/*
* Lazy Load - jQuery plugin for lazy loading images
*
* Copyright (c) 2007-2009 Mika Tuupola
*
* Licensed under the MIT license:
*   http://www.opensource.org/licenses/mit-license.php
*
* Project home:
*   http://www.appelsiini.net/projects/lazyload
*
* Version:  1.5.0
*
*/
(function($) {

	$.fn.lazyload = function(options) {
		var settings = {
			threshold: 0,
			failurelimit: 0,
			event: "scroll",
			effect: "show",
			container: window
		};

		if (options) {
			$.extend(settings, options);
		}

		/* Fire one scroll event per scroll. Not one scroll event per image. */
		var elements = this;
		if ("scroll" == settings.event) {
			$(settings.container).bind("scroll", function(event) {

				var counter = 0;
				elements.each(function() {
					if ($.abovethetop(this, settings) ||
                        $.leftofbegin(this, settings)) {
						/* Nothing. */
					} else if (!$.belowthefold(this, settings) &&
                        !$.rightoffold(this, settings)) {
						$(this).trigger("appear");
					} else {
						if (counter++ > settings.failurelimit) {
							return false;
						}
					}
				});
				/* Remove image from array so it is not looped next time. */
				var temp = $.grep(elements, function(element) {
					return !element.loaded;
				});
				elements = $(temp);
			});
		}

		this.each(function() {
			var self = this;

			/* Save original only if it is not defined in HTML. */
			if (undefined == $(self).attr("original")) {
				$(self).attr("original", $(self).attr("src"));
			}

			if ("scroll" != settings.event ||
                    undefined == $(self).attr("src") ||
                    settings.placeholder == $(self).attr("src") ||
                    ($.abovethetop(self, settings) ||
                     $.leftofbegin(self, settings) ||
                     $.belowthefold(self, settings) ||
                     $.rightoffold(self, settings))) {

				if (settings.placeholder) {
					$(self).attr("src", settings.placeholder);
				} else {
					$(self).removeAttr("src");
				}
				self.loaded = false;
			} else {
				self.loaded = true;
			}

			/* When appear is triggered load original image. */
			$(self).one("appear", function() {
				if (!this.loaded) {
					$("<img />")
                        .bind("load", function() {
                        	$(self)
                                .hide()
                                .attr("src", $(self).attr("original"))
                                [settings.effect](settings.effectspeed);
                        	self.loaded = true;
                        })
                        .attr("src", $(self).attr("original"));
				};
			});

			/* When wanted event is triggered load original image */
			/* by triggering appear.                              */
			if ("scroll" != settings.event) {
				$(self).bind(settings.event, function(event) {
					if (!self.loaded) {
						$(self).trigger("appear");
					}
				});
			}
		});

		/* Force initial check if images should appear. */
		$(settings.container).trigger(settings.event);

		return this;

	};

	/* Convenience methods in jQuery namespace.           */
	/* Use as  $.belowthefold(element, {threshold : 100, container : window}) */

	$.belowthefold = function(element, settings) {
		if (settings.container === undefined || settings.container === window) {
			var fold = $(window).height() + $(window).scrollTop();
		} else {
			var fold = $(settings.container).offset().top + $(settings.container).height();
		}
		return fold <= $(element).offset().top - settings.threshold;
	};

	$.rightoffold = function(element, settings) {
		if (settings.container === undefined || settings.container === window) {
			var fold = $(window).width() + $(window).scrollLeft();
		} else {
			var fold = $(settings.container).offset().left + $(settings.container).width();
		}
		return fold <= $(element).offset().left - settings.threshold;
	};

	$.abovethetop = function(element, settings) {
		if (settings.container === undefined || settings.container === window) {
			var fold = $(window).scrollTop();
		} else {
			var fold = $(settings.container).offset().top;
		}
		return fold >= $(element).offset().top + settings.threshold + $(element).height();
	};

	$.leftofbegin = function(element, settings) {
		if (settings.container === undefined || settings.container === window) {
			var fold = $(window).scrollLeft();
		} else {
			var fold = $(settings.container).offset().left;
		}
		return fold >= $(element).offset().left + settings.threshold + $(element).width();
	};
	/* Custom selectors for your convenience.   */
	/* Use as $("img:below-the-fold").something() */

	$.extend($.expr[':'], {
		"below-the-fold": "$.belowthefold(a, {threshold : 0, container: window})",
		"above-the-fold": "!$.belowthefold(a, {threshold : 0, container: window})",
		"right-of-fold": "$.rightoffold(a, {threshold : 0, container: window})",
		"left-of-fold": "!$.rightoffold(a, {threshold : 0, container: window})"
	});

})(jQuery);