/**
 * Simulates a connection to a database by making asynchronous http requests to 
 * a remote PHP script that returns the results in JSON format.
 * Using this class can perform any operation that can be done with a database,
 * like open/close a connection or selecion/updating queries.
 **/
Db.Conn = new Class ().extend
({
	 Flag:
	{
		 NOT_NULL : 1
		,PRI_KEY  : 2
		,AI       : 512 | 2 | 1
	}
	
	,Type:
	{
		 BOOLEAN   : 1
		,INTEGER   : 3
		,DOUBLE    : 4
		,STRING    : 5
		,DATE      : 8
		,DATE_TIME : 9
	}
});

Db.Conn.implement
({
	Extends: Vn.Object

	,_connected: false
	,_requestsCount: 0

	/**
	 * Initilizes the connection object.
	 **/
	,initialize: function ()
	{
		this.parent ();
	}

	/**
	 * Opens the connection to the database.
	 *
	 * @param {string} user The user name
	 * @param {String} password The user password
	 * @param {Boolean} remember Specifies if the user should be remembered
	 * @param {Function} openCallback The function to call when operation is done
	 **/
	,open: function (user, pass, remember, callback, guest)
	{		
		this.signalEmit ('loading-changed', true);

		if (user != null)
		{
			var params = {
				 'user': user
				,'password': pass
				,'remember': remember
			};
		}
		else if (guest)
			var params = {'guest': true};

		var request = new Vn.JsonRequest ('core/login');
		request.send (params,
			this._onOpen.bind (this, callback));
	}

	/*
	 * Called when open operation is done.
	 */
	,_onOpen: function (callback, request, json, error)
	{
		this._connected = json == true;

		this.signalEmit ('loading-changed', false);
	
		if (this._connected)
			this.signalEmit ('openned');
		
		if (error)
			this.signalEmit ('error', error);
		if (callback)
			callback (this, this._connected, error);
	}

	/**
	 * Closes the connection to the database.
	 *
	 * @param {Function} callback The function to call when operation is done
	 **/
	,close: function (callback)
	{
		this.signalEmit ('loading-changed', true);

		var request = new Vn.JsonRequest ('core/logout');
		request.send (null,
			this._onClose.bind (this, callback));
	}

	/*
	 * Called when close operation is done.
	 */
	,_onClose: function (callback, request, json, error)
	{
		this._connected = false;
		this.signalEmit ('loading-changed', false);
		this.signalEmit ('closed');

		if (error)
			this.signalEmit ('error', error);
		if (callback)
			callback (this, json == true, error);
	}

	/**
	 * Runs a SQL query on the database.
	 *
	 * @param {String} sql The SQL statement
	 * @param {Function} callback The function to call when operation is done
	 **/
	,execSql: function (sql, callback)
	{
		this._requestsCount++;
		
		if (this._requestsCount === 1)
			this.signalEmit ('loading-changed', true);

		var request = new Vn.JsonRequest ('core/query');
		request.send ({'sql': sql},
			this._onExec.bind (this, callback));
	}
	
	/**
	 * Runs a stmt on the database.
	 *
	 * @param {Sql.Stmt} stmt The statement
	 * @param {Function} callback The function to call when operation is done
	 * @param {Sql.Batch} batch The batch used to set the parameters
	 **/
	,execStmt: function (stmt, callback, batch)
	{
		this.execSql (stmt.render (batch), callback);
	}

	/**
	 * Runs a query on the database.
	 *
	 * @param {String} query The SQL statement
	 * @param {Function} callback The function to call when operation is done
	 * @param {Sql.Batch} batch The batch used to set the parameters
	 **/
	,execQuery: function (query, callback, batch)
	{
		this.execStmt (new Sql.String ({query: query}), callback, batch);
	}

	/*
	 * Parses a value to date.
	 */
	,valueToDate: function (value)
	{
		return new Date (value * 1000);
	}

	/*
	 * Called when a query is executed.
	 */
	,_onExec: function (callback, request, json, error)
	{
		this._requestsCount--;
		
		if (this._requestsCount === 0)
			this.signalEmit ('loading-changed', false);

		if (json)
		try {
			if (json && json instanceof Array)
			for (var i = 0; i < json.length; i++)
			if (json[i] !== true)
			{
				var data = json[i].data;
				var columns = json[i].columns;

				for (var j = 0; j < columns.length; j++)
				{
					var castFunc = null;
			
					switch (columns[j].type)
					{
						case Db.Conn.Type.DATE:
						case Db.Conn.Type.DATE_TIME:
						case Db.Conn.Type.TIMESTAMP:
							castFunc = this.valueToDate;
							break;
					}
			
					if (castFunc !== null)
					{
						if (columns[j].def != null)
							columns[j].def = castFunc (columns[j].def);

						for (var k = 0; k < data.length; k++)
							if (data[k][j] != null)
								data[k][j] = castFunc (data[k][j]);
					}
				}
			}
		}
		catch (e)
		{
			error = e;
		}

		if (error)
			this.signalEmit ('error', error);

		if (callback)
		try {
			callback (new Db.ResultSet (json, error));
		}
		catch (e)
		{
			this.signalEmit ('error', e);
		}
	}
});