rx.backpressure.js

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

;(function (factory) {
  var objectTypes = {
    'function': true,
    'object': true
  };

  function checkGlobal(value) {
    return (value && value.Object === Object) ? value : null;
  }

  var freeExports = (objectTypes[typeof exports] && exports && !exports.nodeType) ? exports : null;
  var freeModule = (objectTypes[typeof module] && module && !module.nodeType) ? module : null;
  var freeGlobal = checkGlobal(freeExports && freeModule && typeof global === 'object' && global);
  var freeSelf = checkGlobal(objectTypes[typeof self] && self);
  var freeWindow = checkGlobal(objectTypes[typeof window] && window);
  var moduleExports = (freeModule && freeModule.exports === freeExports) ? freeExports : null;
  var thisGlobal = checkGlobal(objectTypes[typeof this] && this);
  var root = freeGlobal || ((freeWindow !== (thisGlobal && thisGlobal.window)) && freeWindow) || freeSelf || thisGlobal || Function('return this')();

  // Because of build optimizers
  if (typeof define === 'function' && define.amd) {
    define(['./rx'], function (Rx, exports) {
      return factory(root, exports, 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) {

  // References
  var Observable = Rx.Observable,
    observableProto = Observable.prototype,
    AnonymousObservable = Rx.AnonymousObservable,
    AbstractObserver = Rx.internals.AbstractObserver,
    CompositeDisposable = Rx.CompositeDisposable,
    BinaryDisposable = Rx.BinaryDisposable,
    NAryDisposable = Rx.NAryDisposable,
    Notification = Rx.Notification,
    Subject = Rx.Subject,
    Observer = Rx.Observer,
    disposableEmpty = Rx.Disposable.empty,
    disposableCreate = Rx.Disposable.create,
    inherits = Rx.internals.inherits,
    addProperties = Rx.internals.addProperties,
    defaultScheduler = Rx.Scheduler['default'],
    currentThreadScheduler = Rx.Scheduler.currentThread,
    identity = Rx.helpers.identity,
    isScheduler = Rx.Scheduler.isScheduler,
    isFunction = Rx.helpers.isFunction,
    checkDisposed = Rx.Disposable.checkDisposed;

  var errorObj = {e: {}};
  
  function tryCatcherGen(tryCatchTarget) {
    return function tryCatcher() {
      try {
        return tryCatchTarget.apply(this, arguments);
      } catch (e) {
        errorObj.e = e;
        return errorObj;
      }
    };
  }

  var tryCatch = Rx.internals.tryCatch = function tryCatch(fn) {
    if (!isFunction(fn)) { throw new TypeError('fn must be a function'); }
    return tryCatcherGen(fn);
  };

  function thrower(e) {
    throw e;
  }

  /**
  * Used to pause and resume streams.
  */
  Rx.Pauser = (function (__super__) {
    inherits(Pauser, __super__);
    function Pauser() {
      __super__.call(this);
    }

    /**
     * Pauses the underlying sequence.
     */
    Pauser.prototype.pause = function () { this.onNext(false); };

    /**
    * Resumes the underlying sequence.
    */
    Pauser.prototype.resume = function () { this.onNext(true); };

    return Pauser;
  }(Subject));

  var PausableObservable = (function (__super__) {
    inherits(PausableObservable, __super__);
    function PausableObservable(source, pauser) {
      this.source = source;
      this.controller = new Subject();
      this.paused = true;

      if (pauser && pauser.subscribe) {
        this.pauser = this.controller.merge(pauser);
      } else {
        this.pauser = this.controller;
      }

      __super__.call(this);
    }

    PausableObservable.prototype._subscribe = function (o) {
      var conn = this.source.publish(),
        subscription = conn.subscribe(o),
        connection = disposableEmpty;

      var pausable = this.pauser.startWith(!this.paused).distinctUntilChanged().subscribe(function (b) {
        if (b) {
          connection = conn.connect();
        } else {
          connection.dispose();
          connection = disposableEmpty;
        }
      });

      return new NAryDisposable([subscription, connection, pausable]);
    };

    PausableObservable.prototype.pause = function () {
      this.paused = true;
      this.controller.onNext(false);
    };

    PausableObservable.prototype.resume = function () {
      this.paused = false;
      this.controller.onNext(true);
    };

    return PausableObservable;

  }(Observable));

  /**
   * Pauses the underlying observable sequence based upon the observable sequence which yields true/false.
   * @example
   * var pauser = new Rx.Subject();
   * var source = Rx.Observable.interval(100).pausable(pauser);
   * @param {Observable} pauser The observable sequence used to pause the underlying sequence.
   * @returns {Observable} The observable sequence which is paused based upon the pauser.
   */
  observableProto.pausable = function (pauser) {
    return new PausableObservable(this, pauser);
  };

  function combineLatestSource(source, subject, resultSelector) {
    return new AnonymousObservable(function (o) {
      var hasValue = [false, false],
        hasValueAll = false,
        isDone = false,
        values = new Array(2),
        err;

      function next(x, i) {
        values[i] = x;
        hasValue[i] = true;
        if (hasValueAll || (hasValueAll = hasValue.every(identity))) {
          if (err) { return o.onError(err); }
          var res = tryCatch(resultSelector).apply(null, values);
          if (res === errorObj) { return o.onError(res.e); }
          o.onNext(res);
        }
        isDone && values[1] && o.onCompleted();
      }

      return new BinaryDisposable(
        source.subscribe(
          function (x) {
            next(x, 0);
          },
          function (e) {
            if (values[1]) {
              o.onError(e);
            } else {
              err = e;
            }
          },
          function () {
            isDone = true;
            values[1] && o.onCompleted();
          }),
        subject.subscribe(
          function (x) {
            next(x, 1);
          },
          function (e) { o.onError(e); },
          function () {
            isDone = true;
            next(true, 1);
          })
        );
    }, source);
  }

  var PausableBufferedObservable = (function (__super__) {
    inherits(PausableBufferedObservable, __super__);
    function PausableBufferedObservable(source, pauser) {
      this.source = source;
      this.controller = new Subject();
      this.paused = true;

      if (pauser && pauser.subscribe) {
        this.pauser = this.controller.merge(pauser);
      } else {
        this.pauser = this.controller;
      }

      __super__.call(this);
    }

    PausableBufferedObservable.prototype._subscribe = function (o) {
      var q = [], previousShouldFire;

      function drainQueue() { while (q.length > 0) { o.onNext(q.shift()); } }

      var subscription =
        combineLatestSource(
          this.source,
          this.pauser.startWith(!this.paused).distinctUntilChanged(),
          function (data, shouldFire) {
            return { data: data, shouldFire: shouldFire };
          })
          .subscribe(
            function (results) {
              if (previousShouldFire !== undefined && results.shouldFire !== previousShouldFire) {
                previousShouldFire = results.shouldFire;
                // change in shouldFire
                if (results.shouldFire) { drainQueue(); }
              } else {
                previousShouldFire = results.shouldFire;
                // new data
                if (results.shouldFire) {
                  o.onNext(results.data);
                } else {
                  q.push(results.data);
                }
              }
            },
            function (err) {
              drainQueue();
              o.onError(err);
            },
            function () {
              drainQueue();
              o.onCompleted();
            }
          );
      return subscription;      
    };

    PausableBufferedObservable.prototype.pause = function () {
      this.paused = true;
      this.controller.onNext(false);
    };

    PausableBufferedObservable.prototype.resume = function () {
      this.paused = false;
      this.controller.onNext(true);
    };

    return PausableBufferedObservable;

  }(Observable));

  /**
   * Pauses the underlying observable sequence based upon the observable sequence which yields true/false,
   * and yields the values that were buffered while paused.
   * @example
   * var pauser = new Rx.Subject();
   * var source = Rx.Observable.interval(100).pausableBuffered(pauser);
   * @param {Observable} pauser The observable sequence used to pause the underlying sequence.
   * @returns {Observable} The observable sequence which is paused based upon the pauser.
   */
  observableProto.pausableBuffered = function (pauser) {
    return new PausableBufferedObservable(this, pauser);
  };

  var ControlledObservable = (function (__super__) {
    inherits(ControlledObservable, __super__);
    function ControlledObservable (source, enableQueue, scheduler) {
      __super__.call(this);
      this.subject = new ControlledSubject(enableQueue, scheduler);
      this.source = source.multicast(this.subject).refCount();
    }

    ControlledObservable.prototype._subscribe = function (o) {
      return this.source.subscribe(o);
    };

    ControlledObservable.prototype.request = function (numberOfItems) {
      return this.subject.request(numberOfItems == null ? -1 : numberOfItems);
    };

    return ControlledObservable;

  }(Observable));

  var ControlledSubject = (function (__super__) {
    inherits(ControlledSubject, __super__);
    function ControlledSubject(enableQueue, scheduler) {
      enableQueue == null && (enableQueue = true);

      __super__.call(this);
      this.subject = new Subject();
      this.enableQueue = enableQueue;
      this.queue = enableQueue ? [] : null;
      this.requestedCount = 0;
      this.requestedDisposable = null;
      this.error = null;
      this.hasFailed = false;
      this.hasCompleted = false;
      this.scheduler = scheduler || currentThreadScheduler;
    }

    addProperties(ControlledSubject.prototype, Observer, {
      _subscribe: function (o) {
        return this.subject.subscribe(o);
      },
      onCompleted: function () {
        this.hasCompleted = true;
        if (!this.enableQueue || this.queue.length === 0) {
          this.subject.onCompleted();
          this.disposeCurrentRequest();
        } else {
          this.queue.push(Notification.createOnCompleted());
        }
      },
      onError: function (error) {
        this.hasFailed = true;
        this.error = error;
        if (!this.enableQueue || this.queue.length === 0) {
          this.subject.onError(error);
          this.disposeCurrentRequest();
        } else {
          this.queue.push(Notification.createOnError(error));
        }
      },
      onNext: function (value) {
        if (this.requestedCount <= 0) {
          this.enableQueue && this.queue.push(Notification.createOnNext(value));
        } else {
          (this.requestedCount-- === 0) && this.disposeCurrentRequest();
          this.subject.onNext(value);
        }
      },
      _processRequest: function (numberOfItems) {
        if (this.enableQueue) {
          while (this.queue.length > 0 && (numberOfItems > 0 || this.queue[0].kind !== 'N')) {
            var first = this.queue.shift();
            first.accept(this.subject);
            if (first.kind === 'N') {
              numberOfItems--;
            } else {
              this.disposeCurrentRequest();
              this.queue = [];
            }
          }
        }

        return numberOfItems;
      },
      request: function (number) {
        this.disposeCurrentRequest();
        var self = this;

        this.requestedDisposable = this.scheduler.schedule(number,
        function(s, i) {
          var remaining = self._processRequest(i);
          var stopped = self.hasCompleted || self.hasFailed;
          if (!stopped && remaining > 0) {
            self.requestedCount = remaining;

            return disposableCreate(function () {
              self.requestedCount = 0;
            });
              // Scheduled item is still in progress. Return a new
              // disposable to allow the request to be interrupted
              // via dispose.
          }
        });

        return this.requestedDisposable;
      },
      disposeCurrentRequest: function () {
        if (this.requestedDisposable) {
          this.requestedDisposable.dispose();
          this.requestedDisposable = null;
        }
      }
    });

    return ControlledSubject;
  }(Observable));

  /**
   * Attaches a controller to the observable sequence with the ability to queue.
   * @example
   * var source = Rx.Observable.interval(100).controlled();
   * source.request(3); // Reads 3 values
   * @param {bool} enableQueue truthy value to determine if values should be queued pending the next request
   * @param {Scheduler} scheduler determines how the requests will be scheduled
   * @returns {Observable} The observable sequence which only propagates values on request.
   */
  observableProto.controlled = function (enableQueue, scheduler) {

    if (enableQueue && isScheduler(enableQueue)) {
      scheduler = enableQueue;
      enableQueue = true;
    }

    if (enableQueue == null) {  enableQueue = true; }
    return new ControlledObservable(this, enableQueue, scheduler);
  };

  var StopAndWaitObservable = (function (__super__) {
    inherits(StopAndWaitObservable, __super__);
    function StopAndWaitObservable (source) {
      __super__.call(this);
      this.source = source;
    }

    function scheduleMethod(s, self) {
      return self.source.request(1);
    }

    StopAndWaitObservable.prototype._subscribe = function (o) {
      this.subscription = this.source.subscribe(new StopAndWaitObserver(o, this, this.subscription));
      return new BinaryDisposable(
        this.subscription,
        defaultScheduler.schedule(this, scheduleMethod)
      );
    };

    var StopAndWaitObserver = (function (__sub__) {
      inherits(StopAndWaitObserver, __sub__);
      function StopAndWaitObserver (observer, observable, cancel) {
        __sub__.call(this);
        this.observer = observer;
        this.observable = observable;
        this.cancel = cancel;
        this.scheduleDisposable = null;
      }

      StopAndWaitObserver.prototype.completed = function () {
        this.observer.onCompleted();
        this.dispose();
      };

      StopAndWaitObserver.prototype.error = function (error) {
        this.observer.onError(error);
        this.dispose();
      };

      function innerScheduleMethod(s, self) {
        return self.observable.source.request(1);
      }

      StopAndWaitObserver.prototype.next = function (value) {
        this.observer.onNext(value);
        this.scheduleDisposable = defaultScheduler.schedule(this, innerScheduleMethod);
      };

      StopAndWaitObserver.dispose = function () {
        this.observer = null;
        if (this.cancel) {
          this.cancel.dispose();
          this.cancel = null;
        }
        if (this.scheduleDisposable) {
          this.scheduleDisposable.dispose();
          this.scheduleDisposable = null;
        }
        __sub__.prototype.dispose.call(this);
      };

      return StopAndWaitObserver;
    }(AbstractObserver));

    return StopAndWaitObservable;
  }(Observable));


  /**
   * Attaches a stop and wait observable to the current observable.
   * @returns {Observable} A stop and wait observable.
   */
  ControlledObservable.prototype.stopAndWait = function () {
    return new StopAndWaitObservable(this);
  };

  var WindowedObservable = (function (__super__) {
    inherits(WindowedObservable, __super__);
    function WindowedObservable(source, windowSize) {
      __super__.call(this);
      this.source = source;
      this.windowSize = windowSize;
    }

    function scheduleMethod(s, self) {
      return self.source.request(self.windowSize);
    }

    WindowedObservable.prototype._subscribe = function (o) {
      this.subscription = this.source.subscribe(new WindowedObserver(o, this, this.subscription));
      return new BinaryDisposable(
        this.subscription,
        defaultScheduler.schedule(this, scheduleMethod)
      );
    };

    var WindowedObserver = (function (__sub__) {
      inherits(WindowedObserver, __sub__);
      function WindowedObserver(observer, observable, cancel) {
        this.observer = observer;
        this.observable = observable;
        this.cancel = cancel;
        this.received = 0;
        this.scheduleDisposable = null;
        __sub__.call(this);
      }

      WindowedObserver.prototype.completed = function () {
        this.observer.onCompleted();
        this.dispose();
      };

      WindowedObserver.prototype.error = function (error) {
        this.observer.onError(error);
        this.dispose();
      };

      function innerScheduleMethod(s, self) {
        return self.observable.source.request(self.observable.windowSize);
      }

      WindowedObserver.prototype.next = function (value) {
        this.observer.onNext(value);
        this.received = ++this.received % this.observable.windowSize;
        this.received === 0 && (this.scheduleDisposable = defaultScheduler.schedule(this, innerScheduleMethod));
      };

      WindowedObserver.prototype.dispose = function () {
        this.observer = null;
        if (this.cancel) {
          this.cancel.dispose();
          this.cancel = null;
        }
        if (this.scheduleDisposable) {
          this.scheduleDisposable.dispose();
          this.scheduleDisposable = null;
        }
        __sub__.prototype.dispose.call(this);
      };

      return WindowedObserver;
    }(AbstractObserver));

    return WindowedObservable;
  }(Observable));

  /**
   * Creates a sliding windowed observable based upon the window size.
   * @param {Number} windowSize The number of items in the window
   * @returns {Observable} A windowed observable based upon the window size.
   */
  ControlledObservable.prototype.windowed = function (windowSize) {
    return new WindowedObservable(this, windowSize);
  };

  /**
   * Pipes the existing Observable sequence into a Node.js Stream.
   * @param {Stream} dest The destination Node.js stream.
   * @returns {Stream} The destination stream.
   */
  observableProto.pipe = function (dest) {
    var source = this.pausableBuffered();

    function onDrain() {
      source.resume();
    }

    dest.addListener('drain', onDrain);

    source.subscribe(
      function (x) {
        !dest.write(x) && source.pause();
      },
      function (err) {
        dest.emit('error', err);
      },
      function () {
        // Hack check because STDIO is not closable
        !dest._isStdio && dest.end();
        dest.removeListener('drain', onDrain);
      });

    source.resume();

    return dest;
  };

  return Rx;
}));