/**
 * usage:
 * <input type="button" value="OFF" onclick="javascript: OverlayController.setDisplayMode(OverlayController.DISPLAY_OFF);" />
 * <input type="button" value="ON"  onclick="javascript: OverlayController.setDisplayMode(OverlayController.DISPLAY_ON);" />
 */
var OverlayController = {

	TOP_PADDING		:	10,
	RIGHT_PADDING	:	10,

	CONTROL_ELEMENT	:	null,

	DISPLAY_ON		:	"block",
	DISPLAY_OFF		:	"none",

    SWITCH_ON_COUNT : 0,
    /** displays  the indicator in the right-top corner
	*	according to the scroller Use in IE6 only
	*/

	indicate		: 	function() {
		var pos=document.documentElement.scrollTop ?
        	      document.documentElement.scrollTop : document.body.scrollTop;
		OverlayController.CONTROL_ELEMENT.style.top=pos.toString()  + "px";
		},

    /**
	 * @param overlay_id Overlay ID
	 *
	 * NOTE: Overlay container must have already setup CSS rules
	 */
	setup			:	function(overlay_id) {
		OverlayController.CONTROL_ELEMENT = (typeof overlay_id == "object")
			? overlay_id
			: document.getElementById(overlay_id);
		if(typeof OverlayController.CONTROL_ELEMENT != "object")
			OverlayController.CONTROL_ELEMENT = null;
		else
			this.indicate();
	},


	isAvailable		: 	function() {
		return (typeof OverlayController.CONTROL_ELEMENT == "object");
	},

	/**
	 * @param mode one of OverlayController.DISPLAY_ON or OverlayController.DISPLAY_OFF
	 */
	setDisplayMode	:	function(mode) {
		if(OverlayController.isAvailable()) {
            if (mode == OverlayController.DISPLAY_ON) {
                OverlayController.SWITCH_ON_COUNT = OverlayController.SWITCH_ON_COUNT + 1;
            } else {
                OverlayController.SWITCH_ON_COUNT = OverlayController.SWITCH_ON_COUNT - 1;
                if (OverlayController.SWITCH_ON_COUNT  > 0) {
                    return;
                } else {
                    OverlayController.SWITCH_ON_COUNT = 0;    
                }
            }
            OverlayController.CONTROL_ELEMENT.parentNode.style.display = mode;
		};
	}
};