// UTF-8
/**
 * scrollsmoothly.js
 * Copyright ( c ) 2008 KAZUMiX
 * http://d.hatena.ne.jp/KAZUMiX/20080418/scrollsmoothly
 * Licensed under the MIT License:
 * http://www.opensource.org/licenses/mit-license.php
 *
 * 更新履歴
 * 2009/02/12
 * スクロール先が画面左上にならない場合の挙動を修正
 * 2008/04/18
 * 公開
 *
 */

( function() {
	var easing = 0.25;
	var interval = 20;
	var d = document;
	var targetX = 0;
	var targetY = 0;
	var targetHash = '';
	var scrolling = false;
	var splitHref = location.href.split( '#' );
	var currentHref_WOHash = splitHref[ 0 ];
	var incomingHash = splitHref[ 1 ];
	var prevX = null;
	var prevY = null;

	addEvent( window, 'load', init );

	function init() {
		setOnClickHandler();
		if ( incomingHash ) {
			if ( window.attachEvent && !window.opera ) {
				setTimeout( function() { scrollTo( 0, 0 );setScroll( '#'+incomingHash ); }, 50 );
			}else {
				scrollTo( 0, 0 );
				setScroll( '#'+incomingHash );
			}
		}
	}

	function addEvent( eventTarget, eventName, func ) {
		if ( eventTarget.addEventListener ) {
			eventTarget.addEventListener( eventName, func, false );
		}else if ( window.attachEvent ) {
			eventTarget.attachEvent( 'on'+eventName, function() { func.apply( eventTarget ); } );
		}
	}

	function setOnClickHandler() {
		var links = d.links;
		for ( var i = 0; i<links.length; i += 1 ) {
			var link = links[ i ];
			var splitLinkHref = link.href.split( '#' );
			if ( currentHref_WOHash == splitLinkHref[ 0 ] && d.getElementById( splitLinkHref[ 1 ] ) ) addEvent( link, 'click', startScroll );
		}
	}

	function startScroll( event ) {
		if ( event ) {
			event.preventDefault();
		}else if ( window.event ) {
			window.event.returnValue = false;
		}
		setScroll( this.hash );
	}

	function setScroll( hash ) {
		var targetEle = d.getElementById( hash.substr( 1 ) );
		if ( !targetEle ) return;
		var ele = targetEle;
		var x = 0;
		var y = 0;
		while( ele ) {
			x += ele.offsetLeft;
			y += ele.offsetTop;
			ele = ele.offsetParent;
		}
		var maxScroll = getScrollMaxXY();
		targetX = Math.min( x, maxScroll.x );
		targetY = Math.min( y, maxScroll.y );
		targetHash = hash;
		if ( !scrolling ) {
			scrolling = true;
			scroll();
		}
	}

	function scroll() {
		var currentX = d.documentElement.scrollLeft||d.body.scrollLeft;
		var currentY = d.documentElement.scrollTop||d.body.scrollTop;
		var vx = ( targetX - currentX ) * easing;
		var vy = ( targetY - currentY ) * easing;
		var nextX = currentX + vx;
		var nextY = currentY + vy;
		if ( ( Math.abs( vx ) < 1 && Math.abs( vy ) < 1 )
		|| ( prevX === currentX && prevY === currentY ) ) {
			scrollTo( targetX, targetY );
			scrolling = false;
			location.hash = targetHash;
			prevX = prevY = null;
			return;
		}else {
			scrollTo( parseInt( nextX ), parseInt( nextY ) );
			prevX = currentX;
			prevY = currentY;
			setTimeout( function() { scroll() }, interval );
		}
	}

	function getDocumentSize() {
		return { width:Math.max( document.body.scrollWidth, document.documentElement.scrollWidth ), height:Math.max( document.body.scrollHeight, document.documentElement.scrollHeight ) };
	}

	function getWindowSize() {
		var result = {};
		if ( window.innerWidth ) {
			var box = d.createElement( 'div' );
			with( box.style ) {
				position = 'absolute';
				top = '0px';
				left = '0px';
				width = '100%';
				height = '100%';
				margin = '0px';
				padding = '0px';
				border = 'none';
				visibility = 'hidden';
			}
			d.body.appendChild( box );
			var width = box.offsetWidth;
			var height = box.offsetHeight;
			d.body.removeChild( box );
			result = { width:width, height:height };
		}
		else result = { width:d.documentElement.clientWidth || d.body.clientWidth, height:d.documentElement.clientHeight || d.body.clientHeight };
		return result;
	}

	function getScrollMaxXY() {
		if ( window.scrollMaxX && window.scrollMaxY ) return { x:window.scrollMaxX, y:window.scrollMaxY };
		var documentSize = getDocumentSize();
		var windowSize = getWindowSize();
		return { x:documentSize.width - windowSize.width, y:documentSize.height - windowSize.height };
	}

}() );