if (typeof (UploaderControl) == "undefined" || UploaderControl == null) {

    UploaderControls = {};

    UploaderControl = function(id) {

        if (arguments.length > 0)
            this.init(id);
    };

    UploaderControl.getInstance = function(id) {
        var x = UploaderControls[id];
        if (x == null)
            x = UploaderControls[id] = new UploaderControl(id);
        return x;
    };

    UploaderControl.eventObjects = {};

    UploaderControl.prototype = {

        id: null,
        silverlightClientId: null,
        loaded: false,
        uploadInProgress: false,
        userContext: null,

        init: function(id) {

            this.id = id;
            this.events = {};

            UploaderControl.eventObjects[this.id] = this;

            //
            // These are the available js events that you can handle on the UploaderControl.  See attachEvent for details on how to use.
            //
            this.events["onuploadstarted"] = null; // the user has started uploading some files; this is your last chance to set the user context
            this.events["onfileuploaded"] = null; // (fileGuid, fileName, fileSize) called for each file when it has completed uploading
            this.events["onallfilesuploaded"] = null; // all files have completed uploading (or been canceled or removed from the list)
            this.events["onerror"] = null; // (errorMessage)
        },

        initialize: function(userContext) {

            this.userContext = userContext;
            this.silverlightClientId = "silverlight" + this.id;

            // it's possible that the control can finish loading before the load handling js function is written to the page, so do a check
            if (!this.loaded) {
                try {
                    var obj = document.getElementById(this.silverlightClientId);
                    if (obj && obj.Content && obj.Content.Files)
                        this.onLoad();
                } catch (ex) { }
            }
        },

        //
        // Public methods.
        //

        setUserContext: function(ctx) {
            /// <summary>
            /// A string that is sent as the Context parameter to server-side file upload processors.  Must be set before
            /// file uploading has begun.
            /// </summary>

            this.userContext = ctx;
        },

        attachEvent: function(eventName, func, context) {
            /// <summary>
            /// Public method for attaching event handlers to this control.
            /// </summary>
            /// <param name="eventName">the name of the event</param>
            /// <param name="func">function pointer to the event handler</param>
            /// <param name="context">context to use when calling func (becomes the 'this' keyword within your function)</param>
            /// <example>
            /// var uploader = UploaderControl.getInstance("upload1");
            /// uploader.attachEvent("onfileuploaded", myFunc);
            /// ...
            /// function myFunc(fileGuid, fileName, fileSize) {
            ///     ...
            /// }
            /// </example>

            if (context == null) context = this;
            if (func == null)
                this.events[eventName] = null;
            else
                this.events[eventName] = { func: func, context: context };
        },


        //
        // below are some example utility methods that access methods on the silverlight object
        //

        clearFileList: function() {

            if (this.loaded) {
                var obj = document.getElementById(this.silverlightClientId);
                try {
                    if (obj && obj.Content && obj.Content.UploaderControl)
                        obj.Content.UploaderControl.ClearFileList();
                } catch (ex) { }
            }
        },

        getFileCount: function() {

            var ret = -1;
            if (this.loaded) {
                var obj = document.getElementById(this.silverlightClientId);
                try {
                    if (obj && obj.Content && obj.Content.Files)
                        ret = obj.Content.Files.TotalFilesSelected;
                } catch (ex) { }
            }

            return ret;
        },


        //
        // private methods for hooking stuff up to the silverlight control
        //
        onLoad: function() {

            this.loaded = true;

            var obj = document.getElementById(this.silverlightClientId);
            obj.Content.UploaderControl.UploadStarted = window["UploaderControl_uploadStarted_" + this.id];
            obj.Content.Files.SingleFileUploadFinished = window["UploaderControl_singleFileUploadFinished_" + this.id];
            obj.Content.Files.AllFilesFinished = window["UploaderControl_allFilesFinished_" + this.id];
            obj.Content.Files.ErrorOccurred = window["UploaderControl_errorOccurred_" + this.id];
        },

        uploadStarted: function(sender, e) {

            this.invokeEventHandler("onuploadstarted");

            this.uploadInProgress = true;
            var obj = document.getElementById(this.silverlightClientId);
            obj.Content.Files.UserContextParameter = this.userContext;
        },

        singleFileUploadFinished: function(sender, e) {

            this.invokeEventHandler("onfileuploaded", e.FileGuid, e.FileName, e.FileSize);
        },

        allFilesFinished: function(sender, e) {

            this.uploadInProgress = false;
            this.invokeEventHandler("onallfilesuploaded");
        },

        errorOccurred: function(sender, e) {

            this.invokeEventHandler("onerror", e.ErrorMessage);
        },

        getEventHandler: function(eventName) {
            return this.events[eventName];
        },

        invokeEventHandler: function(eventName) {

            if ((handler = this.events[eventName]) != null) {
                var args = new Array();
                for (var i = 1; i < arguments.length; i++)
                    args.push(arguments[i]);
                return handler.func.apply(handler.context, args);
            }

            return null;
        }
    };

}