(function($){

	$.fn.twentytwenty = function(options) {
		var options = $.extend({default_offset_pct: 0.5, orientation: 'horizontal'}, options);
		return this.each(function() {

			var sliderPct = options.default_offset_pct;
			var container = $(this);
			var sliderOrientation = options.orientation;
			var beforeDirection = (sliderOrientation === 'vertical') ? 'down' : 'left';
			var afterDirection = (sliderOrientation === 'vertical') ? 'up' : 'right';


			container.wrap("<div class='twentytwenty-wrapper twentytwenty-" + sliderOrientation + "'></div>");
			container.append("<div class='twentytwenty-overlay'></div>");
			var beforeImg = container.find("img:first");
			var afterImg = container.find("img:last");
			container.append("<div class='twentytwenty-handle'></div>");
			var slider = container.find(".twentytwenty-handle");
			slider.append("<span class='twentytwenty-" + beforeDirection + "-arrow'></span>");
			slider.append("<span class='twentytwenty-" + afterDirection + "-arrow'></span>");
			container.addClass("twentytwenty-container");
			beforeImg.addClass("twentytwenty-before");
			afterImg.addClass("twentytwenty-after");

			var overlay = container.find(".twentytwenty-overlay");
			overlay.append("<div class='twentytwenty-before-label'></div>");
			overlay.append("<div class='twentytwenty-after-label'></div>");

			var calcOffset = function(dimensionPct) {
				var w = beforeImg.width();
				var h = beforeImg.height();
				return {
					w: w+"px",
					h: h+"px",
					cw: (dimensionPct*w)+"px",
					ch: (dimensionPct*h)+"px"
				};
			};

			var adjustContainer = function(offset) {
				if (sliderOrientation === 'vertical') {
					beforeImg.css("clip", "rect(0,"+offset.w+","+offset.ch+",0)");
				}
				else {
					beforeImg.css("clip", "rect(0,"+offset.cw+","+offset.h+",0)");
			}
				container.css("height", offset.h);
			};

			var adjustSlider = function(pct) {
				var offset = calcOffset(pct);
				slider.css((sliderOrientation==="vertical") ? "top" : "left", (sliderOrientation==="vertical") ? offset.ch : offset.cw);
				adjustContainer(offset);
			}

			$(window).on("resize.twentytwenty", function(e) {
				adjustSlider(sliderPct);
			});

			var offsetX = 0;
			var imgWidth = 0;

			slider.on("movestart", function(e) {
				if (((e.distX > e.distY && e.distX < -e.distY) || (e.distX < e.distY && e.distX > -e.distY)) && sliderOrientation !== 'vertical') {
					e.preventDefault();
				}
				else if (((e.distX < e.distY && e.distX < -e.distY) || (e.distX > e.distY && e.distX > -e.distY)) && sliderOrientation === 'vertical') {
					e.preventDefault();
				}
				container.addClass("active");
				offsetX = container.offset().left;
				offsetY = container.offset().top;
				imgWidth = beforeImg.width();
				imgHeight = beforeImg.height();
			});

			slider.on("moveend", function(e) {
				container.removeClass("active");
			});

			slider.on("move", function(e) {
				if (container.hasClass("active")) {
					sliderPct = (sliderOrientation === 'vertical') ? (e.pageY-offsetY)/imgHeight : (e.pageX-offsetX)/imgWidth;
					if (sliderPct < 0) {
						sliderPct = 0;
					}
					if (sliderPct > 1) {
						sliderPct = 1;
					}
					adjustSlider(sliderPct);
				}
			});

			container.find("img").on("mousedown", function(event) {
				event.preventDefault();
			});

			$(window).trigger("resize.twentytwenty");
		});
	};

})(jQuery);