/*
 * $.tinyscroller
 *
 * version 0.1.1 (2010/11/29)
 * Copyright (c) 2010 Takeshi Takatsudo (takazudo[at]gmail.com)
 * MIT license
 * original: Tiny Scrolling http://lab.centralscrutinizer.it/the-tiny-scrollings/ (thanks Marco Rosella)
 *
=============================================================================
 depends on
-----------------------------------------------------------------------------
 * jQuery 1.4.4
 *
 */
(function($){ // start $=jQuery encapsulation

/* for reuse */
var $win = $(window);
var $doc = $(document);

/* $.fn.offset has bug in iOS ver.3.0-4.0 Safari so use this instead. */
function yOf(el){
    var y = 0;
    while(el.offsetParent){
        y += el.offsetTop;
        el = el.offsetParent;
    }
    return y;
}
/* i don't know why but $.fn.scrollTop was not worked on IE 6,7,8 w/ jQuery1.4.3 */
function scrollTop(){
    return $doc.scrollTop() || document.documentElement.scrollTop || document.body.scrollTop || window.pageYOffset || 0;
}


/**
 * $.Tinyscroller
 */
$.Tinyscroller = function(){

    this.options = {

        speed : 30, // scrollstep interval
        maxStep: 2000, // max distance(px) per scrollstep
        slowdownRate: 3, // something to define slowdown rate
        stepInterval: 5,

        /* callbacks */
        everyscrollstart: $.noop,
        everyscrollend: $.noop,
        scrollstart: $.noop,
        scrollend: $.noop,

        changeHash: false, // change hash after scrolling or not
        hash: null, // '#foo'

        // scroll till scrollTop reaches...
        endpointElement: null, // element
        endY: null // or px from top

    };

};

$.Tinyscroller.prototype = {

    _currentScrollOptions: null,
    _whileScrolling: false,
    _endY: null,
    _cancelNext: false,

    _scrollEndHandler: function(){
        var o = this._currentScrollOptions;
        this._whileScrolling = false;
        if($.isFunction(o.scrollend)){
            o.scrollend();
        }
        if($.isFunction(o.everyscrollend)){
            o.everyscrollend();
        }
        if(o.changeHash && $.type(o.hash)==='string'){
            location.hash = o.hash;
        }
        if($.isFunction(this._cancelCallback)){
            this._cancelCallback();
        }
        return this;
    },
    _stepToNext: function(){
        var self = this;
        setTimeout(function(){
            var top  = scrollTop();
            var o = self._currentScrollOptions;
            var endDistance, offset;
            if(self._endY > top) {  
                endDistance = Math.round( ($doc.height() - (top + $win.height())) /o.slowdownRate);
                endDistance = Math.min(Math.round((self._endY-top)/ o.slowdownRate), endDistance);
                offset = Math.max(2, Math.min(endDistance, o.maxStep));
            } else {
                offset = - Math.min(Math.abs(Math.round((self._endY-top)/ o.slowdownRate)), o.maxStep);
            }
            window.scrollTo(0, top + offset);
            if(self._cancelNext){
                self._cancelNext = false;
                self._scrollEndHandler();
            }else if(Math.abs(top - self._endY) <= 1 || scrollTop() == top){
                window.scrollTo(0, self._endY);
                self._scrollEndHandler();
            }else{
                setTimeout( $.proxy(self._stepToNext, self), o.speed );
            }
        },self.options.stepInterval);
        return this;
    },
    _start: function(){
        var o = this._currentScrollOptions;
        if($.isFunction(o.scrollstart)){
            o.scrollstart();
        }
        if($.isFunction(o.everyscrollstart)){
            o.everyscrollstart();
        }
        this._stepToNext();
        return this;
    },
    stop: function(callback){
        var o = this._currentScrollOptions;
        if(this._whileScrolling){
            this._cancelNext = true;
            this._cancelCallback = callback;
        }else if($.isFunction(callback)){
            callback();
        }
        return this;
    },
    scrollTo: function(endY, callback){ // endY:number
        var o = {
            endY: endY
        };
        if($.isFunction(callback)){
            o.scrollend = callback;
        }
        this.scroll(o);
        return this;
    },
    scroll: function(options){
        var self = this;
        this.stop(function(){
            var o = self._currentScrollOptions = $.extend({}, self.options, options);
            if(null != o.endY && $.type(o.endY)==='number'){
                self._endY = o.endY;
                self._start();
            }else{
                var $end = $(o.endpointElement);
                if($end.size()){
                    self._endY = yOf($end[0]);
                    self._start();
                }
            }
        });
        return this;
    },
    setOptions: function(options){
        $.extend(this.options, options);
        return this;
    },
    liveEventify: function(selector){
        selector = selector || 'a[href^=#]:not([href^=#!)';
        var self = this;
        $(selector).live('click', function(e){
            if(!self.isValidAnchor(this)){
                return;
            }
            e.preventDefault();
            $(this).invokeTinyscroll();
        });
    },
    isValidAnchor: function(element){
        var $el = $(element);
        if(!$el.is('[href]')){
            return false;
        }
        var hash = $el.attr('href');
        if(!/^#.+$/.test(hash)){
            return false;
        }
        var $target = $(hash);
        if(!$target.size()){
            return false;
        }
        return true;
    }

};

// create instance
$.tinyscroller = new $.Tinyscroller();


/**
 * $.fn.invokeTinyscroll
 * invoke scroll
 */
$.fn.invokeTinyscroll = function(options){

    return this.each(function(){

        if(!$.tinyscroller.isValidAnchor(this)){
            return;
        }

        var $el = $(this);
        var hash = $el.attr('href');
        var target = $(hash)[0];

        var o = $.extend({}, options, {
            hash: hash,
            endpointElement: target
        });

        // invoke
        $.tinyscroller.scroll(o);

    });

};

/**
 * $.fn.tinyscrollable
 * catch click for anchors
 */
$.fn.tinyscrollable = function(options){

    return this.each(function(){

        var $el = $(this);

        if(!$el.is('a')){
            return;
        }

        // put flag to avoid double bind
        if($el.data('tinyscrollable.attached')){
            return;
        }else{
            $el.data('tinyscrollable.attached', true)
        }

        // bind
        $el.bind('click', function(e){
            if(!$.tinyscroller.isValidAnchor(this)){
                return;
            }
            e.preventDefault();
            $el.invokeTinyscroll(options);
        });
        
    });

};


})(jQuery); // end $=jQuery encapsulation