rx.async.js

// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.txt in the project root for license information.

;(function (factory) {
    var objectTypes = {
        'boolean': false,
        'function': true,
        'object': true,
        'number': false,
        'string': false,
        'undefined': false
    };

    var root = (objectTypes[typeof window] && window) || this,
        freeExports = objectTypes[typeof exports] && exports && !exports.nodeType && exports,
        freeModule = objectTypes[typeof module] && module && !module.nodeType && module,
        moduleExports = freeModule && freeModule.exports === freeExports && freeExports,
        freeGlobal = objectTypes[typeof global] && global;
    
    if (freeGlobal && (freeGlobal.global === freeGlobal || freeGlobal.window === freeGlobal)) {
        root = freeGlobal;
    }

    // Because of build optimizers
    if (typeof define === 'function' && define.amd) {
        define(['rx.binding', 'exports'], function (Rx, exports) {
            root.Rx = factory(root, exports, Rx);
            return root.Rx;
        });
    } else if (typeof module === 'object' && module && module.exports === freeExports) {
        module.exports = factory(root, module.exports, require('./rx'));
    } else {
        root.Rx = factory(root, {}, root.Rx);
    }
}.call(this, function (root, exp, Rx, undefined) {
    
    // Aliases
    var Observable = Rx.Observable,
    	observableProto = Observable.prototype,
      observableFromPromise = Observable.fromPromise,
      observableThrow = Observable.throwException,
      AnonymousObservable = Rx.AnonymousObservable,
      AsyncSubject = Rx.AsyncSubject,
      disposableCreate = Rx.Disposable.create,
      CompositeDisposable= Rx.CompositeDisposable,
      immediateScheduler = Rx.Scheduler.immediate,
      timeoutScheduler = Rx.Scheduler.timeout,
      slice = Array.prototype.slice;

    /**
     * Invokes the specified function asynchronously on the specified scheduler, surfacing the result through an observable sequence.
     * 
     * @example
     * var res = Rx.Observable.start(function () { console.log('hello'); });
     * var res = Rx.Observable.start(function () { console.log('hello'); }, Rx.Scheduler.timeout);
     * var res = Rx.Observable.start(function () { this.log('hello'); }, Rx.Scheduler.timeout, console);
     * 
     * @param {Function} func Function to run asynchronously.
     * @param {Scheduler} [scheduler]  Scheduler to run the function on. If not specified, defaults to Scheduler.timeout.
     * @param [context]  The context for the func parameter to be executed.  If not specified, defaults to undefined.
     * @returns {Observable} An observable sequence exposing the function's result value, or an exception.
     * 
     * Remarks
     * * The function is called immediately, not during the subscription of the resulting sequence.
     * * Multiple subscriptions to the resulting sequence can observe the function's result.  
     */
    Observable.start = function (func, scheduler, context) {
        return observableToAsync(func, scheduler, context)();
    };

    /**
     * Converts the function into an asynchronous function. Each invocation of the resulting asynchronous function causes an invocation of the original synchronous function on the specified scheduler.
     * 
     * @example
     * var res = Rx.Observable.toAsync(function (x, y) { return x + y; })(4, 3);
     * var res = Rx.Observable.toAsync(function (x, y) { return x + y; }, Rx.Scheduler.timeout)(4, 3);
     * var res = Rx.Observable.toAsync(function (x) { this.log(x); }, Rx.Scheduler.timeout, console)('hello');
     * 
     * @param {Function} function Function to convert to an asynchronous function.
     * @param {Scheduler} [scheduler] Scheduler to run the function on. If not specified, defaults to Scheduler.timeout.
     * @param {Mixed} [context] The context for the func parameter to be executed.  If not specified, defaults to undefined.
     * @returns {Function} Asynchronous function.
     */
    var observableToAsync = Observable.toAsync = function (func, scheduler, context) {
        scheduler || (scheduler = timeoutScheduler);
        return function () {
            var args = arguments, 
                subject = new AsyncSubject();

            scheduler.schedule(function () {
                var result;
                try {
                    result = func.apply(context, args);
                } catch (e) {
                    subject.onError(e);
                    return;
                }
                subject.onNext(result);
                subject.onCompleted();
            });
            return subject.asObservable();
        };
    };

    /**
     * Converts a callback function to an observable sequence. 
     * 
     * @param {Function} function Function with a callback as the last parameter to convert to an Observable sequence.
     * @param {Scheduler} [scheduler] Scheduler to run the function on. If not specified, defaults to Scheduler.timeout.
     * @param {Mixed} [context] The context for the func parameter to be executed.  If not specified, defaults to undefined.
     * @param {Function} [selector] A selector which takes the arguments from the callback to produce a single item to yield on next.
     * @returns {Function} A function, when executed with the required parameters minus the callback, produces an Observable sequence with a single value of the arguments to the callback as an array.
     */
    Observable.fromCallback = function (func, scheduler, context, selector) {
        scheduler || (scheduler = immediateScheduler);
        return function () {
            var args = slice.call(arguments, 0);

            return new AnonymousObservable(function (observer) {
                return scheduler.schedule(function () {
                    function handler(e) {
                        var results = e;
                        
                        if (selector) {
                            try {
                                results = selector(arguments);
                            } catch (err) {
                                observer.onError(err);
                                return;
                            }
                        } else {
                            if (results.length === 1) {
                                results = results[0];
                            }
                        }

                        observer.onNext(results);
                        observer.onCompleted();
                    }

                    args.push(handler);
                    func.apply(context, args);
                });
            });
        };
    };

    /**
     * Converts a Node.js callback style function to an observable sequence.  This must be in function (err, ...) format.
     * @param {Function} func The function to call
     * @param {Scheduler} [scheduler] Scheduler to run the function on. If not specified, defaults to Scheduler.timeout.
     * @param {Mixed} [context] The context for the func parameter to be executed.  If not specified, defaults to undefined.
     * @param {Function} [selector] A selector which takes the arguments from the callback minus the error to produce a single item to yield on next.     
     * @returns {Function} An async function which when applied, returns an observable sequence with the callback arguments as an array.
     */
    Observable.fromNodeCallback = function (func, scheduler, context, selector) {
        scheduler || (scheduler = immediateScheduler);
        return function () {
            var args = slice.call(arguments, 0);

            return new AnonymousObservable(function (observer) {
                return scheduler.schedule(function () {
                    
                    function handler(err) {
                        if (err) {
                            observer.onError(err);
                            return;
                        }

                        var results = slice.call(arguments, 1);
                        
                        if (selector) {
                            try {
                                results = selector(results);
                            } catch (e) {
                                observer.onError(e);
                                return;
                            }
                        } else {
                            if (results.length === 1) {
                                results = results[0];
                            }
                        }

                        observer.onNext(results);
                        observer.onCompleted();
                    }

                    args.push(handler);
                    func.apply(context, args);
                });
            });
        };
    };

  function createListener (element, name, handler) {
    // Node.js specific
    if (element.addListener) {
      element.addListener(name, handler);
      return disposableCreate(function () {
        element.removeListener(name, handler);
      });
    } 
    if (element.addEventListener) {
      element.addEventListener(name, handler, false);
      return disposableCreate(function () {
        element.removeEventListener(name, handler, false);
      });
    }
    throw new Error('No listener found');
  }

  function createEventListener (el, eventName, handler) {
    var disposables = new CompositeDisposable();

    // Asume NodeList
    if (typeof el.item === 'function' && typeof el.length === 'number') {
      for (var i = 0, len = el.length; i < len; i++) {
        disposables.add(createEventListener(el.item(i), eventName, handler));
      }
    } else if (el) {
      disposables.add(createListener(el, eventName, handler));
    }

    return disposables;
  }

  // Check for Angular/jQuery/Zepto support
  var jq =
   !!root.angular && !!angular.element ? angular.element :
   (!!root.jQuery ? root.jQuery : (
     !!root.Zepto ? root.Zepto : null));

  // Check for ember
  var ember = !!root.Ember && typeof root.Ember.addListener === 'function';

  /**
   * Creates an observable sequence by adding an event listener to the matching DOMElement or each item in the NodeList.
   *
   * @example
   *   var source = Rx.Observable.fromEvent(element, 'mouseup');
   * 
   * @param {Object} element The DOMElement or NodeList to attach a listener.
   * @param {String} eventName The event name to attach the observable sequence.
   * @param {Function} [selector] A selector which takes the arguments from the event handler to produce a single item to yield on next.     
   * @returns {Observable} An observable sequence of events from the specified element and the specified event.
   */
  Observable.fromEvent = function (element, eventName, selector) {
    if (ember) {
      return fromEventPattern(
        function (h) { Ember.addListener(element, eventName); },
        function (h) { Ember.removeListener(element, eventName); },
        selector);
    }    
    if (jq) {
      var $elem = jq(element);
      return fromEventPattern(
        function (h) { $elem.on(eventName, h); },
        function (h) { $elem.off(eventName, h); },
        selector);
    }
    return new AnonymousObservable(function (observer) {
      return createEventListener(
        element, 
        eventName, 
        function handler (e) { 
          var results = e;

          if (selector) {
            try {
              results = selector(arguments);
            } catch (err) {
              observer.onError(err);
              return
            }
          }

          observer.onNext(results); 
        });
    }).publish().refCount();
  };
  /**
   * Creates an observable sequence from an event emitter via an addHandler/removeHandler pair.
   * @param {Function} addHandler The function to add a handler to the emitter.
   * @param {Function} [removeHandler] The optional function to remove a handler from an emitter.
   * @param {Function} [selector] A selector which takes the arguments from the event handler to produce a single item to yield on next.
   * @returns {Observable} An observable sequence which wraps an event from an event emitter
   */
  var fromEventPattern = Observable.fromEventPattern = function (addHandler, removeHandler, selector) {
    return new AnonymousObservable(function (observer) {
      function innerHandler (e) {
        var result = e;
        if (selector) {
          try {
            result = selector(arguments);
          } catch (err) {
            observer.onError(err);
            return;
          }
        }
        observer.onNext(result);
      }

      var returnValue = addHandler(innerHandler);
      return disposableCreate(function () {
        if (removeHandler) {
          removeHandler(innerHandler, returnValue);
        }
      });
    }).publish().refCount();
  };

  /**
   * Invokes the asynchronous function, surfacing the result through an observable sequence.
   * @param {Function} functionAsync Asynchronous function which returns a Promise to run.
   * @returns {Observable} An observable sequence exposing the function's result value, or an exception.
   */
  Observable.startAsync = function (functionAsync) {
    var promise;
    try {
      promise = functionAsync();
    } catch (e) {
      return observableThrow(e);
    }
    return observableFromPromise(promise);
  }

    return Rx;
}));