/**
 * @name		jQuery touchTouch plugin
 * @author		Martin Angelov
 * @version 	1.0
 * @url			http://tutorialzine.com/2012/04/mobile-touch-gallery/
 * @license		MIT License
 */

(function($){
	
	/* Private variables */
	
	var overlay = $('<div id="galleryOverlay">'),
		slider = $('<div id="gallerySlider">'),
		prevArrow = $('<a id="prevArrow"></a>'),
		nextArrow = $('<a id="nextArrow"></a>'),
		overlayVisible = false;
		
		
	/* Creating the plugin */
	
	$.fn.touchTouch = function(){
		
		var placeholders = $([]),
			index = 0,
			items = this;
		
		// Appending the markup to the page
		overlay.hide().appendTo('body');
		slider.appendTo(overlay);
		
		// Creating a placeholder for each image
		items.each(function(){
			placeholders = placeholders.add($('<div class="placeholder">'));
		});
	
		// Hide the gallery if the background is touched / clicked
		slider.append(placeholders).on('click',function(e){
			if(!$(e.target).is('img')){
				hideOverlay();
			}
		});
		
		// Listen for touch events on the body and check if they
		// originated in #gallerySlider img - the images in the slider.
		$('body').on('touchstart', '#gallerySlider img', function(e){
			
			var touch = e.originalEvent,
				startX = touch.changedTouches[0].pageX;
	
			slider.on('touchmove',function(e){
				
				e.preventDefault();
				
				touch = e.originalEvent.touches[0] ||
						e.originalEvent.changedTouches[0];
				
				if(touch.pageX - startX > 10){
					slider.off('touchmove');
					showPrevious();
				}
				else if (touch.pageX - startX < -10){
					slider.off('touchmove');
					showNext();
				}
			});

			// Return false to prevent image 
			// highlighting on Android
			return false;
			
		}).on('touchend',function(){
			slider.off('touchmove');
		});
		
		// Listening for clicks on the thumbnails
		
		items.on('click', function(e){
			e.preventDefault();
			
			// Find the position of this image
			// in the collection
			
			index = items.index(this);
			showOverlay(index);
			showImage(index);
			
			// Preload the next image
			preload(index+1);
			
			// Preload the previous
			preload(index-1);
			
		});
		
		// If the browser does not have support 
		// for touch, display the arrows
		if ( !("ontouchstart" in window) ){
			overlay.append(prevArrow).append(nextArrow);
			
			prevArrow.click(function(e){
				e.preventDefault();
				showPrevious();
			});
			
			nextArrow.click(function(e){
				e.preventDefault();
				showNext();
			});
		}
		
		// Listen for arrow keys
		$(window).bind('keydown', function(e){
		
			if (e.keyCode == 37){
				showPrevious();
			}
			else if (e.keyCode==39){
				showNext();
			}
	
		});
		
		
		/* Private functions */
		
	
		function showOverlay(index){
			
			// If the overlay is already shown, exit
			if (overlayVisible){
				return false;
			}
			
			// Show the overlay
			overlay.show();
			
			setTimeout(function(){
				// Trigger the opacity CSS transition
				overlay.addClass('visible');
			}, 100);
	
			// Move the slider to the correct image
			offsetSlider(index);
			
			// Raise the visible flag
			overlayVisible = true;
		}
	
		function hideOverlay(){
			// If the overlay is not shown, exit
			if(!overlayVisible){
				return false;
			}
			
			// Hide the overlay
			overlay.hide().removeClass('visible');
			overlayVisible = false;
		}
	
		function offsetSlider(index){
			// This will trigger a smooth css transition
			slider.css('left',(-index*100)+'%');
		}
	
		// Preload an image by its index in the items array
		function preload(index){
			setTimeout(function(){
				showImage(index);
			}, 1000);
		}
		
		// Show image in the slider
		function showImage(index){
	
			// If the index is outside the bonds of the array
			if(index < 0 || index >= items.length){
				return false;
			}
			
			// Call the load function with the href attribute of the item
			loadImage(items.eq(index).attr('href'), function(){
				placeholders.eq(index).html(this);
			});
		}
		
		// Load the image and execute a callback function.
		// Returns a jQuery object
		
		function loadImage(src, callback){
			var img = $('<img>').on('load', function(){
				callback.call(img);
			});
			
			img.attr('src',src);
		}
		
		function showNext(){
			
			// If this is not the last image
			if(index+1 < items.length){
				index++;
				offsetSlider(index);
				preload(index+1);
			}
			else{
				// Trigger the spring animation
				
				slider.addClass('rightSpring');
				setTimeout(function(){
					slider.removeClass('rightSpring');
				},500);
			}
		}
		
		function showPrevious(){
			
			// If this is not the first image
			if(index>0){
				index--;
				offsetSlider(index);
				preload(index-1);
			}
			else{
				// Trigger the spring animation
				
				slider.addClass('leftSpring');
				setTimeout(function(){
					slider.removeClass('leftSpring');
				},500);
			}
		}
	};
	
})(jQuery);