/*
 * @name DoubleScroll
 * @desc displays scroll bar on top and on the bottom of the div
 * @requires jQuery
 *
 * @author Pawel Suwala - http://suwala.eu/
 * @author Antoine Vianey - http://www.astek.fr/
 * @version 0.4 (18-06-2014)
 *
 * Dual licensed under the MIT and GPL licenses:
 * http://www.opensource.org/licenses/mit-license.php
 * http://www.gnu.org/licenses/gpl.html
 * 
 * Usage:
 * https://github.com/avianey/jqDoubleScroll
 */

jQuery.fn.doubleScroll = function(userOptions) {
	var $ = jQuery;
	// Default options
	var options = {
		contentElement: undefined, // Widest element, if not specified first child element will be used
		scrollCss: {                
			'overflow-x': 'auto',
			'overflow-y': 'hidden'
        },
		contentCss: {
			'overflow-x': 'auto',
			'overflow-y': 'hidden'
		},
		onlyIfScroll: true, // top scrollbar is not shown if the bottom one is not present
		resetOnWindowResize: true, // recompute the top ScrollBar requirements when the window is resized
		timeToWaitForResize: 30 // wait for the last update event (usefull when browser fire resize event constantly during ressing)
	};
	$.extend(true, options, userOptions);
	// do not modify
	// internal stuff
	$.extend(options, {
		topScrollBarMarkup: '<div class="doubleScroll-scroll-wrapper" style="height: 20px;"><div class="doubleScroll-scroll" style="height: 20px;"></div></div>',
		topScrollBarWrapperSelector: '.doubleScroll-scroll-wrapper',
		topScrollBarInnerSelector: '.doubleScroll-scroll'
	});
	
	var _showScrollBar = function($self, options) {
		
		if (options.onlyIfScroll && $self.get(0).scrollWidth <= $self.width()) {
			// content doesn't scroll
	    	// remove any existing occurrence...
			$self.prev(options.topScrollBarWrapperSelector).remove();
			return;
		}
		
	    // add div that will act as an upper scroll only if not already added to the DOM
	    var $topScrollBar = $self.prev(options.topScrollBarWrapperSelector);
	    if ($topScrollBar.length == 0) {
	    	
	    	// creating the scrollbar
	    	// added before in the DOM
	    	$topScrollBar = $(options.topScrollBarMarkup);
		    $self.before($topScrollBar);
		    
		    // apply the css
		    $topScrollBar.css(options.scrollCss);
		    $self.css(options.contentCss);

		    // bind upper scroll to bottom scroll
		    $topScrollBar.bind('scroll.doubleScroll', function() {
		    	$self.scrollLeft($topScrollBar.scrollLeft());
		    });

		    // bind bottom scroll to upper scroll
		    var selfScrollHandler = function() {
		        $topScrollBar.scrollLeft($self.scrollLeft());
		    };
		    $self.bind('scroll.doubleScroll', selfScrollHandler);
	    }

	    // find the content element (should be the widest one)	
		var $contentElement;		
	    if (options.contentElement !== undefined && $self.find(options.contentElement).length !== 0) {
	        $contentElement = $self.find(options.contentElement);
	    } else {
	        $contentElement = $self.find('>:first-child');
	    }
	    
	    // set the width of the wrappers
	    $(options.topScrollBarInnerSelector, $topScrollBar).width($contentElement.outerWidth());
	    $topScrollBar.width($self.width());
        $topScrollBar.scrollLeft($self.scrollLeft());
	    
	}
	
	return this.each(function() {
		var $self = $(this);
		_showScrollBar($self, options);
	    
	    // bind the resize handler 
		// do it once
	    if (options.resetOnWindowResize) {
	    	var id;
	    	var handler = function(e) {
	    		_showScrollBar($self, options);
	    	};
	    	$(window).bind('resize.doubleScroll', function() {
    			// adding/removing/replacing the scrollbar might resize the window
    			// so the resizing flag will avoid the infinite loop here...
	    	    clearTimeout(id);
	    	    id = setTimeout(handler, options.timeToWaitForResize);
	    	});
	    }
	});
}