/src/models/thumbnailjobcollection.js

define([
  'config!',
  'underscore',
  'backbone',
  'models/livecollection',
  'lib/template',
  'lib/translatekeys'
], function (config, util, Backbone, LiveCollection, template, translateKeys) {
  
  // Cache underscore templates for URL endpoints.
  var makeStatusUrl = template(config.thumbnailerStatus),
      makeThumbnailUrl = template(config.thumbnailUrl);
  
  var ThumbnailModel = Backbone.Model.extend({
    // Builds you a thumbnail URL
    src: function () {
      return makeThumbnailUrl({
        thumbnail_key: this.get('id')
      });
    }
  });
  
  var ThumbnailJobCollection = LiveCollection.extend({
    model: ThumbnailModel,
    
    initialize: function (attributes, options) {
      this.jobID = '';
      // Create a URL from jobID, if none set.
      if (options && options.jobID && !this.url) {
        this.jobID = options.jobID;

        this.url = makeStatusUrl({ jobId: this.jobID });
      }
      console.log('New Thumbnail Job Collection ' + this.jobID);
    },
    
    pollUntilFinishedProcessing: function () {
      this.stream({
        interval: 5000,
        tries: 5,
        
        success: function (collection, resp) {
          console.log('Polled Thumbnail Job API (' +
            collection.length + 'ct) ' +
            collection.jobID);
          
          // If it's an XHR success, but not an API success do nothing.
          // TODO: handle API errors.
          if (!collection.isSuccess) return;

          // Get all of the statuses from thumbnails
          var statuses = collection.pluck('status');

          // If all thumbnails are processed, stop polling.
          if (util.indexOf(statuses, 'processing') === -1) 
            collection.unstream();
        }
      });
    },
    
    // Defining a custom parse implementation that massages data
    // from our JSON API into a Backbone.Model-compatible format.
    //
    // Sample return data:
    //
    //     {
    //       "job": "...",
    //       "sites": [
    //           {
    //               "key": "...", 
    //               "status": "processing", 
    //               "url": "http://instapaper.com/"
    //           }
    //           ...
    //       ],
    //       "success": true
    //     }
    //
    // ...which is turned into:
    //
    //       [
    //           {
    //               "id": "...", 
    //               "status": "processing", 
    //               "url": "http://instapaper.com/"
    //           }
    //           ...
    //       ]
    parse: function (resp) {
      var results = resp.sites,
          translator = util.bind(translateKeys, this, {
            // Convert key to id, so we can use all of the nice
            // collection/model getters.
            key: 'id',
            status: 'status',
            url: 'url'
          });
      // Make sure JobID is correct
      this.jobID = resp.job;
      // Set if this is an API success
      this.isSuccess = resp.success;
      return (resp && resp.success ? util.map(results, translator) : []);
    }
  });
  return ThumbnailJobCollection;
});