examples/hoofbeats/javascripts/resolvers/musicbrainz.js

   1 /* vi: set et sw=4 ts=4 si: */
   2 /*
   3  * Copyright (c) 2012, Intel Corporation.
   4  *
   5  * This program is licensed under the terms and conditions of the
   6  * Apache License, version 2.0.  The full text of the Apache License is at
   7  * http://www.apache.org/licenses/LICENSE-2.0
   8  *
   9  */
  10
  11 (function(win, $) {
  12     var musicbrainz = function() {
  13         var _priv = {
  14             _baseUrl: 'http://musicbrainz.org/ws/2/',
  15             _fmtArg: 'fmt=json',
  16             _interval: undefined,
  17             _queue: [],
  18             _url_cache: {},
  19
  20
  21             /* Internal methods to perform XHR requests. */
  22
  23             _get: function(request) {
  24                 if (request.url in _priv._url_cache) {
  25                     request.deferred.resolve(_priv._url_cache[request.url]);
  26                 } else {
  27                     $.getJSON(request.url)
  28                     .done(function(data, statusText, xhr) {
  29                         _priv._url_cache[request.url] = data;
  30                         request.deferred.resolve(data);
  31                     })
  32                     .error(function(xhr) {
  33                         if (xhr.status === 503) {
  34                             _priv._enqueue(request); // put it back in the queue
  35                         }
  36                     });
  37                 }
  38
  39                 return request.deferred.promise();
  40             },
  41
  42
  43             /* Internal methods for the handling of the request queue */
  44
  45             _startQueue: function() {
  46                 if (_priv._interval === undefined) {
  47                     _priv._interval = setInterval(function() {
  48                         _priv._dequeue();
  49                     }, 2000);
  50                 }
  51             },
  52
  53             _stopQueue: function() {
  54                 clearInterval(_priv._interval);
  55                 _priv._interval = undefined;
  56             },
  57
  58             _enqueue: function(request) {
  59                 if ($.inArray(request.url, _priv._queue) < 0) {
  60                     _priv._queue.push(request);
  61                 }
  62             },
  63
  64             _dequeue: function() {
  65                 var request = _priv._queue.shift();
  66                 if (request !== undefined) {
  67                     _priv._get(request);
  68                 }
  69             }
  70         }; // _priv
  71
  72
  73         /* Public methods */
  74         return {
  75             name: function() { return "MusicBrainz"; },
  76
  77             getArtist: function(q) {
  78                 var lookup_url = _priv._baseUrl + 'artist/?query="' + q +
  79                                  '"&' + _priv._fmtArg,
  80                     lookup_deferred = new $.Deferred(),
  81                     returned_deferred = new $.Deferred();
  82
  83                 if (q !== undefined) {
  84                     if (_priv._interval === undefined) {
  85                         _priv._startQueue();
  86                     }
  87
  88                     _priv._enqueue({url: lookup_url, deferred: lookup_deferred});
  89                     lookup_deferred.done(function(data) {
  90                         if (data.count > 0) {
  91                             var artist_url = _priv._baseUrl + 'artist/' +
  92                                              data.artist[0].id + '?' + _priv._fmtArg,
  93                                 artist_deferred = new $.Deferred();
  94
  95                             _priv._get({url: artist_url, deferred: artist_deferred});
  96                             artist_deferred.done(function(data) {
  97                                 returned_deferred.resolve(data);
  98                             });
  99                         } else {
 100                             returned_deferred.reject();
 101                         }
 102                     });
 103                 } else {
 104                     returned_deferred.reject();
 105                 }
 106
 107                 return returned_deferred.promise();
 108             }
 109         };
 110     };
 111
 112     win.MusicBrainz = new musicbrainz();
 113 }(window, jQuery));