var App = App || {};
App.Util = App.Util || {};

App.Util.Draggable = function(jQuery) {
	var KEY_LEFT = 37;
	var KEY_UP = 38;
	var KEY_RIGHT = 39;
	var KEY_DOWN = 40;

	function relativeDragStrategy($element) {
		var $parent = $element.parent();
		var delta;
		var x = $element.offset().left - $parent.offset().left;
		var y = $element.offset().top - $parent.offset().top;

		var getPosition = function() {
			return {x: x, y: y};
		};

		var setPosition = function(newX, newY) {
			x = newX;
			y = newY;
			var screenX = Math.min(Math.max(newX, 0), $parent.outerWidth() - $element.outerWidth());
			var screenY = Math.min(Math.max(newY, 0), $parent.outerHeight() - $element.outerHeight());
			screenX *= 100.0 / $parent.outerWidth();
			screenY *= 100.0 / $parent.outerHeight();
			$element.css({
				left: screenX + '%',
				top: screenY + '%'});
		};

		return {
			mouseClicked: function(e) {
				delta = {
					x: $element.offset().left - e.clientX,
					y: $element.offset().top - e.clientY,
				};
			},

			mouseMoved: function(e) {
				setPosition(
					e.clientX + delta.x - $parent.offset().left,
					e.clientY + delta.y - $parent.offset().top);
			},

			getPosition: getPosition,
			setPosition: setPosition,
		};
	}

	function absoluteDragStrategy($element) {
		var delta;
		var x = $element.offset().left;
		var y = $element.offset().top;

		var getPosition = function() {
			return {x: x, y: y};
		};

		var setPosition = function(newX, newY) {
			x = newX;
			y = newY;
			$element.css({
				left: x + 'px',
				top: y + 'px'});
		};

		return {
			mouseClicked: function(e) {
				delta = {
					x: $element.position().left - e.clientX,
					y: $element.position().top - e.clientY,
				};
			},

			mouseMoved: function(e) {
				setPosition(e.clientX + delta.x, e.clientY + delta.y);
			},

			getPosition: getPosition,
			setPosition: setPosition,
		};
	}

	function makeDraggable($element, dragStrategy, enableHotkeys) {
		var strategy = dragStrategy($element);
		$element.data('drag-strategy', strategy);

		$element.addClass('draggable');

		$element.mousedown(function(e) {
			if (e.target !== $element.get(0)) {
				return;
			}
			e.preventDefault();
			$element.focus();
			$element.addClass('dragging');

			strategy.mouseClicked(e);
			jQuery(window).bind('mousemove.elemmove', function(e) {
				strategy.mouseMoved(e);
			}).bind('mouseup.elemmove', function(e) {
				e.preventDefault();
				strategy.mouseMoved(e);
				$element.removeClass('dragging');
				jQuery(window).unbind('mousemove.elemmove');
				jQuery(window).unbind('mouseup.elemmove');
			});
		});

		if (enableHotkeys) {
			$element.keydown(function(e) {
				var position = strategy.getPosition();
				var oldPosition = {x: position.x, y: position.y};
				if (e.shiftKey) {
					return;
				}

				var delta = e.ctrlKey ? 10 : 1;
				if (e.which === KEY_LEFT) {
					position.x -= delta;
				} else if (e.which === KEY_RIGHT) {
					position.x += delta;
				} else if (e.which === KEY_UP) {
					position.y -= delta;
				} else if (e.which === KEY_DOWN) {
					position.y += delta;
				}

				if (position.x !== oldPosition.x || position.y !== oldPosition.y) {
					e.stopPropagation();
					e.stopImmediatePropagation();
					e.preventDefault();
					strategy.setPosition(position.x, position.y);
				}
			});
		}
	}

	return {
		makeDraggable: makeDraggable,
		absoluteDragStrategy: absoluteDragStrategy,
		relativeDragStrategy: relativeDragStrategy,
	};

};

App.DI.registerSingleton('draggable', ['jQuery'], App.Util.Draggable);