/**
* Global Static Event Utilities helper that assists us to add
* cross platform events to any DOM object as well retrieving
* their target if any exists.
*
* @author Mohamed Mansour (http://mohamedmansour.com)
*/
var event_utils = {
    add: function (obj, type, callback) {
        if (obj.addEventListener)
            obj.addEventListener(type, callback, false);
        else if (obj.attachEvent)
            obj.attachEvent("on" + type, callback);
    }
}


/**
* Preloads an IFrame since it may take time to load.
*
* @param {string} id The identifier for the Iframe you want preloaded.
* @author Mohamed Mansour (http://mohamedmansour.com)
*/
IFramePreloader = function (id) {
    that = this;
    this.id = id;
    this.iframe = document.getElementById(id);
    this.placeholder = this.createPlaceholder();
}

IFramePreloader.prototype = {

    /**
    * Initializes the preloader to wait till a load event occurs in the iframe.
    */
    init: function () {
        if (this.iframe == null) {
            return;
        }
        this.iframe.style.display = 'none';
        event_utils.add(this.iframe, 'load', function (e) { that.handleLoad(e); });
    },

    /**
    * Creates the placeholder for that Iframe.
    * @return {Element} The placeholder element.
    */
    createPlaceholder: function () {
        // Create placeholder.
        var newElement = document.createElement('div');
        newElement.id = this.id + '-placeholder';
        newElement.appendChild(document.createTextNode('Loading ...'));

        if (this.iframe == null) {
            return;
        }

        // Adding that placeholder right after the iframe. We first check if its the
        // last child, if so, we just append it. Otherwise, we insert it before the
        // next sibling.
        var parent = this.iframe.parentNode;
        if (parent.lastChild == this.iframe) {
            parent.appendChild(newElement);
        } else {
            parent.insertBefore(newElement, this.iframe.nextSibling);
        }
        return newElement;
    },

    /**
    * Show the frame, hide the preloader. Since it has been loaded!
    */
    handleLoad: function () {
        this.iframe.style.display = 'block';
        this.placeholder.style.display = 'none';
    }
}