/*
 * yuga.js 0.7.0 - 優雅なWeb制作のためのJS
 *
 * Copyright (c) 2007 Kyosuke Nakamura (kyosuke.jp)
 * Licensed under the MIT License:
 * http://www.opensource.org/licenses/mit-license.php
 *
 * Since:     2006-10-30
 * Modified:  2008-12-26
 *
 */


(function($) {

	$(function() {
		$.common.scroll();
	});

	//---------------------------------------------------------------------

	$.common = {
		scroll: function(options) {	// anchor scroller
			var scroller = (function() {
				var c = $.extend({
					easing:100,
					step:30,
					fps:60,
					fragment:''
				}, options);
				c.ms = Math.floor(1000/c.fps);
				var timerId;
				var param = {
					stepCount:0,
					startY:0,
					endY:0,
					lastY:0
				};
				
				// fnc
				function move() {
					if (param.stepCount == c.step) {
						// scroll end
						setFragment(param.fragment);
						window.scrollTo(getCurrentX(), param.endY);
					} else if (param.lastY == getCurrentY()) {
						// scroll
						param.stepCount++;
						window.scrollTo(getCurrentX(), getEasingY());
						param.lastY = getEasingY();
						timerId = setTimeout(move, c.ms); 
					} else {
						// error	
						if (getCurrentY()+getViewportHeight() == getDocumentHeight()) {
							setFragment(param.fragment);
						}
					}
				}
				function setFragment(fragment){
					location.href = location.href.split('#')[0] + fragment;
				}

				function getEasingY() {
					return Math.floor(getEasing(param.startY, param.endY, param.stepCount, c.step, c.easing));
				}
				function getEasing(start, end, stepCount, step, easing) {
					var s = stepCount / step;
					return (end - start) * (s + easing / (100 * Math.PI) * Math.sin(Math.PI * s)) + start;
				}
				function targetOffsetTop(target){
					return target.offset().top;
				}
				return {
					set: function(options) {
						this.stop();
						if (options.startY == undefined) options.startY = getCurrentY();
						param = $.extend(param, options);						
						param.lastY = param.startY;
						param.fragment = options.fragment;
						timerId = setTimeout(move, c.ms); 
					},
					stop: function(){
						clearTimeout(timerId);
						param.stepCount = 0;
					}
				};
			})();
			function getCurrentY() {
					return document.body.scrollTop  || document.documentElement.scrollTop;
			}
			function getCurrentX() {
					return document.body.scrollLeft  || document.documentElement.scrollLeft;
			}
			function getDocumentHeight(){
					return (document.compatMode && document.compatMode != 
"BackCompat")?document.documentElement.scrollHeight:document.body.scrollHeight;
			}
			function getViewportHeight(){
					return (!$.browser.safari && !$.browser.opera) ? document.documentElement.clientHeight || document.body.clientHeight || document.body.scrollHeight : window.innerHeight;
			}
			// init
			$('a[href^=#], area[href^=#]').not('a[href=#], area[href=#]').click(function(){
				var fragment = $(this).attr('href');
				var target = $(fragment);
				
				if (target.length == 0) target = $('a[name='+fragment+']');
				
				if (target.length) {
					scroller.set({
						endY: ((getDocumentHeight() - target.offset().top )) < getViewportHeight() ? getDocumentHeight() - getViewportHeight() : target.offset().top,
						fragment: fragment,
						_target :	target
					});

					return false;
				}
			});
		}
	};
})(jQuery);