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                            /**
                            * The class manages a queue of files that should be uploaded to the server.
                            * It initializes the required number of uploads, tracks them as they progress,
                            * and automatically advances to the next upload when a preceding one has completed.
                            * @module uploader-queue
                            */
                            
                            
                            
                            /**
                            * This class manages a queue of files to be uploaded to the server.
                            * @class Uploader.Queue
                            * @extends Base
                            * @constructor
                            */
                            var UploaderQueue = function() {
                                this.queuedFiles = [];
                                this.uploadRetries = {};
                                this.numberOfUploads = 0;
                                this.currentUploadedByteValues = {};
                                this.currentFiles = {};
                                this.totalBytesUploaded = 0;
                                this.totalBytes = 0;
                            
                                UploaderQueue.superclass.constructor.apply(this, arguments);
                            };
                            
                            
                            Y.extend(UploaderQueue, Y.Base, {
                            
                                /**
                                * Stored value of the current queue state
                                * @property _currentState
                                * @type {String}
                                * @protected
                                * @default UploaderQueue.STOPPED
                                */
                                _currentState: UploaderQueue.STOPPED,
                            
                                /**
                                * Construction logic executed during UploaderQueue instantiation.
                                *
                                * @method initializer
                                * @protected
                                */
                                initializer : function () {},
                            
                                /**
                                * Handles and retransmits upload start event.
                                *
                                * @method _uploadStartHandler
                                * @param event The event dispatched during the upload process.
                                * @private
                                */
                                _uploadStartHandler : function (event) {
                                    var updatedEvent = event;
                                    updatedEvent.file = event.target;
                                    updatedEvent.originEvent = event;
                            
                                    this.fire("uploadstart", updatedEvent);
                                },
                            
                                /**
                                * Handles and retransmits upload error event.
                                *
                                * @method _uploadErrorHandler
                                * @param event The event dispatched during the upload process.
                                * @private
                                */
                                _uploadErrorHandler : function (event) {
                                    var errorAction = this.get("errorAction"),
                                        updatedEvent = event,
                                        fileid,
                                        retries;
                            
                                    updatedEvent.file = event.target;
                                    updatedEvent.originEvent = event;
                            
                                    this.numberOfUploads-=1;
                                    delete this.currentFiles[event.target.get("id")];
                                    this._detachFileEvents(event.target);
                            
                                    event.target.cancelUpload();
                            
                                    if (errorAction === UploaderQueue.STOP) {
                                        this.pauseUpload();
                                    }
                            
                                    else if (errorAction === UploaderQueue.RESTART_ASAP) {
                                        fileid = event.target.get("id");
                                        retries = this.uploadRetries[fileid] || 0;
                            
                                        if (retries < this.get("retryCount")) {
                                            this.uploadRetries[fileid] = retries + 1;
                                            this.addToQueueTop(event.target);
                                        }
                                        this._startNextFile();
                                    }
                                    else if (errorAction === UploaderQueue.RESTART_AFTER) {
                                        fileid = event.target.get("id");
                                        retries = this.uploadRetries[fileid] || 0;
                            
                                        if (retries < this.get("retryCount")) {
                                            this.uploadRetries[fileid] = retries + 1;
                                            this.addToQueueBottom(event.target);
                                        }
                                        this._startNextFile();
                                    }
                            
                                    this.fire("uploaderror", updatedEvent);
                                },
                            
                                /**
                                * Launches the upload of the next file in the queue.
                                *
                                * @method _startNextFile
                                * @private
                                */
                                _startNextFile : function () {
                                    if (this.queuedFiles.length > 0) {
                                        var currentFile = this.queuedFiles.shift(),
                                            fileId = currentFile.get("id"),
                                            parameters = this.get("perFileParameters"),
                                            fileParameters = parameters.hasOwnProperty(fileId) ? parameters[fileId] : parameters;
                            
                                        this.currentUploadedByteValues[fileId] = 0;
                            
                                        currentFile.on("uploadstart", this._uploadStartHandler, this);
                                        currentFile.on("uploadprogress", this._uploadProgressHandler, this);
                                        currentFile.on("uploadcomplete", this._uploadCompleteHandler, this);
                                        currentFile.on("uploaderror", this._uploadErrorHandler, this);
                                        currentFile.on("uploadcancel", this._uploadCancelHandler, this);
                            
                                        currentFile.set("xhrHeaders", this.get("uploadHeaders"));
                                        currentFile.set("xhrWithCredentials", this.get("withCredentials"));
                            
                                        currentFile.startUpload(this.get("uploadURL"), fileParameters, this.get("fileFieldName"));
                            
                                        this._registerUpload(currentFile);
                                    }
                                },
                            
                                /**
                                * Register a new upload process.
                                *
                                * @method _registerUpload
                                * @private
                                */
                                _registerUpload : function (file) {
                                    this.numberOfUploads += 1;
                                    this.currentFiles[file.get("id")] = file;
                                },
                            
                                /**
                                * Unregisters a new upload process.
                                *
                                * @method _unregisterUpload
                                * @private
                                */
                                _unregisterUpload : function (file) {
                                    if (this.numberOfUploads > 0) {
                                        this.numberOfUploads -= 1;
                                    }
                            
                                    delete this.currentFiles[file.get("id")];
                                    delete this.uploadRetries[file.get("id")];
                            
                                    this._detachFileEvents(file);
                                },
                            
                                _detachFileEvents : function (file) {
                                    file.detach("uploadstart", this._uploadStartHandler);
                                    file.detach("uploadprogress", this._uploadProgressHandler);
                                    file.detach("uploadcomplete", this._uploadCompleteHandler);
                                    file.detach("uploaderror", this._uploadErrorHandler);
                                    file.detach("uploadcancel", this._uploadCancelHandler);
                                },
                            
                                /**
                                * Handles and retransmits upload complete event.
                                *
                                * @method _uploadCompleteHandler
                                * @param event The event dispatched during the upload process.
                                * @private
                                */
                                _uploadCompleteHandler : function (event) {
                            
                                    this._unregisterUpload(event.target);
                            
                                    this.totalBytesUploaded += event.target.get("size");
                                    delete this.currentUploadedByteValues[event.target.get("id")];
                            
                            
                                    if (this.queuedFiles.length > 0 && this._currentState === UploaderQueue.UPLOADING) {
                                        this._startNextFile();
                                    }
                            
                                    var updatedEvent = event,
                                        uploadedTotal = this.totalBytesUploaded,
                                        percentLoaded = Math.min(100, Math.round(10000*uploadedTotal/this.totalBytes) / 100);
                            
                                    updatedEvent.file = event.target;
                                    updatedEvent.originEvent = event;
                            
                                    Y.each(this.currentUploadedByteValues, function (value) {
                                        uploadedTotal += value;
                                    });
                            
                                    this.fire("totaluploadprogress", {
                                        bytesLoaded: uploadedTotal,
                                        bytesTotal: this.totalBytes,
                                        percentLoaded: percentLoaded
                                    });
                            
                                    this.fire("uploadcomplete", updatedEvent);
                            
                                    if (this.queuedFiles.length === 0 && this.numberOfUploads <= 0) {
                                        this.fire("alluploadscomplete");
                                        this._currentState = UploaderQueue.STOPPED;
                                    }
                                },
                            
                                /**
                                * Handles and retransmits upload cancel event.
                                *
                                * @method _uploadCancelHandler
                                * @param event The event dispatched during the upload process.
                                * @private
                                */
                                _uploadCancelHandler : function (event) {
                            
                                    var updatedEvent = event;
                                    updatedEvent.originEvent = event;
                                    updatedEvent.file = event.target;
                            
                                    this.fire("uploadcancel", updatedEvent);
                                },
                            
                            
                            
                                /**
                                * Handles and retransmits upload progress event.
                                *
                                * @method _uploadProgressHandler
                                * @param event The event dispatched during the upload process.
                                * @private
                                */
                                _uploadProgressHandler : function (event) {
                            
                                    this.currentUploadedByteValues[event.target.get("id")] = event.bytesLoaded;
                            
                                    var updatedEvent = event,
                                        uploadedTotal = this.totalBytesUploaded,
                                        percentLoaded = Math.min(100, Math.round(10000*uploadedTotal/this.totalBytes) / 100);
                            
                                    updatedEvent.originEvent = event;
                                    updatedEvent.file = event.target;
                            
                                    this.fire("uploadprogress", updatedEvent);
                            
                                    Y.each(this.currentUploadedByteValues, function (value) {
                                        uploadedTotal += value;
                                    });
                            
                                    this.fire("totaluploadprogress", {
                                        bytesLoaded: uploadedTotal,
                                        bytesTotal: this.totalBytes,
                                        percentLoaded: percentLoaded
                                    });
                                },
                            
                                /**
                                * Starts uploading the queued up file list.
                                *
                                * @method startUpload
                                */
                                startUpload: function() {
                                    this.queuedFiles = this.get("fileList").slice(0);
                                    this.numberOfUploads = 0;
                                    this.currentUploadedByteValues = {};
                                    this.currentFiles = {};
                                    this.totalBytesUploaded = 0;
                            
                                    this._currentState = UploaderQueue.UPLOADING;
                            
                                    while (this.numberOfUploads < this.get("simUploads") && this.queuedFiles.length > 0) {
                                        this._startNextFile();
                                    }
                                },
                            
                                /**
                                * Pauses the upload process. The ongoing file uploads
                                * will complete after this method is called, but no
                                * new ones will be launched.
                                *
                                * @method pauseUpload
                                */
                                pauseUpload: function () {
                                    this._currentState = UploaderQueue.STOPPED;
                                },
                            
                                /**
                                * Restarts a paused upload process.
                                *
                                * @method restartUpload
                                */
                                restartUpload: function () {
                                    this._currentState = UploaderQueue.UPLOADING;
                                    while (this.numberOfUploads < this.get("simUploads")) {
                                         this._startNextFile();
                                    }
                                },
                            
                                /**
                                * If a particular file is stuck in an ongoing upload without
                                * any progress events, this method allows to force its reupload
                                * by cancelling its upload and immediately relaunching it.
                                *
                                * @method forceReupload
                                * @param file {File} The file to force reupload on.
                                */
                                forceReupload : function (file) {
                                    var id = file.get("id");
                                    if (this.currentFiles.hasOwnProperty(id)) {
                                        file.cancelUpload();
                                        this._unregisterUpload(file);
                                        this.addToQueueTop(file);
                                        this._startNextFile();
                                    }
                                },
                            
                                /**
                                * Add a new file to the top of the queue (the upload will be
                                * launched as soon as the current number of uploading files
                                * drops below the maximum permissible value).
                                *
                                * @method addToQueueTop
                                * @param file {File} The file to add to the top of the queue.
                                */
                                addToQueueTop: function (file) {
                                        this.queuedFiles.unshift(file);
                                },
                            
                                /**
                                * Add a new file to the bottom of the queue (the upload will be
                                * launched after all the other queued files are uploaded.)
                                *
                                * @method addToQueueBottom
                                * @param file {File} The file to add to the bottom of the queue.
                                */
                                addToQueueBottom: function (file) {
                                        this.queuedFiles.push(file);
                                },
                            
                                /**
                                * Cancels a specific file's upload. If no argument is passed,
                                * all ongoing uploads are cancelled and the upload process is
                                * stopped.
                                *
                                * @method cancelUpload
                                * @param file {File} An optional parameter - the file whose upload
                                * should be cancelled.
                                */
                                cancelUpload: function (file) {
                                    var id,
                                        i,
                                        fid;
                            
                                    if (file) {
                                        id = file.get("id");
                            
                                        if (this.currentFiles[id]) {
                                            this.currentFiles[id].cancelUpload();
                                            this._unregisterUpload(this.currentFiles[id]);
                                            if (this._currentState === UploaderQueue.UPLOADING) {
                                                this._startNextFile();
                                            }
                                        }
                                        else {
                                            for (i = 0, len = this.queuedFiles.length; i < len; i++) {
                                                if (this.queuedFiles[i].get("id") === id) {
                                                    this.queuedFiles.splice(i, 1);
                                                    break;
                                                }
                                            }
                                        }
                                    }
                                    else {
                                        for (fid in this.currentFiles) {
                                            this.currentFiles[fid].cancelUpload();
                                            this._unregisterUpload(this.currentFiles[fid]);
                                        }
                            
                                        this.currentUploadedByteValues = {};
                                        this.currentFiles = {};
                                        this.totalBytesUploaded = 0;
                                        this.fire("alluploadscancelled");
                                        this._currentState = UploaderQueue.STOPPED;
                                    }
                                }
                            }, {
                                /**
                                * Static constant for the value of the `errorAction` attribute:
                                * prescribes the queue to continue uploading files in case of
                                * an error.
                                * @property CONTINUE
                                * @readOnly
                                * @type {String}
                                * @static
                                */
                                CONTINUE: "continue",
                            
                                /**
                                * Static constant for the value of the `errorAction` attribute:
                                * prescribes the queue to stop uploading files in case of
                                * an error.
                                * @property STOP
                                * @readOnly
                                * @type {String}
                                * @static
                                */
                                STOP: "stop",
                            
                                /**
                                * Static constant for the value of the `errorAction` attribute:
                                * prescribes the queue to restart a file upload immediately in case of
                                * an error.
                                * @property RESTART_ASAP
                                * @readOnly
                                * @type {String}
                                * @static
                                */
                                RESTART_ASAP: "restartasap",
                            
                                /**
                                * Static constant for the value of the `errorAction` attribute:
                                * prescribes the queue to restart an errored out file upload after
                                * other files have finished uploading.
                                * @property RESTART_AFTER
                                * @readOnly
                                * @type {String}
                                * @static
                                */
                                RESTART_AFTER: "restartafter",
                            
                                /**
                                * Static constant for the value of the `_currentState` property:
                                * implies that the queue is currently not uploading files.
                                * @property STOPPED
                                * @readOnly
                                * @type {String}
                                * @static
                                */
                                STOPPED: "stopped",
                            
                                /**
                                * Static constant for the value of the `_currentState` property:
                                * implies that the queue is currently uploading files.
                                * @property UPLOADING
                                * @readOnly
                                * @type {String}
                                * @static
                                */
                                UPLOADING: "uploading",
                            
                                /**
                                * The identity of the class.
                                *
                                * @property NAME
                                * @type String
                                * @default 'uploaderqueue'
                                * @readOnly
                                * @protected
                                * @static
                                */
                                NAME: 'uploaderqueue',
                            
                                /**
                                * Static property used to define the default attribute configuration of
                                * the class.
                                *
                                * @property ATTRS
                                * @type {Object}
                                * @protected
                                * @static
                                */
                                ATTRS: {
                            
                                    /**
                                    * Maximum number of simultaneous uploads; must be in the
                                    * range between 1 and 5. The value of `2` is default. It
                                    * is recommended that this value does not exceed 3.
                                    * @attribute simUploads
                                    * @type Number
                                    * @default 2
                                    */
                                     simUploads: {
                                             value: 2,
                                             validator: function (val) {
                                                     return (val >= 1 && val <= 5);
                                             }
                                     },
                            
                                    /**
                                    * The action to take in case of error. The valid values for this attribute are:
                                    * `Y.Uploader.Queue.CONTINUE` (the upload process should continue on other files,
                                    * ignoring the error), `Y.Uploader.Queue.STOP` (the upload process
                                    * should stop completely), `Y.Uploader.Queue.RESTART_ASAP` (the upload
                                    * should restart immediately on the errored out file and continue as planned), or
                                    * Y.Uploader.Queue.RESTART_AFTER (the upload of the errored out file should restart
                                    * after all other files have uploaded)
                                    * @attribute errorAction
                                    * @type String
                                    * @default Y.Uploader.Queue.CONTINUE
                                    */
                                    errorAction: {
                                        value: "continue",
                                            validator: function (val) {
                                            return (
                                                val === UploaderQueue.CONTINUE ||
                                                val === UploaderQueue.STOP ||
                                                val === UploaderQueue.RESTART_ASAP ||
                                                val === UploaderQueue.RESTART_AFTER
                                            );
                                        }
                                    },
                            
                                    /**
                                    * The total number of bytes that has been uploaded.
                                    * @attribute bytesUploaded
                                    * @type Number
                                    */
                                    bytesUploaded: {
                                        readOnly: true,
                                        value: 0
                                    },
                            
                                    /**
                                    * The total number of bytes in the queue.
                                    * @attribute bytesTotal
                                    * @type Number
                                    */
                                    bytesTotal: {
                                        readOnly: true,
                                        value: 0
                                    },
                            
                                    /**
                                    * The queue file list. This file list should only be modified
                                    * before the upload has been started; modifying it after starting
                                    * the upload has no effect, and `addToQueueTop` or `addToQueueBottom` methods
                                    * should be used instead.
                                    * @attribute fileList
                                    * @type Array
                                    */
                                    fileList: {
                                        value: [],
                                        lazyAdd: false,
                                        setter: function (val) {
                                            var newValue = val;
                                            Y.Array.each(newValue, function (value) {
                                                this.totalBytes += value.get("size");
                                            }, this);
                            
                                            return val;
                                        }
                                    },
                            
                                    /**
                                    * A String specifying what should be the POST field name for the file
                                    * content in the upload request.
                                    *
                                    * @attribute fileFieldName
                                    * @type {String}
                                    * @default Filedata
                                    */
                                    fileFieldName: {
                                        value: "Filedata"
                                    },
                            
                                    /**
                                    * The URL to POST the file upload requests to.
                                    *
                                    * @attribute uploadURL
                                    * @type {String}
                                    * @default ""
                                    */
                                    uploadURL: {
                                        value: ""
                                    },
                            
                                    /**
                                    * Additional HTTP headers that should be included
                                    * in the upload request. Due to Flash Player security
                                    * restrictions, this attribute is only honored in the
                                    * HTML5 Uploader.
                                    *
                                    * @attribute uploadHeaders
                                    * @type {Object}
                                    * @default {}
                                    */
                                    uploadHeaders: {
                                        value: {}
                                    },
                            
                                    /**
                                    * A Boolean that specifies whether the file should be
                                    * uploaded with the appropriate user credentials for the
                                    * domain. Due to Flash Player security restrictions, this
                                    * attribute is only honored in the HTML5 Uploader.
                                    *
                                    * @attribute withCredentials
                                    * @type {Boolean}
                                    * @default true
                                    */
                                    withCredentials: {
                                        value: true
                                    },
                            
                            
                                    /**
                                    * An object, keyed by `fileId`, containing sets of key-value pairs
                                    * that should be passed as POST variables along with each corresponding
                                    * file.
                                    *
                                    * @attribute perFileParameters
                                    * @type {Object}
                                    * @default {}
                                    */
                                    perFileParameters: {
                                        value: {}
                                    },
                            
                                    /**
                                    * The number of times to try re-uploading a file that failed to upload before
                                    * cancelling its upload.
                                    *
                                    * @attribute retryCount
                                    * @type {Number}
                                    * @default 3
                                    */
                                    retryCount: {
                                        value: 3
                                    }
                            
                                }
                            });
                            
                            
                            Y.namespace('Uploader');
                            Y.Uploader.Queue = UploaderQueue;