Add bulk subscribe support.

static/cosmopolite.js

@@ -254,57 +254,84 @@ Cosmopolite.prototype.shutdown = function() {
  *
  * Start receiving messages sent to this subject via the onMessage callback.
  *
- * @param {Cosmopolite.typeSubjectLoose} subject
+ * @param {Cosmopolite.typeSubjectLoose|Array.<Cosmopolite.typeSubjectLoose>}
+ *     subjects
  * @param {?number=} opt_messages Number of recent messages to request;
  *     0 for none, -1 for all
  * @param {?number=} opt_lastID ID of last message received; fetch messages
  *     since
- * @return {Promise}
+ * @return {Promise|Array.<Promise>}
  */
-Cosmopolite.prototype.subscribe = function(subject, opt_messages, opt_lastID) {
-  return this.newPromise_(function(resolve, reject) {
-    /** @type {Cosmopolite.typeSubject} */
-    var canonicalSubject = this.canonicalSubject_(subject);
-    /** @type {string} */
-    var subjectString = this.subjectString_(canonicalSubject);
-    if (!(subjectString in this.subscriptions_)) {
-      this.subscriptions_[subjectString] = {
-        'subject': canonicalSubject,
-        'messages': [],
-        'pins': [],
-        'state': Cosmopolite.SubscriptionState_.PENDING
-      };
-    }
+Cosmopolite.prototype.subscribe = function(subjects, opt_messages, opt_lastID) {
+  var single = false;
 
-    var args = {
-      'subject': canonicalSubject
-    };
-    if (opt_messages) {
-      args['messages'] = opt_messages;
-    }
-    if (opt_lastID != null) {
-      args['last_id'] = opt_lastID;
-    }
+  if (!(subjects instanceof Array)) {
+    single = true;
+    subjects = [subjects];
+  }
 
-    this.sendRPC_('subscribe', args, function(response) {
+  var ret = [];
+  var rpcs = [];
+  for (var i = 0; i < subjects.length; i++) {
+    var subject = subjects[i];
+
+    ret.push(this.newPromise_(function(resolve, reject) {
+      /** @type {Cosmopolite.typeSubject} */
+      var canonicalSubject = this.canonicalSubject_(subject);
       /** @type {string} */
-      var result = response['result'];
-      if (result == 'ok') {
-        // unsubscribe may have been called since we sent the RPC. That's racy
-        // without waiting for the promise, but do our best
-        if (subjectString in this.subscriptions_) {
-          this.subscriptions_[subjectString].state =
-              Cosmopolite.SubscriptionState_.ACTIVE;
-        }
-        resolve();
-        this.trackEvent(
-            'send', 'event', 'cosmopolite', 'subscribe', subjectString);
-      } else {
-        delete this.subscriptions_[subjectString];
-        reject(new Error(result));
+      var subjectString = this.subjectString_(canonicalSubject);
+      if (!(subjectString in this.subscriptions_)) {
+        this.subscriptions_[subjectString] = {
+          'subject': canonicalSubject,
+          'messages': [],
+          'pins': [],
+          'state': Cosmopolite.SubscriptionState_.PENDING
+        };
       }
-    });
-  }.bind(this));
+
+      var args = {
+        'subject': canonicalSubject
+      };
+      if (opt_messages) {
+        args['messages'] = opt_messages;
+      }
+      if (opt_lastID != null) {
+        args['last_id'] = opt_lastID;
+      }
+
+      var onSuccess = function(response) {
+        /** @type {string} */
+        var result = response['result'];
+        if (result == 'ok') {
+          // unsubscribe may have been called since we sent the RPC. That's racy
+          // without waiting for the promise, but do our best
+          if (subjectString in this.subscriptions_) {
+            this.subscriptions_[subjectString].state =
+                Cosmopolite.SubscriptionState_.ACTIVE;
+          }
+          resolve();
+          this.trackEvent(
+              'send', 'event', 'cosmopolite', 'subscribe', subjectString);
+        } else {
+          delete this.subscriptions_[subjectString];
+          reject(new Error(result));
+        }
+      };
+      rpcs.push({
+        'command': 'subscribe',
+        'arguments': args,
+        'onSuccess': onSuccess
+      });
+    }.bind(this)));
+  }
+
+  this.sendRPCs_(rpcs);
+
+  if (single) {
+    return ret[0];
+  } else {
+    return ret;
+  }
 };