YUI.add('node-scroll-info', function (Y, NAME) {

/*jshint onevar:false */

/**

Provides the ScrollInfo Node plugin, which exposes convenient events and methods

related to scrolling.

@module node-scroll-info

@since 3.7.0

**/

/**

Provides convenient events and methods related to scrolling. This could be used,

for example, to implement infinite scrolling, or to lazy-load content based on

the current scroll position.

### Example

    var body = Y.one('body');

    body.plug(Y.Plugin.ScrollInfo);

    body.scrollInfo.on('scrollToBottom', function (e) {

        // Load more content when the user scrolls to the bottom of the page.

    });

@class Plugin.ScrollInfo

@extends Plugin.Base

@since 3.7.0

**/

var doc = Y.config.doc,

    win = Y.config.win;

/**

Fired when the user scrolls within the host node.

This event (like all scroll events exposed by ScrollInfo) is throttled and fired

only after the number of milliseconds specified by the `scrollDelay` attribute

have passed in order to prevent thrashing.

This event passes along the event facade for the standard DOM `scroll` event and

mixes in the following additional properties.

@event scroll

@param {Boolean} atBottom Whether the current scroll position is at the bottom

    of the scrollable region.

@param {Boolean} atLeft Whether the current scroll position is at the extreme

    left of the scrollable region.

@param {Boolean} atRight Whether the current scroll position is at the extreme

    right of the scrollable region.

@param {Boolean} atTop Whether the current scroll position is at the top of the

    scrollable region.

@param {Boolean} isScrollDown `true` if the user scrolled down.

@param {Boolean} isScrollLeft `true` if the user scrolled left.

@param {Boolean} isScrollRight `true` if the user scrolled right.

@param {Boolean} isScrollUp `true` if the user scrolled up.

@param {Number} scrollBottom Y value of the bottom-most onscreen pixel of the

    scrollable region.

@param {Number} scrollHeight Total height in pixels of the scrollable region,

    including offscreen pixels.

@param {Number} scrollLeft X value of the left-most onscreen pixel of the

    scrollable region.

@param {Number} scrollRight X value of the right-most onscreen pixel of the

    scrollable region.

@param {Number} scrollTop Y value of the top-most onscreen pixel of the

    scrollable region.

@param {Number} scrollWidth Total width in pixels of the scrollable region,

    including offscreen pixels.

@see scrollDelay

@see scrollMargin

**/

var EVT_SCROLL = 'scroll',

    /**

    Fired when the user scrolls down within the host node.

    This event provides the same event facade as the `scroll` event. See that

    event for details.

    @event scrollDown

    @see scroll

    **/

    EVT_SCROLL_DOWN = 'scrollDown',

    /**

    Fired when the user scrolls left within the host node.

    This event provides the same event facade as the `scroll` event. See that

    event for details.

    @event scrollLeft

    @see scroll

    **/

    EVT_SCROLL_LEFT = 'scrollLeft',

    /**

    Fired when the user scrolls right within the host node.

    This event provides the same event facade as the `scroll` event. See that

    event for details.

    @event scrollRight

    @see scroll

    **/

    EVT_SCROLL_RIGHT = 'scrollRight',

    /**

    Fired when the user scrolls up within the host node.

    This event provides the same event facade as the `scroll` event. See that

    event for details.

    @event scrollUp

    @see scroll

    **/

    EVT_SCROLL_UP = 'scrollUp',

    /**

    Fired when the user scrolls to the bottom of the scrollable region within

    the host node.

    This event provides the same event facade as the `scroll` event. See that

    event for details.

    @event scrollToBottom

    @see scroll

    **/

    EVT_SCROLL_TO_BOTTOM = 'scrollToBottom',

    /**

    Fired when the user scrolls to the extreme left of the scrollable region

    within the host node.

    This event provides the same event facade as the `scroll` event. See that

    event for details.

    @event scrollToLeft

    @see scroll

    **/

    EVT_SCROLL_TO_LEFT = 'scrollToLeft',

    /**

    Fired when the user scrolls to the extreme right of the scrollable region

    within the host node.

    This event provides the same event facade as the `scroll` event. See that

    event for details.

    @event scrollToRight

    @see scroll

    **/

    EVT_SCROLL_TO_RIGHT = 'scrollToRight',

    /**

    Fired when the user scrolls to the top of the scrollable region within the

    host node.

    This event provides the same event facade as the `scroll` event. See that

    event for details.

    @event scrollToTop

    @see scroll

    **/

    EVT_SCROLL_TO_TOP = 'scrollToTop';

Y.Plugin.ScrollInfo = Y.Base.create('scrollInfoPlugin', Y.Plugin.Base, [], {

    // -- Protected Properties -------------------------------------------------

    /**

    Height of the visible region of the host node in pixels. If the host node is

    the body, this will be the same as `_winHeight`.

    @property {Number} _height

    @protected

    **/

    /**

    Whether or not the host node is the `<body>` element.

    @property {Boolean} _hostIsBody

    @protected

    **/

    /**

    Width of the visible region of the host node in pixels. If the host node is

    the body, this will be the same as `_winWidth`.

    @property {Number} _width

    @protected

    **/

    /**

    Height of the viewport in pixels.

    @property {Number} _winHeight

    @protected

    **/

    /**

    Width of the viewport in pixels.

    @property {Number} _winWidth

    @protected

    **/

    // -- Lifecycle Methods ----------------------------------------------------

    initializer: function (config) {

        // Cache for quicker lookups in the critical path.

        this._host                  = config.host;

        this._hostIsBody            = this._host.get('nodeName').toLowerCase() === 'body';

        this._scrollDelay           = this.get('scrollDelay');

        this._scrollMargin          = this.get('scrollMargin');

        this._scrollNode            = this._getScrollNode();

        this.refreshDimensions();

        this._lastScroll = this.getScrollInfo();

        this._bind();

    },

    destructor: function () {

        new Y.EventHandle(this._events).detach();

        this._events = null;

    },

    // -- Public Methods -------------------------------------------------------

    /**

    Returns a NodeList containing all offscreen nodes inside the host node that

    match the given CSS selector. An offscreen node is any node that is entirely

    outside the visible (onscreen) region of the host node based on the current

    scroll location.

    @method getOffscreenNodes

    @param {String} [selector] CSS selector. If omitted, all offscreen nodes

        will be returned.

    @param {Number} [margin] Additional margin in pixels beyond the actual

        onscreen region that should be considered "onscreen" for the purposes of

        this query. Defaults to the value of the `scrollMargin` attribute.

    @return {NodeList} Offscreen nodes matching _selector_.

    @see scrollMargin

    **/

    getOffscreenNodes: function (selector, margin) {

        if (typeof margin === 'undefined') {

            margin = this._scrollMargin;

        }

        var elements = Y.Selector.query(selector || '*', this._host._node);

        return new Y.NodeList(Y.Array.filter(elements, function (el) {

            return !this._isElementOnscreen(el, margin);

        }, this));

    },

    /**

    Returns a NodeList containing all onscreen nodes inside the host node that

    match the given CSS selector. An onscreen node is any node that is fully or

    partially within the visible (onscreen) region of the host node based on the

    current scroll location.

    @method getOnscreenNodes

    @param {String} [selector] CSS selector. If omitted, all onscreen nodes will

        be returned.

    @param {Number} [margin] Additional margin in pixels beyond the actual

        onscreen region that should be considered "onscreen" for the purposes of

        this query. Defaults to the value of the `scrollMargin` attribute.

    @return {NodeList} Onscreen nodes matching _selector_.

    @see scrollMargin

    **/

    getOnscreenNodes: function (selector, margin) {

        if (typeof margin === 'undefined') {

            margin = this._scrollMargin;

        }

        var elements = Y.Selector.query(selector || '*', this._host._node);

        return new Y.NodeList(Y.Array.filter(elements, function (el) {

            return this._isElementOnscreen(el, margin);

        }, this));

    },

    /**

    Returns an object hash containing information about the current scroll

    position of the host node. This is the same information that's mixed into

    the event facade of the `scroll` event and other scroll-related events.

    @method getScrollInfo

    @return {Object} Object hash containing information about the current scroll

        position. See the `scroll` event for details on what properties this

        object contains.

    @see scroll

    **/

    getScrollInfo: function () {

        var domNode    = this._scrollNode,

            lastScroll = this._lastScroll,

            margin     = this._scrollMargin,

            scrollLeft   = domNode.scrollLeft,

            scrollHeight = domNode.scrollHeight,

            scrollTop    = domNode.scrollTop,

            scrollWidth  = domNode.scrollWidth,

            scrollBottom = scrollTop + this._height,

            scrollRight  = scrollLeft + this._width;

        return {

            atBottom: scrollBottom > (scrollHeight - margin),

            atLeft  : scrollLeft < margin,

            atRight : scrollRight > (scrollWidth - margin),

            atTop   : scrollTop < margin,

            isScrollDown : lastScroll && scrollTop > lastScroll.scrollTop,

            isScrollLeft : lastScroll && scrollLeft < lastScroll.scrollLeft,

            isScrollRight: lastScroll && scrollLeft > lastScroll.scrollLeft,

            isScrollUp   : lastScroll && scrollTop < lastScroll.scrollTop,

            scrollBottom: scrollBottom,

            scrollHeight: scrollHeight,

            scrollLeft  : scrollLeft,

            scrollRight : scrollRight,

            scrollTop   : scrollTop,

            scrollWidth : scrollWidth

        };

    },

    /**

    Returns `true` if _node_ is at least partially onscreen within the host

    node, `false` otherwise.

    @method isNodeOnscreen

    @param {HTMLElement|Node|String} node Node or selector to check.

    @param {Number} [margin] Additional margin in pixels beyond the actual

        onscreen region that should be considered "onscreen" for the purposes of

        this query. Defaults to the value of the `scrollMargin` attribute.

    @return {Boolean} `true` if _node_ is at least partially onscreen within the

        host node, `false` otherwise.

    @since 3.11.0

    **/

    isNodeOnscreen: function (node, margin) {

        node = Y.one(node);

        return !!(node && this._isElementOnscreen(node._node, margin));

    },

    /**

    Refreshes cached position, height, and width dimensions for the host node.

    If the host node is the body, then the viewport height and width will be

    used.

    This info is cached to improve performance during scroll events, since it's

    expensive to touch the DOM for these values. Dimensions are automatically

    refreshed whenever the browser is resized, but if you change the dimensions

    or position of the host node in JS, you may need to call

    `refreshDimensions()` manually to cache the new dimensions.

    @method refreshDimensions

    **/

    refreshDimensions: function () {

        var docEl = doc.documentElement;

        // On iOS devices and on Chrome for Android,

        // documentElement.clientHeight/Width aren't reliable, but

        // window.innerHeight/Width are. The dom-screen module's viewport size

        // methods don't account for this, which is why we do it here.

        if (Y.UA.ios || (Y.UA.android && Y.UA.chrome)) {

            this._winHeight = win.innerHeight;

            this._winWidth  = win.innerWidth;

        } else {

            this._winHeight = docEl.clientHeight;

            this._winWidth  = docEl.clientWidth;

        }

        if (this._hostIsBody) {

            this._height = this._winHeight;

            this._width  = this._winWidth;

        } else {

            this._height = this._scrollNode.clientHeight;

            this._width  = this._scrollNode.clientWidth;

        }

        this._refreshHostBoundingRect();

    },

    // -- Protected Methods ----------------------------------------------------

    /**

    Binds event handlers.

    @method _bind

    @protected

    **/

    _bind: function () {

        var winNode = Y.one('win');

        this._events = [

            this.after({

                scrollDelayChange : this._afterScrollDelayChange,

                scrollMarginChange: this._afterScrollMarginChange

            }),

            winNode.on('windowresize', this._afterResize, this)

        ];

        // If the host node is the body, listen for the scroll event on the

        // window, since <body> doesn't have a scroll event.

        if (this._hostIsBody) {

            this._events.push(winNode.after('scroll', this._afterHostScroll, this));

        } else {

            // The host node is not the body, but we still need to listen for

            // window scroll events so we can determine whether nodes are

            // onscreen.

            this._events.push(

                winNode.after('scroll', this._afterWindowScroll, this),

                this._host.after('scroll', this._afterHostScroll, this)

            );

        }

    },

    /**

    Returns the DOM node that should be used to lookup scroll coordinates. In

    some browsers, the `<body>` element doesn't return scroll coordinates, and

    the documentElement must be used instead; this method takes care of

    determining which node should be used.

    @method _getScrollNode

    @return {HTMLElement} DOM node.

    @protected

    **/

    _getScrollNode: function () {

        // WebKit returns scroll coordinates on the body element, but other

        // browsers don't, so we have to use the documentElement.

        return this._hostIsBody && !Y.UA.webkit ? doc.documentElement :