package flare.query
{	
	/**
	 * Expression operator that performs function invocation. The set of
	 * available functions is determined by a static function table maintained
	 * by this class. The function table can be extended to introduce custom
	 * functions into the query language.
	 */
	public class Fn extends CompositeExpression
	{
		private var _name:String;
		private var _func:Function;
		private var _args:Array;
		
		/**
		 * Creates a new Fn (function) operator.
		 * @param name the name of the function. This should map to an entry
		 *  in the static function table.
		 * @params args sub-expressions for the function arguments
		 */
		public function Fn(name:String=null, ...args) {
			if(name)this.name = name;
			super(args);
		}
		
		/**
		 * Sets the name of the function. This should map to an entry
		 *  in the static function table.
		 */
		public function set name(n:String):void{
			_name = n.toUpperCase();
			_func = table[_name];
		}
		
		/**
		 * @inheritDoc
		 */
		public override function clone():Expression
		{
			return new Fn(_name, _children);
		}
		
		/**
		 * @inheritDoc
		 */
		public override function eval(o:Object=null):*
		{
			// first, initialize the argument array as needed
			if (_args == null || _args.length != _children.length) {
				_args = new Array(_children.length);
			}
			// now evaluate all sub-expressions
			for (var i:int=0; i<_children.length; ++i) {
				_args[i] = _children[i].eval(o);
			}
			// now evaluate the function
			return _func.apply(null, _args);
		}
		
		/**
		 * @inheritDoc
		 */
		public override function toString():String
		{
			return _name + getString();
		}
		
		// --------------------------------------------------------------------
		
		/** 
		 * Function table mapping function names to Function instances.
		 * Functions can be added or removed at run-time by editing this
		 * object.
		 */
		public static var table:Object = {
			// Math Functions
			ABS:		Math.abs,
			ACOS:		Math.acos,
			ASIN:		Math.asin,
			ATAN:		Math.atan,
			ATAN2:		Math.atan2,
			CEIL:		Math.ceil,
			CEILING:	Math.ceil,
			COS:		Math.cos,
			EXP:		Math.exp,
			FLOOR:		Math.floor,
			LOG:		Math.log,
			MAX:		Math.max,
			MIN:		Math.min,
			POW:		Math.pow,
			POWER:		Math.pow,
			RANDOM:		Math.random,
			ROUND:		Math.round,
			SIN:		Math.sin,
			SQRT:		Math.sqrt,
			TAN:		Math.tan,
			
			// String Functions
			CONCAT:		StringUtil.concat,
			CONCAT_WS:	StringUtil.concat_ws,
			FORMAT:		StringUtil.format,
			INSERT:		StringUtil.insert,
			LEFT:		StringUtil.left,
			LENGTH:		StringUtil.length,
			LOWER:		StringUtil.lower,
			LCASE:		StringUtil.lower,
			LPAD:		StringUtil.lpad,
			MID:		StringUtil.substring,
			POSITION:	StringUtil.position,
			REVERSE:	StringUtil.reverse,
			REPEAT:		StringUtil.repeat,
			REPLACE:	StringUtil.replace,
			RIGHT:		StringUtil.right,
			RPAD:		StringUtil.rpad,
			SPACE:		StringUtil.space,
			SUBSTRING:	StringUtil.substring,
			UPPER:		StringUtil.upper,
			UCASE:		StringUtil.upper,
			
			// Date/Time Functions
			DATE:		DateUtil.date,
			DAY:		DateUtil.day,
			DAYOFWEEK:	DateUtil.dayOfWeek,
			HOUR:		DateUtil.hour,
			MICROSECOND:DateUtil.microsecond,
			MINUTE:		DateUtil.minute,
			MONTH:		DateUtil.month,
			NOW:		DateUtil.now,
			SECOND:		DateUtil.second,
			YEAR:		DateUtil.year
		};
		
	} // end of class Fn
}