Yahoo! UI Library

(function(Y) {
var TOP = 'top',
    RIGHT = 'right',
    BOTTOM = 'bottom',
    LEFT = 'left',

    getOffsets = function(r1, r2) {
        var t = Math.max(r1[TOP], r2[TOP]),
            r = Math.min(r1[RIGHT], r2[RIGHT]),
            b = Math.min(r1[BOTTOM], r2[BOTTOM]),
            l = Math.max(r1[LEFT], r2[LEFT]),
            ret = {};
        
        ret[TOP] = t;
        ret[RIGHT] = r;
        ret[BOTTOM] = b;
        ret[LEFT] = l;
        return ret;
    },

    DOM = Y.DOM;

Y.mix(DOM, {
    /**
     * Returns an Object literal containing the following about this element: (top, right, bottom, left)
     * @method region
     * @param {HTMLElement} element The DOM element. 
     @return {Object} Object literal containing the following about this element: (top, right, bottom, left)
     */
    region: function(node) {
        var xy = DOM.getXY(node),
            ret = false;
        
        if (node && xy) {
            ret = DOM._getRegion(
                xy[1], // top
                xy[0] + node.offsetWidth, // right
                xy[1] + node.offsetHeight, // bottom
                xy[0] // left
            );
        }

        return ret;
    },

    /**
     * Find the intersect information for the passes nodes.
     * @method intersect
     * @param {HTMLElement} element The first element 
     * @param {HTMLElement | Object} element2 The element or region to check the interect with
     * @param {Object} altRegion An object literal containing the region for the first element if we already have the data (for performance i.e. DragDrop)
     @return {Object} Object literal containing the following intersection data: (top, right, bottom, left, area, yoff, xoff, inRegion)
     */
    intersect: function(node, node2, altRegion) {
        var r = altRegion || DOM.region(node), region = {},
            n = node2,
            off;

        if (n.tagName) {
            region = DOM.region(n);
        } else if (Y.Lang.isObject(node2)) {
            region = node2;
        } else {
            return false;
        }
        
        off = getOffsets(region, r);
        return {
            top: off[TOP],
            right: off[RIGHT],
            bottom: off[BOTTOM],
            left: off[LEFT],
            area: ((off[BOTTOM] - off[TOP]) * (off[RIGHT] - off[LEFT])),
            yoff: ((off[BOTTOM] - off[TOP])),
            xoff: (off[RIGHT] - off[LEFT]),
            inRegion: DOM.inRegion(node, node2, false, altRegion)
        };
        
    },
    /**
     * Check if any part of this node is in the passed region
     * @method inRegion
     * @param {Object} node2 The node to get the region from or an Object literal of the region
     * $param {Boolean} all Should all of the node be inside the region
     * @param {Object} altRegion An object literal containing the region for this node if we already have the data (for performance i.e. DragDrop)
     * @return {Boolean} True if in region, false if not.
     */
    inRegion: function(node, node2, all, altRegion) {
        var region = {},
            r = altRegion || DOM.region(node),
            n = node2,
            off;

        if (n.tagName) {
            region = DOM.region(n);
        } else if (Y.Lang.isObject(node2)) {
            region = node2;
        } else {
            return false;
        }
            
        if (all) {
            return (
                r[LEFT]   >= region[LEFT]   &&
                r[RIGHT]  <= region[RIGHT]  && 
                r[TOP]    >= region[TOP]    && 
                r[BOTTOM] <= region[BOTTOM]  );
        } else {
            off = getOffsets(region, r);
            if (off[BOTTOM] >= off[TOP] && off[RIGHT] >= off[LEFT]) {
                return true;
            } else {
                return false;
            }
            
        }
    },

    /**
     * Check if any part of this element is in the viewport
     * @method inViewportRegion
     * @param {HTMLElement} element The DOM element. 
     * @param {Boolean} all Should all of the node be inside the region
     * @param {Object} altRegion An object literal containing the region for this node if we already have the data (for performance i.e. DragDrop)
     * @return {Boolean} True if in region, false if not.
     */
    inViewportRegion: function(node, all, altRegion) {
        return DOM.inRegion(node, DOM.viewportRegion(node), all, altRegion);
            
    },

    _getRegion: function(t, r, b, l) {
        var region = {};

        region[TOP] = region[1] = t;
        region[LEFT] = region[0] = l;
        region[BOTTOM] = b;
        region[RIGHT] = r;
        region.width = region[RIGHT] - region[LEFT];
        region.height = region[BOTTOM] - region[TOP];

        return region;
    },

    /**
     * Returns an Object literal containing the following about the visible region of viewport: (top, right, bottom, left)
     * @method viewportRegion
     @return {Object} Object literal containing the following about the visible region of the viewport: (top, right, bottom, left)
     */
    viewportRegion: function(node) {
        node = node || Y.config.doc.documentElement;
        var ret = false,
            scrollX,
            scrollY;

        if (node) {
            scrollX = DOM.docScrollX(node);
            scrollY = DOM.docScrollY(node);

            ret = DOM._getRegion(scrollY, // top
                DOM.winWidth(node) + scrollX, // right
                scrollY + DOM.winHeight(node), // bottom
                scrollX); // left
        }

        return ret;
    }
});
})(Y);