/* classe API */
export class APIClient{



	/* (1) Constructs an API client manager
	*
	* @_hostname<String>				Server hostname (without http, port number, etc)
	* @_baseuri<String>						Server base URI
	* @_ssl<bool>						[OPT] Whether SSL is activated (http vs https) (default: https)
	* @_port<int>						[OPT] optional HTTP port (default: none)
	*
	* @return http_url<String>			Built http_url
	*
	---------------------------------------------------------*/
	constructor(_hostname, _baseuri, _ssl=true, _port=null){

		/* (1) Build URL parts */
		this.http_parts = {

			ssl:      _ssl === true,
			hostname: _hostname,
			baseuri:  this.fix_uri(_baseuri),
			port:     !isNaN(_port) ? _port:  null

		};

		this.xhr_stack = [];   // Ajax request stack
		this.buffer    = null; // Last request buffer

	}


	fix_uri(_uri){

		if( typeof _uri !== 'string' )
			return '';

		return _uri.split('/').filter((r) => r.trim().length).join('/')

	}


	/* (2) HTTP url dynamic getter
	*
	* @_uri<String>						[OPT] optional URI string
	* @_token<String>					[OPT] optional HTTP token
	*
	* @return http_url<String>			Built http_url
	*
	---------------------------------------------------------*/
	build_url(_uri, _token=null){

		/* (1) Initialize URL buffer */
		let bufurl = 'http';

		/* (2) Manage @ssl */
		this.http_parts.ssl && ( bufurl = bufurl.concat('s') );
		bufurl = bufurl.concat('://');

		/* (3) Manage token */
		( typeof _token === 'string' ) && ( bufurl = bufurl.concat(`${_token}@`) );

		/* (4) Manage hostname */
		bufurl = bufurl.concat(this.http_parts.hostname);

		/* (5) Manage port */
		( this.http_parts.port !== null ) && ( bufurl = bufurl.concat(`:${this.http_parts.port}`) );

		/* (6) Base uri */
		bufurl = bufurl.concat(`/${this.http_parts.baseuri}/`);

		/* (7) Manage URI */
		bufurl = bufurl.concat( this.fix_uri(_uri) );

		return bufurl;

	}



	/* Server Transaction
	*
	* @param _path<String>				target path (format "HTTP_METHOD uri/uri/uri")
	* @param _args<Object>				formdata object (as raw object)
	* @param _callback<Function>		Response callback
	* @param _token<String>				[OPT] http token
	*
	***************************************************************************************************
	*
	* @usecase
	*	1.		api.call(
	*	2.			'PUT newspaper/article/4'
	*	3.			{ content: "new content" },
	*	4.			(r) => alert(r.error),
	*	5.			'sometoken'
	*	6.		);
	*
	*/
	call(_path, _args, _callback, _token=null){


		/* (1) Argument management
		---------------------------------------------------------*/
		/* (1) Set default callback if @callback not callable */
		if( !(_callback instanceof Function) )
			_callback = function(r){ console.warn('The API callback function is missing, default callback set.', 'Response', r); };

		/* (2) Check @path format */
		if( !/^([A-Z]+) (.+)/i.test(_path) ){
			_callback({ error: -1 });
			return false;
		}

		var http_method = RegExp.$1;
		var http_uri    = RegExp.$2;

		/* (3) Default @_token */
		if( typeof _token !== 'string' )
			_token = null;




		/* (3) Create form data
		---------------------------------------------------------*/
		/* (1) Create virtual form */
		var form_data = new FormData();

		/* (2) Add attributes */
		for( var key in _args ){

			// {2.1} If a file -> send as it //
			if( _args[key] instanceof File )
				form_data.append(key, _args[key]);

			// {2.2} Else -> JSON stringify //
			else
				form_data.append(key, JSON.stringify(_args[key]));

		}



		/* (4) Create XHR request
		---------------------------------------------------------*/
		/* (1) Clean ended requests */
		for( var i = this.xhr_stack.length-1 ; i >= 0 ; i-- ){

			if( this.xhr_stack[i] != null )
				break;

			this.xhr_stack.pop();

		}

		/* (2) Push a new entry -> fetch its index */
		i = this.xhr_stack.push(null) - 1;

		/* (3) Create XHR object */
		this.xhr_stack[i] = (window.XMLHttpRequest) ? new XMLHttpRequest() : new ActiveXObject('Microsoft.XMLHttpRequest');



		/* (5) Bind response event
		---------------------------------------------------------*/
		this.xhr_stack[i].onreadystatechange = function(i, parent){

			/* (1) If request over */
			if( this[i].readyState === 4 ){

				/* (2) Update buffer (for debug) */
				parent.buffer = this[i].responseText;

				/* (3) If request success */
				if( [0, 200].indexOf(this[i].status) > -1 ){


					/* (3.1) Create default response (if JSON error) */
					var response = { error: -2 };

					/* (3.2) Try to parse JSON */
					try{ response = JSON.parse(this[i].responseText); }catch(e){}

					/* (3.3) Launch @_callback with response */
					_callback(response);

				/* (4) If request error */
				}else
					_callback({ error: -3 });

				/* (5) Notify current xhr instance is done */
				this[i] = null;

			}

		}.bind(this.xhr_stack, i, this);


		/* (6) Finish & send request
		---------------------------------------------------------*/
		/* (1) Open the XHR */
		console.log(http_method, this.build_url(http_uri, _token));
		this.xhr_stack[i].open(http_method, this.build_url(http_uri, _token), true);

		/* (2) Custom header to notify we're using Ajax */
		this.xhr_stack[i].setRequestHeader('X-Requested-With', 'XMLHttpRequest');

		/* (3) Make the call */
		this.xhr_stack[i].send(form_data);

		return true;

	}


}