/**
   * ajax文件上传插件
   * 参考文档： http://www.cnblogs.com/kissdodog/archive/2012/12/15/2819025.html
   * github: https://github.com/carlcarl/AjaxFileUpload
   */
  
  jQuery.extend({
  
  
      createUploadIframe: function(id, uri)
      {
          //create frame
          var frameId = 'jUploadFrame' + id;
  
          if(window.ActiveXObject) {
              var io = document.createElement('<iframe id="' + frameId + '" name="' + frameId + '" />');
              if(typeof uri== 'boolean'){
                  io.src = 'javascript:false';
              }
              else if(typeof uri== 'string'){
                  io.src = uri;
              }
          }
          else {
              var io = document.createElement('iframe');
              io.id = frameId;
              io.name = frameId;
          }
          io.style.position = 'absolute';
          io.style.top = '-1000px';
          io.style.left = '-1000px';
  
          document.body.appendChild(io);
  
          return io
      },
      createUploadForm: function(id, fileElementId)
      {
          //create form
          var formId = 'jUploadForm' + id;
          var fileId = 'jUploadFile' + id;
          var form = $('<form  action="" method="POST" name="' + formId + '" id="' + formId + '" enctype="multipart/form-data"></form>');
          var oldElement = $('#' + fileElementId);
          var newElement = $(oldElement).clone();
          $(oldElement).attr('id', fileId);
          $(oldElement).before(newElement);
          $(oldElement).appendTo(form);
          //set attributes
          $(form).css('position', 'absolute');
          $(form).css('top', '-1200px');
          $(form).css('left', '-1200px');
          $(form).appendTo('body');
          return form;
      },
      addOtherRequestsToForm: function(form,data)
      {
          // add extra parameter
          var originalElement = $('<input type="hidden" name="" value="">');
          for (var key in data) {
              name = key;
              value = data[key];
              var cloneElement = originalElement.clone();
              cloneElement.attr({'name':name,'value':value});
              $(cloneElement).appendTo(form);
          }
          return form;
      },
  
      ajaxFileUpload: function(s) {
          // TODO introduce global settings, allowing the client to modify them for all requests, not only timeout
          s = jQuery.extend({}, jQuery.ajaxSettings, s);
          var id = new Date().getTime()
          var form = jQuery.createUploadForm(id, s.fileElementId);
          if ( s.data ) form = jQuery.addOtherRequestsToForm(form,s.data);
          var io = jQuery.createUploadIframe(id, s.secureuri);
          var frameId = 'jUploadFrame' + id;
          var formId = 'jUploadForm' + id;
          // Watch for a new set of requests
          if ( s.global && ! jQuery.active++ )
          {
              jQuery.event.trigger( "ajaxStart" );
          }
          var requestDone = false;
          // Create the request object
          var xml = {}
          if ( s.global )
              jQuery.event.trigger("ajaxSend", [xml, s]);
          // Wait for a response to come back
          var uploadCallback = function(isTimeout)
          {
              var io = document.getElementById(frameId);
              try
              {
                  if(io.contentWindow)
                  {
                      xml.responseText = io.contentWindow.document.body?io.contentWindow.document.body.innerHTML:null;
                      xml.responseXML = io.contentWindow.document.XMLDocument?io.contentWindow.document.XMLDocument:io.contentWindow.document;
  
                  }else if(io.contentDocument)
                  {
                      xml.responseText = io.contentDocument.document.body?io.contentDocument.document.body.innerHTML:null;
                      xml.responseXML = io.contentDocument.document.XMLDocument?io.contentDocument.document.XMLDocument:io.contentDocument.document;
                  }
              }catch(e)
              {
                  jQuery.handleError(s, xml, null, e);
              }
              if ( xml || isTimeout == "timeout")
              {
                  requestDone = true;
                  var status;
                  try {
                      status = isTimeout != "timeout" ? "success" : "error";
                      // Make sure that the request was successful or notmodified
                      if ( status != "error" )
                      {
                          // process the data (runs the xml through httpData regardless of callback)
                          var data = jQuery.uploadHttpData( xml, s.dataType );
                          // If a local callback was specified, fire it and pass it the data
                          if ( s.success )
                              s.success( data, status );
  
                          // Fire the global callback
                          if( s.global )
                              jQuery.event.trigger( "ajaxSuccess", [xml, s] );
                      } else
                          jQuery.handleError(s, xml, status);
                  } catch(e)
                  {
                      status = "error";
                      jQuery.handleError(s, xml, status, e);
                  }
  
                  // The request was completed
                  if( s.global )
                      jQuery.event.trigger( "ajaxComplete", [xml, s] );
  
                  // Handle the global AJAX counter
                  if ( s.global && ! --jQuery.active )
                      jQuery.event.trigger( "ajaxStop" );
  
                  // Process result
                  if ( s.complete )
                      s.complete(xml, status);
  
                  jQuery(io).unbind()
  
                  setTimeout(function()
                  {	try
                      {
                          $(io).remove();
                          $(form).remove();
  
                      } catch(e)
                      {
                          jQuery.handleError(s, xml, null, e);
                      }
  
                  }, 100)
  
                  xml = null
  
              }
          }
          // Timeout checker
          if ( s.timeout > 0 )
          {
              setTimeout(function(){
                  // Check to see if the request is still happening
                  if( !requestDone ) uploadCallback( "timeout" );
              }, s.timeout);
          }
          try
          {
              // var io = $('#' + frameId);
              var form = $('#' + formId);
              $(form).attr('action', s.url);
              $(form).attr('method', 'POST');
              $(form).attr('target', frameId);
              if(form.encoding)
              {
                  form.encoding = 'multipart/form-data';
              }
              else
              {
                  form.enctype = 'multipart/form-data';
              }
              $(form).submit();
  
          } catch(e)
          {
              jQuery.handleError(s, xml, null, e);
          }
          if(window.attachEvent){
              document.getElementById(frameId).attachEvent('onload', uploadCallback);
          }
          else{
              document.getElementById(frameId).addEventListener('load', uploadCallback, false);
          }
          return {abort: function () {}};
  
      },
  
      uploadHttpData: function( r, type ) {
          var data = !type;
          data = type == "xml" || data ? r.responseXML : r.responseText;
          // If the type is "script", eval it in global context
          if ( type == "script" )
              jQuery.globalEval( data );
          // Get the JavaScript object, if JSON is used.
          if ( type == "json" )
          {
              // If you add mimetype in your response,
              // you have to delete the '<pre></pre>' tag.
              // The pre tag in Chrome has attribute, so have to use regex to remove
              var data = r.responseText;
              var rx = new RegExp("<pre.*?>(.*?)</pre>","i");
              var am = rx.exec(data);
              //this is the desired data extracted
              var data = (am) ? am[1] : "";    //the only submatch or empty
              eval( "data = " + data );
          }
          // evaluate scripts within html
          if ( type == "html" )
              jQuery("<div>").html(data).evalScripts();
          //alert($('param', data).each(function(){alert($(this).attr('value'));}));
          return data;
      }
  })