(function(root){

  // Let's borrow a couple of things from Underscore that we'll need

  // _.each
  var breaker = {},
      AP = Array.prototype,
      OP = Object.prototype,

      hasOwn = OP.hasOwnProperty,
      toString = OP.toString,
      forEach = AP.forEach,
      indexOf = AP.indexOf,
      slice = AP.slice;

  var _each = function( obj, iterator, context ) {
    var key, i, l;

    if ( !obj ) {
      return;
    }
    if ( forEach && obj.forEach === forEach ) {
      obj.forEach( iterator, context );
    } else if ( obj.length === +obj.length ) {
      for ( i = 0, l = obj.length; i < l; i++ ) {
        if ( i in obj && iterator.call( context, obj[i], i, obj ) === breaker ) {
          return;
        }
      }
    } else {
      for ( key in obj ) {
        if ( hasOwn.call( obj, key ) ) {
          if ( iterator.call( context, obj[key], key, obj) === breaker ) {
            return;
          }
        }
      }
    }
  };

  // _.isFunction
  var _isFunction = function( obj ) {
    return !!(obj && obj.constructor && obj.call && obj.apply);
  };

  // _.extend
  var _extend = function( obj ) {

    _each( slice.call( arguments, 1), function( source ) {
      var prop;

      for ( prop in source ) {
        if ( source[prop] !== void 0 ) {
          obj[ prop ] = source[ prop ];
        }
      }
    });
    return obj;
  };

  // $.inArray
  var _inArray = function( elem, arr, i ) {
    var len;

    if ( arr ) {
      if ( indexOf ) {
        return indexOf.call( arr, elem, i );
      }

      len = arr.length;
      i = i ? i < 0 ? Math.max( 0, len + i ) : i : 0;

      for ( ; i < len; i++ ) {
        // Skip accessing in sparse arrays
        if ( i in arr && arr[ i ] === elem ) {
          return i;
        }
      }
    }

    return -1;
  };

  // And some jQuery specific helpers

  var class2type = {};

  // Populate the class2type map
  _each("Boolean Number String Function Array Date RegExp Object".split(" "), function(name, i) {
    class2type[ "[object " + name + "]" ] = name.toLowerCase();
  });

  var _type = function( obj ) {
    return obj == null ?
      String( obj ) :
      class2type[ toString.call(obj) ] || "object";
  };

  // Now start the jQuery-cum-Underscore implementation. Some very
  // minor changes to the jQuery source to get this working.

  // Internal Deferred namespace
  var _d = {};
  // String to Object options format cache
  var optionsCache = {};

  // Convert String-formatted options into Object-formatted ones and store in cache
  function createOptions( options ) {
    var object = optionsCache[ options ] = {};
    _each( options.split( /\s+/ ), function( flag ) {
      object[ flag ] = true;
    });
    return object;
  }

  _d.Callbacks = function( options ) {

    // Convert options from String-formatted to Object-formatted if needed
    // (we check in cache first)
    options = typeof options === "string" ?
      ( optionsCache[ options ] || createOptions( options ) ) :
      _extend( {}, options );

    var // Last fire value (for non-forgettable lists)
      memory,
      // Flag to know if list was already fired
      fired,
      // Flag to know if list is currently firing
      firing,
      // First callback to fire (used internally by add and fireWith)
      firingStart,
      // End of the loop when firing
      firingLength,
      // Index of currently firing callback (modified by remove if needed)
      firingIndex,
      // Actual callback list
      list = [],
      // Stack of fire calls for repeatable lists
      stack = !options.once && [],
      // Fire callbacks
      fire = function( data ) {
        memory = options.memory && data;
        fired = true;
        firingIndex = firingStart || 0;
        firingStart = 0;
        firingLength = list.length;
        firing = true;
        for ( ; list && firingIndex < firingLength; firingIndex++ ) {
          if ( list[ firingIndex ].apply( data[ 0 ], data[ 1 ] ) === false && options.stopOnFalse ) {
            memory = false; // To prevent further calls using add
            break;
          }
        }
        firing = false;
        if ( list ) {
          if ( stack ) {
            if ( stack.length ) {
              fire( stack.shift() );
            }
          } else if ( memory ) {
            list = [];
          } else {
            self.disable();
          }
        }
      },
      // Actual Callbacks object
      self = {
        // Add a callback or a collection of callbacks to the list
        add: function() {
          if ( list ) {
            // First, we save the current length
            var start = list.length;
            (function add( args ) {
              _each( args, function( arg ) {
                var type = _type( arg );
                if ( type === "function" ) {
                  if ( !options.unique || !self.has( arg ) ) {
                    list.push( arg );
                  }
                } else if ( arg && arg.length && type !== "string" ) {
                  // Inspect recursively
                  add( arg );
                }
              });
            })( arguments );
            // Do we need to add the callbacks to the
            // current firing batch?
            if ( firing ) {
              firingLength = list.length;
            // With memory, if we're not firing then
            // we should call right away
            } else if ( memory ) {
              firingStart = start;
              fire( memory );
            }
          }
          return this;
        },
        // Remove a callback from the list
        remove: function() {
          if ( list ) {
            _each( arguments, function( arg ) {
              var index;
              while( ( index = _inArray( arg, list, index ) ) > -1 ) {
                list.splice( index, 1 );
                // Handle firing indexes
                if ( firing ) {
                  if ( index <= firingLength ) {
                    firingLength--;
                  }
                  if ( index <= firingIndex ) {
                    firingIndex--;
                  }
                }
              }
            });
          }
          return this;
        },
        // Control if a given callback is in the list
        has: function( fn ) {
          return _inArray( fn, list ) > -1;
        },
        // Remove all callbacks from the list
        empty: function() {
          list = [];
          return this;
        },
        // Have the list do nothing anymore
        disable: function() {
          list = stack = memory = undefined;
          return this;
        },
        // Is it disabled?
        disabled: function() {
          return !list;
        },
        // Lock the list in its current state
        lock: function() {
          stack = undefined;
          if ( !memory ) {
            self.disable();
          }
          return this;
        },
        // Is it locked?
        locked: function() {
          return !stack;
        },
        // Call all callbacks with the given context and arguments
        fireWith: function( context, args ) {
          args = args || [];
          args = [ context, args.slice ? args.slice() : args ];
          if ( list && ( !fired || stack ) ) {
            if ( firing ) {
              stack.push( args );
            } else {
              fire( args );
            }
          }
          return this;
        },
        // Call all the callbacks with the given arguments
        fire: function() {
          self.fireWith( this, arguments );
          return this;
        },
        // To know if the callbacks have already been called at least once
        fired: function() {
          return !!fired;
        }
      };

    return self;
  };

  _d.Deferred = function( func ) {

    var tuples = [
        // action, add listener, listener list, final state
        [ "resolve", "done", _d.Callbacks("once memory"), "resolved" ],
        [ "reject", "fail", _d.Callbacks("once memory"), "rejected" ],
        [ "notify", "progress", _d.Callbacks("memory") ]
      ],
      state = "pending",
      promise = {
        state: function() {
          return state;
        },
        always: function() {
          deferred.done( arguments ).fail( arguments );
          return this;
        },
        then: function( /* fnDone, fnFail, fnProgress */ ) {
          var fns = arguments;

          return _d.Deferred(function( newDefer ) {

            _each( tuples, function( tuple, i ) {
              var action = tuple[ 0 ],
                fn = fns[ i ];

              // deferred[ done | fail | progress ] for forwarding actions to newDefer
              deferred[ tuple[1] ]( _isFunction( fn ) ?

                function() {
                  var returned;
                  try { returned = fn.apply( this, arguments ); } catch(e){
                    newDefer.reject(e);
                    return;
                  }

                  if ( returned && _isFunction( returned.promise ) ) {
                    returned.promise()
                      .done( newDefer.resolve )
                      .fail( newDefer.reject )
                      .progress( newDefer.notify );
                  } else {
                    newDefer[ action !== "notify" ? 'resolveWith' : action + 'With']( this === deferred ? newDefer : this, [ returned ] );
                  }
                } :

                newDefer[ action ]
              );
            });

            fns = null;

          }).promise();

        },
        // Get a promise for this deferred
        // If obj is provided, the promise aspect is added to the object
        promise: function( obj ) {
          return obj != null ? _extend( obj, promise ) : promise;
        }
      },
      deferred = {};

    // Keep pipe for back-compat
    promise.pipe = promise.then;

    // Add list-specific methods
    _each( tuples, function( tuple, i ) {
      var list = tuple[ 2 ],
        stateString = tuple[ 3 ];

      // promise[ done | fail | progress ] = list.add
      promise[ tuple[1] ] = list.add;

      // Handle state
      if ( stateString ) {
        list.add(function() {
          // state = [ resolved | rejected ]
          state = stateString;

        // [ reject_list | resolve_list ].disable; progress_list.lock
        }, tuples[ i ^ 1 ][ 2 ].disable, tuples[ 2 ][ 2 ].lock );
      }

      // deferred[ resolve | reject | notify ] = list.fire
      deferred[ tuple[0] ] = list.fire;
      deferred[ tuple[0] + "With" ] = list.fireWith;
    });

    // Make the deferred a promise
    promise.promise( deferred );

    // Call given func if any
    if ( func ) {
      func.call( deferred, deferred );
    }

    // All done!
    return deferred;
  };

  // Deferred helper
  _d.when = function( subordinate /* , ..., subordinateN */ ) { 

    var i = 0,
      resolveValues = ( _type(subordinate) === 'array' && arguments.length === 1 ) ? subordinate : slice.call( arguments ),
      length = resolveValues.length;

      if ( _type(subordinate) === 'array' && subordinate.length === 1 ) {
        subordinate = subordinate[ 0 ];
      }

      // the count of uncompleted subordinates
      var remaining = length !== 1 || ( subordinate && _isFunction( subordinate.promise ) ) ? length : 0,

      // the master Deferred. If resolveValues consist of only a single Deferred, just use that.
      deferred = remaining === 1 ? subordinate : _d.Deferred(),

      // Update function for both resolve and progress values
      updateFunc = function( i, contexts, values ) {
        return function( value ) {
          contexts[ i ] = this;
          values[ i ] = arguments.length > 1 ? slice.call( arguments ) : value;
          if( values === progressValues ) {
            deferred.notifyWith( contexts, values );
          } else if ( !( --remaining ) ) {
            deferred.resolveWith( contexts, values );
          }
        };
      },

      progressValues, progressContexts, resolveContexts;

    // add listeners to Deferred subordinates; treat others as resolved
    if ( length > 1 ) {
      progressValues = new Array( length );
      progressContexts = new Array( length );
      resolveContexts = new Array( length );
      for ( ; i < length; i++ ) {
        if ( resolveValues[ i ] && _isFunction( resolveValues[ i ].promise ) ) {
          resolveValues[ i ].promise()
            .done( updateFunc( i, resolveContexts, resolveValues ) )
            .fail( deferred.reject )
            .progress( updateFunc( i, progressContexts, progressValues ) );
        } else {
          --remaining;
        }
      }
    }

    // if we're not waiting on anything, resolve the master
    if ( !remaining ) {
      deferred.resolveWith( resolveContexts, resolveValues );
    }

    return deferred.promise();
  };

  // Try exporting as a Common.js Module
  if ( typeof module !== "undefined" && module.exports ) {
    module.exports = _d;

  // Or mixin to Underscore.js
  } else if ( typeof root._ !== "undefined" ) {
    root._.mixin(_d);

  // Or assign it to window._
  } else {
    root._ = _d;
  }

})(this);