package
{
	// Import built-in classes for use.
	import flash.events.*;
	import flash.display.Stage;
	
	public class Keys
	{
		// Common.
		public static const shift :Number	= 16;
		public static const ctrl :Number	= 17;
		public static const space :Number	= 32;

		// Arrow keys.
		public static const left :Number	= 37;
		public static const up :Number 	= 38;
		public static const right :Number	= 39;
		public static const down :Number	= 40;

		// Numpad keys.
		public static const num0 :Number	= 96;
		public static const num1 :Number	= 97;
		public static const num2 :Number	= 98;
		public static const num3 :Number	= 99;
		public static const num4 :Number	= 100;
		public static const num5 :Number	= 101;
		public static const num6 :Number	= 102;
		public static const num7 :Number	= 103;
		public static const num8 :Number	= 104;
		public static const num9 :Number	= 105;
		public static const num_mul :Number	= 106;
		public static const num_add :Number	= 107;
		public static const num_sub :Number	= 109;
		public static const num_dec :Number	= 110;
		public static const num_div :Number	= 111;

		// Letter keys.
		public static const A :Number	= 65;
		public static const B :Number	= 66;
		public static const C :Number	= 67;
		public static const D :Number	= 68;
		public static const E :Number	= 69;
		public static const F :Number	= 70;
		public static const G :Number	= 71;
		public static const H :Number	= 72;
		public static const I :Number	= 73;
		public static const J :Number	= 74;
		public static const K :Number	= 75;
		public static const L :Number	= 76;
		public static const M :Number	= 77;
		public static const N :Number	= 78;
		public static const O :Number	= 79;
		public static const P :Number	= 80;
		public static const Q :Number	= 81;
		public static const R :Number	= 82;
		public static const S :Number	= 83;
		public static const T :Number	= 84;
		public static const U :Number	= 85;
		public static const V :Number	= 86;
		public static const W :Number	= 87;
		public static const X :Number	= 88;
		public static const Y :Number	= 89;
		public static const Z :Number	= 90;
		
		// Boolean array. Keeps track of which keys are down (true) and which are up (false).
		public var isDown :Array = new Array();
	
		// METHODS
		
		// Updates array index of pressed key to reflect down state (true).
		private function setKeysDown ( e :KeyboardEvent ) :void
		{
			isDown[e.keyCode] = true;
		}
		
		//  Updates array index of released key to reflect up state (false).
		private function setKeysUp ( e :KeyboardEvent ) :void
		{
			isDown[e.keyCode] = false;
		}
		
		// Constructor function. You MUST pass the stage as a parameter!
		public function Keys ( stage :Stage )
		{
			// Initialize all keys (index up to 255) as up (false).
			for(var count = 0; count <= 255; count++)
			{
				isDown[count] = false;
			}
			// Set listeners to update key states.
			stage.addEventListener(KeyboardEvent.KEY_DOWN, setKeysDown);
			stage.addEventListener(KeyboardEvent.KEY_UP, setKeysUp);
		}
	}
}