Add support for re-subscribing to the same subject with different message fetching parameters.

static/cosmopolite.js

@@ -52,6 +52,9 @@ var Cosmopolite = function(callbacks, urlPrefix, namespace) {
           this.loggingPrefix_(), '(re-)sending queued messages:', messages);
     }
     messages.forEach(function(message) {
+      // We don't use sendMessage because we need to preserve the first
+      // message's client_message_id, which is intentionally not exposed via
+      // the sendMessage API
       this.sendRPC_(
         'sendMessage', message, this.onMessageSent_.bind(this, message, null));
     }.bind(this));
@@ -125,12 +128,14 @@ Cosmopolite.prototype.shutdown = function() {
  */
 Cosmopolite.prototype.subscribe = function(subject, messages, last_id, keys) {
   return new Promise(function(resolve, reject) {
-    if (subject in this.subscriptions_) {
-      console.log(
-        this.loggingPrefix_(),
-        'not sending duplicate subscription request for subject:', subject);
-      resolve();
+    if (!(subject in this.subscriptions_)) {
+      this.subscriptions_[subject] = {
+        'messages': [],
+        'keys':     {},
+        'state':    this.SubscriptionState.PENDING,
+      };
     }
+
     var args = {
       'subject': subject,
     };
@@ -143,15 +148,13 @@ Cosmopolite.prototype.subscribe = function(subject, messages, last_id, keys) {
     if (keys != null) {
       args['keys'] = keys;
     }
-    var subscription = {
-      'messages': [],
-      'keys':     {},
-      'state':    this.SubscriptionState.PENDING,
-    };
-    this.subscriptions_[subject] = subscription;
 
     this.sendRPC_('subscribe', args, function() {
-      subscription.state = this.SubscriptionState.ACTIVE;
+      // unsubscribe may have been called since we sent the RPC. That's racy
+      // without waiting for the promise, but do our best
+      if (subject in this.subscriptions_) {
+        this.subscriptions_[subject].state = this.SubscriptionState.ACTIVE;
+      }
       resolve();
     }.bind(this));
   }.bind(this));
@@ -619,7 +622,19 @@ Cosmopolite.prototype.onMessage_ = function(e) {
     return;
   }
   e['message'] = JSON.parse(e['message']);
-  subscription.messages.push(e);
+
+  // Reverse search for the position to insert this message, as iit will most
+  // likely be at the end.
+  var insertAfter;
+  for (var insertAfter = subscription.messages.length - 1;
+       insertAfter >= 0; insertAfter++) {
+    var message = subscription.messages[insertAfter];
+    if (message['id'] < e['message']['id']) {
+      break;
+    }
+  }
+  subscription.messages.splice(insertAfter + 1, 0, e);
+
   if (e['key']) {
     subscription.keys[e['key']] = e;
   }