apiStore.js

define([
  'dojo/store/JsonRest', 
  'dojo/store/Memory', 
  'dojo/store/Observable',
  'dojo/_base/lang',
  'dojo/_base/array',
  'dojo/request',
  'dojo/aspect',
  '../xhrerror'
  ], function(
    JsonRest, Memory, Observable, lang, array, request, aspect, xhrerror
  ) {
    var refreshTimeout = 1250;
    var storeList = {};
    var timerList = [];

    /** 
    * Grid store wrapper class. Uses a JSON REST store for getting and
    * setting data. Caches all data locally in a Memory store. 
    *
    * Receives update diffs from server and applies to Memory store.
    * Write actions are passed on to server.
    *
    * Keeps record of created stores and returns the already
    * created instance if present.
    *
    * @class apiStore
    * @module Common
    * @static
    * */

    /**
    * @method apiStore
    * @param target {String} API Target.
    * @return {Store} Store object.
    * */
    var createApiStore = function (target) {
      var apiStore, cacheStore, dataStore, pollTimestamp = 0;

      // don't create multiple instances of the same store
      if (storeList.hasOwnProperty(target)) {
        return storeList[target];
      }

      cacheStore = new Observable(new Memory());
      dataStore = new JsonRest({ target: target });

      // create a store object for the grid
      // get and query uses local store
      // all other actions use data store
      apiStore = lang.delegate(cacheStore, {
        add: lang.hitch(dataStore, dataStore.add),
        put: lang.hitch(dataStore, dataStore.put),
        remove: lang.hitch(dataStore, dataStore.remove)
      });

      // poll for changes to dataset
      function poll(arg) {
        request.get(
          target + 'diff/' + pollTimestamp,
          { handleAs: 'json' }
        ).then(function (data) {
          pollTimestamp = data.timestamp;

          array.forEach(data.updated, function (element) {
            cacheStore.put(element);
          });
          array.forEach(data.deleted, function (element) {
            cacheStore.remove(element);
          });
        }, xhrerror);

        // pass on return value (for aspect.after)
        return arg;
      }

      // poll() before populating store with initial data to 
      // get initial timestamp
      poll();

      // populate local store with all data
      // add Deferred to apiStore to notify Grid when store is ready
      apiStore.ready = dataStore.query({}).forEach(function (element) {
        cacheStore.put(element);
      });

      aspect.after(apiStore, 'add', poll);
      aspect.after(apiStore, 'put', poll);
      aspect.after(apiStore, 'remove', poll);
      timerList.push(setInterval(poll, refreshTimeout));

      storeList[target] = apiStore;
      return apiStore;
    };

    /** 
    * Clears all saved and active stores
    * @method apiStore.clearStores
    * */
    createApiStore.clearStores = function () {
      var i;
      for (i = 0; i < timerList.length; i += 1) {
        clearInterval(timerList[i]);
      }
      timerList = [];
      storeList = {};
    };

    return createApiStore;
  });