packages/node_modules/pouchdb-adapter-utils/src/processDocs.js

import { createError, MISSING_DOC, REV_CONFLICT } from 'pouchdb-errors';
import updateDoc from './updateDoc';
import {
  isDeleted,
  isLocalId,
  merge,
  winningRev as calculateWinningRev
} from 'pouchdb-merge';

function rootIsMissing(docInfo) {
  return docInfo.metadata.rev_tree[0].ids[1].status === 'missing';
}

function insertDoc(docInfo, results, resultsIdx, newEdits, wasDelete, writeDoc, callback) {
  // Cant insert new deleted documents
  var winningRev = calculateWinningRev(docInfo.metadata);
  var deleted = isDeleted(docInfo.metadata, winningRev);
  if (wasDelete && deleted) {
    results[resultsIdx] = createError(MISSING_DOC, 'deleted');
    return callback();
  }

  // 4712 - detect whether a new document was inserted with a _rev
  var inConflict = newEdits && rootIsMissing(docInfo);

  if (inConflict) {
    var err = createError(REV_CONFLICT);
    results[resultsIdx] = err;
    return callback();
  }

  var delta = deleted ? 0 : 1;

  writeDoc(docInfo, winningRev, deleted, deleted, false,
    delta, resultsIdx, callback);
}

function mergeDoc(currentDoc, results, resultsIdx, revLimit, newEdits, wasDelete, writeDoc, docWritten) {
  // Ensure stemming applies to new writes as well
  var merged = merge([], currentDoc.metadata.rev_tree[0], revLimit);
  currentDoc.metadata.rev_tree = merged.tree;
  currentDoc.stemmedRevs = merged.stemmedRevs || [];
  insertDoc(currentDoc, results, resultsIdx, newEdits, wasDelete, writeDoc, docWritten);
}

function mergeOrUpdateDoc(id, fetchedDocs, currentDoc, results, resultsIdx, revLimit, newEdits,
                          wasDelete, writeDoc, docWritten) {
  if (fetchedDocs.has(id)) {
    updateDoc(revLimit, fetchedDocs.get(id), currentDoc, results,
      resultsIdx, docWritten, writeDoc, newEdits);
  } else {
    mergeDoc(currentDoc, results, resultsIdx, revLimit, newEdits, wasDelete, writeDoc, docWritten);
  }
}

function processsMultipleDocsWithSameId(id, docs, fetchedDocs, results, revLimit, newEdits,
                                        wasDelete, writeDoc, checkAllDocsDone) {
  var numDone = 0;

  function docWritten() {
    if (++numDone < docs.length) {
      nextDoc();
    } else {
      checkAllDocsDone();
    }
  }
  function nextDoc() {
    var value = docs[numDone];
    var currentDoc = value[0];
    var resultsIdx = value[1];

    mergeOrUpdateDoc(id, fetchedDocs, currentDoc, results, resultsIdx, revLimit, newEdits,
      wasDelete, writeDoc, docWritten);
  }
  nextDoc();
}

function afterLocalPutOrRemove(i, results, checkAllDocsDone) {
  return function (err, res) {
    results[i] = err || res;
    checkAllDocsDone();
  };
}

function processDocs(revLimit, docInfos, api, fetchedDocs, tx, results,
                     writeDoc, opts, callback) {

  // Default to 1000 locally
  revLimit = revLimit || 1000;
  var newEdits = opts.new_edits;
  var wasDelete = 'was_delete' in opts;
  var idsToDocs = {};
  var docsDone = 0;
  var docsToDo = docInfos.length;

  function checkAllDocsDone() {
    if (++docsDone === docsToDo && callback) {
      callback();
    }
  }

  for (var i = 0, len = docInfos.length; i < len ; i++) {
    var currentDocInfo = docInfos[i];
    if (currentDocInfo._id && isLocalId(currentDocInfo._id)) {
      var fun = currentDocInfo._deleted ? '_removeLocal' : '_putLocal';
      api[fun](currentDocInfo, {ctx: tx}, afterLocalPutOrRemove(i, results, checkAllDocsDone));
    } else {
      var currentDocId = currentDocInfo.metadata.id;
      var currentKey = '$' + currentDocId;
      var currentValue = idsToDocs[currentKey];
      if (currentValue) {
        docsToDo--; // duplicate
        currentValue.push([currentDocInfo, i]);
      } else {
        idsToDocs[currentKey] = [[currentDocInfo, i]];
      }
    }
  }

  // in the case of new_edits, the user can provide multiple docs
  // with the same id. these need to be processed sequentially
  for (var thisKey in idsToDocs) {
    if (idsToDocs.hasOwnProperty(thisKey)) {
      var id = thisKey.substring(1); // cut off initial '$'
      var docs = idsToDocs[thisKey];
      if (docs.length === 1) { // fast case
        var thisDoc = docs[0];
        mergeOrUpdateDoc(id, fetchedDocs, thisDoc[0], results, thisDoc[1], revLimit, newEdits,
          wasDelete, writeDoc, checkAllDocsDone);
      } else { // slow case
        processsMultipleDocsWithSameId(id, docs, fetchedDocs, results, revLimit, newEdits,
          wasDelete, writeDoc, checkAllDocsDone);
      }
    }
  }
}

export default processDocs;