client/events: improve event dispatching

This commit introduces timer-less retry system:

1. Any change to URL is going to stop listening to any messages.
2. If a message is sent and there's no handler that could pick it up,
   the message gets enqueued.
3. The message is sent again to the first handler that attaches itself
   to given event type.

While in theory this is full of holes (no control over the first
handler), in practice, it works quite well.

Additionally, views.listenToMessages was attaching to completely wrong
DOM node; this commit fixes this as well.

1 files changed, 27 insertions, 13 deletions

diff --git a/client/js/events.js b/client/js/events.js
index 0493c3b..0dd010a 100644
--- a/client/js/events.js
+++ b/client/js/events.js
@@ -1,34 +1,48 @@
 'use strict';
 
-let listeners = [];
+let pendingMessages = new Map();
+let listeners = new Map();
 
 function unlisten(messageClass) {
-    listeners[messageClass] = [];
+    listeners.set(messageClass, []);
 }
 
 function listen(messageClass, handler) {
-    if (!(messageClass in listeners)) {
-        listeners[messageClass] = [];
+    if (pendingMessages.has(messageClass)) {
+        let newPendingMessages = [];
+        for (let message of pendingMessages.get(messageClass)) {
+            if (!handler(message)) {
+                newPendingMessages.push(message);
+            }
+        }
+        pendingMessages.set(messageClass, newPendingMessages);
     }
-    listeners[messageClass].push(handler);
+    if (!listeners.has(messageClass)) {
+        listeners.set(messageClass, []);
+    }
+    listeners.get(messageClass).push(handler);
 }
 
 function notify(messageClass, message) {
-    if (!(messageClass in listeners)) {
+    if (!listeners.has(messageClass) || !listeners.get(messageClass).length) {
+        if (!pendingMessages.has(messageClass)) {
+            pendingMessages.set(messageClass, []);
+        }
+        pendingMessages.get(messageClass).push(message);
         return;
     }
-    for (let handler of listeners[messageClass]) {
+    for (let handler of listeners.get(messageClass)) {
         handler(message);
     }
 }
 
 module.exports = {
-    Success: 1,
-    Error: 2,
-    Info: 3,
-    Authentication: 4,
-    SettingsChange: 5,
-    TagsChange: 6,
+    Success: 'success',
+    Error: 'error',
+    Info: 'info',
+    Authentication: 'auth',
+    SettingsChange: 'settings-change',
+    TagsChange: 'tags-change',
 
     notify: notify,
     listen: listen,