/*

Copyright (c) 2009, Yahoo! Inc. All rights reserved.

Code licensed under the BSD License:

http://developer.yahoo.net/yui/license.txt

version: 3.0.0b1

build: 1163

*/

YUI.add('dd-ddm', function(Y) {

    /**

     * Extends the dd-ddm-base Class to add support for the viewport shim to allow a draggable node to drag to be dragged over an iframe or any other node that traps mousemove events.

     * It is also required to have Drop Targets enabled, as the viewport shim will contain the shims for the Drop Targets.

     * @module dd

     * @submodule dd-ddm

     * @for DDM

     * @namespace DD

     */

    Y.mix(Y.DD.DDM, {

        /**

        * @private

        * @property _pg

        * @description The shim placed over the screen to track the mousemove event.

        * @type {Node}

        */

        _pg: null,

        /**

        * @private

        * @property _debugShim

        * @description Set this to true to set the shims opacity to .5 for debugging it, default: false.

        * @type {Boolean}

        */

        _debugShim: false,

        _activateTargets: function() {},

        _deactivateTargets: function() {},

        _startDrag: function() {

            if (this.activeDrag.get('useShim')) {

                this._pg_activate();

                this._activateTargets();

            }

        },

        _endDrag: function() {

            this._pg_deactivate();

            this._deactivateTargets();

        },

        /**

        * @private

        * @method _pg_deactivate

        * @description Deactivates the shim

        */

        _pg_deactivate: function() {

            this._pg.setStyle('display', 'none');

        },

        /**

        * @private

        * @method _pg_activate

        * @description Activates the shim

        */

        _pg_activate: function() {

            var ah = this.activeDrag.get('activeHandle'), cur = 'auto';

            if (ah) {

                cur = ah.getStyle('cursor');

            }

            if (cur == 'auto') {

                cur = this.get('dragCursor');

            }

            this._pg_size();

            this._pg.setStyles({

                top: 0,

                left: 0,

                display: 'block',

                opacity: ((this._debugShim) ? '.5' : '0'),

                cursor: cur

            });

        },

        /**

        * @private

        * @method _pg_size

        * @description Sizes the shim on: activatation, window:scroll, window:resize

        */

        _pg_size: function() {

            if (this.activeDrag) {

                var b = Y.get('body'),

                h = b.get('docHeight'),

                w = b.get('docWidth');

                this._pg.setStyles({

                    height: h + 'px',

                    width: w + 'px'

                });

            }

        },

        /**

        * @private

        * @method _createPG

        * @description Creates the shim and adds it's listeners to it.

        */

        _createPG: function() {

            var pg = Y.Node.create('<div></div>'),

            bd = Y.get('body');

            pg.setStyles({

                top: '0',

                left: '0',

                position: 'absolute',

                zIndex: '9999',

                overflow: 'hidden',

                backgroundColor: 'red',

                display: 'none',

                height: '5px',

                width: '5px'

            });

            pg.set('id', Y.stamp(pg));

            pg.addClass('yui-dd-shim');

            if (bd.get('firstChild')) {

                bd.insertBefore(pg, bd.get('firstChild'));

            } else {

                bd.appendChild(pg);

            }

            this._pg = pg;

            this._pg.on('mouseup', Y.bind(this._end, this));

            this._pg.on('mousemove', Y.bind(this._move, this));

            var win = Y.get(window);

            win.on('resize', Y.bind(this._pg_size, this));

            win.on('scroll', Y.bind(this._pg_size, this));

        }   

    }, true);

    Y.on('domready', Y.bind(Y.DD.DDM._createPG, Y.DD.DDM));

}, '3.0.0b1' ,{requires:['dd-ddm-base'], skinnable:false});