package {
    import flash.display.Stage;
    import flash.events.Event;
    import flash.events.KeyboardEvent;
   /*
This is the Key class by Senocular. 
It is here to replace the old Key class form AS2.
The new KeyBoard class in AS3 relies completely on events, 
which means that checking key state as Key.isDown(Key.enter) is no longer available.
This Key class restores the functionality.
*/
    /**
     * The Key class recreates functionality of
     * Key.isDown of ActionScript 1 and 2. Before using
     * Key.isDown, you first need to initialize the
     * Key class with a reference to the stage using
     * its Key.initialize() method. For key
     * codes use the flash.ui.Keyboard class.
     *
     * Usage:
     * Key.initialize(stage);
     * if (Key.isDown(Keyboard.LEFT)) {
     *    // Left key is being pressed
     * }
     */
    public class Key {
       
        private static var initialized:Boolean = false;  // marks whether or not the class has been initialized
        private static var keysDown:Object = new Object();  // stores key codes of all keys pressed
       
        /**
         * Initializes the key class creating assigning event
         * handlers to capture necessary key events from the stage
         */
        public static function initialize(stage:Stage) {
            if (!initialized) {
                // assign listeners for key presses and deactivation of the player
                stage.addEventListener(KeyboardEvent.KEY_DOWN, keyPressed);
                stage.addEventListener(KeyboardEvent.KEY_UP, keyReleased);
                stage.addEventListener(Event.DEACTIVATE, clearKeys);
               
                // mark initialization as true so redundant
                // calls do not reassign the event handlers
                initialized = true;
            }
        }
       
        /**
         * Returns true or false if the key represented by the
         * keyCode passed is being pressed
         */
        public static function isDown(keyCode:uint):Boolean {
            if (!initialized) {
                // throw an error if isDown is used
                // prior to Key class initialization
                throw new Error("Key class has yet been initialized.");
            }
            return Boolean(keyCode in keysDown);
        }
       
        /**
         * Event handler for capturing keys being pressed
         */
        private static function keyPressed(event:KeyboardEvent):void {
            // create a property in keysDown with the name of the keyCode
            keysDown[event.keyCode] = true;
        }
       
        /**
         * Event handler for capturing keys being released
         */
        private static function keyReleased(event:KeyboardEvent):void {
            if (event.keyCode in keysDown) {
                // delete the property in keysDown if it exists
                delete keysDown[event.keyCode];
            }
        }
       
        /**
         * Event handler for Flash Player deactivation
         */
        private static function clearKeys(event:Event):void {
            // clear all keys in keysDown since the player cannot
            // detect keys being pressed or released when not focused
            keysDown = new Object();
        }
    }
}