val, byteOffset, encoding, dir) {
    // Empty buffer means no match
    if (buffer.length === 0) return -1

    // Normalize byteOffset
    if (typeof byteOffset === 'string') {
      encoding = byteOffset;
      byteOffset = 0;
    } else if (byteOffset > 0x7fffffff) {
      byteOffset = 0x7fffffff;
    } else if (byteOffset < -0x80000000) {
      byteOffset = -0x80000000;
    }
    byteOffset = +byteOffset;  // Coerce to Number.
    if (isNaN(byteOffset)) {
      // byteOffset: it it's undefined, null, NaN, "foo", etc, search whole buffer
      byteOffset = dir ? 0 : (buffer.length - 1);
    }

    // Normalize byteOffset: negative offsets start from the end of the buffer
    if (byteOffset < 0) byteOffset = buffer.length + byteOffset;
    if (byteOffset >= buffer.length) {
      if (dir) return -1
      else byteOffset = buffer.length - 1;
    } else if (byteOffset < 0) {
      if (dir) byteOffset = 0;
      else return -1
    }

    // Normalize val
    if (typeof val === 'string') {
      val = Buffer.from(val, encoding);
    }

    // Finally, search either indexOf (if dir is true) or lastIndexOf
    if (internalIsBuffer(val)) {
      // Special case: looking for empty string/buffer always fails
      if (val.length === 0) {
        return -1
      }
      return arrayIndexOf(buffer, val, byteOffset, encoding, dir)
    } else if (typeof val === 'number') {
      val = val & 0xFF; // Search for a byte value [0-255]
      if (Buffer.TYPED_ARRAY_SUPPORT &&
          typeof Uint8Array.prototype.indexOf === 'function') {
        if (dir) {
          return Uint8Array.prototype.indexOf.call(buffer, val, byteOffset)
        } else {
          return Uint8Array.prototype.lastIndexOf.call(buffer, val, byteOffset)
        }
      }
      return arrayIndexOf(buffer, [ val ], byteOffset, encoding, dir)
    }

    throw new TypeError('val must be string, number or Buffer')
  }

  function arrayIndexOf (arr, val, byteOffset, encoding, dir) {
    var indexSize = 1;
    var arrLength = arr.length;
    var valLength = val.length;

    if (encoding !== undefined) {
      encoding = String(encoding).toLowerCase();
      if (encoding === 'ucs2' || encoding === 'ucs-2' ||
          encoding === 'utf16le' || encoding === 'utf-16le') {
        if (arr.length < 2 || val.length < 2) {
          return -1
        }
        indexSize = 2;
        arrLength /= 2;
        valLength /= 2;
        byteOffset /= 2;
      }
    }

    function read (buf, i) {
      if (indexSize === 1) {
        return buf[i]
      } else {
        return buf.readUInt16BE(i * indexSize)
      }
    }

    var i;
    if (dir) {
      var foundIndex = -1;
      for (i = byteOffset; i < arrLength; i++) {
        if (read(arr, i) === read(val, foundIndex === -1 ? 0 : i - foundIndex)) {
          if (foundIndex === -1) foundIndex = i;
          if (i - foundIndex + 1 === valLength) return foundIndex * indexSize
        } else {
          if (foundIndex !== -1) i -= i - foundIndex;
          foundIndex = -1;
        }
      }
    } else {
      if (byteOffset + valLength > arrLength) byteOffset = arrLength - valLength;
      for (i = byteOffset; i >= 0; i--) {
        var found = true;
        for (var j = 0; j < valLength; j++) {
          if (read(arr, i + j) !== read(val, j)) {
            found = false;
            break
          }
        }
        if (found) return i
      }
    }

    return -1
  }

  Buffer.prototype.includes = function includes (val, byteOffset, encoding) {
    return this.indexOf(val, byteOffset, encoding) !== -1
  };

  Buffer.prototype.indexOf = function indexOf (val, byteOffset, encoding) {
    return bidirectionalIndexOf(this, val, byteOffset, encoding, true)
  };

  Buffer.prototype.lastIndexOf = function lastIndexOf (val, byteOffset, encoding) {
    return bidirectionalIndexOf(this, val, byteOffset, encoding, false)
  };

  function hexWrite (buf, string, offset, length) {
    offset = Number(offset) || 0;
    var remaining = buf.length - offset;
    if (!length) {
      length = remaining;
    } else {
      length = Number(length);
      if (length > remaining) {
        length = remaining;
      }
    }

    // must be an even number of digits
    var strLen = string.length;
    if (strLen % 2 !== 0) throw new TypeError('Invalid hex string')

    if (length > strLen / 2) {
      length = strLen / 2;
    }
    for (var i = 0; i < length; ++i) {
      var parsed = parseInt(string.substr(i * 2, 2), 16);
      if (isNaN(parsed)) return i
      buf[offset + i] = parsed;
    }
    return i
  }

  function utf8Write (buf, string, offset, length) {
    return blitBuffer(utf8ToBytes(string, buf.length - offset), buf, offset, length)
  }

  function asciiWrite (buf, string, offset, length) {
    return blitBuffer(asciiToBytes(string), buf, offset, length)
  }

  function latin1Write (buf, string, offset, length) {
    return asciiWrite(buf, string, offset, length)
  }

  function base64Write (buf, string, offset, length) {
    return blitBuffer(base64ToBytes(string), buf, offset, length)
  }

  function ucs2Write (buf, string, offset, length) {
    return blitBuffer(utf16leToBytes(string, buf.length - offset), buf, offset, length)
  }

  Buffer.prototype.write = function write (string, offset, length, encoding) {
    // Buffer#write(string)
    if (offset === undefined) {
      encoding = 'utf8';
      length = this.length;
      offset = 0;
    // Buffer#write(string, encoding)
    } else if (length === undefined && typeof offset === 'string') {
      encoding = offset;
      length = this.length;
      offset = 0;
    // Buffer#write(string, offset[, length][, encoding])
    } else if (isFinite(offset)) {
      offset = offset | 0;
      if (isFinite(length)) {
        length = length | 0;
        if (encoding === undefined) encoding = 'utf8';
      } else {
        encoding = length;
        length = undefined;
      }
    // legacy write(string, encoding, offset, length) - remove in v0.13
    } else {
      throw new Error(
        'Buffer.write(string, encoding, offset[, length]) is no longer supported'
      )
    }

    var remaining = this.length - offset;
    if (length === undefined || length > remaining) length = remaining;

    if ((string.length > 0 && (length < 0 || offset < 0)) || offset > this.length) {
      throw new RangeError('Attempt to write outside buffer bounds')
    }

    if (!encoding) encoding = 'utf8';

    var loweredCase = false;
    for (;;) {
      switch (encoding) {
        case 'hex':
          return hexWrite(this, string, offset, length)

        case 'utf8':
        case 'utf-8':
          return utf8Write(this, string, offset, length)

        case 'ascii':
          return asciiWrite(this, string, offset, length)

        case 'latin1':
        case 'binary':
          return latin1Write(this, string, offset, length)

        case 'base64':
          // Warning: maxLength not taken into account in base64Write
          return base64Write(this, string, offset, length)

        case 'ucs2':
        case 'ucs-2':
        case 'utf16le':
        case 'utf-16le':
          return ucs2Write(this, string, offset, length)

        default:
          if (loweredCase) throw new TypeError('Unknown encoding: ' + encoding)
          encoding = ('' + encoding).toLowerCase();
          loweredCase = true;
      }
    }
  };

  Buffer.prototype.toJSON = function toJSON () {
    return {
      type: 'Buffer',
      data: Array.prototype.slice.call(this._arr || this, 0)
    }
  };

  function base64Slice (buf, start, end) {
    if (start === 0 && end === buf.length) {
      return fromByteArray(buf)
    } else {
      return fromByteArray(buf.slice(start, end))
    }
  }

  function utf8Slice (buf, start, end) {
    end = Math.min(buf.length, end);
    var res = [];

    var i = start;
    while (i < end) {
      var firstByte = buf[i];
      var codePoint = null;
      var bytesPerSequence = (firstByte > 0xEF) ? 4
        : (firstByte > 0xDF) ? 3
        : (firstByte > 0xBF) ? 2
        : 1;

      if (i + bytesPerSequence <= end) {
        var secondByte, thirdByte, fourthByte, tempCodePoint;

        switch (bytesPerSequence) {
          case 1:
            if (firstByte < 0x80) {
              codePoint = firstByte;
            }
            break
          case 2:
            secondByte = buf[i + 1];
            if ((secondByte & 0xC0) === 0x80) {
              tempCodePoint = (firstByte & 0x1F) << 0x6 | (secondByte & 0x3F);
              if (tempCodePoint > 0x7F) {
                codePoint = tempCodePoint;
              }
            }
            break
          case 3:
            secondByte = buf[i + 1];
            thirdByte = buf[i + 2];
            if ((secondByte & 0xC0) === 0x80 && (thirdByte & 0xC0) === 0x80) {
              tempCodePoint = (firstByte & 0xF) << 0xC | (secondByte & 0x3F) << 0x6 | (thirdByte & 0x3F);
              if (tempCodePoint > 0x7FF && (tempCodePoint < 0xD800 || tempCodePoint > 0xDFFF)) {
                codePoint = tempCodePoint;
              }
            }
            break
          case 4:
            secondByte = buf[i + 1];
            thirdByte = buf[i + 2];
            fourthByte = buf[i + 3];
            if ((secondByte & 0xC0) === 0x80 && (thirdByte & 0xC0) === 0x80 && (fourthByte & 0xC0) === 0x80) {
              tempCodePoint = (firstByte & 0xF) << 0x12 | (secondByte & 0x3F) << 0xC | (thirdByte & 0x3F) << 0x6 | (fourthByte & 0x3F);
              if (tempCodePoint > 0xFFFF && tempCodePoint < 0x110000) {
                codePoint = tempCodePoint;
              }
            }
        }
      }

      if (codePoint === null) {
        // we did not generate a valid codePoint so insert a
        // replacement char (U+FFFD) and advance only 1 byte
        codePoint = 0xFFFD;
        bytesPerSequence = 1;
      } else if (codePoint > 0xFFFF) {
        // encode to utf16 (surrogate pair dance)
        codePoint -= 0x10000;
        res.push(codePoint >>> 10 & 0x3FF | 0xD800);
        codePoint = 0xDC00 | codePoint & 0x3FF;
      }

      res.push(codePoint);
      i += bytesPerSequence;
    }

    return decodeCodePointsArray(res)
  }

  // Based on http://stackoverflow.com/a/22747272/680742, the browser with
  // the lowest limit is Chrome, with 0x10000 args.
  // We go 1 magnitude less, for safety
  var MAX_ARGUMENTS_LENGTH = 0x1000;

  function decodeCodePointsArray (codePoints) {
    var len = codePoints.length;
    if (len <= MAX_ARGUMENTS_LENGTH) {
      return String.fromCharCode.apply(String, codePoints) // avoid extra slice()
    }

    // Decode in chunks to avoid "call stack size exceeded".
    var res = '';
    var i = 0;
    while (i < len) {
      res += String.fromCharCode.apply(
        String,
        codePoints.slice(i, i += MAX_ARGUMENTS_LENGTH)
      );
    }
    return res
  }

  function asciiSlice (buf, start, end) {
    var ret = '';
    end = Math.min(buf.length, end);

    for (var i = start; i < end; ++i) {
      ret += String.fromCharCode(buf[i] & 0x7F);
    }
    return ret
  }

  function latin1Slice (buf, start, end) {
    var ret = '';
    end = Math.min(buf.length, end);

    for (var i = start; i < end; ++i) {
      ret += String.fromCharCode(buf[i]);
    }
    return ret
  }

  function hexSlice (buf, start, end) {
    var len = buf.length;

    if (!start || start < 0) start = 0;
    if (!end || end < 0 || end > len) end = len;

    var out = '';
    for (var i = start; i < end; ++i) {
      out += toHex(buf[i]);
    }
    return out
  }

  function utf16leSlice (buf, start, end) {
    var bytes = buf.slice(start, end);
    var res = '';
    for (var i = 0; i < bytes.length; i += 2) {
      res += String.fromCharCode(bytes[i] + bytes[i + 1] * 256);
    }
    return res
  }

  Buffer.prototype.slice = function slice (start, end) {
    var len = this.length;
    start = ~~start;
    end = end === undefined ? len : ~~end;

    if (start < 0) {
      start += len;
      if (start < 0) start = 0;
    } else if (start > len) {
      start = len;
    }

    if (end < 0) {
      end += len;
      if (end < 0) end = 0;
    } else if (end > len) {
      end = len;
    }

    if (end < start) end = start;

    var newBuf;
    if (Buffer.TYPED_ARRAY_SUPPORT) {
      newBuf = this.subarray(start, end);
      newBuf.__proto__ = Buffer.prototype;
    } else {
      var sliceLen = end - start;
      newBuf = new Buffer(sliceLen, undefined);
      for (var i = 0; i < sliceLen; ++i) {
        newBuf[i] = this[i + start];
      }
    }

    return newBuf
  };

  /*
   * Need to make sure that buffer isn't trying to write out of bounds.
   */
  function checkOffset (offset, ext, length) {
    if ((offset % 1) !== 0 || offset < 0) throw new RangeError('offset is not uint')
    if (offset + ext > length) throw new RangeError('Trying to access beyond buffer length')
  }

  Buffer.prototype.readUIntLE = function readUIntLE (offset, byteLength, noAssert) {
    offset = offset | 0;
    byteLength = byteLength | 0;
    if (!noAssert) checkOffset(offset, byteLength, this.length);

    var val = this[offset];
    var mul = 1;
    var i = 0;
    while (++i < byteLength && (mul *= 0x100)) {
      val += this[offset + i] * mul;
    }

    return val
  };

  Buffer.prototype.readUIntBE = function readUIntBE (offset, byteLength, noAssert) {
    offset = offset | 0;
    byteLength = byteLength | 0;
    if (!noAssert) {
      checkOffset(offset, byteLength, this.length);
    }

    var val = this[offset + --byteLength];
    var mul = 1;
    while (byteLength > 0 && (mul *= 0x100)) {
      val += this[offset + --byteLength] * mul;
    }

    return val
  };

  Buffer.prototype.readUInt8 = function readUInt8 (offset, noAssert) {
    if (!noAssert) checkOffset(offset, 1, this.length);
    return this[offset]
  };

  Buffer.prototype.readUInt16LE = function readUInt16LE (offset, noAssert) {
    if (!noAssert) checkOffset(offset, 2, this.length);
    return this[offset] | (this[offset + 1] << 8)
  };

  Buffer.prototype.readUInt16BE = function readUInt16BE (offset, noAssert) {
    if (!noAssert) checkOffset(offset, 2, this.length);
    return (this[offset] << 8) | this[offset + 1]
  };

  Buffer.prototype.readUInt32LE = function readUInt32LE (offset, noAssert) {
    if (!noAssert) checkOffset(offset, 4, this.length);

    return ((this[offset]) |
        (this[offset + 1] << 8) |
        (this[offset + 2] << 16)) +
        (this[offset + 3] * 0x1000000)
  };

  Buffer.prototype.readUInt32BE = function readUInt32BE (offset, noAssert) {
    if (!noAssert) checkOffset(offset, 4, this.length);

    return (this[offset] * 0x1000000) +
      ((this[offset + 1] << 16) |
      (this[offset + 2] << 8) |
      this[offset + 3])
  };

  Buffer.prototype.readIntLE = function readIntLE (offset, byteLength, noAssert) {
    offset = offset | 0;
    byteLength = byteLength | 0;
    if (!noAssert) checkOffset(offset, byteLength, this.length);

    var val = this[offset];
    var mul = 1;
    var i = 0;
    while (++i < byteLength && (mul *= 0x100)) {
      val += this[offset + i] * mul;
    }
    mul *= 0x80;

    if (val >= mul) val -= Math.pow(2, 8 * byteLength);

    return val
  };

  Buffer.prototype.readIntBE = function readIntBE (offset, byteLength, noAssert) {
    offset = offset | 0;
    byteLength = byteLength | 0;
    if (!noAssert) checkOffset(offset, byteLength, this.length);

    var i = byteLength;
    var mul = 1;
    var val = this[offset + --i];
    while (i > 0 && (mul *= 0x100)) {
      val += this[offset + --i] * mul;
    }
    mul *= 0x80;

    if (val >= mul) val -= Math.pow(2, 8 * byteLength);

    return val
  };

  Buffer.prototype.readInt8 = function readInt8 (offset, noAssert) {
    if (!noAssert) checkOffset(offset, 1, this.length);
    if (!(this[offset] & 0x80)) return (this[offset])
    return ((0xff - this[offset] + 1) * -1)
  };

  Buffer.prototype.readInt16LE = function readInt16LE (offset, noAssert) {
    if (!noAssert) checkOffset(offset, 2, this.length);
    var val = this[offset] | (this[offset + 1] << 8);
    return (val & 0x8000) ? val | 0xFFFF0000 : val
  };

  Buffer.prototype.readInt16BE = function readInt16BE (offset, noAssert) {
    if (!noAssert) checkOffset(offset, 2, this.length);
    var val = this[offset + 1] | (this[offset] << 8);
    return (val & 0x8000) ? val | 0xFFFF0000 : val
  };

  Buffer.prototype.readInt32LE = function readInt32LE (offset, noAssert) {
    if (!noAssert) checkOffset(offset, 4, this.length);

    return (this[offset]) |
      (this[offset + 1] << 8) |
      (this[offset + 2] << 16) |
      (this[offset + 3] << 24)
  };

  Buffer.prototype.readInt32BE = function readInt32BE (offset, noAssert) {
    if (!noAssert) checkOffset(offset, 4, this.length);

    return (this[offset] << 24) |
      (this[offset + 1] << 16) |
      (this[offset + 2] << 8) |
      (this[offset + 3])
  };

  Buffer.prototype.readFloatLE = function readFloatLE (offset, noAssert) {
    if (!noAssert) checkOffset(offset, 4, this.length);
    return read(this, offset, true, 23, 4)
  };

  Buffer.prototype.readFloatBE = function readFloatBE (offset, noAssert) {
    if (!noAssert) checkOffset(offset, 4, this.length);
    return read(this, offset, false, 23, 4)
  };

  Buffer.prototype.readDoubleLE = function readDoubleLE (offset, noAssert) {
    if (!noAssert) checkOffset(offset, 8, this.length);
    return read(this, offset, true, 52, 8)
  };

  Buffer.prototype.readDoubleBE = function readDoubleBE (offset, noAssert) {
    if (!noAssert) checkOffset(offset, 8, this.length);
    return read(this, offset, false, 52, 8)
  };

  function checkInt (buf, value, offset, ext, max, min) {
    if (!internalIsBuffer(buf)) throw new TypeError('"buffer" argument must be a Buffer instance')
    if (value > max || value < min) throw new RangeError('"value" argument is out of bounds')
    if (offset + ext > buf.length) throw new RangeError('Index out of range')
  }

  Buffer.prototype.writeUIntLE = function writeUIntLE (value, offset, byteLength, noAssert) {
    value = +value;
    offset = offset | 0;
    byteLength = byteLength | 0;
    if (!noAssert) {
      var maxBytes = Math.pow(2, 8 * byteLength) - 1;
      checkInt(this, value, offset, byteLength, maxBytes, 0);
    }

    var mul = 1;
    var i = 0;
    this[offset] = value & 0xFF;
    while (++i < byteLength && (mul *= 0x100)) {
      this[offset + i] = (value / mul) & 0xFF;
    }

    return offset + byteLength
  };

  Buffer.prototype.writeUIntBE = function writeUIntBE (value, offset, byteLength, noAssert) {
    value = +value;
    offset = offset | 0;
    byteLength = byteLength | 0;
    if (!noAssert) {
      var maxBytes = Math.pow(2, 8 * byteLength) - 1;
      checkInt(this, value, offset, byteLength, maxBytes, 0);
    }

    var i = byteLength - 1;
    var mul = 1;
    this[offset + i] = value & 0xFF;
    while (--i >= 0 && (mul *= 0x100)) {
      this[offset + i] = (value / mul) & 0xFF;
    }

    return offset + byteLength
  };

  Buffer.prototype.writeUInt8 = function writeUInt8 (value, offset, noAssert) {
    value = +value;
    offset = offset | 0;
    if (!noAssert) checkInt(this, value, offset, 1, 0xff, 0);
    if (!Buffer.TYPED_ARRAY_SUPPORT) value = Math.floor(value);
    this[offset] = (value & 0xff);
    return offset + 1
  };

  function objectWriteUInt16 (buf, value, offset, littleEndian) {
    if (value < 0) value = 0xffff + value + 1;
    for (var i = 0, j = Math.min(buf.length - offset, 2); i < j; ++i) {
      buf[offset + i] = (value & (0xff << (8 * (littleEndian ? i : 1 - i)))) >>>
        (littleEndian ? i : 1 - i) * 8;
    }
  }

  Buffer.prototype.writeUInt16LE = function writeUInt16LE (value, offset, noAssert) {
    value = +value;
    offset = offset | 0;
    if (!noAssert) checkInt(this, value, offset, 2, 0xffff, 0);
    if (Buffer.TYPED_ARRAY_SUPPORT) {
      this[offset] = (value & 0xff);
      this[offset + 1] = (value >>> 8);
    } else {
      objectWriteUInt16(this, value, offset, true);
    }
    return offset + 2
  };

  Buffer.prototype.writeUInt16BE = function writeUInt16BE (value, offset, noAssert) {
    value = +value;
    offset = offset | 0;
    if (!noAssert) checkInt(this, value, offset, 2, 0xffff, 0);
    if (Buffer.TYPED_ARRAY_SUPPORT) {
      this[offset] = (value >>> 8);
      this[offset + 1] = (value & 0xff);
    } else {
      objectWriteUInt16(this, value, offset, false);
    }
    return offset + 2
  };

  function objectWriteUInt32 (buf, value, offset, littleEndian) {
    if (value < 0) value = 0xffffffff + value + 1;
    for (var i = 0, j = Math.min(buf.length - offset, 4); i < j; ++i) {
      buf[offset + i] = (value >>> (littleEndian ? i : 3 - i) * 8) & 0xff;
    }
  }

  Buffer.prototype.writeUInt32LE = function writeUInt32LE (value, offset, noAssert) {
    value = +value;
    offset = offset | 0;
    if (!noAssert) checkInt(this, value, offset, 4, 0xffffffff, 0);
    if (Buffer.TYPED_ARRAY_SUPPORT) {
      this[offset + 3] = (value >>> 24);
      this[offset + 2] = (value >>> 16);
      this[offset + 1] = (value >>> 8);
      this[offset] = (value & 0xff);
    } else {
      objectWriteUInt32(this, value, offset, true);
    }
    return offset + 4
  };

  Buffer.prototype.writeUInt32BE = function writeUInt32BE (value, offset, noAssert) {
    value = +value;
    offset = offset | 0;
    if (!noAssert) checkInt(this, value, offset, 4, 0xffffffff, 0);
    if (Buffer.TYPED_ARRAY_SUPPORT) {
      this[offset] = (value >>> 24);
      this[offset + 1] = (value >>> 16);
      this[offset + 2] = (value >>> 8);
      this[offset + 3] = (value & 0xff);
    } else {
      objectWriteUInt32(this, value, offset, false);
    }
    return offset + 4
  };

  Buffer.prototype.writeIntLE = function writeIntLE (value, offset, byteLength, noAssert) {
    value = +value;
    offset = offset | 0;
    if (!noAssert) {
      var limit = Math.pow(2, 8 * byteLength - 1);

      checkInt(this, value, offset, byteLength, limit - 1, -limit);
    }

    var i = 0;
    var mul = 1;
    var sub = 0;
    this[offset] = value & 0xFF;
    while (++i < byteLength && (mul *= 0x100)) {
      if (value < 0 && sub === 0 && this[offset + i - 1] !== 0) {
        sub = 1;
      }
      this[offset + i] = ((value / mul) >> 0) - sub & 0xFF;
    }

    return offset + byteLength
  };

  Buffer.prototype.writeIntBE = function writeIntBE (value, offset, byteLength, noAssert) {
    value = +value;
    offset = offset | 0;
    if (!noAssert) {
      var limit = Math.pow(2, 8 * byteLength - 1);

      checkInt(this, value, offset, byteLength, limit - 1, -limit);
    }

    var i = byteLength - 1;
    var mul = 1;
    var sub = 0;
    this[offset + i] = value & 0xFF;
    while (--i >= 0 && (mul *= 0x100)) {
      if (value < 0 && sub === 0 && this[offset + i + 1] !== 0) {
        sub = 1;
      }
      this[offset + i] = ((value / mul) >> 0) - sub & 0xFF;
    }

    return offset + byteLength
  };

  Buffer.prototype.writeInt8 = function writeInt8 (value, offset, noAssert) {
    value = +value;
    offset = offset | 0;
    if (!noAssert) checkInt(this, value, offset, 1, 0x7f, -0x80);
    if (!Buffer.TYPED_ARRAY_SUPPORT) value = Math.floor(value);
    if (value < 0) value = 0xff + value + 1;
    this[offset] = (value & 0xff);
    return offset + 1
  };

  Buffer.prototype.writeInt16LE = function writeInt16LE (value, offset, noAssert) {
    value = +value;
    offset = offset | 0;
    if (!noAssert) checkInt(this, value, offset, 2, 0x7fff, -0x8000);
    if (Buffer.TYPED_ARRAY_SUPPORT) {
      this[offset] = (value & 0xff);
      this[offset + 1] = (value >>> 8);
    } else {
      objectWriteUInt16(this, value, offset, true);
    }
    return offset + 2
  };

  Buffer.prototype.writeInt16BE = function writeInt16BE (value, offset, noAssert) {
    value = +value;
    offset = offset | 0;
    if (!noAssert) checkInt(this, value, offset, 2, 0x7fff, -0x8000);
    if (Buffer.TYPED_ARRAY_SUPPORT) {
      this[offset] = (value >>> 8);
      this[offset + 1] = (value & 0xff);
    } else {
      objectWriteUInt16(this, value, offset, false);
    }
    return offset + 2
  };

  Buffer.prototype.writeInt32LE = function writeInt32LE (value, offset, noAssert) {
    value = +value;
    offset = offset | 0;
    if (!noAssert) checkInt(this, value, offset, 4, 0x7fffffff, -0x80000000);
    if (Buffer.TYPED_ARRAY_SUPPORT) {
      this[offset] = (value & 0xff);
      this[offset + 1] = (value >>> 8);
      this[offset + 2] = (value >>> 16);
      this[offset + 3] = (value >>> 24);
    } else {
      objectWriteUInt32(this, value, offset, true);
    }
    return offset + 4
  };

  Buffer.prototype.writeInt32BE = function writeInt32BE (value, offset, noAssert) {
    value = +value;
    offset = offset | 0;
    if (!noAssert) checkInt(this, value, offset, 4, 0x7fffffff, -0x80000000);
    if (value < 0) value = 0xffffffff + value + 1;
    if (Buffer.TYPED_ARRAY_SUPPORT) {
      this[offset] = (value >>> 24);
      this[offset + 1] = (value >>> 16);
      this[offset + 2] = (value >>> 8);
      this[offset + 3] = (value & 0xff);
    } else {
      objectWriteUInt32(this, value, offset, false);
    }
    return offset + 4
  };

  function checkIEEE754 (buf, value, offset, ext, max, min) {
    if (offset + ext > buf.length) throw new RangeError('Index out of range')
    if (offset < 0) throw new RangeError('Index out of range')
  }

  function writeFloat (buf, value, offset, littleEndian, noAssert) {
    if (!noAssert) {
      checkIEEE754(buf, value, offset, 4);
    }
    write(buf, value, offset, littleEndian, 23, 4);
    return offset + 4
  }

  Buffer.prototype.writeFloatLE = function writeFloatLE (value, offset, noAssert) {
    return writeFloat(this, value, offset, true, noAssert)
  };

  Buffer.prototype.writeFloatBE = function writeFloatBE (value, offset, noAssert) {
    return writeFloat(this, value, offset, false, noAssert)
  };

  function writeDouble (buf, value, offset, littleEndian, noAssert) {
    if (!noAssert) {
      checkIEEE754(buf, value, offset, 8);
    }
    write(buf, value, offset, littleEndian, 52, 8);
    return offset + 8
  }

  Buffer.prototype.writeDoubleLE = function writeDoubleLE (value, offset, noAssert) {
    return writeDouble(this, value, offset, true, noAssert)
  };

  Buffer.prototype.writeDoubleBE = function writeDoubleBE (value, offset, noAssert) {
    return writeDouble(this, value, offset, false, noAssert)
  };

  // copy(targetBuffer, targetStart=0, sourceStart=0, sourceEnd=buffer.length)
  Buffer.prototype.copy = function copy (target, targetStart, start, end) {
    if (!start) start = 0;
    if (!end && end !== 0) end = this.length;
    if (targetStart >= target.length) targetStart = target.length;
    if (!targetStart) targetStart = 0;
    if (end > 0 && end < start) end = start;

    // Copy 0 bytes; we're done
    if (end === start) return 0
    if (target.length === 0 || this.length === 0) return 0

    // Fatal error conditions
    if (targetStart < 0) {
      throw new RangeError('targetStart out of bounds')
    }
    if (start < 0 || start >= this.length) throw new RangeError('sourceStart out of bounds')
    if (end < 0) throw new RangeError('sourceEnd out of bounds')

    // Are we oob?
    if (end > this.length) end = this.length;
    if (target.length - targetStart < end - start) {
      end = target.length - targetStart + start;
    }

    var len = end - start;
    var i;

    if (this === target && start < targetStart && targetStart < end) {
      // descending copy from end
      for (i = len - 1; i >= 0; --i) {
        target[i + targetStart] = this[i + start];
      }
    } else if (len < 1000 || !Buffer.TYPED_ARRAY_SUPPORT) {
      // ascending copy from start
      for (i = 0; i < len; ++i) {
        target[i + targetStart] = this[i + start];
      }
    } else {
      Uint8Array.prototype.set.call(
        target,
        this.subarray(start, start + len),
        targetStart
      );
    }

    return len
  };

  // Usage:
  //    buffer.fill(number[, offset[, end]])
  //    buffer.fill(buffer[, offset[, end]])
  //    buffer.fill(string[, offset[, end]][, encoding])
  Buffer.prototype.fill = function fill (val, start, end, encoding) {
    // Handle string cases:
    if (typeof val === 'string') {
      if (typeof start === 'string') {
        encoding = start;
        start = 0;
        end = this.length;
      } else if (typeof end === 'string') {
        encoding = end;
        end = this.length;
      }
      if (val.length === 1) {
        var code = val.charCodeAt(0);
        if (code < 256) {
          val = code;
        }
      }
      if (encoding !== undefined && typeof encoding !== 'string') {
        throw new TypeError('encoding must be a string')
      }
      if (typeof encoding === 'string' && !Buffer.isEncoding(encoding)) {
        throw new TypeError('Unknown encoding: ' + encoding)
      }
    } else if (typeof val === 'number') {
      val = val & 255;
    }

    // Invalid ranges are not set to a default, so can range check early.
    if (start < 0 || this.length < start || this.length < end) {
      throw new RangeError('Out of range index')
    }

    if (end <= start) {
      return this
    }

    start = start >>> 0;
    end = end === undefined ? this.length : end >>> 0;

    if (!val) val = 0;

    var i;
    if (typeof val === 'number') {
      for (i = start; i < end; ++i) {
        this[i] = val;
      }
    } else {
      var bytes = internalIsBuffer(val)
        ? val
        : utf8ToBytes(new Buffer(val, encoding).toString());
      var len = bytes.length;
      for (i = 0; i < end - start; ++i) {
        this[i + start] = bytes[i % len];
      }
    }

    return this
  };

  // HELPER FUNCTIONS
  // ================

  var INVALID_BASE64_RE = /[^+\/0-9A-Za-z-_]/g;

  function base64clean (str) {
    // Node strips out invalid characters like \n and \t from the string, base64-js does not
    str = stringtrim(str).replace(INVALID_BASE64_RE, '');
    // Node converts strings with length < 2 to ''
    if (str.length < 2) return ''
    // Node allows for non-padded base64 strings (missing trailing ===), base64-js does not
    while (str.length % 4 !== 0) {
      str = str + '=';
    }
    return str
  }

  function stringtrim (str) {
    if (str.trim) return str.trim()
    return str.replace(/^\s+|\s+$/g, '')
  }

  function toHex (n) {
    if (n < 16) return '0' + n.toString(16)
    return n.toString(16)
  }

  function utf8ToBytes (string, units) {
    units = units || Infinity;
    var codePoint;
    var length = string.length;
    var leadSurrogate = null;
    var bytes = [];

    for (var i = 0; i < length; ++i) {
      codePoint = string.charCodeAt(i);

      // is surrogate component
      if (codePoint > 0xD7FF && codePoint < 0xE000) {
        // last char was a lead
        if (!leadSurrogate) {
          // no lead yet
          if (codePoint > 0xDBFF) {
            // unexpected trail
            if ((units -= 3) > -1) bytes.push(0xEF, 0xBF, 0xBD);
            continue
          } else if (i + 1 === length) {
            // unpaired lead
            if ((units -= 3) > -1) bytes.push(0xEF, 0xBF, 0xBD);
            continue
          }

          // valid lead
          leadSurrogate = codePoint;

          continue
        }

        // 2 leads in a row
        if (codePoint < 0xDC00) {
          if ((units -= 3) > -1) bytes.push(0xEF, 0xBF, 0xBD);
          leadSurrogate = codePoint;
          continue
        }

        // valid surrogate pair
        codePoint = (leadSurrogate - 0xD800 << 10 | codePoint - 0xDC00) + 0x10000;
      } else if (leadSurrogate) {
        // valid bmp char, but last char was a lead
        if ((units -= 3) > -1) bytes.push(0xEF, 0xBF, 0xBD);
      }

      leadSurrogate = null;

      // encode utf8
      if (codePoint < 0x80) {
        if ((units -= 1) < 0) break
        bytes.push(codePoint);
      } else if (codePoint < 0x800) {
        if ((units -= 2) < 0) break
        bytes.push(
          codePoint >> 0x6 | 0xC0,
          codePoint & 0x3F | 0x80
        );
      } else if (codePoint < 0x10000) {
        if ((units -= 3) < 0) break
        bytes.push(
          codePoint >> 0xC | 0xE0,
          codePoint >> 0x6 & 0x3F | 0x80,
          codePoint & 0x3F | 0x80
        );
      } else if (codePoint < 0x110000) {
        if ((units -= 4) < 0) break
        bytes.push(
          codePoint >> 0x12 | 0xF0,
          codePoint >> 0xC & 0x3F | 0x80,
          codePoint >> 0x6 & 0x3F | 0x80,
          codePoint & 0x3F | 0x80
        );
      } else {
        throw new Error('Invalid code point')
      }
    }

    return bytes
  }

  function asciiToBytes (str) {
    var byteArray = [];
    for (var i = 0; i < str.length; ++i) {
      // Node's code seems to be doing this and not & 0x7F..
      byteArray.push(str.charCodeAt(i) & 0xFF);
    }
    return byteArray
  }

  function utf16leToBytes (str, units) {
    var c, hi, lo;
    var byteArray = [];
    for (var i = 0; i < str.length; ++i) {
      if ((units -= 2) < 0) break

      c = str.charCodeAt(i);
      hi = c >> 8;
      lo = c % 256;
      byteArray.push(lo);
      byteArray.push(hi);
    }

    return byteArray
  }


  function base64ToBytes (str) {
    return toByteArray(base64clean(str))
  }

  function blitBuffer (src, dst, offset, length) {
    for (var i = 0; i < length; ++i) {
      if ((i + offset >= dst.length) || (i >= src.length)) break
      dst[i + offset] = src[i];
    }
    return i
  }

  function isnan (val) {
    return val !== val // eslint-disable-line no-self-compare
  }


  // the following is from is-buffer, also by Feross Aboukhadijeh and with same lisence
  // The _isBuffer check is for Safari 5-7 support, because it's missing
  // Object.prototype.constructor. Remove this eventually
  function isBuffer(obj) {
    return obj != null && (!!obj._isBuffer || isFastBuffer(obj) || isSlowBuffer(obj))
  }

  function isFastBuffer (obj) {
    return !!obj.constructor && typeof obj.constructor.isBuffer === 'function' && obj.constructor.isBuffer(obj)
  }

  // For Node v0.10 support. Remove this eventually.
  function isSlowBuffer (obj) {
    return typeof obj.readFloatLE === 'function' && typeof obj.slice === 'function' && isFastBuffer(obj.slice(0, 0))
  }

  // Copyright Joyent, Inc. and other Node contributors.
  var isBufferEncoding = Buffer.isEncoding
    || function(encoding) {
         switch (encoding && encoding.toLowerCase()) {
           case 'hex': case 'utf8': case 'utf-8': case 'ascii': case 'binary': case 'base64': case 'ucs2': case 'ucs-2': case 'utf16le': case 'utf-16le': case 'raw': return true;
           default: return false;
         }
       };


  function assertEncoding(encoding) {
    if (encoding && !isBufferEncoding(encoding)) {
      throw new Error('Unknown encoding: ' + encoding);
    }
  }

  // StringDecoder provides an interface for efficiently splitting a series of
  // buffers into a series of JS strings without breaking apart multi-byte
  // characters. CESU-8 is handled as part of the UTF-8 encoding.
  //
  // @TODO Handling all encodings inside a single object makes it very difficult
  // to reason about this code, so it should be split up in the future.
  // @TODO There should be a utf8-strict encoding that rejects invalid UTF-8 code
  // points as used by CESU-8.
  function StringDecoder(encoding) {
    this.encoding = (encoding || 'utf8').toLowerCase().replace(/[-_]/, '');
    assertEncoding(encoding);
    switch (this.encoding) {
      case 'utf8':
        // CESU-8 represents each of Surrogate Pair by 3-bytes
        this.surrogateSize = 3;
        break;
      case 'ucs2':
      case 'utf16le':
        // UTF-16 represents each of Surrogate Pair by 2-bytes
        this.surrogateSize = 2;
        this.detectIncompleteChar = utf16DetectIncompleteChar;
        break;
      case 'base64':
        // Base-64 stores 3 bytes in 4 chars, and pads the remainder.
        this.surrogateSize = 3;
        this.detectIncompleteChar = base64DetectIncompleteChar;
        break;
      default:
        this.write = passThroughWrite;
        return;
    }

    // Enough space to store all bytes of a single character. UTF-8 needs 4
    // bytes, but CESU-8 may require up to 6 (3 bytes per surrogate).
    this.charBuffer = new Buffer(6);
    // Number of bytes received for the current incomplete multi-byte character.
    this.charReceived = 0;
    // Number of bytes expected for the current incomplete multi-byte character.
    this.charLength = 0;
  }

  // write decodes the given buffer and returns it as JS string that is
  // guaranteed to not contain any partial multi-byte characters. Any partial
  // character found at the end of the buffer is buffered up, and will be
  // returned when calling write again with the remaining bytes.
  //
  // Note: Converting a Buffer containing an orphan surrogate to a String
  // currently works, but converting a String to a Buffer (via `new Buffer`, or
  // Buffer#write) will replace incomplete surrogates with the unicode
  // replacement character. See https://codereview.chromium.org/121173009/ .
  StringDecoder.prototype.write = function(buffer) {
    var charStr = '';
    // if our last write ended with an incomplete multibyte character
    while (this.charLength) {
      // determine how many remaining bytes this buffer has to offer for this char
      var available = (buffer.length >= this.charLength - this.charReceived) ?
          this.charLength - this.charReceived :
          buffer.length;

      // add the new bytes to the char buffer
      buffer.copy(this.charBuffer, this.charReceived, 0, available);
      this.charReceived += available;

      if (this.charReceived < this.charLength) {
        // still not enough chars in this buffer? wait for more ...
        return '';
      }

      // remove bytes belonging to the current character from the buffer
      buffer = buffer.slice(available, buffer.length);

      // get the character that was split
      charStr = this.charBuffer.slice(0, this.charLength).toString(this.encoding);

      // CESU-8: lead surrogate (D800-DBFF) is also the incomplete character
      var charCode = charStr.charCodeAt(charStr.length - 1);
      if (charCode >= 0xD800 && charCode <= 0xDBFF) {
        this.charLength += this.surrogateSize;
        charStr = '';
        continue;
      }
      this.charReceived = this.charLength = 0;

      // if there are no more bytes in this buffer, just emit our char
      if (buffer.length === 0) {
        return charStr;
      }
      break;
    }

    // determine and set charLength / charReceived
    this.detectIncompleteChar(buffer);

    var end = buffer.length;
    if (this.charLength) {
      // buffer the incomplete character bytes we got
      buffer.copy(this.charBuffer, 0, buffer.length - this.charReceived, end);
      end -= this.charReceived;
    }

    charStr += buffer.toString(this.encoding, 0, end);

    var end = charStr.length - 1;
    var charCode = charStr.charCodeAt(end);
    // CESU-8: lead surrogate (D800-DBFF) is also the incomplete character
    if (charCode >= 0xD800 && charCode <= 0xDBFF) {
      var size = this.surrogateSize;
      this.charLength += size;
      this.charReceived += size;
      this.charBuffer.copy(this.charBuffer, size, 0, size);
      buffer.copy(this.charBuffer, 0, 0, size);
      return charStr.substring(0, end);
    }

    // or just emit the charStr
    return charStr;
  };

  // detectIncompleteChar determines if there is an incomplete UTF-8 character at
  // the end of the given buffer. If so, it sets this.charLength to the byte
  // length that character, and sets this.charReceived to the number of bytes
  // that are available for this character.
  StringDecoder.prototype.detectIncompleteChar = function(buffer) {
    // determine how many bytes we have to check at the end of this buffer
    var i = (buffer.length >= 3) ? 3 : buffer.length;

    // Figure out if one of the last i bytes of our buffer announces an
    // incomplete char.
    for (; i > 0; i--) {
      var c = buffer[buffer.length - i];

      // See http://en.wikipedia.org/wiki/UTF-8#Description

      // 110XXXXX
      if (i == 1 && c >> 5 == 0x06) {
        this.charLength = 2;
        break;
      }

      // 1110XXXX
      if (i <= 2 && c >> 4 == 0x0E) {
        this.charLength = 3;
        break;
      }

      // 11110XXX
      if (i <= 3 && c >> 3 == 0x1E) {
        this.charLength = 4;
        break;
      }
    }
    this.charReceived = i;
  };

  StringDecoder.prototype.end = function(buffer) {
    var res = '';
    if (buffer && buffer.length)
      res = this.write(buffer);

    if (this.charReceived) {
      var cr = this.charReceived;
      var buf = this.charBuffer;
      var enc = this.encoding;
      res += buf.slice(0, cr).toString(enc);
    }

    return res;
  };

  function passThroughWrite(buffer) {
    return buffer.toString(this.encoding);
  }

  function utf16DetectIncompleteChar(buffer) {
    this.charReceived = buffer.length % 2;
    this.charLength = this.charReceived ? 2 : 0;
  }

  function base64DetectIncompleteChar(buffer) {
    this.charReceived = buffer.length % 3;
    this.charLength = this.charReceived ? 3 : 0;
  }

  const BUFFER_MAX_BYTES = 524288; // 0.5Mb

  const CONTINUE_READING_RECORDS = "CONTINUE_READING";
  const READ_REMAINING_TEXT = "READ_REMAINING";
  const CANCEL_READ = "CANCEL";

  const getIndexWriter = (hierarchy, indexNode, readableStream, writableStream, end) => {
      const schema = generateSchema(hierarchy, indexNode);

      return ({
          read: read$1(readableStream, schema),
          updateIndex: updateIndex(readableStream, writableStream, schema)
      });
  };

  const getIndexReader = (hierarchy, indexNode, readableStream) => 
      read$1(
          readableStream, 
          generateSchema(hierarchy, indexNode)
      );

  const updateIndex = (readableStream, writableStream, schema) => async (itemsToWrite, keysToRemove) => {
      const write = newOutputWriter(BUFFER_MAX_BYTES, writableStream);
      const writtenItems = []; 
      await read$1(readableStream, schema)(
          async indexedItem => {
              const updated = fp.find(i => indexedItem.key === i.key)(itemsToWrite);
              const removed = fp.find(k => indexedItem.key === k)(keysToRemove);
              
              if(isSomething(removed)) 
                  return CONTINUE_READING_RECORDS;

              if(isSomething(updated)) {
                  const serializedItem =  serializeItem(schema, updated);
                  await write(serializedItem);
                  writtenItems.push(updated);
              } else {
                  await write(
                      serializeItem(schema, indexedItem)
                  );
              } 

              return CONTINUE_READING_RECORDS;

          },
          async text => await write(text)
      );

      if(writtenItems.length !== itemsToWrite.length) {
          const toAdd = fp.difference(itemsToWrite, writtenItems);
          for(let added of toAdd) {
              await write(
                  serializeItem(schema, added)
              );
          }
      } else if(writtenItems.length === 0) {
          // potentially are no records
          await write("");
      }

      await write();
      await writableStream.end();
  };

  const read$1 = (readableStream, schema) => async (onGetItem, onGetText) => {
      const readInput = newInputReader(readableStream);
      let text = await readInput();
      let status = CONTINUE_READING_RECORDS;
      while(text.length > 0) {

          if(status === READ_REMAINING_TEXT) {
              await onGetText(text);
              continue;
          }

          if(status === CANCEL_READ) {
              return;
          }

          let rowText = "";
          let currentCharIndex=0;
          for(let currentChar of text) {
              rowText += currentChar;
              if(currentChar === "\r") {
                  status = await onGetItem(
                      deserializeRow(schema, rowText)
                  );
                  rowText = "";
                  if(status === READ_REMAINING_TEXT) {
                      break;
                  }
              }
              currentCharIndex++;
          }

          if(currentCharIndex < text.length -1) {
              await onGetText(text.substring(currentCharIndex + 1));
          }

          text = await readInput();
      }

      await readableStream.destroy();

  };

  const newOutputWriter = (flushBoundary, writableStream) => {
      
      let currentBuffer = null;

      return async (text) => {

          if(fp.isString(text) && currentBuffer === null)
              currentBuffer = safeBuffer.Buffer.from(text, "utf8");
          else if(fp.isString(text))
              currentBuffer = safeBuffer.Buffer.concat([
                  currentBuffer,
                  safeBuffer.Buffer.from(text, "utf8")
              ]);
          
          if(currentBuffer !== null &&
              (currentBuffer.length > flushBoundary
               || !fp.isString(text))) {

              await writableStream.write(currentBuffer);
              currentBuffer = null;
          }
      }
  };

  const newInputReader = (readableStream) => {

      const decoder = new StringDecoder('utf8');
      let remainingBytes = [];

      return async () => {

          let nextBytesBuffer = await readableStream.read(BUFFER_MAX_BYTES);
          const remainingBuffer = safeBuffer.Buffer.from(remainingBytes);

          if(!nextBytesBuffer) nextBytesBuffer = safeBuffer.Buffer.from([]);

          const moreToRead = nextBytesBuffer.length === BUFFER_MAX_BYTES;

          const buffer = safeBuffer.Buffer.concat(
              [remainingBuffer, nextBytesBuffer],
              remainingBuffer.length + nextBytesBuffer.length);

          const text = decoder.write(buffer);
          remainingBytes = decoder.end(buffer);

          if(!moreToRead && remainingBytes.length > 0) {
              // if for any reason, we have remaining bytes at the end
              // of the stream, just discard - dont see why this should
              // ever happen, but if it does, it could cause a stack overflow
              remainingBytes = [];
          }

          return text;
      };
  };

  const deserializeRow = (schema, rowText) => {
      let currentPropIndex = 0;
      let currentCharIndex = 0;
      let currentValueText = "";
      let isEscaped = false;
      const item = {};

      const setCurrentProp = () => {
          const currentProp = schema[currentPropIndex];
          const type = getType(currentProp.type);
          const value = currentValueText === ""
                        ? type.getDefaultValue()
                        : type.safeParseValue(
                            currentValueText);
          item[currentProp.name] = value;
      };
      
      while(currentPropIndex < schema.length) {

          if(currentCharIndex < rowText.length) {
              const currentChar = rowText[currentCharIndex];
              if(isEscaped) {
                  if(currentChar === "r") {
                      currentValueText += "\r";
                  } else {
                      currentValueText += currentChar;
                  }
                  isEscaped = false;
              } else {
                  if(currentChar === ",") {
                      setCurrentProp();
                      currentValueText = "";
                      currentPropIndex++;
                  } else if(currentChar === "\\") {
                      isEscaped = true;
                  } else {
                      currentValueText += currentChar;
                  }
              }
              currentCharIndex++; 
          } else {
              currentValueText = "";
              setCurrentProp();
              currentPropIndex++;
          }
      }

      return item;
  };

  const serializeItem = (schema, item)  => {

      let rowText = "";

      for(let prop of schema) {
          const type = getType(prop.type);
          const value = fp.has(prop.name)(item)
                        ? item[prop.name]
                        : type.getDefaultValue();
          
          const valStr = type.stringify(value);

          for(let i = 0; i < valStr.length; i++) {
              const currentChar = valStr[i];
              if(currentChar === "," 
                 || currentChar === "\r" 
                 || currentChar === "\\") {
                  rowText += "\\";
              }

              if(currentChar === "\r") {
                  rowText += "r";
              } else {
                  rowText += currentChar;
              }
          }

          rowText += ",";
      }

      rowText += "\r";
      return rowText;
  };

  const readIndex$1 = async (hierarchy, datastore, index, indexedDataKey) => {
    const records = [];
    const doRead = iterateIndex(
          async item => {
        records.push(item);
        return CONTINUE_READING_RECORDS;
      },
          async () => records
    );

    return await doRead(hierarchy, datastore, index, indexedDataKey);
  };

  const searchIndex = async (hierarchy, datastore, index, indexedDataKey, searchPhrase) => {
    const records = [];
    const schema = generateSchema(hierarchy, index);
    const doRead = iterateIndex(
          async item => {
        const idx = lunr(function () {
          this.ref('key');
          for (const field of schema) {
            this.field(field.name);
          }
          this.add(item);
        });
        const searchResults = idx.search(searchPhrase);
        if (searchResults.length === 1) {
          item._searchResult = searchResults[0];
          records.push(item);
        }
        return CONTINUE_READING_RECORDS;
      },
          async () => records
    );

    return await doRead(hierarchy, datastore, index, indexedDataKey);
  };

  const iterateIndex = (onGetItem, getFinalResult) => async (hierarchy, datastore, index, indexedDataKey) => {
    try {
      const readableStream = promiseReadableStream(
          await datastore.readableFileStream(indexedDataKey)
      );

      const read = getIndexReader(hierarchy, index, readableStream);
      await read(onGetItem);
      return getFinalResult();
    } catch (e) {
      if (await datastore.exists(indexedDataKey)) {
        throw e;
      } else {
        await createIndexFile(
          datastore,
          indexedDataKey,
          index,
        );
      }
      return [];
    }
  };

  const listItems = app => async (indexKey, options) => apiWrapper(
    app,
    events.indexApi.listItems,
    permission.readIndex.isAuthorized(indexKey),
    { indexKey, options },
    _listItems, app, indexKey, options,
  );

  const defaultOptions = { rangeStartParams: null, rangeEndParams: null, searchPhrase: null };

  const _listItems = async (app, indexKey, options = defaultOptions) => {
    const { searchPhrase, rangeStartParams, rangeEndParams } = $({}, [
      fp.merge(options),
      fp.merge(defaultOptions),
    ]);

    const getItems = async key => (isNonEmptyString(searchPhrase)
      ? await searchIndex(
        app.hierarchy,
        app.datastore,
        indexNode,
        key,
        searchPhrase,
      )
      : await readIndex$1(
        app.hierarchy,
        app.datastore,
        indexNode,
        key,
      ));

    indexKey = safeKey(indexKey);
    const indexNode = getExactNodeForPath(app.hierarchy)(indexKey);

    if (!isIndex(indexNode)) { throw new Error('supplied key is not an index'); }

    if (isShardedIndex(indexNode)) {
      const shardKeys = await getShardKeysInRange(
        app, indexKey, rangeStartParams, rangeEndParams,
      );
      const items = [];
      for (const k of shardKeys) {
        items.push(await getItems(k));
      }
      return fp.flatten(items);
    }
    return await getItems(
      getUnshardedIndexDataKey(indexKey),
    );
  };

  const getContext = app => recordKey => apiWrapperSync(
    app,
    events.recordApi.getContext,
    permission.readRecord.isAuthorized(recordKey),
    { recordKey },
    _getContext, app, recordKey,
  );

  const _getContext = (app, recordKey) => {
    const recordNode = getExactNodeForPath(app.hierarchy)(recordKey);

    const cachedReferenceIndexes = {};

    const lazyLoadReferenceIndex = async (typeOptions) => {
      if (!_.has(cachedReferenceIndexes, typeOptions.indexNodeKey)) {
        cachedReferenceIndexes[typeOptions.indexNodeKey] = {
          typeOptions,
          data: await readReferenceIndex(
            app, recordKey, typeOptions,
          ),
        };
      }

      return cachedReferenceIndexes[typeOptions.indexNodeKey];
    };

    const getTypeOptions = typeOptions_or_fieldName => (fp.isString(typeOptions_or_fieldName)
      ? findField(recordNode, typeOptions_or_fieldName)
        .typeOptions
      : typeOptions_or_fieldName);

    return {
      referenceExists: async (typeOptions_or_fieldName, key) => {
        const typeOptions = getTypeOptions(typeOptions_or_fieldName);
        const { data } = await lazyLoadReferenceIndex(typeOptions);
        return _.some(data, i => i.key === key);
      },
      referenceOptions: async (typeOptions_or_fieldName) => {
        const typeOptions = getTypeOptions(typeOptions_or_fieldName);
        const { data } = await lazyLoadReferenceIndex(typeOptions);
        return data;
      },
      recordNode,
    };
  };

  const readReferenceIndex = async (app, recordKey, typeOptions) => {
    const indexNode = getNode(app.hierarchy, typeOptions.indexNodeKey);
    const indexKey = isGlobalIndex(indexNode)
      ? indexNode.nodeKey()
      : getIndexKey_BasedOnDecendant(
        recordKey, indexNode,
      );

    const items = await listItems(app)(indexKey);
    return $(items, [
      fp.map(i => ({
        key: i.key,
        value: i[typeOptions.displayValue],
      })),
    ]);
  };

  const fieldParseError = (fieldName, value) => ({
    fields: [fieldName],
    message: `Could not parse field ${fieldName}:${value}`,
  });

  const validateAllFieldParse = (record, recordNode) => $(recordNode.fields, [
    fp.map(f => ({ name: f.name, parseResult: validateFieldParse(f, record) })),
    fp.reduce((errors, f) => {
      if (f.parseResult.success) return errors;
      errors.push(
        fieldParseError(f.name, f.parseResult.value),
      );
      return errors;
    }, []),
  ]);

  const validateAllTypeConstraints = async (record, recordNode, context) => {
    const errors = [];
    for (const field of recordNode.fields) {
      $(await validateTypeConstraints$1(field, record, context), [
        fp.filter(isNonEmptyString),
        fp.map(m => ({ message: m, fields: [field.name] })),
        fp.each(e => errors.push(e)),
      ]);
    }
    return errors;
  };

  const runRecordValidationRules = (record, recordNode) => {
    const runValidationRule = (rule) => {
      const isValid = compilerUtil.compileExpression(rule.expressionWhenValid);
      const expressionContext = { record, _: ___default };
      return (isValid(expressionContext)
        ? { valid: true }
        : ({
          valid: false,
          fields: rule.invalidFields,
          message: rule.messageWhenInvalid,
        }));
    };

    return $(recordNode.validationRules, [
      fp.map(runValidationRule),
      fp.flatten,
      fp.filter(r => r.valid === false),
      fp.map(r => ({ fields: r.fields, message: r.message })),
    ]);
  };

  const validate = app => async (record, context) => {
    context = isNothing(context)
      ? _getContext(app, record.key)
      : context;

    const recordNode = getExactNodeForPath(app.hierarchy)(record.key);
    const fieldParseFails = validateAllFieldParse(record, recordNode);

    // non parsing would cause further issues - exit here
    if (!fp.isEmpty(fieldParseFails)) { return ({ isValid: false, errors: fieldParseFails }); }

    const recordValidationRuleFails = runRecordValidationRules(record, recordNode);
    const typeContraintFails = await validateAllTypeConstraints(record, recordNode, context);

    if (fp.isEmpty(fieldParseFails)
         && fp.isEmpty(recordValidationRuleFails)
         && fp.isEmpty(typeContraintFails)) {
      return ({ isValid: true, errors: [] });
    }

    return ({
      isValid: false,
      errors: ___default.union(fieldParseFails, typeContraintFails, recordValidationRuleFails),
    });
  };

  const ensureCollectionIsInitialised = async (datastore, node, parentKey) => {
    if (!await datastore.exists(parentKey)) {
      await datastore.createFolder(parentKey);
      await datastore.createFolder(
        joinKey(parentKey, 'allids'),
      );
      await datastore.createFolder(
        joinKey(
          parentKey,
          'allids',
          node.nodeId.toString(),
        ),
      );
    }
  };

  const initialiseRootCollections = async (datastore, hierarchy) => {
    const rootCollectionRecord = allTrue(
      n => isRoot(n.parent()),
      isCollectionRecord,
    );

    const flathierarchy = getFlattenedHierarchy(hierarchy);

    const collectionRecords = $(flathierarchy, [
      fp.filter(rootCollectionRecord),
    ]);

    for (const col of collectionRecords) {
      await ensureCollectionIsInitialised(
        datastore,
        col,
        col.collectionPathRegx(),
      );
    }
  };

  const initialiseChildCollections = async (app, recordKey) => {
    const childCollectionRecords = $(recordKey, [
      getExactNodeForPath(app.hierarchy),
      n => n.children,
      fp.filter(isCollectionRecord),
    ]);

    for (const child of childCollectionRecords) {
      await ensureCollectionIsInitialised(
        app.datastore,
        child,
        joinKey(recordKey, child.collectionName),
      );
    }
  };

  const allIdChars = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_-';

  const allIdsStringsForFactor = (collectionNode) => {
    const factor = collectionNode.allidsShardFactor;
    const charRangePerShard = 64 / factor;
    const allIdStrings = [];
    let index = 0;
    let currentIdsShard = '';
    while (index < 64) {
      currentIdsShard += allIdChars[index];
      if ((index + 1) % charRangePerShard === 0) {
        allIdStrings.push(currentIdsShard);
        currentIdsShard = '';
      }
      index++;
    }

    return allIdStrings;
  };

  const getAllIdsShardNames = (appHierarchy, collectionKey) => {
    const collectionRecordNode = getNodeForCollectionPath(appHierarchy)(collectionKey);
    return $(collectionRecordNode, [
      c => [c.nodeId],
      fp.map(i => fp.map(c => _allIdsShardKey(collectionKey, i, c))(allIdsStringsForFactor(collectionRecordNode))),
      fp.flatten,
    ]);
  };

  const _allIdsShardKey = (collectionKey, childNo, shardKey) => joinKey(
    collectionKey,
    'allids',
    childNo,
    shardKey,
  );

  const getAllIdsShardKey = (appHierarchy, collectionKey, recordId) => {
    const indexOfFirstDash = recordId.indexOf('-');

    const collectionNode = getNodeForCollectionPath(appHierarchy)(collectionKey);

    const idFirstChar = recordId[indexOfFirstDash + 1];
    const allIdsShardId = $(collectionNode, [
      allIdsStringsForFactor,
      fp.find(i => i.includes(idFirstChar)),
    ]);

    return _allIdsShardKey(
      collectionKey,
      recordId.slice(0, indexOfFirstDash),
      allIdsShardId,
    );
  };

  const getOrCreateShardFile = async (datastore, allIdsKey) => {
    try {
      return await datastore.loadFile(allIdsKey);
    } catch (eLoad) {
      try {
        await datastore.createFile(allIdsKey, '');
        return '';
      } catch (eCreate) {
        throw new Error(
          `Error loading, then creating allIds ${allIdsKey
        } : LOAD : ${eLoad.message
        } : CREATE : ${eCreate}`,
        );
      }
    }
  };

  const getShardFile = async (datastore, allIdsKey) => {
    try {
      return await datastore.loadFile(allIdsKey);
    } catch (eLoad) {
      return '';
    }
  };

  const addToAllIds = (appHierarchy, datastore) => async (record) => {
    const allIdsKey = getAllIdsShardKey(
      appHierarchy,
      getParentKey(record.key),
      record.id,
    );

    let allIds = await getOrCreateShardFile(datastore, allIdsKey);

    allIds += `${allIds.length > 0 ? ',' : ''}${record.id}`;

    await datastore.updateFile(allIdsKey, allIds);
  };

  const getAllIdsIterator = app => async (collection_Key_or_NodeKey) => {
    collection_Key_or_NodeKey = safeKey(collection_Key_or_NodeKey);
    const targetNode = getCollectionNodeByKeyOrNodeKey(
      app.hierarchy,
      collection_Key_or_NodeKey,
    );

    const getAllIdsIteratorForCollectionKey = async (collectionKey) => {
      const all_allIdsKeys = getAllIdsShardNames(app.hierarchy, collectionKey);
      let shardIndex = 0;

      const allIdsFromShardIterator = async () => {
        if (shardIndex === all_allIdsKeys.length) { return ({ done: true, result: { ids: [], collectionKey } }); }

        const shardKey = all_allIdsKeys[shardIndex];

        const allIds = await getAllIdsFromShard(app.datastore, shardKey);

        shardIndex++;

        return ({
          result: {
            ids: allIds,
            collectionKey,
          },
          done: false,
        });
      };

      return allIdsFromShardIterator;
    };

    const ancestors = $(getFlattenedHierarchy(app.hierarchy), [
      fp.filter(isCollectionRecord),
      fp.filter(n => isAncestor(targetNode)(n)
                      || n.nodeKey() === targetNode.nodeKey()),
      fp.orderBy([n => n.nodeKey().length], ['asc']),
    ]); // parents first

    const traverseForIteraterators = async (parentRecordKey = '', currentNodeIndex = 0) => {
      const currentNode = ancestors[currentNodeIndex];
      const currentCollectionKey = joinKey(
        parentRecordKey,
        currentNode.collectionName,
      );
      if (currentNode.nodeKey() === targetNode.nodeKey()) {
        return [
          await getAllIdsIteratorForCollectionKey(
            currentCollectionKey,
          )];
      }
      const allIterators = [];
      const currentIterator = await getAllIdsIteratorForCollectionKey(
        currentCollectionKey,
      );

      let ids = await currentIterator();
      while (ids.done === false) {
        for (const id of ids.result.ids) {
          allIterators.push(
            await traverseForIteraterators(
              joinKey(currentCollectionKey, id),
              currentNodeIndex + 1,
            ),
          );
        }

        ids = await currentIterator();
      }

      return fp.flatten(allIterators);
    };

    const iteratorsArray = await traverseForIteraterators();
    let currentIteratorIndex = 0;
    return async () => {
      if (iteratorsArray.length === 0) { return { done: true, result: [] }; }
      const innerResult = await iteratorsArray[currentIteratorIndex]();
      if (!innerResult.done) { return innerResult; }
      if (currentIteratorIndex == iteratorsArray.length - 1) {
        return { done: true, result: innerResult.result };
      }
      currentIteratorIndex++;
      return { done: false, result: innerResult.result };
    };
  };

  const getAllIdsFromShard = async (datastore, shardKey) => {
    const allIdsStr = await getShardFile(datastore, shardKey);

    const allIds = [];
    let currentId = '';
    for (let i = 0; i < allIdsStr.length; i++) {
      const currentChar = allIdsStr.charAt(i);
      const isLast = (i === allIdsStr.length - 1);
      if (currentChar === ',' || isLast) {
        if (isLast) currentId += currentChar;
        allIds.push(currentId);
        currentId = '';
      } else {
        currentId += currentChar;
      }
    }
    return allIds;
  };

  const removeFromAllIds = (appHierarchy, datastore) => async (record) => {
    const shardKey = getAllIdsShardKey(
      appHierarchy,
      getParentKey(record.key),
      record.id,
    );
    const allIds = await getAllIdsFromShard(datastore, shardKey);

    const newIds = $(allIds, [
      fp.pull(record.id),
      fp.join(','),
    ]);

    await datastore.updateFile(shardKey, newIds);
  };

  const TRANSACTIONS_FOLDER = `${keySep}.transactions`;
  const LOCK_FILENAME = 'lock';
  const LOCK_FILE_KEY = joinKey(
    TRANSACTIONS_FOLDER, LOCK_FILENAME,
  );
  const idSep = '$';

  const isOfType = typ => trans => trans.transactionType === typ;

  const CREATE_RECORD_TRANSACTION = 'create';
  const UPDATE_RECORD_TRANSACTION = 'update';
  const DELETE_RECORD_TRANSACTION = 'delete';
  const BUILD_INDEX_TRANSACTION = 'build';

  const isUpdate = isOfType(UPDATE_RECORD_TRANSACTION);
  const isDelete = isOfType(DELETE_RECORD_TRANSACTION);
  const isCreate = isOfType(CREATE_RECORD_TRANSACTION);
  const isBuildIndex = isOfType(BUILD_INDEX_TRANSACTION);

  const keyToFolderName = nodeKey => getHashCode(nodeKey);

  const getTransactionId = (recordId, transactionType, uniqueId) => 
    `${recordId}${idSep}${transactionType}${idSep}${uniqueId}`;

  const buildIndexFolder = '.BUILD-';
  const nodeKeyHashFromBuildFolder = folder => folder.replace(buildIndexFolder, '');

  const isBuildIndexFolder = key => getLastPartInKey(key).startsWith(buildIndexFolder);

  const IndexNodeKeyFolder = indexNodeKey => joinKey(
    TRANSACTIONS_FOLDER,
    buildIndexFolder + keyToFolderName(indexNodeKey),
  );

  const IndexNodeKeyBatchFolder = (indexNodeKey, count) => 
    joinKey(IndexNodeKeyFolder(indexNodeKey), Math.floor(count / BUILDINDEX_BATCH_COUNT).toString());

  const BUILDINDEX_BATCH_COUNT = 1000;
  const timeoutMilliseconds = 30 * 1000; // 30 secs
  const maxLockRetries = 1;

  const transactionForCreateRecord = async (app, record) => await transaction(
    app.datastore, CREATE_RECORD_TRANSACTION,
    record.key, { record },
    getTransactionKey_Records,
  );

  const transactionForUpdateRecord = async (app, oldRecord, newRecord) => await transaction(
    app.datastore, UPDATE_RECORD_TRANSACTION,
    newRecord.key, { oldRecord, record: newRecord },
    getTransactionKey_Records,
  );

  const transactionForDeleteRecord = async (app, record) => await transaction(
    app.datastore, DELETE_RECORD_TRANSACTION,
    record.key, { record },
    getTransactionKey_Records,
  );

  const transactionForBuildIndex = async (app, indexNodeKey, recordKey, count) => {
    const transactionFolder = IndexNodeKeyBatchFolder(indexNodeKey, count);
    if (count % BUILDINDEX_BATCH_COUNT === 0) {
      await app.datastore.createFolder(transactionFolder);
    }

    return await transaction(
      app.datastore, BUILD_INDEX_TRANSACTION,
      recordKey, { recordKey },
      id => joinKey(transactionFolder, id),
    );
  };

  const createBuildIndexFolder = async (datastore, indexNodeKey) => await datastore.createFolder(
    IndexNodeKeyFolder(indexNodeKey),
  );

  const getTransactionKey_Records = id => joinKey(TRANSACTIONS_FOLDER, id);

  const transaction = async (datastore, transactionType, recordKey, data, getTransactionKey) => {
    const recordId = getLastPartInKey(recordKey);
    const uniqueId = shortid.generate();
    const id = getTransactionId(
      recordId, transactionType, uniqueId,
    );

    const key = getTransactionKey(id);

    const trans = {
      transactionType,
      recordKey,
      ...data,
      id,
    };

    await datastore.createJson(
      key, trans,
    );

    return trans;
  };

  const initialiseIndex = async (datastore, parentKey, index) => {
    const indexKey = joinKey(parentKey, index.name);

    await datastore.createFolder(indexKey);

    if (isShardedIndex(index)) {
      await datastore.createFile(
        getShardMapKey(indexKey),
        '[]',
      );
    } else {
      await createIndexFile(
        datastore,
        getUnshardedIndexDataKey(indexKey),
        index,
      );
    }
  };

  const save = app => async (record, context) => apiWrapper(
    app,
    events.recordApi.save,
    record.isNew
      ? permission.createRecord.isAuthorized(record.key)
      : permission.updateRecord.isAuthorized(record.key), { record },
    _save, app, record, context, false,
  );


  const _save = async (app, record, context, skipValidation = false) => {
    const recordClone = fp.cloneDeep(record);
    if (!skipValidation) {
      const validationResult = await validate(app)(recordClone, context);
      if (!validationResult.isValid) {
        await app.publish(events.recordApi.save.onInvalid, { record, validationResult });
        throw new BadRequestError(`Save : Record Invalid : ${
        JSON.stringify(validationResult.errors)}`);
      }
    }

    if (recordClone.isNew) {
      await addToAllIds(app.hierarchy, app.datastore)(recordClone);
      const transaction = await transactionForCreateRecord(
        app, recordClone,
      );
      recordClone.transactionId = transaction.id;
      await app.datastore.createFolder(recordClone.key);
      await app.datastore.createFolder(
        joinKey(recordClone.key, 'files'),
      );
      await app.datastore.createJson(
        getRecordFileName(recordClone.key),
        recordClone,
      );
      await initialiseReverseReferenceIndexes(app, record);
      await initialiseAncestorIndexes(app, record);
      await initialiseChildCollections(app, recordClone.key);
      await app.publish(events.recordApi.save.onRecordCreated, {
        record: recordClone,
      });
    } else {
      const oldRecord = await _load(app, recordClone.key);
      const transaction = await transactionForUpdateRecord(
        app, oldRecord, recordClone,
      );
      recordClone.transactionId = transaction.id;
      await app.datastore.updateJson(
        getRecordFileName(recordClone.key),
        recordClone,
      );
      await app.publish(events.recordApi.save.onRecordUpdated, {
        old: oldRecord,
        new: recordClone,
      });
    }

    await app.cleanupTransactions();

    const returnedClone = fp.cloneDeep(recordClone);
    returnedClone.isNew = false;
    return returnedClone;
  };

  const initialiseAncestorIndexes = async (app, record) => {
    const recordNode = getExactNodeForPath(app.hierarchy)(record.key);

    for (const index of recordNode.indexes) {
      const indexKey = joinKey(record.key, index.name);
      if (!await app.datastore.exists(indexKey)) { await initialiseIndex(app.datastore, record.key, index); }
    }
  };

  const initialiseReverseReferenceIndexes = async (app, record) => {
    const recordNode = getExactNodeForPath(app.hierarchy)(record.key);

    const indexNodes = $(fieldsThatReferenceThisRecord(app, recordNode), [
      fp.map(f => $(f.typeOptions.reverseIndexNodeKeys, [
        fp.map(n => getNode(
          app.hierarchy,
          n,
        )),
      ])),
      fp.flatten,
    ]);

    for (const indexNode of indexNodes) {
      await initialiseIndex(
        app.datastore, record.key, indexNode,
      );
    }
  };

  const fieldsThatReferenceThisRecord = (app, recordNode) => $(app.hierarchy, [
    getFlattenedHierarchy,
    fp.filter(isRecord),
    fp.map(n => n.fields),
    fp.flatten,
    fp.filter(fieldReversesReferenceToNode(recordNode)),
  ]);

  const deleteCollection = (app, disableCleanup = false) => async key => apiWrapper(
    app,
    events.collectionApi.delete,
    permission.manageCollection.isAuthorized,
    { key },
    _deleteCollection, app, key, disableCleanup,
  );


  const _deleteCollection = async (app, key, disableCleanup) => {
    key = safeKey(key);
    const node = getNodeForCollectionPath(app.hierarchy)(key);

    await deleteRecords(app, key);
    await deleteAllIdsFolders(app, node, key);
    await deleteCollectionFolder(app, key);
    if (!disableCleanup) { await app.cleanupTransactions(); }
  };

  const deleteCollectionFolder = async (app, key) => await app.datastore.deleteFolder(key);


  const deleteAllIdsFolders = async (app, node, key) => {
    await app.datastore.deleteFolder(
      joinKey(
        key, 'allids',
        node.nodeId,
      ),
    );

    await app.datastore.deleteFolder(
      joinKey(key, 'allids'),
    );
  };

  const deleteRecords = async (app, key) => {
    const deletedAllIdsShards = [];
    const deleteAllIdsShard = async (recordId) => {
      const shardKey = getAllIdsShardKey(
        app.hierarchy, key, recordId,
      );

      if (fp.includes(shardKey)(deletedAllIdsShards)) {
        return;
      }

      deletedAllIdsShards.push(shardKey);

      await app.datastore.deleteFile(shardKey);
    };

    const iterate = await getAllIdsIterator(app)(key);

    let ids = await iterate();
    while (!ids.done) {
      if (ids.result.collectionKey === key) {
        for (const id of ids.result.ids) {
          await _deleteRecord(
            app,
            joinKey(key, id),
            true,
          );
          await deleteAllIdsShard(id);
        }
      }

      ids = await iterate();
    }
  };

  const _deleteIndex = async (app, indexKey, includeFolder) => {
    const indexNode = getExactNodeForPath(app.hierarchy)(indexKey);

    if (!isIndex(indexNode)) { throw new Error('Supplied key is not an index'); }

    if (isShardedIndex(indexNode)) {
      const shardKeys = await getAllShardKeys(app, indexKey);
      for (const k of shardKeys) {
        await tryAwaitOrIgnore(
          app.datastore.deleteFile(k),
        );
      }
      tryAwaitOrIgnore(
        await app.datastore.deleteFile(
          getShardMapKey(indexKey),
        ),
      );
    } else {
      await tryAwaitOrIgnore(
        app.datastore.deleteFile(
          getUnshardedIndexDataKey(indexKey),
        ),
      );
    }

    if (includeFolder) {
      tryAwaitOrIgnore(
        await app.datastore.deleteFolder(indexKey),
      );
    }
  };

  const deleteRecord$1 = (app, disableCleanup = false) => async key => apiWrapper(
    app,
    events.recordApi.delete,
    permission.deleteRecord.isAuthorized(key),
    { key },
    _deleteRecord, app, key, disableCleanup,
  );

  // called deleteRecord because delete is a keyword
  const _deleteRecord = async (app, key, disableCleanup) => {
    key = safeKey(key);
    const node = getExactNodeForPath(app.hierarchy)(key);

    const record = await _load(app, key);
    await transactionForDeleteRecord(app, record);

    for (const collectionRecord of node.children) {
      const collectionKey = joinKey(
        key, collectionRecord.collectionName,
      );
      await _deleteCollection(app, collectionKey, true);
    }

    await app.datastore.deleteFile(
      getRecordFileName(key),
    );

    await deleteFiles(app, key);

    await removeFromAllIds(app.hierarchy, app.datastore)(record);

    if (!disableCleanup) { await app.cleanupTransactions(); }

    await app.datastore.deleteFolder(key);
    await deleteIndexes(app, key);
  };

  const deleteIndexes = async (app, key) => {
    const node = getExactNodeForPath(app.hierarchy)(key);
    /* const reverseIndexKeys = $(app.hierarchy, [
          getFlattenedHierarchy,
          map(n => n.fields),
          flatten,
          filter(isSomething),
          filter(fieldReversesReferenceToNode(node)),
          map(f => $(f.typeOptions.reverseIndexNodeKeys, [
                      map(n => getNode(
                                  app.hierarchy,
                                  n))
                  ])
          ),
          flatten,
          map(n => joinKey(key, n.name))
      ]);

      for(let i of reverseIndexKeys) {
          await _deleteIndex(app, i, true);
      } */


    for (const index of node.indexes) {
      const indexKey = joinKey(key, index.name);
      await _deleteIndex(app, indexKey, true);
    }
  };

  const deleteFiles = async (app, key) => {
    const filesFolder = joinKey(key, 'files');
    const allFiles = await app.datastore.getFolderContents(
      filesFolder,
    );

    for (const file of allFiles) {
      await app.datastore.deleteFile(file);
    }

    await app.datastore.deleteFolder(
      joinKey(key, 'files'),
    );
  };

  const uploadFile = app => async (recordKey, readableStream, relativeFilePath) => apiWrapper(
    app,
    events.recordApi.uploadFile,
    permission.updateRecord.isAuthorized(recordKey),
    { recordKey, readableStream, relativeFilePath },
    _uploadFile, app, recordKey, readableStream, relativeFilePath,
  );

  const _uploadFile = async (app, recordKey, readableStream, relativeFilePath) => {
    if (isNothing(recordKey)) { throw new BadRequestError('Record Key not supplied'); }
    if (isNothing(relativeFilePath)) { throw new BadRequestError('file path not supplied'); }
    if (!isLegalFilename(relativeFilePath)) { throw new BadRequestError('Illegal filename'); }

    const record = await _load(app, recordKey);

    const fullFilePath = safeGetFullFilePath(
      recordKey, relativeFilePath,
    );

    const tempFilePath = `${fullFilePath}_${shortid.generate()}.temp`;

    const outputStream = await app.datastore.writableFileStream(
      tempFilePath,
    );

    return new Promise((resolve,reject) => {
      readableStream.pipe(outputStream);
      outputStream.on('error', reject);
      outputStream.on('finish', resolve);
    })
    .then(() => app.datastore.getFileSize(tempFilePath))
    .then(size => {
      const isExpectedFileSize = checkFileSizeAgainstFields(
        app, record, relativeFilePath, size
      );  
      if (!isExpectedFileSize) { throw new BadRequestError(`Fields for ${relativeFilePath} do not have expected size: ${join(',')(incorrectFields)}`); }  

    })
    .then(() => tryAwaitOrIgnore(app.datastore.deleteFile, fullFilePath))
    .then(() => app.datastore.renameFile(tempFilePath, fullFilePath));

    /*
    readableStream.pipe(outputStream);

    await new Promise(fulfill => outputStream.on('finish', fulfill));

    const isExpectedFileSize = checkFileSizeAgainstFields(
      app,
      record, relativeFilePath,
      await app.datastore.getFileSize(tempFilePath),
    );

    if (!isExpectedFileSize) {
      throw new Error(
        `Fields for ${relativeFilePath} do not have expected size`);
    }

    await tryAwaitOrIgnore(app.datastore.deleteFile, fullFilePath);

    await app.datastore.renameFile(tempFilePath, fullFilePath);
    */
  };

  const checkFileSizeAgainstFields = (app, record, relativeFilePath, expectedSize) => {
    const recordNode = getExactNodeForPath(app.hierarchy)(record.key);

    const incorrectFileFields = $(recordNode.fields, [
      fp.filter(f => f.type === 'file'
        && record[f.name].relativePath === relativeFilePath
        && record[f.name].size !== expectedSize),
      fp.map(f => f.name),
    ]);

    const incorrectFileArrayFields = $(recordNode.fields, [
      fp.filter(a => a.type === 'array<file>'
        && $(record[a.name], [
          fp.some(f => record[f.name].relativePath === relativeFilePath
            && record[f.name].size !== expectedSize),
        ])),
      fp.map(f => f.name),
    ]);

    const incorrectFields = [
      ...incorrectFileFields,
      ...incorrectFileArrayFields,
    ];

    if (incorrectFields.length > 0) {
      return false;
    }

    return true;
  };

  const safeGetFullFilePath = (recordKey, relativeFilePath) => {
    const naughtyUser = () => { throw new ForbiddenError('naughty naughty'); };

    if (relativeFilePath.startsWith('..')) naughtyUser();

    const pathParts = splitKey(relativeFilePath);

    if (fp.includes('..')(pathParts)) naughtyUser();

    const recordKeyParts = splitKey(recordKey);

    const fullPathParts = [
      ...recordKeyParts,
      'files',
      ...fp.filter(p => p !== '.')(pathParts),
    ];

    return joinKey(fullPathParts);
  };

  const downloadFile = app => async (recordKey, relativePath) => apiWrapper(
    app,
    events.recordApi.uploadFile,
    permission.readRecord.isAuthorized(recordKey),
    { recordKey, relativePath },//remove dupe key 'recordKey' from object
    _downloadFile, app, recordKey, relativePath,
  ); 


  const _downloadFile = async (app, recordKey, relativePath) => {
    if (isNothing(recordKey)) { throw new BadRequestError('Record Key not supplied'); }
    if (isNothing(relativePath)) { throw new BadRequestError('file path not supplied'); }

    return await app.datastore.readableFileStream(
      safeGetFullFilePath(
        recordKey, relativePath,
      ),
    );
  };

  const customId = app => (nodeName, id) => {
    const node = $(app.hierarchy, [
      getFlattenedHierarchy,
      fp.find(n => n.name === nodeName),
    ]);

    if (!node) throw new NotFoundError(`Cannot find node ${nodeName}`);

    return `${node.nodeId}-${id}`;
  };

  const setCustomId = app => (record, id) => {
    record.id = customId(app)(record.type, id);

    const keyParts = splitKey(record.key);

    record.key = $(keyParts, [
      fp.take(keyParts.length - 1),
      fp.union([record.id]),
      joinKey,
    ]);

    return record;
  };

  const api = app => ({
    getNew: getNew(app),
    getNewChild: getNewChild(app),
    save: save(app),
    load: load(app),
    delete: deleteRecord$1(app, false),
    validate: validate(app),
    getContext: getContext(app),
    uploadFile: uploadFile(app),
    downloadFile: downloadFile(app),
    customId: customId(app),
    setCustomId: setCustomId(app),
  });


  const getRecordApi = app => api(app);

  const getAllowedRecordTypes = app => key => apiWrapperSync(
    app,
    events.collectionApi.getAllowedRecordTypes,
    alwaysAuthorized,
    { key },
    _getAllowedRecordTypes, app, key,
  );

  const _getAllowedRecordTypes = (app, key) => {
    key = safeKey(key);
    const node = getNodeForCollectionPath(app.hierarchy)(key);
    return isNothing(node) ? [] : [node.name];
  };

  const getCollectionApi = app => ({
    getAllowedRecordTypes: getAllowedRecordTypes(app),
    getAllIdsIterator: getAllIdsIterator(app),
    delete: deleteCollection(app),
  });

  /** rebuilds an index
   * @param {object} app - the application container
   * @param {string} indexNodeKey - node key of the index, which the index belongs to
   */
  const buildIndex = app => async indexNodeKey => apiWrapper(
    app,
    events.indexApi.buildIndex,
    permission.manageIndex.isAuthorized,
    { indexNodeKey },
    _buildIndex, app, indexNodeKey,
  );

  const _buildIndex = async (app, indexNodeKey) => {
    const indexNode = getNode(app.hierarchy, indexNodeKey);

    await createBuildIndexFolder(app.datastore, indexNodeKey);

    if (!isIndex(indexNode)) { throw new BadRequestError('BuildIndex: must supply an indexnode'); }

    if (indexNode.indexType === 'reference') {
      await buildReverseReferenceIndex(
        app, indexNode,
      );
    } else {
      await buildHeirarchalIndex(
        app, indexNode,
      );
    }

    await app.cleanupTransactions();
  };

  const buildReverseReferenceIndex = async (app, indexNode) => {
    // Iterate through all referencING records,
    // and update referenced index for each record
    let recordCount = 0;
    const referencingNodes = $(app.hierarchy, [
      getFlattenedHierarchy,
      fp.filter(n => isRecord(n)
                      && fp.some(fieldReversesReferenceToIndex(indexNode))(n.fields)),
    ]);

    const createTransactionsForReferencingNode = async (referencingNode) => {
      const iterateReferencingNodes = await getAllIdsIterator(app)(referencingNode.collectionNodeKey());

      let referencingIdIterator = await iterateReferencingNodes();
      while (!referencingIdIterator.done) {
        const { result } = referencingIdIterator;
        for (const id of result.ids) {
          const recordKey = joinKey(result.collectionKey, id);
          await transactionForBuildIndex(app, indexNode.nodeKey(), recordKey, recordCount);
          recordCount++;
        }
        referencingIdIterator = await iterateReferencingNodes();
      }
    };

    for (const referencingNode of referencingNodes) {
      await createTransactionsForReferencingNode(referencingNode);
    }
  };

  const buildHeirarchalIndex = async (app, indexNode) => {
    let recordCount = 0;

    const createTransactionsForIds = async (collectionKey, ids) => {
      for (const recordId of ids) {
        const recordKey = joinKey(collectionKey, recordId);

        const recordNode = getRecordNodeById(
          app.hierarchy,
          recordId,
        );

        if (recordNodeApplies(indexNode)(recordNode)) {
          await transactionForBuildIndex(
            app, indexNode.nodeKey(),
            recordKey, recordCount,
          );
          recordCount++;
        }
      }
    };


    const collectionRecords = getAllowedRecordNodesForIndex(app.hierarchy, indexNode);

    for (const targetCollectionRecordNode of collectionRecords) {
      const allIdsIterator = await getAllIdsIterator(app)(targetCollectionRecordNode.collectionNodeKey());

      let allIds = await allIdsIterator();
      while (allIds.done === false) {
        await createTransactionsForIds(
          allIds.result.collectionKey,
          allIds.result.ids,
        );
        allIds = await allIdsIterator();
      }
    }

    return recordCount;
  };

  const recordNodeApplies = indexNode => recordNode => fp.includes(recordNode.nodeId)(indexNode.allowedRecordNodeIds);

  const aggregates = app => async (indexKey, rangeStartParams = null, rangeEndParams = null) => apiWrapper(
    app,
    events.indexApi.aggregates,
    permission.readIndex.isAuthorized(indexKey),
    { indexKey, rangeStartParams, rangeEndParams },
    _aggregates, app, indexKey, rangeStartParams, rangeEndParams,
  );

  const _aggregates = async (app, indexKey, rangeStartParams, rangeEndParams) => {
    indexKey = safeKey(indexKey);
    const indexNode = getExactNodeForPath(app.hierarchy)(indexKey);

    if (!isIndex(indexNode)) { throw new BadRequestError('supplied key is not an index'); }

    if (isShardedIndex(indexNode)) {
      const shardKeys = await getShardKeysInRange(
        app, indexKey, rangeStartParams, rangeEndParams,
      );
      let aggregateResult = null;
      for (const k of shardKeys) {
        const shardResult = await getAggregates(app.hierarchy, app.datastore, indexNode, k);
        if (aggregateResult === null) {
          aggregateResult = shardResult;
        } else {
          aggregateResult = mergeShardAggregate(
            aggregateResult,
            shardResult,
          );
        }
      }
      return aggregateResult;
    }
    return await getAggregates(
      app.hierarchy,
      app.datastore,
      indexNode,
      getUnshardedIndexDataKey(indexKey),
    );
  };

  const mergeShardAggregate = (totals, shard) => {
    const mergeGrouping = (tot, shr) => {
      tot.count += shr.count;
      for (const aggName in tot) {
        if (aggName === 'count') continue;
        const totagg = tot[aggName];
        const shragg = shr[aggName];
        totagg.sum += shragg.sum;
        totagg.max = totagg.max > shragg.max
          ? totagg.max
          : shragg.max;
        totagg.min = totagg.min < shragg.min
          ? totagg.min
          : shragg.min;
        totagg.mean = totagg.sum / tot.count;
      }
      return tot;
    };

    for (const aggGroupDef in totals) {
      for (const grouping in shard[aggGroupDef]) {
        const groupingTotal = totals[aggGroupDef][grouping];
        totals[aggGroupDef][grouping] = fp.isUndefined(groupingTotal)
          ? shard[aggGroupDef][grouping]
          : mergeGrouping(
            totals[aggGroupDef][grouping],
            shard[aggGroupDef][grouping],
          );
      }
    }

    return totals;
  };

  const getAggregates = async (hierarchy, datastore, index, indexedDataKey) => {
    const aggregateResult = {};
    const doRead = iterateIndex(
          async item => {
        applyItemToAggregateResult(
          index, aggregateResult, item,
        );
        return CONTINUE_READING_RECORDS;
      },
          async () => aggregateResult
    );

    return await doRead(hierarchy, datastore, index, indexedDataKey);
  };


  const applyItemToAggregateResult = (indexNode, result, item) => {
    const getInitialAggregateResult = () => ({
      sum: 0, mean: null, max: null, min: null,
    });

    const applyAggregateResult = (agg, existing, count) => {
      const value = compilerUtil.compileCode(agg.aggregatedValue)({ record: item });

      if (!fp.isNumber(value)) return existing;

      existing.sum += value;
      existing.max = value > existing.max || existing.max === null
        ? value
        : existing.max;
      existing.min = value < existing.min || existing.min === null
        ? value
        : existing.min;
      existing.mean = existing.sum / count;
      return existing;
    };

    for (const aggGroup of indexNode.aggregateGroups) {
      if (!fp.has(aggGroup.name)(result)) {
        result[aggGroup.name] = {};
      }

      const thisGroupResult = result[aggGroup.name];

      if (isNonEmptyString(aggGroup.condition)) {
        if (!compilerUtil.compileExpression(aggGroup.condition)({ record: item })) {
          continue;
        }
      }

      let group = isNonEmptyString(aggGroup.groupBy)
        ? compilerUtil.compileCode(aggGroup.groupBy)({ record: item })
        : 'all';
      if (!isNonEmptyString(group)) {
        group = '(none)';
      }

      if (!fp.has(group)(thisGroupResult)) {
        thisGroupResult[group] = { count: 0 };
        for (const agg of aggGroup.aggregates) {
          thisGroupResult[group][agg.name] = getInitialAggregateResult();
        }
      }

      thisGroupResult[group].count++;

      for (const agg of aggGroup.aggregates) {
        const existingValues = thisGroupResult[group][agg.name];
        thisGroupResult[group][agg.name] = applyAggregateResult(
          agg, existingValues,
          thisGroupResult[group].count,
        );
      }
    }
  };

  const getIndexApi = app => ({
    listItems: listItems(app),
    buildIndex: buildIndex(app),
    aggregates: aggregates(app),
  });

  const createNodeErrors = {
    indexCannotBeParent: 'Index template cannot be a parent',
    allNonRootNodesMustHaveParent: 'Only the root node may have no parent',
    indexParentMustBeRecordOrRoot: 'An index may only have a record or root as a parent',
    aggregateParentMustBeAnIndex: 'aggregateGroup parent must be an index',
  };

  const pathRegxMaker = node => () => node.nodeKey().replace(/{id}/g, '[a-zA-Z0-9_-]+');

  const nodeKeyMaker = node => () => switchCase(

    [n => isRecord(n) && !isSingleRecord(n),
      n => joinKey(
        node.parent().nodeKey(),
        node.collectionName,
        `${n.nodeId}-{id}`,
      )],

    [isRoot,
      _.constant('/')],

    [defaultCase,
      n => joinKey(node.parent().nodeKey(), n.name)],

  )(node);


  const validate$1 = parent => (node) => {
    if (isIndex(node)
          && isSomething(parent)
          && !isRoot(parent)
          && !isRecord(parent)) {
      throw new BadRequestError(createNodeErrors.indexParentMustBeRecordOrRoot);
    }

    if (isaggregateGroup(node)
          && isSomething(parent)
          && !isIndex(parent)) {
      throw new BadRequestError(createNodeErrors.aggregateParentMustBeAnIndex);
    }

    if (isNothing(parent) && !isRoot(node)) { throw new BadRequestError(createNodeErrors.allNonRootNodesMustHaveParent); }

    return node;
  };

  const construct = parent => (node) => {
    node.nodeKey = nodeKeyMaker(node);
    node.pathRegx = pathRegxMaker(node);
    node.parent = _.constant(parent);
    node.isRoot = () => isNothing(parent)
                          && node.name === 'root'
                          && node.type === 'root';
    if (isCollectionRecord(node)) {
      node.collectionNodeKey = () => joinKey(
        parent.nodeKey(), node.collectionName,
      );
      node.collectionPathRegx = () => joinKey(
        parent.pathRegx(), node.collectionName,
      );
    }
    return node;
  };

  const addToParent = (obj) => {
    const parent = obj.parent();
    if (isSomething(parent)) {
      if (isIndex(obj))
      // Q: why are indexes not children ?
      // A: because they cannot have children of their own.
      { parent.indexes.push(obj); } else if (isaggregateGroup(obj)) { parent.aggregateGroups.push(obj); } else { parent.children.push(obj); }

      if (isRecord(obj)) {
        const defaultIndex = _.find(
          parent.indexes,
          i => i.name === `${parent.name}_index`,
        );
        if (defaultIndex) {
          defaultIndex.allowedRecordNodeIds.push(obj.nodeId);
        }
      }
    }
    return obj;
  };

  const constructNode = (parent, obj) => $(obj, [
    construct(parent),
    validate$1(parent),
    addToParent,
  ]);

  const getNodeId = (parentNode) => {
    // this case is handled better elsewhere
    if (!parentNode) return null;
    const findRoot = n => (isRoot(n) ? n : findRoot(n.parent()));
    const root = findRoot(parentNode);

    return ($(root, [
      getFlattenedHierarchy,
      fp.map(n => n.nodeId),
      fp.max]) + 1);
  };

  const constructHierarchy = (node, parent) => {
    construct(parent)(node);
    if (node.indexes) {
      _.each(node.indexes,
        child => constructHierarchy(child, node));
    }
    if (node.aggregateGroups) {
      _.each(node.aggregateGroups,
        child => constructHierarchy(child, node));
    }
    if (node.children && node.children.length > 0) {
      _.each(node.children,
        child => constructHierarchy(child, node));
    }
    if (node.fields) {
      _.each(node.fields,
        f => _.each(f.typeOptions, (val, key) => {
          const def = all$1[f.type].optionDefinitions[key];
          if (!def) {
            // unknown typeOption
            delete f.typeOptions[key];
          } else {
            f.typeOptions[key] = def.parse(val);
          }
        }));
    }
    return node;
  };


  const getNewRootLevel = () => construct()({
    name: 'root',
    type: 'root',
    children: [],
    pathMaps: [],
    indexes: [],
    nodeId: 0,
  });

  const _getNewRecordTemplate = (parent, name, createDefaultIndex, isSingle) => {
    const node = constructNode(parent, {
      name,
      type: 'record',
      fields: [],
      children: [],
      validationRules: [],
      nodeId: getNodeId(parent),
      indexes: [],
      allidsShardFactor: isRecord(parent) ? 1 : 64,
      collectionName: '',
      isSingle,
    });

    if (createDefaultIndex) {
      const defaultIndex = getNewIndexTemplate(parent);
      defaultIndex.name = `${name}_index`;
      defaultIndex.allowedRecordNodeIds.push(node.nodeId);
    }

    return node;
  };

  const getNewRecordTemplate = (parent, name = '', createDefaultIndex = true) => _getNewRecordTemplate(parent, name, createDefaultIndex, false);

  const getNewSingleRecordTemplate = parent => _getNewRecordTemplate(parent, '', false, true);

  const getNewIndexTemplate = (parent, type = 'ancestor') => constructNode(parent, {
    name: '',
    type: 'index',
    map: 'return {...record};',
    filter: '',
    indexType: type,
    getShardName: '',
    getSortKey: 'record.id',
    aggregateGroups: [],
    allowedRecordNodeIds: [],
    nodeId: getNodeId(parent),
  });

  const getNewAggregateGroupTemplate = index => constructNode(index, {
    name: '',
    type: 'aggregateGroup',
    groupBy: '',
    aggregates: [],
    condition: '',
    nodeId: getNodeId(index),
  });

  const getNewAggregateTemplate = (set) => {
    const aggregatedValue = {
      name: '',
      aggregatedValue: '',
    };
    set.aggregates.push(aggregatedValue);
    return aggregatedValue;
  };

  const fieldErrors = {
    AddFieldValidationFailed: 'Add field validation: ',
  };

  const allowedTypes = () => fp.keys(all$1);

  const getNewField = type => ({
    name: '', // how field is referenced internally
    type,
    typeOptions: getDefaultOptions$1(type),
    label: '', // how field is displayed
    getInitialValue: 'default', // function that gets value when initially created
    getUndefinedValue: 'default', // function that gets value when field undefined on record
  });

  const fieldRules = allFields => [
    makerule('name', 'field name is not set',
      f => isNonEmptyString(f.name)),
    makerule('type', 'field type is not set',
      f => isNonEmptyString(f.type)),
    makerule('label', 'field label is not set',
      f => isNonEmptyString(f.label)),
    makerule('getInitialValue', 'getInitialValue function is not set',
      f => isNonEmptyString(f.getInitialValue)),
    makerule('getUndefinedValue', 'getUndefinedValue function is not set',
      f => isNonEmptyString(f.getUndefinedValue)),
    makerule('name', 'field name is duplicated',
      f => isNothingOrEmpty(f.name)
               || fp.countBy('name')(allFields)[f.name] === 1),
    makerule('type', 'type is unknown',
      f => isNothingOrEmpty(f.type)
               || fp.some(t => f.type === t)(allowedTypes())),
  ];

  const typeOptionsRules = (field) => {
    const type = all$1[field.type];
    if (isNothing(type)) return [];

    const def = optName => type.optionDefinitions[optName];

    return $(field.typeOptions, [
      fp.keys,
      fp.filter(o => isSomething(def(o))
                      && isSomething(def(o).isValid)),
      fp.map(o => makerule(
        `typeOptions.${o}`,
        `${def(o).requirementDescription}`,
        field => def(o).isValid(field.typeOptions[o]),
      )),
    ]);
  };

  const validateField = allFields => (field) => {
    const everySingleField = fp.includes(field)(allFields) ? allFields : [...allFields, field];
    return applyRuleSet([...fieldRules(everySingleField), ...typeOptionsRules(field)])(field);
  };

  const validateAllFields = recordNode => $(recordNode.fields, [
    fp.map(validateField(recordNode.fields)),
    fp.flatten,
  ]);

  const addField = (recordTemplate, field) => {
    if (isNothingOrEmpty(field.label)) {
      field.label = field.name;
    }
    const validationMessages = validateField([...recordTemplate.fields, field])(field);
    if (validationMessages.length > 0) {
      const errors = fp.map(m => m.error)(validationMessages);
      throw new BadRequestError(`${fieldErrors.AddFieldValidationFailed} ${errors.join(', ')}`);
    }
    recordTemplate.fields.push(field);
  };

  const getNewRecordValidationRule = (invalidFields,
    messageWhenInvalid,
    expressionWhenValid) => ({
    invalidFields, messageWhenInvalid, expressionWhenValid,
  });

  const getStaticValue = switchCase(
    [fp.isNumber, v => v.toString()],
    [fp.isBoolean, v => v.toString()],
    [fp.defaultCase, v => `'${v}'`],
  );

  const commonRecordValidationRules = ({

    fieldNotEmpty: fieldName => getNewRecordValidationRule(
      [fieldName],
      `${fieldName} is empty`,
      `!_.isEmpty(record['${fieldName}'])`,
    ),

    fieldBetween: (fieldName, min, max) => getNewRecordValidationRule(
      [fieldName],
      `${fieldName} must be between ${min.toString()} and ${max.toString()}`,
      `record['${fieldName}'] >= ${getStaticValue(min)} &&  record['${fieldName}'] <= ${getStaticValue(max)} `,
    ),

    fieldGreaterThan: (fieldName, min, max) => getNewRecordValidationRule(
      [fieldName],
      `${fieldName} must be greater than ${min.toString()} and ${max.toString()}`,
      `record['${fieldName}'] >= ${getStaticValue(min)}  `,
    ),
  });

  const addRecordValidationRule = recordNode => rule => recordNode.validationRules.push(rule);

  const createTrigger = () => ({
    actionName: '',
    eventName: '',
    // function, has access to event context,
    // returns object that is used as parameter to action
    // only used if triggered by event
    optionsCreator: '',
    // action runs if true,
    // has access to event context
    condition: '',
  });

  const createAction = () => ({
    name: '',
    behaviourSource: '',
    // name of function in actionSource
    behaviourName: '',
    // parameter passed into behaviour.
    // any other parms passed at runtime e.g.
    // by trigger, or manually, will be merged into this
    initialOptions: {},
  });

  const aggregateRules = [
    makerule('name', 'choose a name for the aggregate',
      a => isNonEmptyString(a.name)),
    makerule('aggregatedValue', 'aggregatedValue does not compile',
      a => _.isEmpty(a.aggregatedValue)
              || executesWithoutException(
                () => compilerUtil.compileCode(a.aggregatedValue),
              )),
  ];

  const validateAggregate = aggregate => applyRuleSet(aggregateRules)(aggregate);

  const validateAllAggregates = all => $(all, [
    fp.map(validateAggregate),
    fp.flatten,
  ]);

  const ruleSet = (...sets) => fp.constant(fp.flatten([...sets]));

  const commonRules = [
    makerule('name', 'node name is not set',
      node => stringNotEmpty(node.name)),
    makerule('type', 'node type not recognised',
      anyTrue(isRecord, isRoot, isIndex, isaggregateGroup)),
  ];

  const recordRules = [
    makerule('fields', 'no fields have been added to the record',
      node => isNonEmptyArray(node.fields)),
    makerule('validationRules', "validation rule is missing a 'messageWhenValid' member",
      node => fp.every(r => _.has(r, 'messageWhenInvalid'))(node.validationRules)),
    makerule('validationRules', "validation rule is missing a 'expressionWhenValid' member",
      node => fp.every(r => _.has(r, 'expressionWhenValid'))(node.validationRules)),
  ];


  const aggregateGroupRules = [
    makerule('condition', 'condition does not compile',
      a => fp.isEmpty(a.condition)
               || executesWithoutException(
                 () => compilerUtil.compileExpression(a.condition),
               )),
  ];

  const getRuleSet = node => switchCase(

    [isRecord, ruleSet(
      commonRules,
      recordRules,
    )],

    [isIndex, ruleSet(
      commonRules,
      indexRuleSet,
    )],

    [isaggregateGroup, ruleSet(
      commonRules,
      aggregateGroupRules,
    )],

    [defaultCase, ruleSet(commonRules, [])],
  )(node);

  const validateNode = node => applyRuleSet(getRuleSet(node))(node);

  const validateAll = (appHierarchy) => {
    const flattened = getFlattenedHierarchy(
      appHierarchy,
    );

    const duplicateNameRule = makerule(
      'name', 'node names must be unique under shared parent',
      n => fp.filter(f => f.parent() === n.parent()
                            && f.name === n.name)(flattened).length === 1,
    );

    const duplicateNodeKeyErrors = $(flattened, [
      fp.map(n => applyRuleSet([duplicateNameRule])(n)),
      fp.filter(isSomething),
      fp.flatten,
    ]);

    const fieldErrors = $(flattened, [
      fp.filter(isRecord),
      fp.map(validateAllFields),
      fp.flatten,
    ]);

    const aggregateErrors = $(flattened, [
      fp.filter(isaggregateGroup),
      fp.map(s => validateAllAggregates(
        s.aggregates,
      )),
      fp.flatten,
    ]);

    return $(flattened, [
      fp.map(validateNode),
      fp.flatten,
      fp.union(duplicateNodeKeyErrors),
      fp.union(fieldErrors),
      fp.union(aggregateErrors),
    ]);
  };

  const actionRules = [
    makerule('name', 'action must have a name',
      a => isNonEmptyString(a.name)),
    makerule('behaviourName', 'must supply a behaviour name to the action',
      a => isNonEmptyString(a.behaviourName)),
    makerule('behaviourSource', 'must supply a behaviour source for the action',
      a => isNonEmptyString(a.behaviourSource)),
  ];

  const duplicateActionRule = makerule('', 'action name must be unique', () => {});

  const validateAction = action => applyRuleSet(actionRules)(action);


  const validateActions = (allActions) => {
    const duplicateActions = $(allActions, [
      fp.filter(a => fp.filter(a2 => a2.name === a.name)(allActions).length > 1),
      fp.map(a => validationError(duplicateActionRule, a)),
    ]);

    const errors = $(allActions, [
      fp.map(validateAction),
      fp.flatten,
      fp.union(duplicateActions),
      fp.uniqBy('name'),
    ]);

    return errors;
  };

  const triggerRules = actions => ([
    makerule('actionName', 'must specify an action',
      t => isNonEmptyString(t.actionName)),
    makerule('eventName', 'must specify and event',
      t => isNonEmptyString(t.eventName)),
    makerule('actionName', 'specified action not supplied',
      t => !t.actionName
               || fp.some(a => a.name === t.actionName)(actions)),
    makerule('eventName', 'invalid Event Name',
      t => !t.eventName
               || fp.includes(t.eventName)(eventsList)),
    makerule('optionsCreator', 'Options Creator does not compile - check your expression',
      (t) => {
        if (!t.optionsCreator) return true;
        try {
          compilerUtil.compileCode(t.optionsCreator);
          return true;
        } catch (_) { return false; }
      }),
    makerule('condition', 'Trigger condition does not compile - check your expression',
      (t) => {
        if (!t.condition) return true;
        try {
          compilerUtil.compileExpression(t.condition);
          return true;
        } catch (_) { return false; }
      }),
  ]);

  const validateTrigger = (trigger, allActions) => {
    const errors = applyRuleSet(triggerRules(allActions))(trigger);

    return errors;
  };

  const validateTriggers = (triggers, allActions) => $(triggers, [
    fp.map(t => validateTrigger(t, allActions)),
    fp.flatten,
  ]);

  const getApplicationDefinition = datastore => async () => {
    const exists = await datastore.exists(appDefinitionFile);

    if (!exists) throw new Error('Application definition does not exist');

    const appDefinition = await datastore.loadJson(appDefinitionFile);
    appDefinition.hierarchy = constructHierarchy(
      appDefinition.hierarchy,
    );
    return appDefinition;
  };

  const saveApplicationHierarchy = app => async hierarchy => apiWrapper(
    app,
    events.templateApi.saveApplicationHierarchy,
    permission.writeTemplates.isAuthorized,
    { hierarchy },
    _saveApplicationHierarchy, app.datastore, hierarchy,
  );


  const _saveApplicationHierarchy = async (datastore, hierarchy) => {
    const validationErrors = await validateAll(hierarchy);
    if (validationErrors.length > 0) {
      throw new Error(`Hierarchy is invalid: ${_.join(
      validationErrors.map(e => `${e.item.nodeKey ? e.item.nodeKey() : ''} : ${e.error}`),
      ',',
    )}`);
    }

    if (await datastore.exists(appDefinitionFile)) {
      const appDefinition = await datastore.loadJson(appDefinitionFile);
      appDefinition.hierarchy = hierarchy;
      await datastore.updateJson(appDefinitionFile, appDefinition);
    } else {
      await datastore.createFolder('/.config');
      const appDefinition = { actions: [], triggers: [], hierarchy };
      await datastore.createJson(appDefinitionFile, appDefinition);
    }
  };

  const saveActionsAndTriggers = app => async (actions, triggers) => apiWrapper(
    app,
    events.templateApi.saveActionsAndTriggers,
    permission.writeTemplates.isAuthorized,
    { actions, triggers },
    _saveActionsAndTriggers, app.datastore, actions, triggers,
  );

  const _saveActionsAndTriggers = async (datastore, actions, triggers) => {
    if (await datastore.exists(appDefinitionFile)) {
      const appDefinition = await datastore.loadJson(appDefinitionFile);
      appDefinition.actions = actions;
      appDefinition.triggers = triggers;

      const actionValidErrs = fp.map(e => e.error)(validateActions(actions));

      if (actionValidErrs.length > 0) {
        throw new BadRequestError(`Actions are invalid: ${_.join(actionValidErrs, ', ')}`);
      }

      const triggerValidErrs = fp.map(e => e.error)(validateTriggers(triggers, actions));

      if (triggerValidErrs.length > 0) {
        throw new BadRequestError(`Triggers are invalid: ${_.join(triggerValidErrs, ', ')}`);
      }

      await datastore.updateJson(appDefinitionFile, appDefinition);
    } else {
      throw new BadRequestError('Cannot save actions: Application definition does not exist');
    }
  };

  const getBehaviourSources = async (datastore) => {
      await datastore.loadFile('/.config/behaviourSources.js');
  };

  const api$1 = app => ({

    getApplicationDefinition: getApplicationDefinition(app.datastore),
    saveApplicationHierarchy: saveApplicationHierarchy(app),
    saveActionsAndTriggers: saveActionsAndTriggers(app),
    getBehaviourSources: () => getBehaviourSources(app.datastore),
    getNewRootLevel,
    constructNode,
    getNewIndexTemplate,
    getNewRecordTemplate,
    getNewField,
    validateField,
    addField,
    fieldErrors,
    getNewRecordValidationRule,
    commonRecordValidationRules,
    addRecordValidationRule,
    createAction,
    createTrigger,
    validateActions,
    validateTrigger,
    getNewAggregateGroupTemplate,
    getNewAggregateTemplate,
    constructHierarchy,
    getNewSingleRecordTemplate,
    allTypes: all$1,
    validateNode,
    validateAll,
    validateTriggers,
  });


  const getTemplateApi = app => api$1(app);

  const getUsers = app => async () => apiWrapper(
    app,
    events.authApi.getUsers,
    permission.listUsers.isAuthorized,
    {},
    _getUsers, app,
  );

  const _getUsers = async app => $(await app.datastore.loadJson(USERS_LIST_FILE), [
    fp.map(stripUserOfSensitiveStuff),
  ]);

  const loadAccessLevels = app => async () => apiWrapper(
    app,
    events.authApi.loadAccessLevels,
    permission.listAccessLevels.isAuthorized,
    {},
    _loadAccessLevels, app,
  );

  const _loadAccessLevels = async app => await app.datastore.loadJson(ACCESS_LEVELS_FILE);

  const dummyHash = '$argon2i$v=19$m=4096,t=3,p=1$UZRo409UYBGjHJS3CV6Uxw$rU84qUqPeORFzKYmYY0ceBLDaPO+JWSH4PfNiKXfIKk';

  const authenticate = app => async (username, password) => apiWrapper(
    app,
    events.authApi.authenticate,
    alwaysAuthorized,
    { username, password },
    _authenticate, app, username, password,
  );

  const _authenticate = async (app, username, password) => {
    if (isNothingOrEmpty(username) || isNothingOrEmpty(password)) { return null; }

    const allUsers = await _getUsers(app);
    let user = getUserByName(
      allUsers,
      username,
    );

    const notAUser = 'not-a-user';
    // continue with non-user - so time to verify remains consistent
    // with verification of a valid user
    if (!user || !user.enabled) { user = notAUser; }

    let userAuth;
    try {
      userAuth = await app.datastore.loadJson(
        userAuthFile(username),
      );
    } catch (_) {
      userAuth = { accessLevels: [], passwordHash: dummyHash };
    }

    const permissions = await buildUserPermissions(app, user.accessLevels);

    const verified = await app.crypto.verify(
      userAuth.passwordHash,
      password,
    );

    if (user === notAUser) { return null; }

    return verified
      ? {
        ...user, permissions, temp: false, isUser: true,
      }
      : null;
  };

  const authenticateTemporaryAccess = app => async (tempAccessCode) => {
    if (isNothingOrEmpty(tempAccessCode)) { return null; }

    const temp = parseTemporaryCode(tempAccessCode);
    let user = $(await _getUsers(app), [
      fp.find(u => u.temporaryAccessId === temp.id),
    ]);

    const notAUser = 'not-a-user';
    if (!user || !user.enabled) { user = notAUser; }

    let userAuth;
    try {
      userAuth = await app.datastore.loadJson(
        userAuthFile(user.name),
      );
    } catch (e) {
      userAuth = {
        temporaryAccessHash: dummyHash,
        temporaryAccessExpiryEpoch: (await app.getEpochTime() + 10000),
      };
    }

    if (userAuth.temporaryAccessExpiryEpoch < await app.getEpochTime()) { user = notAUser; }

    const tempCode = !temp.code ? shortid.generate() : temp.code;
    const verified = await app.crypto.verify(
      userAuth.temporaryAccessHash,
      tempCode,
    );

    if (user === notAUser) { return null; }

    return verified
      ? {
        ...user,
        permissions: [],
        temp: true,
        isUser: true,
      }
      : null;
  };

  const buildUserPermissions = async (app, userAccessLevels) => {
    const allAccessLevels = await _loadAccessLevels(app);

    return $(allAccessLevels.levels, [
      fp.filter(l => fp.some(ua => l.name === ua)(userAccessLevels)),
      fp.map(l => l.permissions),
      fp.flatten,
    ]);
  };

  const createTemporaryAccess$1 = app => async userName => apiWrapper(
    app,
    events.authApi.createTemporaryAccess,
    alwaysAuthorized,
    { userName },
    _createTemporaryAccess, app, userName,
  );

  const _createTemporaryAccess = async (app, userName) => {
    const tempCode = await getTemporaryCode(app);

    const lock = await getLock(
      app, USERS_LOCK_FILE, 1000, 2,
    );

    if (isNolock(lock)) { throw new Error('Unable to create temporary access, could not get lock - try again'); }

    try {
      const users = await app.datastore.loadJson(USERS_LIST_FILE);

      const user = getUserByName(users, userName);
      user.temporaryAccessId = tempCode.temporaryAccessId;

      await app.datastore.updateJson(
        USERS_LIST_FILE,
        users,
      );
    } finally {
      await releaseLock(app, lock);
    }

    const userAuth = await app.datastore.loadJson(
      userAuthFile(userName),
    );
    userAuth.temporaryAccessHash = tempCode.temporaryAccessHash;

    userAuth.temporaryAccessExpiryEpoch = tempCode.temporaryAccessExpiryEpoch;

    await app.datastore.updateJson(
      userAuthFile(userName),
      userAuth,
    );

    return tempCode.tempCode;
  };

  const getTemporaryCode = async (app) => {
    const tempCode = shortid.generate()
          + shortid.generate()
          + shortid.generate()
          + shortid.generate();

    const tempId = shortid.generate();

    return {
      temporaryAccessHash: await app.crypto.hash(
        tempCode,
      ),
      temporaryAccessExpiryEpoch:
              (await app.getEpochTime()) + tempCodeExpiryLength,
      tempCode: `tmp:${tempId}:${tempCode}`,
      temporaryAccessId: tempId,
    };
  };

  const userRules = allUsers => [
    makerule('name', 'username must be set',
      u => isNonEmptyString(u.name)),
    makerule('accessLevels', 'user must have at least one access level',
      u => u.accessLevels.length > 0),
    makerule('name', 'username must be unique',
      u => fp.filter(u2 => insensitiveEquals(u2.name, u.name))(allUsers).length === 1),
    makerule('accessLevels', 'access levels must only contain stings',
      u => all(isNonEmptyString)(u.accessLevels)),
  ];

  const validateUser = () => (allusers, user) => applyRuleSet(userRules(allusers))(user);

  const getNewUser = app => () => apiWrapperSync(
    app,
    events.authApi.getNewUser,
    permission.createUser.isAuthorized,
    {},
    _getNewUser, app,
  );

  const _getNewUser = () => ({
    name: '',
    accessLevels: [],
    enabled: true,
    temporaryAccessId: '',
  });

  const getNewUserAuth = app => () => apiWrapperSync(
    app,
    events.authApi.getNewUserAuth,
    permission.createUser.isAuthorized,
    {},
    _getNewUserAuth, app,
  );

  const _getNewUserAuth = () => ({
    passwordHash: '',
    temporaryAccessHash: '',
    temporaryAccessExpiryEpoch: 0,
  });

  const isValidPassword = app => password => apiWrapperSync(
    app,
    events.authApi.isValidPassword,
    alwaysAuthorized,
    { password },
    _isValidPassword, app, password,
  );

  const _isValidPassword = (app, password) => scorePassword(password).score > 30;

  const changeMyPassword = app => async (currentPw, newpassword) => apiWrapper(
    app,
    events.authApi.changeMyPassword,
    alwaysAuthorized,
    { currentPw, newpassword },
    _changeMyPassword, app, currentPw, newpassword,
  );

  const _changeMyPassword = async (app, currentPw, newpassword) => {
    const existingAuth = await app.datastore.loadJson(
      userAuthFile(app.user.name),
    );

    if (isSomething(existingAuth.passwordHash)) {
      const verified = await app.crypto.verify(
        existingAuth.passwordHash,
        currentPw,
      );

      if (verified) {
        await await doSet(
          app, existingAuth,
          app.user.name, newpassword,
        );
        return true;
      }
    }

    return false;
  };

  const setPasswordFromTemporaryCode = app => async (tempCode, newpassword) => apiWrapper(
    app,
    events.authApi.setPasswordFromTemporaryCode,
    alwaysAuthorized,
    { tempCode, newpassword },
    _setPasswordFromTemporaryCode, app, tempCode, newpassword,
  );


  const _setPasswordFromTemporaryCode = async (app, tempCode, newpassword) => {
    const currentTime = await app.getEpochTime();

    const temp = parseTemporaryCode(tempCode);

    const user = $(await _getUsers(app), [
      fp.find(u => u.temporaryAccessId === temp.id),
    ]);

    if (!user) { return false; }

    const existingAuth = await app.datastore.loadJson(
      userAuthFile(user.name),
    );

    if (isSomething(existingAuth.temporaryAccessHash)
         && existingAuth.temporaryAccessExpiryEpoch > currentTime) {
      const verified = await app.crypto.verify(
        existingAuth.temporaryAccessHash,
        temp.code,
      );

      if (verified) {
        await doSet(
          app, existingAuth,
          user.name, newpassword,
        );
        return true;
      }
    }

    return false;
  };

  const doSet = async (app, auth, username, newpassword) => {
    auth.temporaryAccessHash = '';
    auth.temporaryAccessExpiryEpoch = 0;
    auth.passwordHash = await app.crypto.hash(
      newpassword,
    );
    await app.datastore.updateJson(
      userAuthFile(username),
      auth,
    );
  };

  const scorePassword = app => password => apiWrapperSync(
    app,
    events.authApi.scorePassword,
    alwaysAuthorized,
    { password },
    _scorePassword, password,
  );

  const _scorePassword = (password) => {
    // from https://stackoverflow.com/questions/948172/password-strength-meter
    // thank you https://stackoverflow.com/users/46617/tm-lv

    let score = 0;
    if (!password) { return score; }

    // award every unique letter until 5 repetitions
    const letters = new Object();
    for (let i = 0; i < password.length; i++) {
      letters[password[i]] = (letters[password[i]] || 0) + 1;
      score += 5.0 / letters[password[i]];
    }

    // bonus points for mixing it up
    const variations = {
      digits: /\d/.test(password),
      lower: /[a-z]/.test(password),
      upper: /[A-Z]/.test(password),
      nonWords: /\W/.test(password),
    };

    let variationCount = 0;
    for (const check in variations) {
      variationCount += (variations[check] == true) ? 1 : 0;
    }
    score += (variationCount - 1) * 10;

    const strengthText = score > 80
      ? 'strong'
      : score > 60
        ? 'good'
        : score >= 30
          ? 'weak'
          : 'very weak';

    return {
      score: parseInt(score),
      strengthText,
    };
  };

  const createUser$1 = app => async (user, password = null) => apiWrapper(
    app,
    events.authApi.createUser,
    permission.createUser.isAuthorized,
    { user, password },
    _createUser, app, user, password,
  );

  const _createUser = async (app, user, password = null) => {
    const lock = await getLock(
      app, USERS_LOCK_FILE, 1000, 2,
    );

    if (isNolock(lock)) { throw new Error('Unable to create user, could not get lock - try again'); }

    const users = await app.datastore.loadJson(USERS_LIST_FILE);

    const userErrors = validateUser()([...users, user], user);
    if (userErrors.length > 0) { throw new BadRequestError(`User is invalid. ${fp.join('; ')(userErrors)}`); }

    const { auth, tempCode, temporaryAccessId } = await getAccess(
      app, password,
    );
    user.tempCode = tempCode;
    user.temporaryAccessId = temporaryAccessId;

    if (fp.some(u => insensitiveEquals(u.name, user.name))(users)) { 
      throw new BadRequestError('User already exists'); 
    }

    users.push(
      stripUserOfSensitiveStuff(user),
    );

    await app.datastore.updateJson(
      USERS_LIST_FILE,
      users,
    );

    try {
      await app.datastore.createJson(
        userAuthFile(user.name),
        auth,
      );
    } catch (_) {
      await app.datastore.updateJson(
        userAuthFile(user.name),
        auth,
      );
    }

    await releaseLock(app, lock);

    return user;
  };

  const getAccess = async (app, password) => {
    const auth = getNewUserAuth(app)();

    if (isNonEmptyString(password)) {
      if (isValidPassword(password)) {
        auth.passwordHash = await app.crypto.hash(password);
        auth.temporaryAccessHash = '';
        auth.temporaryAccessId = '';
        auth.temporaryAccessExpiryEpoch = 0;
        return { auth };
      }
      throw new BadRequestError('Password does not meet requirements');
    } else {
      const tempAccess = await getTemporaryCode(app);
      auth.temporaryAccessHash = tempAccess.temporaryAccessHash;
      auth.temporaryAccessExpiryEpoch = tempAccess.temporaryAccessExpiryEpoch;
      auth.passwordHash = '';
      return ({
        auth,
        tempCode: tempAccess.tempCode,
        temporaryAccessId: tempAccess.temporaryAccessId,
      });
    }
  };

  const enableUser = app => async username => apiWrapper(
    app,
    events.authApi.enableUser,
    permission.enableDisableUser.isAuthorized,
    { username },
    _enableUser, app, username,
  );

  const disableUser = app => async username => apiWrapper(
    app,
    events.authApi.disableUser,
    permission.enableDisableUser.isAuthorized,
    { username },
    _disableUser, app, username,
  );

  const _enableUser = async (app, username) => await toggleUser(app, username, true);

  const _disableUser = async (app, username) => await toggleUser(app, username, false);

  const toggleUser = async (app, username, enabled) => {
    const lock = await getLock(app, USERS_LOCK_FILE, 1000, 1, 0);

    const actionName = enabled ? 'enable' : 'disable';

    if (isNolock(lock)) { throw new Error(`Could not ${actionName} user - cannot get lock`); }

    try {
      const users = await app.datastore.loadJson(USERS_LIST_FILE);
      const user = getUserByName(users, username);
      if (!user) { throw new NotFoundError(`Could not find user to ${actionName}`); }

      if (user.enabled === !enabled) {
        user.enabled = enabled;
        await app.datastore.updateJson(USERS_LIST_FILE, users);
      }
    } finally {
      releaseLock(app, lock);
    }
  };

  const getNewAccessLevel = () => () => ({
    name: '',
    permissions: [],
    default:false
  });

  const isAllowedType = t => $(permissionTypes, [
    fp.values,
    fp.includes(t),
  ]);

  const isRecordOrIndexType = t => fp.some(p => p === t)([
    permissionTypes.CREATE_RECORD,
    permissionTypes.UPDATE_RECORD,
    permissionTypes.DELETE_RECORD,
    permissionTypes.READ_RECORD,
    permissionTypes.READ_INDEX,
    permissionTypes.EXECUTE_ACTION,
  ]);


  const permissionRules = app => ([
    makerule('type', 'type must be one of allowed types',
      p => isAllowedType(p.type)),
    makerule('nodeKey', 'record and index permissions must include a valid nodeKey',
      p => (!isRecordOrIndexType(p.type))
               || isSomething(getNode(app.hierarchy, p.nodeKey))),
  ]);

  const applyPermissionRules = app => applyRuleSet(permissionRules(app));

  const accessLevelRules = allLevels => ([
    makerule('name', 'name must be set',
      l => isNonEmptyString(l.name)),
    makerule('name', 'access level names must be unique',
      l => fp.isEmpty(l.name)
               || fp.filter(a => insensitiveEquals(l.name, a.name))(allLevels).length === 1),
  ]);

  const applyLevelRules = allLevels => applyRuleSet(accessLevelRules(allLevels));

  const validateAccessLevel = app => (allLevels, level) => {
    const errs = $(level.permissions, [
      fp.map(applyPermissionRules(app)),
      fp.flatten,
      fp.concat(
        applyLevelRules(allLevels)(level),
      ),
    ]);

    return errs;
  };

  const validateAccessLevels = app => allLevels => apiWrapperSync(
    app,
    events.authApi.validateAccessLevels,
    alwaysAuthorized,
    { allLevels },
    _validateAccessLevels, app, allLevels,
  );

  const _validateAccessLevels = (app, allLevels) => $(allLevels, [
    fp.map(l => validateAccessLevel(app)(allLevels, l)),
    fp.flatten,
    fp.uniqWith((x, y) => x.field === y.field
                          && x.item === y.item
                          && x.error === y.error),
  ]);

  const saveAccessLevels = app => async accessLevels => apiWrapper(
    app,
    events.authApi.saveAccessLevels,
    permission.writeAccessLevels.isAuthorized,
    { accessLevels },
    _saveAccessLevels, app, accessLevels,
  );

  const _saveAccessLevels = async (app, accessLevels) => {
    const validationErrors = validateAccessLevels(app)(accessLevels.levels);
    if (validationErrors.length > 0) {
      const errs = $(validationErrors, [
        fp.map(e => e.error),
        fp.join(', '),
      ]);
      throw new Error(
        `Access Levels Invalid: ${errs}`,
      );
    }

    const lock = await getLock(
      app, ACCESS_LEVELS_LOCK_FILE, 2000, 2,
    );

    if (isNolock(lock)) { throw new Error('Could not get lock to save access levels'); }

    try {
      const existing = await app.datastore.loadJson(ACCESS_LEVELS_FILE);
      if (existing.version !== accessLevels.version) { throw new Error('Access levels have already been updated, since you loaded'); }

      accessLevels.version++;

      app.datastore.updateJson(ACCESS_LEVELS_FILE, accessLevels);
    } finally {
      await releaseLock(app, lock);
    }
  };

  const generateFullPermissions = (app) => {
    const allNodes = getFlattenedHierarchy(app.hierarchy);
    const accessLevel = { permissions: [] };

    const recordNodes = $(allNodes, [
      fp.filter(isRecord),
    ]);

    for (const n of recordNodes) {
      permission.createRecord.add(n.nodeKey(), accessLevel);
      permission.updateRecord.add(n.nodeKey(), accessLevel);
      permission.deleteRecord.add(n.nodeKey(), accessLevel);
      permission.readRecord.add(n.nodeKey(), accessLevel);
    }

    const indexNodes = $(allNodes, [
      fp.filter(isIndex),
    ]);

    for (const n of indexNodes) {
      permission.readIndex.add(n.nodeKey(), accessLevel);
    }

    for (const a of fp.keys(app.actions)) {
      permission.executeAction.add(a, accessLevel);
    }

    $(permission, [
      fp.values,
      fp.filter(p => !p.isNode),
      fp.each(p => p.add(accessLevel)),
    ]);

    return accessLevel.permissions;
  };

  const setUserAccessLevels$1 = app => async (userName, accessLevels) => apiWrapper(
    app,
    events.authApi.setUserAccessLevels,
    permission.setUserAccessLevels.isAuthorized,
    { userName, accessLevels },
    _setUserAccessLevels, app, userName, accessLevels,
  );

  const _setUserAccessLevels = async (app, username, accessLevels) => {
    const lock = await getLock(app, USERS_LOCK_FILE, 1000, 1, 0);

    const actualAccessLevels = $(
      await app.datastore.loadJson(ACCESS_LEVELS_FILE),
      [
        l => l.levels,
        fp.map(l => l.name),
      ],
    );

    const missing = fp.difference(accessLevels)(actualAccessLevels);
    if (missing.length > 0) {
      throw new Error(`Invalid access levels supplied: ${fp.join(', ', missing)}`);
    }

    if (isNolock(lock)) { throw new Error('Could set user access levels cannot get lock'); }

    try {
      const users = await app.datastore.loadJson(USERS_LIST_FILE);
      const user = getUserByName(users, username);
      if (!user) { throw new NotFoundError(`Could not find user with ${username}`); }

      user.accessLevels = accessLevels;
      await app.datastore.updateJson(USERS_LIST_FILE, users);
    } finally {
      releaseLock(app, lock);
    }
  };

  const getAuthApi = app => ({
    authenticate: authenticate(app),
    authenticateTemporaryAccess: authenticateTemporaryAccess(app),
    createTemporaryAccess: createTemporaryAccess$1(app),
    createUser: createUser$1(app),
    loadAccessLevels: loadAccessLevels(app),
    enableUser: enableUser(app),
    disableUser: disableUser(app),
    getNewAccessLevel: getNewAccessLevel(),
    getNewUser: getNewUser(app),
    getNewUserAuth: getNewUserAuth(app),
    getUsers: getUsers(app),
    saveAccessLevels: saveAccessLevels(app),
    isAuthorized: isAuthorized(app),
    changeMyPassword: changeMyPassword(app),
    setPasswordFromTemporaryCode: setPasswordFromTemporaryCode(app),
    scorePassword,
    isValidPassword: isValidPassword(app),
    validateUser: validateUser(),
    validateAccessLevels: validateAccessLevels(app),
    generateFullPermissions: () => generateFullPermissions(app),
    setUserAccessLevels: setUserAccessLevels$1(app),
  });

  const executeAction$1 = app => (actionName, options) => {
    apiWrapperSync(
      app,
      events.actionsApi.execute,
      permission.executeAction.isAuthorized(actionName),
      { actionName, options },
      app.actions[actionName], options,
    );
  };

  const _executeAction = (behaviourSources, action, options) => behaviourSources[action.behaviourSource][action.behaviourName](options);

  const getActionsApi = app => ({
    execute: executeAction$1(app),
  });

  const publish = handlers => async (eventName, context = {}) => {
    if (!_.has(handlers, eventName)) return;

    for (const handler of handlers[eventName]) {
      await handler(eventName, context);
    }
  };

  const subscribe = handlers => (eventName, handler) => {
    if (!_.has(handlers, eventName)) {
      handlers[eventName] = [];
    }
    handlers[eventName].push(handler);
  };

  const createEventAggregator = () => {
    const handlers = {};
    const eventAggregator = ({
      publish: publish(handlers),
      subscribe: subscribe(handlers),
    });
    return eventAggregator;
  };

  const createJson = originalCreateFile => async (key, obj, retries = 5, delay = 500) => await retry(originalCreateFile, retries, delay, key, JSON.stringify(obj));

  const createNewFile = originalCreateFile => async (path, content, retries = 5, delay = 500) => await retry(originalCreateFile, retries, delay, path, content);

  const loadJson = datastore => async (key, retries = 5, delay = 500) => {
    try {
      return await retry(JSON.parse, retries, delay, await datastore.loadFile(key));
    } catch (err) {
      throw new NotFoundError(err.message);
    }
  };

  const updateJson = datastore => async (key, obj, retries = 5, delay = 500) => {
    try {
      return await retry(datastore.updateFile, retries, delay, key, JSON.stringify(obj));
    } catch (err) {
      throw new NotFoundError(err.message);
    }
  };

  const setupDatastore = (datastore) => {
    const originalCreateFile = datastore.createFile;
    datastore.loadJson = loadJson(datastore);
    datastore.createJson = createJson(originalCreateFile);
    datastore.updateJson = updateJson(datastore);
    datastore.createFile = createNewFile(originalCreateFile);
    if (datastore.createEmptyDb) { delete datastore.createEmptyDb; }
    return datastore;
  };

  const compileCode = code => {
    let func;  
      
    try {
      func = compilerUtil.compileCode(code);
    } catch(e) {
      e.message = `Error compiling code : ${code} : ${e.message}`;
      throw e;
    }

    return func;
  };

  const compileExpression = code => {
    let func;  
        
    try {
      func = compilerUtil.compileExpression(code);
    } catch(e) {
      e.message = `Error compiling expression : ${code} : ${e.message}`;
      throw e;
    }
    
    return func;
  };

  const initialiseActions = (subscribe, behaviourSources, actions, triggers, apis) => {
    validateSources(behaviourSources, actions);
    subscribeTriggers(subscribe, behaviourSources, actions, triggers, apis);
    return createActionsCollection(behaviourSources, actions);
  };

  const createActionsCollection = (behaviourSources, actions) => $(actions, [
    fp.reduce((all, a) => {
      all[a.name] = opts => _executeAction(behaviourSources, a, opts);
      return all;
    }, {}),
  ]);

  const subscribeTriggers = (subscribe, behaviourSources, actions, triggers, apis) => {
    const createOptions = (optionsCreator, eventContext) => {
      if (!optionsCreator) return {};
      const create = compileCode(optionsCreator);
      return create({ context: eventContext, apis });
    };

    const shouldRunTrigger = (trigger, eventContext) => {
      if (!trigger.condition) return true;
      const shouldRun = compileExpression(trigger.condition);
      return shouldRun({ context: eventContext });
    };

    for (let trig of triggers) {
      subscribe(trig.eventName, async (ev, ctx) => {
        if (shouldRunTrigger(trig, ctx)) {
          await _executeAction(
            behaviourSources,
            fp.find(a => a.name === trig.actionName)(actions),
            createOptions(trig.optionsCreator, ctx),
          );
        }
      });
    }
  };

  const validateSources = (behaviourSources, actions) => {
    const declaredSources = $(actions, [
      fp.uniqBy(a => a.behaviourSource),
      fp.map(a => a.behaviourSource),
    ]);

    const suppliedSources = fp.keys(behaviourSources);

    const missingSources = fp.difference(
      declaredSources, suppliedSources,
    );

    if (missingSources.length > 0) {
      throw new BadRequestError(`Declared behaviour sources are not supplied: ${fp.join(', ', missingSources)}`);
    }

    const missingBehaviours = $(actions, [
      fp.filter(a => !fp.isFunction(behaviourSources[a.behaviourSource][a.behaviourName])),
      fp.map(a => `Action: ${a.name} : ${a.behaviourSource}.${a.behaviourName}`),
    ]);

    if (missingBehaviours.length > 0) {
      throw new NotFoundError(`Missing behaviours: could not find behaviour functions: ${fp.join(', ', missingBehaviours)}`);
    }
  };

  const retrieve = async (app) => {
    const transactionFiles = await app.datastore.getFolderContents(
      TRANSACTIONS_FOLDER,
    );

    let transactions = [];

    if (fp.some(isBuildIndexFolder)(transactionFiles)) {
      const buildIndexFolder = fp.find(isBuildIndexFolder)(transactionFiles);

      transactions = await retrieveBuildIndexTransactions(
        app,
        joinKey(TRANSACTIONS_FOLDER, buildIndexFolder),
      );
    }

    if (transactions.length > 0) return transactions;

    return await retrieveStandardTransactions(
      app, transactionFiles,
    );
  };

  const retrieveBuildIndexTransactions = async (app, buildIndexFolder) => {
    const childFolders = await app.datastore.getFolderContents(buildIndexFolder);
    if (childFolders.length === 0) {
      // cleanup
      await app.datastore.deleteFolder(buildIndexFolder);
      return [];
    }

    const getTransactionFiles = async (childFolderIndex = 0) => {
      if (childFolderIndex >= childFolders.length) return [];

      const childFolderKey = joinKey(buildIndexFolder, childFolders[childFolderIndex]);
      const files = await app.datastore.getFolderContents(
        childFolderKey,
      );

      if (files.length === 0) {
        await app.datastore.deleteFolder(childFolderKey);
        return await getTransactionFiles(childFolderIndex + 1);
      }

      return { childFolderKey, files };
    };

    const transactionFiles = await getTransactionFiles();

    if (transactionFiles.files.length === 0) return [];

    const transactions = $(transactionFiles.files, [
      fp.map(parseTransactionId),
    ]);

    for (const t of transactions) {
      const transactionContent = await app.datastore.loadJson(
        joinKey(
          transactionFiles.childFolderKey,
          t.fullId,
        ),
      );
      t.record = await _load(app, transactionContent.recordKey);
    }

    transactions.indexNode = $(buildIndexFolder, [
      getLastPartInKey,
      nodeKeyHashFromBuildFolder,
      getNodeFromNodeKeyHash(app.hierarchy),
    ]);

    transactions.folderKey = transactionFiles.childFolderKey;

    return transactions;
  };

  const retrieveStandardTransactions = async (app, transactionFiles) => {
    const transactionIds = $(transactionFiles, [
      fp.filter(f => f !== LOCK_FILENAME
                      && !isBuildIndexFolder(f)),
      fp.map(parseTransactionId),
    ]);

    const transactionIdsByRecord = $(transactionIds, [
      fp.groupBy('recordId'),
    ]);

    const dedupedTransactions = [];

    const verify = async (t) => {
      if (t.verified === true) return t;

      const id = getTransactionId(
        t.recordId,
        t.transactionType,
        t.uniqueId,
      );

      const transaction = await app.datastore.loadJson(
        joinKey(TRANSACTIONS_FOLDER, id),
      );

      if (isDelete(t)) {
        t.record = transaction.record;
        t.verified = true;
        return t;
      }

      const rec = await _load(
        app,
        transaction.recordKey,
      );
      if (rec.transactionId === id) {
        t.record = rec;
        if (transaction.oldRecord) { t.oldRecord = transaction.oldRecord; }
        t.verified = true;
      } else {
        t.verified = false;
      }

      return t;
    };

    const pickOne = async (trans, forType) => {
      const transForType = fp.filter(forType)(trans);
      if (transForType.length === 1) {
        const t = await verify(transForType[0]);
        return (t.verified === true ? t : null);
      }
      for (let t of transForType) {
        t = await verify(t);
        if (t.verified === true) { return t; }
      }

      return null;
    };

    for (const recordId in transactionIdsByRecord) {
      const transIdsForRecord = transactionIdsByRecord[recordId];
      if (transIdsForRecord.length === 1) {
        const t = await verify(transIdsForRecord[0]);
        if (t.verified) { dedupedTransactions.push(t); }
        continue;
      }
      if (fp.some(isDelete)(transIdsForRecord)) {
        const t = await verify(fp.find(isDelete)(transIdsForRecord));
        if (t.verified) { dedupedTransactions.push(t); }
        continue;
      }
      if (fp.some(isUpdate)(transIdsForRecord)) {
        const upd = await pickOne(transIdsForRecord, isUpdate);
        if (isSomething(upd) && upd.verified) { dedupedTransactions.push(upd); }
        continue;
      }
      if (fp.some(isCreate)(transIdsForRecord)) {
        const cre = await pickOne(transIdsForRecord, isCreate);
        if (isSomething(cre)) { dedupedTransactions.push(cre); }
        continue;
      }
    }

    const duplicates = $(transactionIds, [
      fp.filter(t => none(ddt => ddt.uniqueId === t.uniqueId)(dedupedTransactions)),
    ]);


    const deletePromises = fp.map(t => app.datastore.deleteFile(
      joinKey(
        TRANSACTIONS_FOLDER,
        getTransactionId(
          t.recordId,
          t.transactionType,
          t.uniqueId,
        ),
      ),
    ))(duplicates);

    await Promise.all(deletePromises);

    return dedupedTransactions;
  };

  const parseTransactionId = (id) => {
    const splitId = fp.split(idSep)(id);
    return ({
      recordId: splitId[0],
      transactionType: splitId[1],
      uniqueId: splitId[2],
      fullId: id,
    });
  };

  const getRelevantAncestorIndexes = (appHierarchy, record) => {
    const key = record.key;
    const keyParts = splitKey(key);
    const nodeId = getRecordNodeId(key);

    const flatHierarchy = _.orderBy(getFlattenedHierarchy(appHierarchy),
      [node => node.pathRegx().length],
      ['desc']);

    const makeindexNodeAndKey_ForAncestorIndex = (indexNode, indexKey) => makeIndexNodeAndKey(indexNode, joinKey(indexKey, indexNode.name));

    const traverseAncestorIndexesInPath = () => fp.reduce((acc, part) => {
      const currentIndexKey = joinKey(acc.lastIndexKey, part);
      acc.lastIndexKey = currentIndexKey;
      const testPathRegx = p => new RegExp(`${p.pathRegx()}$`).test(currentIndexKey);
      const nodeMatch = fp.find(testPathRegx)(flatHierarchy);

      if (isNothing(nodeMatch)) { return acc; }

      if (!isRecord(nodeMatch)
                  || nodeMatch.indexes.length === 0) { return acc; }

      const indexes = $(nodeMatch.indexes, [
        fp.filter(i => i.indexType === indexTypes.ancestor
                          && (i.allowedRecordNodeIds.length === 0
                           || fp.includes(nodeId)(i.allowedRecordNodeIds))),
      ]);

      fp.each(v => acc.nodesAndKeys.push(
        makeindexNodeAndKey_ForAncestorIndex(v, currentIndexKey),
      ))(indexes);

      return acc;
    }, { lastIndexKey: '', nodesAndKeys: [] })(keyParts).nodesAndKeys;

    const rootIndexes = $(flatHierarchy, [
      fp.filter(n => isGlobalIndex(n) && recordNodeIdIsAllowed(n)(nodeId)),
      fp.map(i => makeIndexNodeAndKey(i, i.nodeKey())),
    ]);

    return fp.union(traverseAncestorIndexesInPath())(rootIndexes);
  };

  const getRelevantReverseReferenceIndexes = (appHierarchy, record) => $(record.key, [
    getExactNodeForPath(appHierarchy),
    n => n.fields,
    fp.filter(f => f.type === 'reference'
                      && isSomething(record[f.name])
                      && isNonEmptyString(record[f.name].key)),
    fp.map(f => $(f.typeOptions.reverseIndexNodeKeys, [
      fp.map(n => ({
        recordNode: getNode(appHierarchy, n),
        field: f,
      })),
    ])),
    fp.flatten,
    fp.map(n => makeIndexNodeAndKey(
      n.recordNode,
      joinKey(record[n.field.name].key, n.recordNode.name),
    )),
  ]);

  const makeIndexNodeAndKey = (indexNode, indexKey) => ({ indexNode, indexKey });

  // adapted from https://github.com/dex4er/js-promise-writable
    // Thank you :) 
    const promiseWriteableStream = stream => {
    
      let _errored;
    
      const _errorHandler = err => {
          _errored = err;
      };

      stream.on("error", _errorHandler);    
    
      const write = chunk => {  
        let rejected = false;
    
        return new Promise((resolve, reject) => {
          if (_errored) {
            const err = _errored;
            _errored = undefined;
            return reject(err);
          }
    
          if (!stream.writable || stream.closed || stream.destroyed) {
            return reject(new Error("write after end"));
          }
    
          const writeErrorHandler = err => {
            _errored = undefined;
            rejected = true;
            reject(err);
          };
    
          stream.once("error", writeErrorHandler);
    
          const canWrite = stream.write(chunk);
    
          stream.removeListener("error", writeErrorHandler);
    
          if (canWrite) {
            if (!rejected) {
              resolve(chunk.length);
            }
          } else {
            const errorHandler = err => {
              _errored = undefined;
              removeListeners();
              reject(err);
            };
    
            const drainHandler = () => {
              removeListeners();
              resolve(chunk.length);
            };
    
            const closeHandler = () => {
              removeListeners();
              resolve(chunk.length);
            };
    
            const finishHandler = () => {
              removeListeners();
              resolve(chunk.length);
            };
    
            const removeListeners = () => {
              stream.removeListener("close", closeHandler);
              stream.removeListener("drain", drainHandler);
              stream.removeListener("error", errorHandler);
              stream.removeListener("finish", finishHandler);
            };
    
            stream.on("close", closeHandler);
            stream.on("drain", drainHandler);
            stream.on("error", errorHandler);
            stream.on("finish", finishHandler);
          }
        })
      };
    
      const end = () => {
    
        return new Promise((resolve, reject) => {
          if (_errored) {
            const err = _errored;
            _errored = undefined;
            return reject(err);
          }
    
          if (!stream.writable || stream.closed || stream.destroyed) {
            return resolve();
          }
    
          const finishHandler = () => {
            removeListeners();
            resolve();
          };
    
          const errorHandler = (err) => {
            _errored = undefined;
            removeListeners();
            reject(err);
          };
    
          const removeListeners = () => {
            stream.removeListener("error", errorHandler);
            stream.removeListener("finish", finishHandler);
          };
    
          stream.on("finish", finishHandler);
          stream.on("error", errorHandler);
    
          stream.end();
        })
      };

      return {write, end};
    };

  const applyToShard = async (hierarchy, store, indexKey,
    indexNode, indexShardKey, recordsToWrite, keysToRemove) => {
    const createIfNotExists = recordsToWrite.length > 0;
    const writer = await getWriter(hierarchy, store, indexKey, indexShardKey, indexNode, createIfNotExists);
    if (writer === SHARD_DELETED) return;

    await writer.updateIndex(recordsToWrite, keysToRemove);
    await swapTempFileIn(store, indexShardKey);
  };

  const SHARD_DELETED = 'SHARD_DELETED';
  const getWriter = async (hierarchy, store, indexKey, indexedDataKey, indexNode, createIfNotExists) => {
    let readableStream = null;

    if (isShardedIndex(indexNode)) {
      await ensureShardNameIsInShardMap(store, indexKey, indexedDataKey);
      if(!await store.exists(indexedDataKey)) {
        await store.createFile(indexedDataKey, "");
      }
    }

    try {

      readableStream = promiseReadableStream(
          await store.readableFileStream(indexedDataKey)
      );

    } catch (e) {

      if (await store.exists(indexedDataKey)) {
        throw e;
      } else {
        if (createIfNotExists) { 
          await store.createFile(indexedDataKey, ''); 
        } else { 
          return SHARD_DELETED; 
        }

        readableStream = promiseReadableStream(
            await store.readableFileStream(indexedDataKey)
        );

      }
    }

    const writableStream = promiseWriteableStream(
        await store.writableFileStream(indexedDataKey + ".temp")
    );

    return getIndexWriter(
      hierarchy, indexNode,
          readableStream, writableStream
    );
  };

  const swapTempFileIn = async (store, indexedDataKey, isRetry = false) => {
    const tempFile = `${indexedDataKey}.temp`;
    try {
      await store.deleteFile(indexedDataKey);
    } catch (e) {
      // ignore failure, incase it has not been created yet
    }
    try {
      await store.renameFile(tempFile, indexedDataKey);
    } catch (e) {
      // retrying in case delete failure was for some other reason
      if (!isRetry) {
        await swapTempFileIn(store, indexedDataKey, true);
      } else {
        throw new Error("Failed to swap in index filed: " + e.message);
      }
    }
  };

  const executeTransactions = app => async (transactions) => {
    const recordsByShard = mappedRecordsByIndexShard(app.hierarchy, transactions);

    for (const shard of fp.keys(recordsByShard)) {
      await applyToShard(
        app.hierarchy, app.datastore,
        recordsByShard[shard].indexKey,
        recordsByShard[shard].indexNode,
        shard,
        recordsByShard[shard].writes,
        recordsByShard[shard].removes,
      );
    }
  };

  const mappedRecordsByIndexShard = (hierarchy, transactions) => {
    const updates = getUpdateTransactionsByShard(
      hierarchy, transactions,
    );

    const created = getCreateTransactionsByShard(
      hierarchy, transactions,
    );
    const deletes = getDeleteTransactionsByShard(
      hierarchy, transactions,
    );

    const indexBuild = getBuildIndexTransactionsByShard(
      hierarchy,
      transactions,
    );

    const toRemove = [
      ...deletes,
      ...updates.toRemove,
    ];

    const toWrite = [
      ...created,
      ...updates.toWrite,
      ...indexBuild,
    ];

    const transByShard = {};

    const initialiseShard = (t) => {
      if (fp.isUndefined(transByShard[t.indexShardKey])) {
        transByShard[t.indexShardKey] = {
          writes: [],
          removes: [],
          indexKey: t.indexKey,
          indexNodeKey: t.indexNodeKey,
          indexNode: t.indexNode,
        };
      }
    };

    for (const trans of toWrite) {
      initialiseShard(trans);
      transByShard[trans.indexShardKey].writes.push(
        trans.mappedRecord.result,
      );
    }

    for (const trans of toRemove) {
      initialiseShard(trans);
      transByShard[trans.indexShardKey].removes.push(
        trans.mappedRecord.result.key,
      );
    }

    return transByShard;
  };

  const getUpdateTransactionsByShard = (hierarchy, transactions) => {
    const updateTransactions = $(transactions, [fp.filter(isUpdate)]);

    const evaluateIndex = (record, indexNodeAndPath) => {
      const mappedRecord = evaluate(record)(indexNodeAndPath.indexNode);
      return ({
        mappedRecord,
        indexNode: indexNodeAndPath.indexNode,
        indexKey: indexNodeAndPath.indexKey,
        indexShardKey: getIndexedDataKey(
          indexNodeAndPath.indexNode,
          indexNodeAndPath.indexKey,
          mappedRecord.result,
        ),
      });
    };

    const getIndexNodesToApply = indexFilter => (t, indexes) => $(indexes, [
      fp.map(n => ({
        old: evaluateIndex(t.oldRecord, n),
        new: evaluateIndex(t.record, n),
      })),
      fp.filter(indexFilter),
    ]);

    const toRemoveFilter = (n, isUnreferenced) => n.old.mappedRecord.passedFilter === true
          && (n.new.mappedRecord.passedFilter === false
              || isUnreferenced);

    const toAddFilter = (n, isNewlyReferenced) => (n.old.mappedRecord.passedFilter === false
          || isNewlyReferenced)
          && n.new.mappedRecord.passedFilter === true;

    const toUpdateFilter = n => n.new.mappedRecord.passedFilter === true
          && n.old.mappedRecord.passedFilter === true
          && !fp.isEqual(n.old.mappedRecord.result,
            n.new.mappedRecord.result);

    const toRemove = [];
    const toWrite = [];

    for (const t of updateTransactions) {
      const ancestorIdxs = getRelevantAncestorIndexes(
        hierarchy, t.record,
      );

      const referenceChanges = diffReverseRefForUpdate(
        hierarchy, t.oldRecord, t.record,
      );

      // old records to remove (filtered out)
      const filteredOut_toRemove = _.union(
        getIndexNodesToApply(toRemoveFilter)(t, ancestorIdxs),
        // still referenced - check filter
        getIndexNodesToApply(toRemoveFilter)(t, referenceChanges.notChanged),
        // un referenced - remove if in there already
        getIndexNodesToApply(n => toRemoveFilter(n, true))(t, referenceChanges.unReferenced),
      );

      // new records to add (filtered in)
      const filteredIn_toAdd = _.union(
        getIndexNodesToApply(toAddFilter)(t, ancestorIdxs),
        // newly referenced - check filter
        getIndexNodesToApply(n => toAddFilter(n, true))(t, referenceChanges.newlyReferenced),
        // reference unchanged - rerun filter in case something else changed
        getIndexNodesToApply(toAddFilter)(t, referenceChanges.notChanged),
      );

      const changed = _.union(
        getIndexNodesToApply(toUpdateFilter)(t, ancestorIdxs),
        // still referenced - recheck filter
        getIndexNodesToApply(toUpdateFilter)(t, referenceChanges.notChanged),
      );

      const shardKeyChanged = $(changed, [
        fp.filter(c => c.old.indexShardKey !== c.new.indexShardKey),
      ]);

      const changedInSameShard = $(shardKeyChanged, [
        fp.difference(changed),
      ]);

      for (const res of shardKeyChanged) {
        fp.pull(res)(changed);
        filteredOut_toRemove.push(res);
        filteredIn_toAdd.push(res);
      }

      toRemove.push(
        $(filteredOut_toRemove, [
          fp.map(i => i.old),
        ]),
      );

      toWrite.push(
        $(filteredIn_toAdd, [
          fp.map(i => i.new),
        ]),
      );

      toWrite.push(
        $(changedInSameShard, [
          fp.map(i => i.new),
        ]),
      );
    }

    return ({
      toRemove: fp.flatten(toRemove),
      toWrite: fp.flatten(toWrite),
    });
  };

  const getBuildIndexTransactionsByShard = (hierarchy, transactions) => {
    const buildTransactions = $(transactions, [fp.filter(isBuildIndex)]);
    if (!isNonEmptyArray(buildTransactions)) return [];
    const indexNode = transactions.indexNode;

    const getIndexKeys = (t) => {
      if (isGlobalIndex(indexNode)) {
        return [indexNode.nodeKey()];
      }

      if (isReferenceIndex(indexNode)) {
        const recordNode = getExactNodeForPath(hierarchy)(t.record.key);
        const refFields = $(recordNode.fields, [
          fp.filter(fieldReversesReferenceToIndex(indexNode)),
        ]);
        const indexKeys = [];
        for (const refField of refFields) {
          const refValue = t.record[refField.name];
          if (isSomething(refValue)
                     && isNonEmptyString(refValue.key)) {
            const indexKey = joinKey(
              refValue.key,
              indexNode.name,
            );

            if (!fp.includes(indexKey)(indexKeys)) { indexKeys.push(indexKey); }
          }
        }
        return indexKeys;
      }

      return [joinKey(
        getActualKeyOfParent(
          indexNode.parent().nodeKey(),
          t.record.key,
        ),
        indexNode.name,
      )];
    };

    return $(buildTransactions, [
      fp.map((t) => {
        const mappedRecord = evaluate(t.record)(indexNode);
        if (!mappedRecord.passedFilter) return null;
        const indexKeys = getIndexKeys(t);
        return $(indexKeys, [
          fp.map(indexKey => ({
            mappedRecord,
            indexNode,
            indexKey,
            indexShardKey: getIndexedDataKey(
              indexNode,
              indexKey,
              mappedRecord.result,
            ),
          })),
        ]);
      }),
      fp.flatten,
      fp.filter(isSomething),
    ]);
  };

  const get_Create_Delete_TransactionsByShard = pred => (hierarchy, transactions) => {
    const createTransactions = $(transactions, [fp.filter(pred)]);

    const getIndexNodesToApply = (t, indexes) => $(indexes, [
      fp.map((n) => {
        const mappedRecord = evaluate(t.record)(n.indexNode);
        return ({
          mappedRecord,
          indexNode: n.indexNode,
          indexKey: n.indexKey,
          indexShardKey: getIndexedDataKey(
            n.indexNode,
            n.indexKey,
            mappedRecord.result,
          ),
        });
      }),
      fp.filter(n => n.mappedRecord.passedFilter),
    ]);

    const allToApply = [];

    for (const t of createTransactions) {
      const ancestorIdxs = getRelevantAncestorIndexes(hierarchy, t.record);
      const reverseRef = getRelevantReverseReferenceIndexes(hierarchy, t.record);

      allToApply.push(
        getIndexNodesToApply(t, ancestorIdxs),
      );
      allToApply.push(
        getIndexNodesToApply(t, reverseRef),
      );
    }

    return fp.flatten(allToApply);
  };

  const getDeleteTransactionsByShard = get_Create_Delete_TransactionsByShard(isDelete);

  const getCreateTransactionsByShard = get_Create_Delete_TransactionsByShard(isCreate);

  const diffReverseRefForUpdate = (appHierarchy, oldRecord, newRecord) => {
    const oldIndexes = getRelevantReverseReferenceIndexes(
      appHierarchy, oldRecord,
    );
    const newIndexes = getRelevantReverseReferenceIndexes(
      appHierarchy, newRecord,
    );

    const unReferenced = fp.differenceBy(
      i => i.indexKey,
      oldIndexes, newIndexes,
    );

    const newlyReferenced = fp.differenceBy(
      i => i.indexKey,
      newIndexes, oldIndexes,
    );

    const notChanged = fp.intersectionBy(
      i => i.indexKey,
      newIndexes, oldIndexes,
    );

    return {
      unReferenced,
      newlyReferenced,
      notChanged,
    };
  };

  const cleanup = async (app) => {
    const lock = await getTransactionLock(app);
    if (isNolock(lock)) return;

    try {
      const transactions = await retrieve(app);
      if (transactions.length > 0) {
        await executeTransactions(app)(transactions);

        const folder = transactions.folderKey
          ? transactions.folderKey
          : TRANSACTIONS_FOLDER;

        const deleteFiles = $(transactions, [
          fp.map(t => joinKey(
            folder,
            getTransactionId(
              t.recordId, t.transactionType,
              t.uniqueId,
            ),
          )),
          fp.map(app.datastore.deleteFile),
        ]);

        await Promise.all(deleteFiles);
      }
    } finally {
      await releaseLock(app, lock);
    }
  };

  const getTransactionLock = async app => await getLock(
    app, LOCK_FILE_KEY,
    timeoutMilliseconds, maxLockRetries,
  );

  const initialiseData = async (datastore, applicationDefinition, accessLevels) => {
    await datastore.createFolder(configFolder);
    await datastore.createJson(appDefinitionFile, applicationDefinition);

    await initialiseRootCollections(datastore, applicationDefinition.hierarchy);
    await initialiseRootIndexes(datastore, applicationDefinition.hierarchy);

    await initialiseRootSingleRecords(datastore, applicationDefinition.hierarchy);

    await datastore.createFolder(TRANSACTIONS_FOLDER);

    await datastore.createFolder(AUTH_FOLDER);

    await datastore.createJson(USERS_LIST_FILE, []);

    await datastore.createJson(
      ACCESS_LEVELS_FILE, 
      accessLevels ? accessLevels : { version: 0, levels: [] });
  };

  const initialiseRootIndexes = async (datastore, hierarchy) => {
    const flathierarchy = getFlattenedHierarchy(hierarchy);
    const globalIndexes = $(flathierarchy, [
      fp.filter(isGlobalIndex),
    ]);

    for (const index of globalIndexes) {
      if (!await datastore.exists(index.nodeKey())) { await initialiseIndex(datastore, '', index); }
    }
  };

  const initialiseRootSingleRecords = async (datastore, hierachy) => {
    const flathierarchy = getFlattenedHierarchy(hierachy);
    const singleRecords = $(flathierarchy, [
      fp.filter(isSingleRecord),
    ]);

    /* for (let record of singleRecords) {
          const result = getNew({ datastore: datastore, hierarchy: appDefinition.hierarchy })
              (record.nodeKey(),
                  record.name
              );

          _save({ datastore: datastore, hierarchy: appDefinition.hierarchy },
              result
          );
      } */
  };

  const getDatabaseManager = databaseManager => ({
    createEmptyMasterDb: createEmptyMasterDb(databaseManager),
    createEmptyInstanceDb: createEmptyInstanceDb(databaseManager),
    getInstanceDbRootConfig: databaseManager.getInstanceDbRootConfig,
    masterDatastoreConfig: getMasterDatastoreConfig(databaseManager),
    getInstanceDatastoreConfig: getInstanceDatastoreConfig(databaseManager),
  });

  const getMasterDatastoreConfig = databaseManager => databaseManager.getDatastoreConfig('master');

  const getInstanceDatastoreConfig = databaseManager => (applicationId, instanceId) => databaseManager.getDatastoreConfig(
    applicationId, instanceId,
  );

  const createEmptyMasterDb = databaseManager => async () => await databaseManager.createEmptyDb('master');

  const createEmptyInstanceDb = databaseManager => async (applicationId, instanceId) => {
    if (isNothing(applicationId)) { throw new Error('CreateDb: application id not supplied'); }
    if (isNothing(instanceId)) { throw new Error('CreateDb: instance id not supplied'); }

    return await databaseManager.createEmptyDb(
      applicationId,
      instanceId,
    );
  };

  const getAppApis = async (store, behaviourSources = null, 
                                  cleanupTransactions = null, 
                                  getEpochTime = null,
                                  crypto = null,
                                  appDefinition = null) => {

      store = setupDatastore(store);

      if(!appDefinition)
          appDefinition = await getApplicationDefinition(store)();

      if(!behaviourSources)
          behaviourSources = await getBehaviourSources(store);

      const eventAggregator = createEventAggregator();

      const app = {
          datastore:store,
          crypto,
          publish:eventAggregator.publish,
          hierarchy:appDefinition.hierarchy,
          actions:appDefinition.actions
      };

      const templateApi = getTemplateApi(app);    

      app.cleanupTransactions = isSomething(cleanupTransactions) 
                                ? cleanupTransactions
                                : async () => await cleanup(app);

      app.getEpochTime = isSomething(getEpochTime)
                         ? getEpochTime
                         : async () => (new Date()).getTime();

      const recordApi = getRecordApi(app);
      const collectionApi = getCollectionApi(app);
      const indexApi = getIndexApi(app);
      const authApi = getAuthApi(app);
      const actionsApi = getActionsApi(app);

      const authenticateAs = async (username, password) => {
          app.user = await authApi.authenticate(username, password);
      };

      const withFullAccess = () => {
          app.user = {
              name: "app",
              permissions : generateFullPermissions(app),
              isUser:false,
              temp:false
          };
      };

      const asUser = (user) => {
          app.user = user;
      };

      

      let apis = {
          recordApi, 
          templateApi,
          collectionApi,
          indexApi,
          authApi,
          actionsApi,
          subscribe: eventAggregator.subscribe,
          authenticateAs,
          withFullAccess,
          asUser
      };

      apis.actions = initialiseActions(
          eventAggregator.subscribe,
          behaviourSources,
          appDefinition.actions,
          appDefinition.triggers,
          apis);


      return apis;
  };

  exports.common = index;
  exports.default = getAppApis;
  exports.events = events;
  exports.eventsList = eventsList;
  exports.getActionsApi = getActionsApi;
  exports.getAppApis = getAppApis;
  exports.getAuthApi = getAuthApi;
  exports.getCollectionApi = getCollectionApi;
  exports.getDatabaseManager = getDatabaseManager;
  exports.getIndexApi = getIndexApi;
  exports.getRecordApi = getRecordApi;
  exports.getTemplateApi = getTemplateApi;
  exports.hierarchy = hierarchy;
  exports.initialiseData = initialiseData;
  exports.setupDatastore = setupDatastore;

  Object.defineProperty(exports, '__esModule', { value: true });

}));
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