/**
 * @class Ext.Shadow
 * Simple class that can provide a shadow effect for any element.  Note that the element MUST be absolutely positioned,
 * and the shadow does not provide any shimming.  This should be used only in simple cases -- for more advanced
 * functionality that can also provide the same shadow effect, see the {@link Ext.Layer} class.
 * @constructor
 * Create a new Shadow
 * @param {Object} config The config object
 */
Ext.Shadow = function(config){
    Ext.apply(this, config);
    if(typeof this.mode != "string"){
        this.mode = this.defaultMode;
    }
    var o = this.offset, a = {h: 0};
    var rad = Math.floor(this.offset/2);
    switch(this.mode.toLowerCase()){ // all this hideous nonsense calculates the various offsets for shadows
        case "drop":
            a.w = 0;
            a.l = a.t = o;
            a.t -= 1;
            if(Ext.isIE){
                a.l -= this.offset + rad;
                a.t -= this.offset + rad;
                a.w -= rad;
                a.h -= rad;
                a.t += 1;
            }
        break;
        case "sides":
            a.w = (o*2);
            a.l = -o;
            a.t = o-1;
            if(Ext.isIE){
                a.l -= (this.offset - rad);
                a.t -= this.offset + rad;
                a.l += 1;
                a.w -= (this.offset - rad)*2;
                a.w -= rad + 1;
                a.h -= 1;
            }
        break;
        case "frame":
            a.w = a.h = (o*2);
            a.l = a.t = -o;
            a.t += 1;
            a.h -= 2;
            if(Ext.isIE){
                a.l -= (this.offset - rad);
                a.t -= (this.offset - rad);
                a.l += 1;
                a.w -= (this.offset + rad + 1);
                a.h -= (this.offset + rad);
                a.h += 1;
            }
        break;
    };

    this.adjusts = a;
};

Ext.Shadow.prototype = {
    
/**
     * @cfg {String} mode
     * The shadow display mode.  Supports the following options:

     * 
sides : Shadow displays on both sides and bottom only
     * 
frame : Shadow displays equally on all four sides
     * 
drop : Traditional bottom-right drop shadow
     * 
     */
    
/**
     * @cfg {String} offset
     * The number of pixels to offset the shadow from the element (defaults to 4)
     */
    offset: 4,

    // private
    defaultMode: "drop",

    
/**
     * Displays the shadow under the target element
     * @param {Mixed} targetEl The id or element under which the shadow should display
     */
    show : function(target){
        target = Ext.get(target);
        if(!this.el){
            this.el = Ext.Shadow.Pool.pull();
            if(this.el.dom.nextSibling != target.dom){
                this.el.insertBefore(target);
            }
        }
        this.el.setStyle("z-index", this.zIndex || parseInt(target.getStyle("z-index"), 10)-1);
        if(Ext.isIE){
            this.el.dom.style.filter="progid:DXImageTransform.Microsoft.alpha(opacity=50) progid:DXImageTransform.Microsoft.Blur(pixelradius="+(this.offset)+")";
        }
        this.realign(
            target.getLeft(true),
            target.getTop(true),
            target.getWidth(),
            target.getHeight()
        );
        this.el.dom.style.display = "block";
    },

    
/**
     * Returns true if the shadow is visible, else false
     */
    isVisible : function(){
        return this.el ? true : false;  
    },

    
/**
     * Direct alignment when values are already available. Show must be called at least once before
     * calling this method to ensure it is initialized.
     * @param {Number} left The target element left position
     * @param {Number} top The target element top position
     * @param {Number} width The target element width
     * @param {Number} height The target element height
     */
    realign : function(l, t, w, h){
        if(!this.el){
            return;
        }
        var a = this.adjusts, d = this.el.dom, s = d.style;
        var iea = 0;
        s.left = (l+a.l)+"px";
        s.top = (t+a.t)+"px";
        var sw = (w+a.w), sh = (h+a.h), sws = sw +"px", shs = sh + "px";
        if(s.width != sws || s.height != shs){
            s.width = sws;
            s.height = shs;
            if(!Ext.isIE){
                var cn = d.childNodes;
                var sww = Math.max(0, (sw-12))+"px";
                cn[0].childNodes[1].style.width = sww;
                cn[1].childNodes[1].style.width = sww;
                cn[2].childNodes[1].style.width = sww;
                cn[1].style.height = Math.max(0, (sh-12))+"px";
            }
        }
    },

    
/**
     * Hides this shadow
     */
    hide : function(){
        if(this.el){
            this.el.dom.style.display = "none";
            Ext.Shadow.Pool.push(this.el);
            delete this.el;
        }
    },

    
/**
     * Adjust the z-index of this shadow
     * @param {Number} zindex The new z-index
     */
    setZIndex : function(z){
        this.zIndex = z;
        if(this.el){
            this.el.setStyle("z-index", z);
        }
    }
};

// Private utility class that manages the internal Shadow cache
Ext.Shadow.Pool = function(){
    var p = [];
    var markup = Ext.isIE ?
                 '
' :
                 '
';
    return {
        pull : function(){
            var sh = p.shift();
            if(!sh){
                sh = Ext.get(Ext.DomHelper.insertHtml("beforeBegin", document.body.firstChild, markup));
                sh.autoBoxAdjust = false;
            }
            return sh;
        },

        push : function(sh){
            p.push(sh);
        }
    };
}();