/**
 * Handler for JSON rest requests.
 **/
Vn.JsonRequest = new Class
({
	initialize: function (methodName)
	{
		this._methodName = methodName;
	}

	,sendWithUrl: function (params, callback, method, url)
	{
		var request = new XMLHttpRequest ();
		request.open (method, url, true);
		request.setRequestHeader ('Content-Type',
			'application/x-www-form-urlencoded');
		request.onreadystatechange =
			this._onStateChange.bind (this, request, callback);
		request.send (Vn.Url.makeUri (params));
	}

	,send: function (params, callback)
	{
		if (!params)
			params = {};
	
		params['srv'] = 'json:'+ this._methodName;
		this.sendWithUrl (params, callback, 'post', '.');
	}
	
	,sendForm: function (form, callback)
	{
		var params = {};
		var elements = form.elements;

		for (var i = 0; i < elements.length; i++)
		if (elements[i].name)
			params[elements[i].name] = elements[i].value;

		this.sendWithUrl (params, callback, 'post', form.action);
	}
	
	,sendFormMultipart: function (form, callback)
	{
		var request = new XMLHttpRequest ();
		request.open ('post', form.action, true);
		request.onreadystatechange =
			this._onStateChange.bind (this, request, callback);
		request.send (new FormData (form));
	}
	
	,_onStateChange: function (request, callback)
	{
		if (request.readyState !== 4)
			return;

		var data = null;
		var error = null;

		try {		
			if (request.status == 0)
			{
				var ex = new Vn.JsonException ();
				ex.message = _('The server does not respond');
				throw ex;
			}
		
			var contentType = null;
			
			try {
				contentType = request
					.getResponseHeader ('Content-Type')
					.split (';')[0]
					.trim ();
			}
			catch (e) {}
				
			if (contentType != 'application/json')
			{
				var ex = new Vn.JsonException ();
				ex.message = request.statusText;
				ex.code = request.status;
				throw ex;
			}
		
			var json = JSON.parse (request.responseText);
			var jsData = json.data;
			var jsWarns = json.warnings;
	
			if (request.status == 200)
			{
				data = jsData;
			}
			else
			{
				var ex = new Vn.JsonException ();
				ex.exception = jsData.exception;
				ex.message = jsData.message;
				ex.code = jsData.code;
				ex.file = jsData.file;
				ex.line = jsData.line;
				ex.trace = jsData.trace;
				throw ex;
			}
		}
		catch (e)
		{
			data = null;
			error = e;
		}

		if (callback)
			callback (this, data, error);
	}
});