import {
  map, filter, groupBy, split,
  some, find,
} from 'lodash/fp';
import {
  LOCK_FILENAME, TRANSACTIONS_FOLDER, idSep, isUpdate,
  nodeKeyHashFromBuildFolder, isBuildIndexFolder, getTransactionId,
  isDelete, isCreate,
} from './transactionsCommon';
import {
  joinKey, $, none, isSomething,
} from '../common';
import { getLastPartInKey, getNodeFromNodeKeyHash } from '../templateApi/hierarchy';
import { _load } from '../recordApi/load';

export const retrieve = async (app) => {
  const transactionFiles = await app.datastore.getFolderContents(
    TRANSACTIONS_FOLDER,
  );

  let transactions = [];

  if (some(isBuildIndexFolder)(transactionFiles)) {
    const buildIndexFolder = 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, [
    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, [
    filter(f => f !== LOCK_FILENAME
                    && !isBuildIndexFolder(f)),
    map(parseTransactionId),
  ]);

  const transactionIdsByRecord = $(transactionIds, [
    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 = 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 (some(isDelete)(transIdsForRecord)) {
      const t = await verify(find(isDelete)(transIdsForRecord));
      if (t.verified) { dedupedTransactions.push(t); }
      continue;
    }
    if (some(isUpdate)(transIdsForRecord)) {
      const upd = await pickOne(transIdsForRecord, isUpdate);
      if (isSomething(upd) && upd.verified) { dedupedTransactions.push(upd); }
      continue;
    }
    if (some(isCreate)(transIdsForRecord)) {
      const cre = await pickOne(transIdsForRecord, isCreate);
      if (isSomething(cre)) { dedupedTransactions.push(cre); }
      continue;
    }
  }

  const duplicates = $(transactionIds, [
    filter(t => none(ddt => ddt.uniqueId === t.uniqueId)(dedupedTransactions)),
  ]);


  const deletePromises = 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 = split(idSep)(id);
  return ({
    recordId: splitId[0],
    transactionType: splitId[1],
    uniqueId: splitId[2],
    fullId: id,
  });
};