From ceca822f974086eab7e927d78079012305386433 Mon Sep 17 00:00:00 2001
From: binaryDiv <binarydiv@gmail.com>
Date: Sun, 20 Jan 2019 21:12:41 +0100
Subject: [PATCH] Client: Implement event system (#4)

---
 public_html/index.html   |  1 +
 public_html/js/client.js | 28 ++++++++++++++++++++-------
 public_html/js/events.js | 42 ++++++++++++++++++++++++++++++++++++++++
 public_html/js/ui.js     | 17 ++++++++++++++++
 4 files changed, 81 insertions(+), 7 deletions(-)
 create mode 100644 public_html/js/events.js

diff --git a/public_html/index.html b/public_html/index.html
index 0c9aec9..743795d 100644
--- a/public_html/index.html
+++ b/public_html/index.html
@@ -12,6 +12,7 @@
 <h1>InstantChat</h1>
 
 <script src="js/settings.js"></script>
+<script src="js/events.js"></script>
 <script src="js/client.js"></script>
 <script src="js/ui.js"></script>
 
diff --git a/public_html/js/client.js b/public_html/js/client.js
index 5b90372..51b6869 100644
--- a/public_html/js/client.js
+++ b/public_html/js/client.js
@@ -1,7 +1,18 @@
 "use strict";
 
-class Client {
+/**
+ * Client class that implements the InstantChat protocol using WebSockets.
+ *
+ * Dispatches the following events which can be subscribed/unsubscribed using .on() and .off():
+ *   - initialized:      Connection to server has been established and initialized, ready to send messages.
+ *   - disconnected:     Connection has been closed.
+ *   - connectionError:  Some connection error occurred.
+ *   - receivedMessage:  Chat message has been received. Data: object {from: 'username', text: 'text'}
+ */
+class Client extends EventDispatcher {
 	constructor(wsUri) {
+		super();
+
 		this.wsUri = wsUri;
 
 		// Create WebSocket and set internal callbacks
@@ -16,17 +27,17 @@ class Client {
 	// Internal WebSocket event handlers
 	_onSocketOpen(evt) {
 		console.log("Connected to " + this.wsUri);
-
-		// Send init command containing chat ID and nickname
 		this.sendInit();
 	}
 
 	_onSocketClose(evt) {
 		console.log("Connection closed (code " + evt.code + ").");
+		this.dispatch("disconnected");
 	}
 
 	_onSocketError(evt) {
 		console.error("Connection error: ", evt);
+		this.dispatch("connectionError");
 	}
 
 	_onSocketMessage(evt) {
@@ -76,16 +87,19 @@ class Client {
 			const msg = JSON.parse(msgString);
 
 			switch (msg.type) {
-				// Response to "init" command
+				// Response to 'init' command (doesn't have much content, I guess)
 				case "init":
-					// TODO
 					console.log("Got init response: ", msg);
+					this.dispatch("initialized");
 					break;
 
 				// Incoming chat message
 				case "message":
-					// TODO
-					console.log("Got message event: from '" + msg.from + "', text '" + msg.text + "'");
+					console.log("Received chat message from '" + msg.from + "', text '" + msg.text + "'");
+					this.dispatch("receivedMessage", {
+						from: msg.from,
+						text: msg.text,
+					});
 					break;
 
 				// TODO Topic change, user join/leave, error, ...
diff --git a/public_html/js/events.js b/public_html/js/events.js
new file mode 100644
index 0000000..7662ff7
--- /dev/null
+++ b/public_html/js/events.js
@@ -0,0 +1,42 @@
+"use strict";
+
+/**
+ * Base class to implement an event system in any class. Events can be dispatched and
+ * subscribed/unsubscribed. Events can have multiple registered callbacks.
+ */
+class EventDispatcher {
+    constructor() {
+        this._events = {};
+    }
+
+    /**
+     * Dispatch a named event. Calls all callbacks that are subscribed to this event.
+     */
+    dispatch(eventName, data = null) {
+        if (this._events[eventName]) {
+            this._events[eventName].forEach((callback) => {
+                callback(data);
+            });
+        }
+    }
+
+    /**
+     * Subscribe to an event.
+     */
+    on(eventName, callback) {
+        if (!this._events[eventName]) {
+            this._events[eventName] = [];
+        }
+        this._events[eventName].push(callback);
+    }
+
+    /**
+     * Unsubscribe from an event. Not sure how to unsubscribe anonymous functions though.
+     * If callback is not found, nothing happens.
+     */
+    off(eventName, callback) {
+        if (this._events[eventName]) {
+            this._events[eventName] = this._events[eventName].filter(item => item !== callback);
+        }
+    }
+}
diff --git a/public_html/js/ui.js b/public_html/js/ui.js
index 1afd0d0..5411255 100644
--- a/public_html/js/ui.js
+++ b/public_html/js/ui.js
@@ -7,4 +7,21 @@ let client;
 (function() {
 	const wsUri = AppSettings.serverWsUri;
 	client = new Client(wsUri);
+
+    // Test events
+    client.on("initialized", () => {
+        console.log("UI: Connection initialized!");
+
+        // Send a test message
+        client.sendChatMessage("Meow meow! :3");
+    });
+    client.on("disconnected", () => {
+        console.log("UI: Connection closed!");
+    });
+    client.on("connectionError", () => {
+        console.log("UI: Connection error! :()");
+    });
+    client.on("receivedMessage", (msg) => {
+        console.log("UI: Message from '" + msg.from + "', text: '" + msg.text + "'");
+    });
 })();