export default class ClientDriver{

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

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

	}


	/* (1) Creates a client driver
	*
	* @_resource<String>				Target resource (typically an URL)
	* @_auth<mixed>						Authentication data (depends on Driver implementation)
	*
	---------------------------------------------------------*/
	constructor(_resource, _auth={}){

		/* (1) Initialize driver
		---------------------------------------------------------*/
		/* (1) Default attributes values */
		this.force_close = false;
		this.state       = ClientDriver.STATE.READY;
		this.stack       = [];
		this.error       = false;

		/* (2) Default User callbacks */
		this.callback = {
			onconnected: function(){},
			onclose:     function(){},
			onreceive:   function(){}
		};

		this.event = {

			/* (3) Manage connection opened */
			onconnected: function(){

				// update state
				this.state = ClientDriver.STATE.CONNECTED;

				// call callback
				this.callback.onconnected();

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

			}.bind(this),

			/* (4) Manage connection closed */
			onclose: function(){

				// if called close() -> CLOSED
				if( this.force_close )
					this.state = ClientDriver.STATE.CLOSED;

				// else set state back to READY
				else
					this.state = ClientDriver.STATE.READY;

				// call callback
				this.callback.onclose();

			}.bind(this),

			/* (5) Manage response received */
			onreceive: function(_response){

				// set state from TRANSFERING to CONNECTED
				this.state = ClientDriver.STATE.CONNECTED;

				// call callback
				this.callback.onreceive(_response);

			}.bind(this)

		};

		/* (2) Manage errors
		---------------------------------------------------------*/
		/* (1) Fail: invalid _resource */
		if( typeof _resource !== 'string' )
			return ( this.error = true );

		/* (2) Set explicit attributes */
		this.resource = _resource;
		this.auth     = _auth;

		return;

	}



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

		/* (1) force_close -> fail */
		if( this.force_close )
			return false;

		/* (2) Fail: not READY */
		if( this.state !== ClientDriver.STATE.READY )
			return false;

		/* (3) Update state */
		this.state = ClientDriver.STATE.CONNECTING;

		/* (4) Child dispatch */
		return true;

	}


	/* (3) Closes the connection
	*
	* @return closed<boolean>			Whether the connection has been closed
	*
	---------------------------------------------------------*/
	close(){

		/* (1) set force_close */
		this.force_close = true;

		/* (2) Update state */
		this.state = ClientDriver.STATE.CLOSED;

		/* (4) Child dispatch */
		return true;

	}


	/* (4) Send request
	*
	* @_request<Object>					Request data
	*
	* @return sent<boolean>				Whether the request has been successful
	*
	---------------------------------------------------------*/
	send(_request){

		/* (1) force_close -> fail */
		if( this.force_close )
			return false;

		/* (2) bufferise 'state' */
		let state = this.state;

		/* (3) Fail: invalid _request */
		if( !(_request instanceof Object) )
			return false;

		/* (4) CLOSED -> abort */
		if( state === ClientDriver.STATE.CLOSED )
			return false;

		/* (5) READY -> stack message + bind() [in case connection failed)] */
		if( state === ClientDriver.STATE.READY )
			return ( this.stack.push(_request) > -1 ) && this.bind();

		/* (6) CONNECTING -> stack message */
		if( state === ClientDriver.STATE.CONNECTING )
			return ( this.stack.push(_request) > -1 );

		/* (7) update state */
		this.state = ClientDriver.STATE.TRANFERING;

		/* (8) Child dispatch */
		return true;

	}


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

		/* (1) Fail: invalid _callback */
		if( !(_callback instanceof Function) )
			return false;

		/* (2) Register _callback */
		this.callback.onconnected = _callback;

		/* (3) By default return success */
		return true;

	}


	/* (6) Bind event to connection closed
	*
	* @_callback<Function>				Callback launched when connection is closed
	*
	* @return bound<boolean>			Whether the callback has successfully been bound
	*
	---------------------------------------------------------*/
	set onclose(_callback){

		/* (1) Fail: invalid _callback */
		if( !(_callback instanceof Function) )
			return false;

		/* (2) Register _callback */
		this.callback.onclose = _callback;

		/* (3) By default return success */
		return true;

	}


	/* (7) Bind event to message reception
	*
	* @_callback<Function>				Callback launched when a message is received
	*
	* @return bound<boolean>			Whether the callback has successfully been bound
	*
	---------------------------------------------------------*/
	set onreceive(_callback){

		/* (1) Fail: invalid _callback */
		if( !(_callback instanceof Function) )
			return false;

		/* (2) Register _callback */
		this.callback.onreceive = _callback;

		/* (3) By default return success */
		return true;

	}



}