pubsub: Implementing subscription listing.

lib/pubsub/index.js

@@ -154,7 +154,42 @@ function Connection(opts) {
   });
 }
 
-// TODO(jbd): List subscriptions.
+/**
+ * Lists subscriptions.
+ * @param  {string}   query.filterByTopic Returns subscriptions that are
+ *                                        subscribed to the topic provided.
+ * @param  {string}   query.pageToken     Page token.
+ * @param  {Number}   query.maxResults    Max number of results to return.
+ * @param  {Function} callback            Callback function.
+ */
+Connection.prototype.listSubscriptions = function(query, callback) {
+  var that = this;
+  if (arguments.length < 2) {
+    callback = query;
+    query = {};
+  }
+  var q = util.extend({}, query);
+  q.query = q.filterByTopic
+      ? 'pubsub.googleapis.com/topic in (' + this.fullTopicName_(q.filterByTopic) + ')'
+      : 'cloud.googleapis.com/project in (' + this.fullProjectName_() + ')';
+  delete q.filterByTopic;
+
+  this.makeReq('GET', 'subscriptions', q, true, function(err, result) {
+    if (err) {
+      return callback(err);
+    }
+    var items = result.subscription || [];
+    var subscriptions = items.map(function(item) {
+      return new Subscription(that, item.name);
+    });
+    var nextQuery = null;
+    if (result.nextPageToken) {
+      nextQuery = q;
+      nextQuery.pageToken = result.nextPageToken;
+    }
+    callback(null, subscriptions, nextQuery);
+  });
+};
 
 /**
  * Subscribe with the provided options.
@@ -219,6 +254,16 @@ Connection.prototype.fullTopicName_ = function(name) {
   });
 };
 
+/**
+ * Returns the fully qualified project name.
+ * Full name is in /projects/<projectId> form.
+ */
+Connection.prototype.fullProjectName_ = function() {
+  return util.format('/projects/{projectId}', {
+    projectId: this.id
+  });
+};
+
 // TOOD(jbd): Don't duplicate, unify this with bucket.makeReq.
 Connection.prototype.makeReq = function(method, path, q, body, callback) {
   var reqOpts = {