/**
 * 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)
	{
		var url = 'rest.php?method='+ encodeURIComponent (this._methodName);
		this.sendWithUrl (params, callback, 'post', url);
	}
	
	,_onStateChange: function (request, callback)
	{
		if (request.readyState !== 4)
			return;

		var jsData = null;
		var error = null;

		try {
			if (request.status !== 200)
				throw new Error (request.statusText);

			var json = JSON.parse (request.responseText);
			var jsData = json.data;
			var jsError = json.error;

			if (jsError)
				throw new Vn.Error (
					jsError.domain,
					jsError.code,
					jsError.message);
		}
		catch (e)
		{
			jsData = null;
			error = e;
		}

		if (callback)
			callback (this, jsData, error);
	}
	
	,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, form.method, form.action);
	}
});