export class ClientDriver{

	/* (0) Constants & Enums
	---------------------------------------------------------*/
	static get STATE(){

		return Object.freeze({
			OPENING:    0,
			OPENED:     1,
			CONNECTING: 2,
			CONNECTED:  3,
			CLOSED:     4
		});

	}


	/* (1) Creates a client driver
	*
	* @_resource<String>				Target resource (typically an URL)
	*
	---------------------------------------------------------*/
	constructor(_resource){

		/* (1) Default attributes values */
		this.error = false;
		this.state = ClientDriver.STATE.OPENING;
		this.stack = [];
		this.callback = {
			onready:   function(){},
			onclose:   function(){},
			onreceive: function(){}
		};

		/* (2) Fail: invalid _resource */
		if( typeof _resource !== 'string' )
			return ( this.error = true );

		/* (3) Set explicit attributes */
		this.resource = _resource;

		return;
	}


	/* (2) Binds the client to the resource
	*
	* @return bound<boolean>			Whether the binding has been successful
	*
	---------------------------------------------------------*/
	bind(){

		/* (1) Fail: not OPENING OR error */
		if( this.error || this.state !== ClientDriver.STATE.OPENING )
			return false;

		/* (2) By default return success */
		return true;

	}


	/* (3) Send request
	*
	* @_request<Object>					Request data
	*
	* @return sent<boolean>				Whether the request has been successful
	*
	---------------------------------------------------------*/
	send(_request){

		/* (1) Fail: if error */
		if( this.error )
			return false;

		/* (2) Fail: invalid _request */
		if( !(_request instanceof Object) )
			return false;

		/* (3) If not already connected -> stack request */
		if( this.state < ClientDriver.STATE.CONNECTED ){

			this.stack.push(_request);
			return false;

		}


		/* (4) By default return success */
		return true;

	}


	/* (4) Bind event to connection opened
	*
	* @_callback<Function>				Callback launched when connection is opened
	*
	* @return bound<boolean>			Whether the callback has successfully been bound
	*
	---------------------------------------------------------*/
	onready(_callback){

		/* (1) Fail: already CONNECTED OR error */
		if( this.error || this.state >= ClientDriver.STATE.CONNECTED )
			return false;

		/* (2) Fail: invalid _callback */
		if( !(_callback instanceof Function) )
			return false;

		/* (3) Register _callback */
		this.callback.onready = function(cback){

			// call callback
			cback();

			// if request(s) in stack -> pop & send them
			while( this.stack.length > 0 )
				this.send(this.stack.shift());

		}.bind(this, _callback);

		/* (5) By default return success */
		return true;

	}


	/* (5) Bind event to connection closed
	*
	* @_callback<Function>				Callback launched when connection is closed
	*
	* @return bound<boolean>			Whether the callback has successfully been bound
	*
	---------------------------------------------------------*/
	onclose(_callback){

		/* (1) Fail: already CLOSED OR error */
		if( this.error || this.state === ClientDriver.STATE.CLOSED )
			return false;

		/* (2) Fail: invalid _callback */
		if( !(_callback instanceof Function) )
			return false;

		/* (3) Register _callback */
		this.callback.onclose = _callback;

		/* (4) By default return success */
		return true;

	}


	/* (6) Bind event to message reception
	*
	* @_callback<Function>				Callback launched when a message is received
	*
	* @return bound<boolean>			Whether the callback has successfully been bound
	*
	---------------------------------------------------------*/
	onreceive(_callback){

		/* (1) Fail: already CONNECTED OR error */
		if( this.error || this.state >= ClientDriver.STATE.CONNECTED )
			return false;

		/* (2) Fail: invalid _callback */
		if( !(_callback instanceof Function) )
			return false;

		/* (3) Register _callback */
		this.callback.onreceive = _callback;

		/* (4) By default return success */
		return true;

	}



}