examples/hoofbeats/javascripts/resolvers/musicbrainz.js

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