tab.js

import PouchDB from 'pouchdb';
import createClass from '../lang/class';
import iobject from '../lang/iobject';

export default createClass({

  constructor: function (localDbName, remoteDbLocation, changesCallback) {
    if (!localDbName || typeof localDbName !== 'string') {
      throw new Error('missing localDbName parameter');
    }

    if (!remoteDbLocation || typeof remoteDbLocation !== 'string') {
      throw new Error('missing remoteDbLocation parameter');
    }

    this.remoteDbLocation = remoteDbLocation;

    this._onChangesHandler = changesCallback;

    this.db = new PouchDB(localDbName);
    this.remoteDb = new PouchDB(remoteDbLocation);
  },

  connect: function () {
    var allDocs;

    return (
      this.replicateFromRemote()
      .then(this.fetchAll.bind(this))
      .then(function (docs) {
        allDocs = docs;
      })
      .then(function () {
        return this.db.info();
      }.bind(this))
      .then(function (info) {
        this._lastSequenceNumber = info.update_seq;
      }.bind(this))
      .then(this.startSyncing.bind(this))
      .then(function () {
        return allDocs;
      })
    );
  },

  createDoc: function (doc) {
    if (doc._id) {
      return (
        this.db.put(doc)
        .then(function (response) {
          console.log('db: put doc (created)', response);
        })
      );
    }

    return (
      this.db.post(doc)
      .then(function (response) {
        console.log('db: posted doc', response);
      })
    );
  },

  updateDoc: function (doc) {
    return (
      this.db.get(doc._id)
      .then(function (fetchedDoc) {
        return iobject.merge(doc, {_rev: fetchedDoc._rev});
      })
      .then(this.db.put.bind(this.db))
      .then(function (response) {
        console.log('db: put doc (updated)', response);
      })
    );
  },

  deleteDoc: function (id) {
    return (
      this.db.get(id)
      .then(function (fetchedDoc) {
        return {
          _id: id,
          _rev: fetchedDoc._rev,
          _deleted: true
        };
      })
      .then(this.db.put.bind(this.db))
      .then(function (response) {
        console.log('db: deleted doc', response);
      })
    );
  },

  replicateFromRemote: function () {
    console.info('replication start');

    return new Promise(function (resolve) {
      this.db.replicate.from(this.remoteDb, {
        batch_size: 100
      })
      .on('paused', function () {
        console.info('replication paused');
      })
      .on('active', function () {
        console.info('replication active');
      })
      .on('complete', function () {
        console.info('replication complete');
        resolve();
      })
      .on('error', function (err) {
        console.error('replication error', err);
        // resolve even in error case
        // incomplete replication can be handled by next sync
        resolve();
      });
    }.bind(this));
  },

  fetchAll: function () {
    return this.db.allDocs({
      include_docs: true,
      attachments: true
    })
    .then(function (result) {
      return result.rows.map(function (row) {
        return row.doc;
      });
    });
  },

  startSyncing: function () {
    this.sync();
    this._startSyncInterval();
  },

  /**
   * This sets up replication between the local database
   * and its remote counterpart
   */
  sync: function () {
    this._isSyncing = true;
    this.syncHandle = this.db.sync(this.remoteDb, {
      batch_size: 100
    })
    .on('error', function (err) {
      console.error('replication error', err);
      this._isSyncing = false;
      this._emitChanges();
    }.bind(this))
    .on('complete', function () {
      this._isSyncing = false;
      this._emitChanges();
    }.bind(this));
  },

  cancelSync: function () {
    this.syncHandle.cancel();
  },

  _startSyncInterval: function () {
    setInterval(function () {
      if (!this._isSyncing) {
        this.sync();
      }
    }.bind(this), 7500);
  },

  _emitChanges: function () {
    this.db.changes({
      since: this._lastSequenceNumber,
      include_docs: true
    })
    .on('complete', function (info) {
      this._lastSequenceNumber = info.last_seq;

      if (!info.results.length) {
        return;
      }

      console.info('db changes', info.results);
      this._onChangesHandler(info.results);
    }.bind(this))
    .on('error', console.error.bind(console));
  },

  /**
   * removes local database without triggering
   * events on objects.
   */
  destroy: function () {
    this.cancelSync();
    this.db.destroy();
  }

});