text: /**
   * http://github.com/valums/file-uploader
   * 
   * Multiple file upload component with progress-bar, drag-and-drop. 
   * © 2010 Andrew Valums ( andrew(at)valums.com ) 
   * 
   * Licensed under GNU GPL 2 or later, see license.txt.
   */    
  
  //
  // Helper functions
  //
  
  var qq = qq || {};
  
  /**
   * Adds all missing properties from second obj to first obj
   */ 
  qq.extend = function(first, second){
      for (var prop in second){
          first[prop] = second[prop];
      }
  };  
  
  /**
   * Searches for a given element in the array, returns -1 if it is not present.
   * @param {Number} [from] The index at which to begin the search
   */
  qq.indexOf = function(arr, elt, from){
      if (arr.indexOf) return arr.indexOf(elt, from);
      
      from = from || 0;
      var len = arr.length;    
      
      if (from < 0) from += len;  
  
      for (; from < len; from++){  
          if (from in arr && arr[from] === elt){  
              return from;
          }
      }  
      return -1;  
  }; 
      
  qq.getUniqueId = (function(){
      var id = 0;
      return function(){ return id++; };
  })();
  
  //
  // Events
  
  qq.attach = function(element, type, fn){
      if (element.addEventListener){
          element.addEventListener(type, fn, false);
      } else if (element.attachEvent){
          element.attachEvent('on' + type, fn);
      }
  };
  qq.detach = function(element, type, fn){
      if (element.removeEventListener){
          element.removeEventListener(type, fn, false);
      } else if (element.attachEvent){
          element.detachEvent('on' + type, fn);
      }
  };
  
  qq.preventDefault = function(e){
      if (e.preventDefault){
          e.preventDefault();
      } else{
          e.returnValue = false;
      }
  };
  
  //
  // Node manipulations
  
  /**
   * Insert node a before node b.
   */
  qq.insertBefore = function(a, b){
      b.parentNode.insertBefore(a, b);
  };
  qq.remove = function(element){
      element.parentNode.removeChild(element);
  };
  
  qq.contains = function(parent, descendant){       
      // compareposition returns false in this case
      if (parent == descendant) return true;
      
      if (parent.contains){
          return parent.contains(descendant);
      } else {
          return !!(descendant.compareDocumentPosition(parent) & 8);
      }
  };
  
  /**
   * Creates and returns element from html string
   * Uses innerHTML to create an element
   */
  qq.toElement = (function(){
      var div = document.createElement('div');
      return function(html){
          div.innerHTML = html;
          var element = div.firstChild;
          div.removeChild(element);
          return element;
      };
  })();
  
  //
  // Node properties and attributes
  
  /**
   * Sets styles for an element.
   * Fixes opacity in IE6-8.
   */
  qq.css = function(element, styles){
      if (styles.opacity != null){
          if (typeof element.style.opacity != 'string' && typeof(element.filters) != 'undefined'){
              styles.filter = 'alpha(opacity=' + Math.round(100 * styles.opacity) + ')';
          }
      }
      qq.extend(element.style, styles);
  };
  qq.hasClass = function(element, name){
      var re = new RegExp('(^| )' + name + '( |$)');
      return re.test(element.className);
  };
  qq.addClass = function(element, name){
      if (!qq.hasClass(element, name)){
          element.className += ' ' + name;
      }
  };
  qq.removeClass = function(element, name){
      var re = new RegExp('(^| )' + name + '( |$)');
      element.className = element.className.replace(re, ' ').replace(/^\s+|\s+$/g, "");
  };
  qq.setText = function(element, text){
      element.innerText = text;
      element.textContent = text;
  };
  
  //
  // Selecting elements
  
  qq.children = function(element){
      var children = [],
      child = element.firstChild;
  
      while (child){
          if (child.nodeType == 1){
              children.push(child);
          }
          child = child.nextSibling;
      }
  
      return children;
  };
  
  qq.getByClass = function(element, className){
      if (element.querySelectorAll){
          return element.querySelectorAll('.' + className);
      }
  
      var result = [];
      var candidates = element.getElementsByTagName("*");
      var len = candidates.length;
  
      for (var i = 0; i < len; i++){
          if (qq.hasClass(candidates[i], className)){
              result.push(candidates[i]);
          }
      }
      return result;
  };
  
  /**
   * obj2url() takes a json-object as argument and generates
   * a querystring. pretty much like jQuery.param()
   * 
   * how to use:
   *
   *    `qq.obj2url({a:'b',c:'d'},'http://any.url/upload?otherParam=value');`
   *
   * will result in:
   *
   *    `http://any.url/upload?otherParam=value&a=b&c=d`
   *
   * @param  Object JSON-Object
   * @param  String current querystring-part
   * @return String encoded querystring
   */
  qq.obj2url = function(obj, temp, prefixDone){
      var uristrings = [],
          prefix = '&',
          add = function(nextObj, i){
              var nextTemp = temp 
                  ? (/\[\]$/.test(temp)) // prevent double-encoding
                     ? temp
                     : temp+'['+i+']'
                  : i;
              if ((nextTemp != 'undefined') && (i != 'undefined')) {  
                  uristrings.push(
                      (typeof nextObj === 'object') 
                          ? qq.obj2url(nextObj, nextTemp, true)
                          : (Object.prototype.toString.call(nextObj) === '[object Function]')
                              ? encodeURIComponent(nextTemp) + '=' + encodeURIComponent(nextObj())
                              : encodeURIComponent(nextTemp) + '=' + encodeURIComponent(nextObj)                                                          
                  );
              }
          }; 
  
      if (!prefixDone && temp) {
        prefix = (/\?/.test(temp)) ? (/\?$/.test(temp)) ? '' : '&' : '?';
        uristrings.push(temp);
        uristrings.push(qq.obj2url(obj));
      } else if ((Object.prototype.toString.call(obj) === '[object Array]') && (typeof obj != 'undefined') ) {
          // we wont use a for-in-loop on an array (performance)
          for (var i = 0, len = obj.length; i < len; ++i){
              add(obj[i], i);
          }
      } else if ((typeof obj != 'undefined') && (obj !== null) && (typeof obj === "object")){
          // for anything else but a scalar, we will use for-in-loop
          for (var i in obj){
              add(obj[i], i);
          }
      } else {
          uristrings.push(encodeURIComponent(temp) + '=' + encodeURIComponent(obj));
      }
  
      return uristrings.join(prefix)
                       .replace(/^&/, '')
                       .replace(/%20/g, '+'); 
  };
  
  //
  //
  // Uploader Classes
  //
  //
  
  var qq = qq || {};
      
  /**
   * Creates upload button, validates upload, but doesn't create file list or dd. 
   */
  qq.FileUploaderBasic = function(o){
      this._options = {
          action: '/server/upload',
          params: {},
          button: null,
          multiple: true,
          maxConnections: 3,
          // validation        
          allowedExtensions: [],               
          sizeLimit: 0,   
          minSizeLimit: 0,                             
          // events
          // return false to cancel submit
          onSubmit: function(id, fileName){},
          onProgress: function(id, fileName, loaded, total){},
          onComplete: function(id, fileName, responseJSON){},
          onCancel: function(id, fileName){},
          // messages                
          messages: {
              typeError: "{file} has invalid extension. Only {extensions} are allowed.",
              sizeError: "{file} is too large, maximum file size is {sizeLimit}.",
              minSizeError: "{file} is too small, minimum file size is {minSizeLimit}.",
              emptyError: "{file} is empty, please select files again without it.",
              onLeave: "The files are being uploaded, if you leave now the upload will be cancelled."            
          },
          showMessage: function(message){
              alert(message);
          }               
      };
      qq.extend(this._options, o);
          
      // number of files being uploaded
      this._filesInProgress = 0;
      this._handler = this._createUploadHandler(); 
      
      if (this._options.button){ 
          this._button = this._createUploadButton(this._options.button);
      }
                          
      this._preventLeaveInProgress();         
  };
     
  qq.FileUploaderBasic.prototype = {
      setParams: function(params){
          this._options.params = params;
      },
      getInProgress: function(){
          return this._filesInProgress;         
      },
      _createUploadButton: function(element){
          var self = this;
          
          return new qq.UploadButton({
              element: element,
              multiple: this._options.multiple && qq.UploadHandlerXhr.isSupported(),
              onChange: function(input){
                  self._onInputChange(input);
              }        
          });           
      },    
      _createUploadHandler: function(){
          var self = this,
              handlerClass;        
          
          if(qq.UploadHandlerXhr.isSupported()){           
              handlerClass = 'UploadHandlerXhr';                        
          } else {
              handlerClass = 'UploadHandlerForm';
          }
  
          var handler = new qq[handlerClass]({
              action: this._options.action,         
              maxConnections: this._options.maxConnections,   
              onProgress: function(id, fileName, loaded, total){                
                  self._onProgress(id, fileName, loaded, total);
                  self._options.onProgress(id, fileName, loaded, total);                    
              },            
              onComplete: function(id, fileName, result){
                  self._onComplete(id, fileName, result);
                  self._options.onComplete(id, fileName, result);
              },
              onCancel: function(id, fileName){
                  self._onCancel(id, fileName);
                  self._options.onCancel(id, fileName);
              }
          });
  
          return handler;
      },    
      _preventLeaveInProgress: function(){
          var self = this;
          
          qq.attach(window, 'beforeunload', function(e){
              if (!self._filesInProgress){return;}
              
              var e = e || window.event;
              // for ie, ff
              e.returnValue = self._options.messages.onLeave;
              // for webkit
              return self._options.messages.onLeave;             
          });        
      },    
      _onSubmit: function(id, fileName){
          this._filesInProgress++;  
      },
      _onProgress: function(id, fileName, loaded, total){        
      },
      _onComplete: function(id, fileName, result){
          this._filesInProgress--;                 
          if (result.error){
              this._options.showMessage(result.error);
          }             
      },
      _onCancel: function(id, fileName){
          this._filesInProgress--;        
      },
      _onInputChange: function(input){
          if (this._handler instanceof qq.UploadHandlerXhr){                
              this._uploadFileList(input.files);                   
          } else {             
              if (this._validateFile(input)){                
                  this._uploadFile(input);                                    
              }                      
          }               
          this._button.reset();   
      },  
      _uploadFileList: function(files){
          for (var i=0; i<files.length; i++){
              if ( !this._validateFile(files[i])){
                  return;
              }            
          }
          
          for (var i=0; i<files.length; i++){
              this._uploadFile(files[i]);        
          }        
      },       
      _uploadFile: function(fileContainer){      
          var id = this._handler.add(fileContainer);
          var fileName = this._handler.getName(id);
          
          if (this._options.onSubmit(id, fileName) !== false){
              this._onSubmit(id, fileName);
              this._handler.upload(id, this._options.params);
          }
      },      
      _validateFile: function(file){
          var name, size;
          
          if (file.value){
              // it is a file input            
              // get input value and remove path to normalize
              name = file.value.replace(/.*(\/|\\)/, "");
          } else {
              // fix missing properties in Safari
              name = file.fileName != null ? file.fileName : file.name;
              size = file.fileSize != null ? file.fileSize : file.size;
          }
                      
          if (! this._isAllowedExtension(name)){            
              this._error('typeError', name);
              return false;
              
          } else if (size === 0){            
              this._error('emptyError', name);
              return false;
                                                       
          } else if (size && this._options.sizeLimit && size > this._options.sizeLimit){            
              this._error('sizeError', name);
              return false;
                          
          } else if (size && size < this._options.minSizeLimit){
              this._error('minSizeError', name);
              return false;            
          }
          
          return true;                
      },
      _error: function(code, fileName){
          var message = this._options.messages[code];        
          function r(name, replacement){ message = message.replace(name, replacement); }
          
          r('{file}', this._formatFileName(fileName));        
          r('{extensions}', this._options.allowedExtensions.join(', '));
          r('{sizeLimit}', this._formatSize(this._options.sizeLimit));
          r('{minSizeLimit}', this._formatSize(this._options.minSizeLimit));
          
          this._options.showMessage(message);                
      },
      _formatFileName: function(name){
          if (name.length > 33){
              name = name.slice(0, 19) + '...' + name.slice(-13);    
          }
          return name;
      },
      _isAllowedExtension: function(fileName){
          var ext = (-1 !== fileName.indexOf('.')) ? fileName.replace(/.*[.]/, '').toLowerCase() : '';
          var allowed = this._options.allowedExtensions;
          
          if (!allowed.length){return true;}        
          
          for (var i=0; i<allowed.length; i++){
              if (allowed[i].toLowerCase() == ext){ return true;}    
          }
          
          return false;
      },    
      _formatSize: function(bytes){
          var i = -1;                                    
          do {
              bytes = bytes / 1024;
              i++;  
          } while (bytes > 99);
          
          return Math.max(bytes, 0.1).toFixed(1) + ['kB', 'MB', 'GB', 'TB', 'PB', 'EB'][i];          
      }
  };
      
         
  /**
   * Class that creates upload widget with drag-and-drop and file list
   * @inherits qq.FileUploaderBasic
   */
  qq.FileUploader = function(o){
      // call parent constructor
      qq.FileUploaderBasic.apply(this, arguments);
      
      // additional options    
      qq.extend(this._options, {
          element: null,
          // if set, will be used instead of qq-upload-list in template
          listElement: null,
                  
          template: '<div class="qq-uploader">' + 
                  '<div class="qq-upload-drop-area"><span>Drop files here to upload</span></div>' +
                  '<div class="qq-upload-button">add photos</div>' +
                  '<ul class="qq-upload-list"></ul>' + 
               '</div>',
  
          // template for one item in file list
          fileTemplate: '<li>' +
                  '<span class="qq-upload-file"></span>' +
                  '<span class="qq-upload-spinner"></span>' +
                  '<span class="qq-upload-size"></span>' +
                  '<a class="qq-upload-cancel" href="#">Cancel</a>' +
                  '<span class="qq-upload-failed-text"></span>' +
              '</li>',        
          
          classes: {
              // used to get elements from templates
              button: 'qq-upload-button',
              drop: 'qq-upload-drop-area',
              dropActive: 'qq-upload-drop-area-active',
              list: 'qq-upload-list',
                          
              file: 'qq-upload-file',
              spinner: 'qq-upload-spinner',
              size: 'qq-upload-size',
              cancel: 'qq-upload-cancel',
  
              // added to list item when upload completes
              // used in css to hide progress spinner
              success: 'qq-upload-success',
              fail: 'qq-upload-fail'
          }
      });
      // overwrite options with user supplied    
      qq.extend(this._options, o);       
  
      this._element = this._options.element;
      this._element.innerHTML = this._options.template;        
      this._listElement = this._options._listElement || this._find(this._element, 'list');
      
      this._classes = this._options.classes;
          
      this._button = this._createUploadButton(this._find(this._element, 'button'));        
      
      this._bindCancelEvent();
      this._setupDragDrop();
  };
  
  // inherit from Basic Uploader
  qq.extend(qq.FileUploader.prototype, qq.FileUploaderBasic.prototype);
  
  qq.extend(qq.FileUploader.prototype, {
      /**
       * Gets one of the elements listed in this._options.classes
       **/
      _find: function(parent, type){                                
          var element = qq.getByClass(parent, this._options.classes[type])[0];        
          if (!element){
              throw new Error('element not found ' + type);
          }
          
          return element;
      },
      _setupDragDrop: function(){
          var self = this,
              dropArea = this._find(this._element, 'drop');                        
  
          var dz = new qq.UploadDropZone({
              element: dropArea,
              onEnter: function(e){
                  qq.addClass(dropArea, self._classes.dropActive);
                  e.stopPropagation();
              },
              onLeave: function(e){
                  e.stopPropagation();
              },
              onLeaveNotDescendants: function(e){
                  qq.removeClass(dropArea, self._classes.dropActive);  
              },
              onDrop: function(e){
                  dropArea.style.display = 'none';
                  qq.removeClass(dropArea, self._classes.dropActive);
                  self._uploadFileList(e.dataTransfer.files);    
              }
          });
                  
          dropArea.style.display = 'none';
  
          qq.attach(document, 'dragenter', function(e){     
              if (!dz._isValidFileDrag(e)) return; 
              
              dropArea.style.display = 'block';            
          });                 
          qq.attach(document, 'dragleave', function(e){
              if (!dz._isValidFileDrag(e)) return;            
              
              var relatedTarget = document.elementFromPoint(e.clientX, e.clientY);
              // only fire when leaving document out
              if ( ! relatedTarget || relatedTarget.nodeName == "HTML"){               
                  dropArea.style.display = 'none';                                            
              }
          });                
      },
      _onSubmit: function(id, fileName){
          qq.FileUploaderBasic.prototype._onSubmit.apply(this, arguments);
          this._addToList(id, fileName);  
      },
      _onProgress: function(id, fileName, loaded, total){
          qq.FileUploaderBasic.prototype._onProgress.apply(this, arguments);
  
          var item = this._getItemByFileId(id);
          var size = this._find(item, 'size');
          size.style.display = 'inline';
          
          var text; 
          if (loaded != total){
              text = Math.round(loaded / total * 100) + '% from ' + this._formatSize(total);
          } else {                                   
              text = this._formatSize(total);
          }          
          
          qq.setText(size, text);         
      },
      _onComplete: function(id, fileName, result){
          qq.FileUploaderBasic.prototype._onComplete.apply(this, arguments);
  
          // mark completed
          var item = this._getItemByFileId(id);                
          qq.remove(this._find(item, 'cancel'));
          qq.remove(this._find(item, 'spinner'));
          
          if (result.success){
              qq.addClass(item, this._classes.success);    
          } else {
              qq.addClass(item, this._classes.fail);
          }         
      },
      _addToList: function(id, fileName){
          var item = qq.toElement(this._options.fileTemplate);                
          item.qqFileId = id;
  
          var fileElement = this._find(item, 'file');        
          qq.setText(fileElement, this._formatFileName(fileName));
          this._find(item, 'size').style.display = 'none';        
  
          this._listElement.appendChild(item);
      },
      _getItemByFileId: function(id){
          var item = this._listElement.firstChild;        
          
          // there can't be txt nodes in dynamically created list
          // and we can  use nextSibling
          while (item){            
              if (item.qqFileId == id) return item;            
              item = item.nextSibling;
          }          
      },
      /**
       * delegate click event for cancel link 
       **/
      _bindCancelEvent: function(){
          var self = this,
              list = this._listElement;            
          
          qq.attach(list, 'click', function(e){            
              e = e || window.event;
              var target = e.target || e.srcElement;
              
              if (qq.hasClass(target, self._classes.cancel)){                
                  qq.preventDefault(e);
                 
                  var item = target.parentNode;
                  self._handler.cancel(item.qqFileId);
                  qq.remove(item);
              }
          });
      }    
  });
      
  qq.UploadDropZone = function(o){
      this._options = {
          element: null,  
          onEnter: function(e){},
          onLeave: function(e){},  
          // is not fired when leaving element by hovering descendants   
          onLeaveNotDescendants: function(e){},   
          onDrop: function(e){}                       
      };
      qq.extend(this._options, o); 
      
      this._element = this._options.element;
      
      this._disableDropOutside();
      this._attachEvents();   
  };
  
  qq.UploadDropZone.prototype = {
      _disableDropOutside: function(e){
          // run only once for all instances
          if (!qq.UploadDropZone.dropOutsideDisabled ){
  
              qq.attach(document, 'dragover', function(e){
                  if (e.dataTransfer){
                      e.dataTransfer.dropEffect = 'none';
                      e.preventDefault(); 
                  }           
              });
              
              qq.UploadDropZone.dropOutsideDisabled = true; 
          }        
      },
      _attachEvents: function(){
          var self = this;              
                    
          qq.attach(self._element, 'dragover', function(e){
              if (!self._isValidFileDrag(e)) return;
              
              var effect = e.dataTransfer.effectAllowed;
              if (effect == 'move' || effect == 'linkMove'){
                  e.dataTransfer.dropEffect = 'move'; // for FF (only move allowed)    
              } else {                    
                  e.dataTransfer.dropEffect = 'copy'; // for Chrome
              }
                                                       
              e.stopPropagation();
              e.preventDefault();                                                                    
          });
          
          qq.attach(self._element, 'dragenter', function(e){
              if (!self._isValidFileDrag(e)) return;
                          
              self._options.onEnter(e);
          });
          
          qq.attach(self._element, 'dragleave', function(e){
              if (!self._isValidFileDrag(e)) return;
              
              self._options.onLeave(e);
              
              var relatedTarget = document.elementFromPoint(e.clientX, e.clientY);                      
              // do not fire when moving a mouse over a descendant
              if (qq.contains(this, relatedTarget)) return;
                          
              self._options.onLeaveNotDescendants(e); 
          });
                  
          qq.attach(self._element, 'drop', function(e){
              if (!self._isValidFileDrag(e)) return;
              
              e.preventDefault();
              self._options.onDrop(e);
          });          
      },
      _isValidFileDrag: function(e){
          var dt = e.dataTransfer,
              // do not check dt.types.contains in webkit, because it crashes safari 4            
              isWebkit = navigator.userAgent.indexOf("AppleWebKit") > -1;                        
  
          // dt.effectAllowed is none in Safari 5
          // dt.types.contains check is for firefox            
          return dt && dt.effectAllowed != 'none' && 
              (dt.files || (!isWebkit && dt.types.contains && dt.types.contains('Files')));
          
      }        
  }; 
  
  qq.UploadButton = function(o){
      this._options = {
          element: null,  
          // if set to true adds multiple attribute to file input      
          multiple: false,
          // name attribute of file input
          name: 'file',
          onChange: function(input){},
          hoverClass: 'qq-upload-button-hover',
          focusClass: 'qq-upload-button-focus'                       
      };
      
      qq.extend(this._options, o);
          
      this._element = this._options.element;
      
      // make button suitable container for input
      qq.css(this._element, {
          position: 'relative',
          overflow: 'hidden',
          // Make sure browse button is in the right side
          // in Internet Explorer
          direction: 'ltr'
      });   
      
      this._input = this._createInput();
  };
  
  qq.UploadButton.prototype = {
      /* returns file input element */    
      getInput: function(){
          return this._input;
      },
      /* cleans/recreates the file input */
      reset: function(){
          if (this._input.parentNode){
              qq.remove(this._input);    
          }                
          
          qq.removeClass(this._element, this._options.focusClass);
          this._input = this._createInput();
      },    
      _createInput: function(){                
          var input = document.createElement("input");
          
          if (this._options.multiple){
              input.setAttribute("multiple", "multiple");
          }
                  
          input.setAttribute("type", "file");
          input.setAttribute("name", this._options.name);
          
          qq.css(input, {
              position: 'absolute',
              // in Opera only 'browse' button
              // is clickable and it is located at
              // the right side of the input
              right: 0,
              top: 0,
              fontFamily: 'Arial',
              // 4 persons reported this, the max values that worked for them were 243, 236, 236, 118
              fontSize: '118px',
              margin: 0,
              padding: 0,
              cursor: 'pointer',
              opacity: 0
          });
          
          this._element.appendChild(input);
  
          var self = this;
          qq.attach(input, 'change', function(){
              self._options.onChange(input);
          });
                  
          qq.attach(input, 'mouseover', function(){
              qq.addClass(self._element, self._options.hoverClass);
          });
          qq.attach(input, 'mouseout', function(){
              qq.removeClass(self._element, self._options.hoverClass);
          });
          qq.attach(input, 'focus', function(){
              qq.addClass(self._element, self._options.focusClass);
          });
          qq.attach(input, 'blur', function(){
              qq.removeClass(self._element, self._options.focusClass);
          });
  
          // IE and Opera, unfortunately have 2 tab stops on file input
          // which is unacceptable in our case, disable keyboard access
          if (window.attachEvent){
              // it is IE or Opera
              input.setAttribute('tabIndex', "-1");
          }
  
          return input;            
      }        
  };
  
  /**
   * Class for uploading files, uploading itself is handled by child classes
   */
  qq.UploadHandlerAbstract = function(o){
      this._options = {
          action: '/upload.php',
          // maximum number of concurrent uploads        
          maxConnections: 999,
          onProgress: function(id, fileName, loaded, total){},
          onComplete: function(id, fileName, response){},
          onCancel: function(id, fileName){}
      };
      qq.extend(this._options, o);    
      
      this._queue = [];
      // params for files in queue
      this._params = [];
  };
  qq.UploadHandlerAbstract.prototype = {
      /**
       * Adds file or file input to the queue
       * @returns id
       **/    
      add: function(file){},
      /**
       * Sends the file identified by id and additional query params to the server
       */
      upload: function(id, params){
          var len = this._queue.push(id);
  
          var copy = {};        
          qq.extend(copy, params);
          this._params[id] = copy;        
                  
          // if too many active uploads, wait...
          if (len <= this._options.maxConnections){               
              this._upload(id, this._params[id]);
          }
      },
      /**
       * Cancels file upload by id
       */
      cancel: function(id){
          this._cancel(id);
          this._dequeue(id);
      },
      /**
       * Cancells all uploads
       */
      cancelAll: function(){
          for (var i=0; i<this._queue.length; i++){
              this._cancel(this._queue[i]);
          }
          this._queue = [];
      },
      /**
       * Returns name of the file identified by id
       */
      getName: function(id){},
      /**
       * Returns size of the file identified by id
       */          
      getSize: function(id){},
      /**
       * Returns id of files being uploaded or
       * waiting for their turn
       */
      getQueue: function(){
          return this._queue;
      },
      /**
       * Actual upload method
       */
      _upload: function(id){},
      /**
       * Actual cancel method
       */
      _cancel: function(id){},     
      /**
       * Removes element from queue, starts upload of next
       */
      _dequeue: function(id){
          var i = qq.indexOf(this._queue, id);
          this._queue.splice(i, 1);
                  
          var max = this._options.maxConnections;
          
          if (this._queue.length >= max){
              var nextId = this._queue[max-1];
              this._upload(nextId, this._params[nextId]);
          }
      }        
  };
  
  /**
   * Class for uploading files using form and iframe
   * @inherits qq.UploadHandlerAbstract
   */
  qq.UploadHandlerForm = function(o){
      qq.UploadHandlerAbstract.apply(this, arguments);
         
      this._inputs = {};
  };
  // @inherits qq.UploadHandlerAbstract
  qq.extend(qq.UploadHandlerForm.prototype, qq.UploadHandlerAbstract.prototype);
  
  qq.extend(qq.UploadHandlerForm.prototype, {
      add: function(fileInput){
          fileInput.setAttribute('name', 'qqfile');
          var id = 'qq-upload-handler-iframe' + qq.getUniqueId();       
          
          this._inputs[id] = fileInput;
          
          // remove file input from DOM
          if (fileInput.parentNode){
              qq.remove(fileInput);
          }
                  
          return id;
      },
      getName: function(id){
          // get input value and remove path to normalize
          return this._inputs[id].value.replace(/.*(\/|\\)/, "");
      },    
      _cancel: function(id){
          this._options.onCancel(id, this.getName(id));
          
          delete this._inputs[id];        
  
          var iframe = document.getElementById(id);
          if (iframe){
              // to cancel request set src to something else
              // we use src="javascript:false;" because it doesn't
              // trigger ie6 prompt on https
              iframe.setAttribute('src', 'javascript:false;');
  
              qq.remove(iframe);
          }
      },     
      _upload: function(id, params){                        
          var input = this._inputs[id];
          
          if (!input){
              throw new Error('file with passed id was not added, or already uploaded or cancelled');
          }                
  
          var fileName = this.getName(id);
                  
          var iframe = this._createIframe(id);
          var form = this._createForm(iframe, params);
          form.appendChild(input);
  
          var self = this;
          this._attachLoadEvent(iframe, function(){                        
              self._options.onComplete(id, fileName, self._getIframeContentJSON(iframe));
              self._dequeue(id);
              
              delete self._inputs[id];
              // timeout added to fix busy state in FF3.6
              setTimeout(function(){
                  qq.remove(iframe);
              }, 1);
          });
  
          form.submit();        
          qq.remove(form);        
          
          return id;
      }, 
      _attachLoadEvent: function(iframe, callback){
          qq.attach(iframe, 'load', function(){
              // when we remove iframe from dom
              // the request stops, but in IE load
              // event fires
              if (!iframe.parentNode){
                  return;
              }
  
              // fixing Opera 10.53
              if (iframe.contentDocument &&
                  iframe.contentDocument.body &&
                  iframe.contentDocument.body.innerHTML == "false"){
                  // In Opera event is fired second time
                  // when body.innerHTML changed from false
                  // to server response approx. after 1 sec
                  // when we upload file with iframe
                  return;
              }
  
              callback();
          });
      },
      /**
       * Returns json object received by iframe from server.
       */
      _getIframeContentJSON: function(iframe){
          // iframe.contentWindow.document - for IE<7
          var doc = iframe.contentDocument ? iframe.contentDocument: iframe.contentWindow.document,
              response;
  
          try {
              response = eval("(" + doc.body.innerHTML + ")");
          } catch(err){
              response = {};
          }
  
          return response;
      },
      /**
       * Creates iframe with unique name
       */
      _createIframe: function(id){
          // We can't use following code as the name attribute
          // won't be properly registered in IE6, and new window
          // on form submit will open
          // var iframe = document.createElement('iframe');
          // iframe.setAttribute('name', id);
  
          var iframe = qq.toElement('<iframe src="javascript:false;" name="' + id + '" />');
          // src="javascript:false;" removes ie6 prompt on https
  
          iframe.setAttribute('id', id);
  
          iframe.style.display = 'none';
          document.body.appendChild(iframe);
  
          return iframe;
      },
      /**
       * Creates form, that will be submitted to iframe
       */
      _createForm: function(iframe, params){
          // We can't use the following code in IE6
          // var form = document.createElement('form');
          // form.setAttribute('method', 'post');
          // form.setAttribute('enctype', 'multipart/form-data');
          // Because in this case file won't be attached to request
          var form = qq.toElement('<form method="post" enctype="multipart/form-data"></form>');
  
          var queryString = qq.obj2url(params, this._options.action);
  
          form.setAttribute('action', queryString);
          form.setAttribute('target', iframe.name);
          form.style.display = 'none';
          document.body.appendChild(form);
  
          return form;
      }
  });
  
  /**
   * Class for uploading files using xhr
   * @inherits qq.UploadHandlerAbstract
   */
  qq.UploadHandlerXhr = function(o){
      qq.UploadHandlerAbstract.apply(this, arguments);
  
      this._files = [];
      this._xhrs = [];
      
      // current loaded size in bytes for each file 
      this._loaded = [];
  };
  
  // static method
  qq.UploadHandlerXhr.isSupported = function(){
      var input = document.createElement('input');
      input.type = 'file';        
      
      return (
          'multiple' in input &&
          typeof File != "undefined" &&
          typeof (new XMLHttpRequest()).upload != "undefined" );       
  };
  
  // @inherits qq.UploadHandlerAbstract
  qq.extend(qq.UploadHandlerXhr.prototype, qq.UploadHandlerAbstract.prototype)
  
  qq.extend(qq.UploadHandlerXhr.prototype, {
      /**
       * Adds file to the queue
       * Returns id to use with upload, cancel
       **/    
      add: function(file){
          if (!(file instanceof File)){
              throw new Error('Passed obj in not a File (in qq.UploadHandlerXhr)');
          }
                  
          return this._files.push(file) - 1;        
      },
      getName: function(id){        
          var file = this._files[id];
          // fix missing name in Safari 4
          return file.fileName != null ? file.fileName : file.name;       
      },
      getSize: function(id){
          var file = this._files[id];
          return file.fileSize != null ? file.fileSize : file.size;
      },    
      /**
       * Returns uploaded bytes for file identified by id 
       */    
      getLoaded: function(id){
          return this._loaded[id] || 0; 
      },
      /**
       * Sends the file identified by id and additional query params to the server
       * @param {Object} params name-value string pairs
       */    
      _upload: function(id, params){
          var file = this._files[id],
              name = this.getName(id),
              size = this.getSize(id);
                  
          this._loaded[id] = 0;
                                  
          var xhr = this._xhrs[id] = new XMLHttpRequest();
          var self = this;
                                          
          xhr.upload.onprogress = function(e){
              if (e.lengthComputable){
                  self._loaded[id] = e.loaded;
                  self._options.onProgress(id, name, e.loaded, e.total);
              }
          };
  
          xhr.onreadystatechange = function(){            
              if (xhr.readyState == 4){
                  self._onComplete(id, xhr);                    
              }
          };
  
          // build query string
          params = params || {};
          params['qqfile'] = name;
          var queryString = qq.obj2url(params, this._options.action);
  
          xhr.open("POST", queryString, true);
          xhr.setRequestHeader("X-Requested-With", "XMLHttpRequest");
          xhr.setRequestHeader("X-File-Name", encodeURIComponent(name));
          xhr.setRequestHeader("Content-Type", "application/octet-stream");
          xhr.send(file);
      },
      _onComplete: function(id, xhr){
          // the request was aborted/cancelled
          if (!this._files[id]) return;
          
          var name = this.getName(id);
          var size = this.getSize(id);
          
          this._options.onProgress(id, name, size, size);
                  
          if (xhr.status == 200){
              var response;
                      
              try {
                  response = eval("(" + xhr.responseText + ")");
              } catch(err){
                  response = {};
              }
              
              this._options.onComplete(id, name, response);
                          
          } else {                   
              this._options.onComplete(id, name, {});
          }
                  
          this._files[id] = null;
          this._xhrs[id] = null;    
          this._dequeue(id);                    
      },
      _cancel: function(id){
          this._options.onCancel(id, this.getName(id));
          
          this._files[id] = null;
          
          if (this._xhrs[id]){
              this._xhrs[id].abort();
              this._xhrs[id] = null;                                   
          }
      }
  });