"use strict";

/**
 * 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, chatID, nickname) {
		super();

		this.wsUri = wsUri;
		this.chatID = chatID;
		this.nickname = nickname;

		// Create WebSocket and set internal callbacks
		console.log("Initialize Client...")
		this.webSocket = new WebSocket(wsUri);
		this.webSocket.onopen = this._onSocketOpen.bind(this);
		this.webSocket.onclose = this._onSocketClose.bind(this);
		this.webSocket.onerror = this._onSocketError.bind(this);
		this.webSocket.onmessage = this._onSocketMessage.bind(this);
	}

	// Internal WebSocket event handlers
	_onSocketOpen(evt) {
		console.log("Connected to " + this.wsUri);
		this.sendInit(this.chatID, this.nickname);
	}

	_onSocketClose(evt) {
		console.log("Connection closed (code " + evt.code + ").");
		this.dispatch("disconnected");
	}

	_onSocketError(evt) {
		console.error("Connection error: ", evt);
		this.dispatch("connectionError");
	}

	_onSocketMessage(evt) {
		console.log("Received: " + evt.data);
		this._parseMessage(evt.data);
	}

	/**
	 * Sends an arbitrary command as JSON.
	 *
	 * commandObj: The command as an object ('action' specifies type of command).
	 */
	sendCommand(commandObj) {
		const commandJson = JSON.stringify(commandObj);
		console.log("Sending command: " + commandJson);
		this.webSocket.send(commandJson);
	}

	/**
	 * Sends the 'init' command which sets up the session. Also sets the chat ID and nickname.
	 *
	 * chatID: The ID of the chat instance.
	 * nickname: The user's nickname.
	 */
	sendInit(chatID, nickname) {
		this.sendCommand({
			action: "init",
			chat_id: chatID,
			nickname: nickname,
		});
	}

	/**
	 * Sends the 'message' command which sends a chat message to the chat.
	 *
	 * msgText: The text of the chat message.
	 */
	sendChatMessage(msgText) {
		this.sendCommand({
			action: "message",
			text: msgText,
		});
	}

	/**
	 * Parses an incoming JSON message and dispatches specific events.
	 *
	 * msgText: The content of the message as a JSON string.
	 */
	_parseMessage(msgString) {
		try {
			const msg = JSON.parse(msgString);

			switch (msg.type) {
				// Response to 'init' command (doesn't have much content, I guess)
				case "init":
					console.log("Got init response: ", msg);
					this.dispatch("initialized");
					break;

				// Incoming chat message
				case "message":
					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, ...

				default:
					console.error("Unknown message type '" + msg.type + "'");
			}
		}
		catch (e) {
			console.error("Error parsing message JSON: " + e.message);
		}
	}
}