Add playPreview method to Track object

example/playPreview.js

@@ -0,0 +1,37 @@
+
+/**
+ * Example script that retrieves a preview of the specified Track through Spotify, 
+ * then decodes the MP3 data through node-lame, and fianally plays the decoded PCM 
+ * data through the speakers using node-speaker.
+ */
+
+var Spotify = require('../');
+var login = require('../login');
+var lame = require('lame');
+var Speaker = require('speaker');
+
+// determine the URI to play, ensure it's a "track" URI
+var uri = process.argv[2] || 'spotify:track:6tdp8sdXrXlPV6AZZN2PE8';
+var type = Spotify.uriType(uri);
+if ('track' != type) {
+  throw new Error('Must pass a "track" URI, got ' + JSON.stringify(type));
+}
+
+// initiate the Spotify session
+Spotify.login(login.username, login.password, function (err, spotify) {
+  if (err) throw err;
+
+  // first get a "Track" instance from the track URI
+  spotify.get(uri, function (err, track) {
+    if (err) throw err;
+    console.log('Playing 30 second preview of: %s - %s', track.artist[0].name, track.name);
+
+    track.playPreview()
+      .pipe(new lame.Decoder())
+      .pipe(new Speaker())
+      .on('finish', function () {
+        spotify.disconnect();
+      });
+
+  });
+});

lib/track.js

@@ -29,6 +29,18 @@ Object.defineProperty(Track.prototype, 'uri', {
   configurable: true
 });
 
+/**
+ * Track Preview URL getter
+ */
+Object.defineProperty(Track.prototype, 'previewUrl', {
+  get: function () {
+    var previewUrlBase = 'http://d318706lgtcm8e.cloudfront.net/mp3-preview/'
+    return this.preview.length && (previewUrlBase + util.gid2id(this.preview[0].fileId));
+  },
+  enumerable: true,
+  configurable: true
+})
+
 /**
  * Loads all the metadata for this Track instance. Useful for when you get an only
  * partially filled Track instance from an Album instance for example.
@@ -100,3 +112,41 @@ Track.prototype.play = function () {
   // return stream immediately so it can be .pipe()'d
   return stream;
 };
+
+/**
+ * Begins playing a preview of the track, returns a Readable stream that outputs MP3 data.
+ *
+ * @api public
+ */
+
+Track.prototype.playPreview = function () {
+  var spotify = this._spotify;
+  var stream = new PassThrough();
+  var previewUrl = this.previewUrl;
+
+  if (!previewUrl) {
+    process.nextTick(function() {
+      stream.emit('error', new Error('Track does not have preview available'));
+    });
+    return stream;
+  }
+
+  debug('GET %s', previewUrl);
+  var req = spotify.agent.get(previewUrl)
+    .set({ 'User-Agent': spotify.userAgent })
+    .end()
+    .request();
+  req.on('response', response);
+
+  function response (res) {
+    debug('HTTP/%s %s', res.httpVersion, res.statusCode);
+    if (res.statusCode == 200) {
+      res.pipe(stream);
+    } else {
+      stream.emit('error', new Error('HTTP Status Code ' + res.statusCode));
+    }
+  }
+
+  // return stream immediately so it can be .pipe()'d
+  return stream;
+};