/* classe client WebSocket */
class WSClient{

	/* (1) Constructor
	*
	* @server_url<String>				The url of the desired server
	* @channel_uri<String>				The url of the desired channel
	*
	---------------------------------------------------------*/
	constructor(server_url, channel_uri){

		/* (1) Store & create data
		---------------------------------------------------------*/
		/* (1) Store the arguments */
		this.server_url  = server_url;
		this.channel_uri = channel_uri;

		/* (2) Initialise event data */
		this.is_opened = false; // Set to TRUE when connection opened
		this.pending   = null;  // Next message to send through connection
		this.handler   = [];    // On reveice handlers

		/* (3) Create the websocket connection */
		this.ws = new WebSocket(this.server_url+'/'+channel_uri);


		/* (2) Bind events
		---------------------------------------------------------*/
		/* (1) OPEN: when connection is established */
		this.ws.onopen = this._onopen.bind(this);

		/* (2) MESSAGE: when message received */
		this.ws.onmessage = this._onmessage.bind(this);

		/* (3) ERROR: when websocket error */
		this.ws.onerror = this._onerror.bind(this);

		/* (4) CLOSE: when websocket closes */
		this.ws.onclose = this._onclose.bind(this);

	}


	/* (2) Binds a handle to the onReceive event (global only)
	*
	* @callback<Function>				Callback function(message, error)
	*
	---------------------------------------------------------*/
	listen(callback){

		/* (1) Check @callback type (default value) */
		if( !(callback instanceof Function) )
			throw new Error('WSClient.bind(callback) expected argument *callback* to be a function');

		/* (2) Store callback */
		this.on_receive = callback;

		return this;

	}


	/* (3) Sends a message through the socket
	*
	* @message<String>					The data to send
	* 		  <Object>					The data to send (will be serialized)
	*
	---------------------------------------------------------*/
	send(message){

		/* (1) Manage arguments
		---------------------------------------------------------*/
		/* (2) Check @message type */
		if( typeof message != 'string' && typeof message != 'object' ){
			this.on_receive(null, 'wrong message type');
			return this;
		}

		/* (2) Stringify JSON if object */
		if( typeof message == 'object' )
			message = JSON.stringify(message);


		/* (2) Send process
		---------------------------------------------------------*/
		/* (1) If not opened -> store message (will send when onopen()) */
		if( !this.is_opened )
			this.pending = message;

		/* (2) If already opened -> send now */
		else
			this.ws.send(message);

		return this;

	}


	/* (4) PRIVATE: Open handler
	*
	---------------------------------------------------------*/
	_onopen(){

		/* (1) Set @is_opened status variable */
		this.is_opened = true;

		/* (2) If message pending */
		if( this.pending != null ){

			this.ws.send(this.pending); // send message
			this.pending = null;        // reset message (optional)

		}

	}


	/* (5) PRIVATE: Receive handler
	*
	---------------------------------------------------------*/
	_onmessage(msg_event){

		/* (1) If not trusted -> error */
		if( !msg_event.isTrusted ){
			this.on_receive(null, 'not trusted');
			return;
		}

		/* (2) If wrong origin -> error */
		if( msg_event.origin != this.server_url ){
			this.on_receive(null, 'unknown origin');
			return;
		}

		/* (3) If not for this channel -> exit */
		if( msg_event.target.url != this.server_url+'/'+this.channel_uri )
			return;

		/* (3) Try to JSON parse */
		var parsedMsg = null;
		try{

			parsedMsg = JSON.parse(msg_event.data);

		}catch(e){
			this.on_receive(null, 'JSON error');
			return;
		}

		/* (4) If all right -> success */
		this.on_receive(parsedMsg, null);

	}


	/* (6) PRIVATE: Error handler
	*
	---------------------------------------------------------*/
	_onerror(){

		/* (1) Remove other handlers (only 1 error) */
		this.ws.onmessage = null;
		this.ws.onclose   = null;

		/* (2) Send error */
		this.on_receive(null, 'websocket error');

	}


	/* (7) PRIVATE: Close handler
	*
	---------------------------------------------------------*/
	_onclose(){

		/* (1) Remove onmessage (not to catch messages) */
		this.ws.onmessage = null;

		/* (2) Send end */
		this.on_receive(null, 'websocket closed');

	}

}




class WSClientBuilder{

	/* (1) Constructor
	*
	* @server_url<String>				The url of the desired server
	*
	---------------------------------------------------------*/
	constructor(server_url){
		/* (1) Store the server url */
		this.server_url = server_url;
	}


	/* (2) Builds a WSClient with desired channel
	*
	* @channel_uri<String>				The uri of the desired channel
	*
	---------------------------------------------------------*/
	channel(channel_uri=''){
		return new WSClient(this.server_url, channel_uri);
	}

}




export{ WSClient, WSClientBuilder }