implab/implabjs-djx Commit - r114:e9a9ed6d7647

added pipe method to observable

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r114:e9a9ed6d7647 v1.5.0 default

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r114:e9a9ed6d7647

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djx/src/main/ts/observable.ts +5 -1

              import { PromiseOrValue } from "@implab/core-amd/interfaces";
              import { isPromise } from "@implab/core-amd/safe";
              /**
               * The interface for the consumer of an observable sequence
               */
              export interface Observer<T> {
                  /**
                   * Called for the next element in the sequence
                   */
                  next: (value: T) => void;
                  /**
                   * Called once when the error occurs in the sequence.
                   */
                  error: (e: unknown) => void;
                  /**
                   * Called once at the end of the sequence.
                   */
                  complete: () => void;
              }
              /**
               * The group of functions to feed an observable. These methods are provided to
               * the producer to generate a stream of events.
               */
              export type Sink<T> = {
                  /**
                   * Call to send the next element in the sequence
                   */
                   next: (value: T) => void;
                   /**
                    * Call to notify about the error occurred in the sequence.
                    */
                   error: (e: unknown) => void;
                   /**
                    * Call to signal the end of the sequence.
                    */
                   complete: () => void;
                   /**
                    * Checks whether the sink is accepting new elements. It's safe to
                    * send elements to the closed sink.
                    */
                   isClosed: () => boolean;
              };
              export type Producer<T> = (sink: Sink<T>) => (void | (() => void));
              export interface Unsubscribable {
                  unsubscribe(): void;
              }
              export const isUnsubsribable = (v: unknown): v is Unsubscribable =>
                  v !== null && v !== undefined && typeof (v as Unsubscribable).unsubscribe === "function";
              export const isSubsribable = <T = unknown>(v: unknown): v is Subscribable<T> =>
                  v !== null && v !== undefined && typeof (v as Subscribable<unknown>).subscribe === "function";
              export interface Subscribable<T> {
                  subscribe(consumer: Partial<Observer<T>>): Unsubscribable;
              }
              /** The observable source of items. */
              export interface Observable<T> extends Subscribable<T> {
                  /** Transforms elements of the sequence with the specified mapper
                   *
                   * @param mapper The mapper used to transform the values
                   */
                  map<T2>(mapper: (value: T) => T2): Observable<T2>;
                  /** Filters elements of the sequence. The resulting sequence will
                   * contain only elements which match the specified predicate.
                   *
                   * @param predicate The filter predicate.
                   */
                  filter(predicate: (value: T) => boolean): Observable<T>;
                  /** Applies accumulator to each value in the sequence and
                   * emits the accumulated value for each source element
                   *
                   * @param accumulator
                   * @param initial
                   */
                  scan<A>(accumulator: (acc: A, value: T) => A, initial: A): Observable<A>;
                  cat(...seq: Subscribable<T>[]): Observable<T>;
+                 pipe<U>(f: (source: Observable<T>) => Producer<U>): Observable<U>;
              }
              const noop = () => { };
              const sink = <T>(consumer: Partial<Observer<T>>) => {
                  const { next, error, complete } = consumer;
                  return {
                      next: next ? next.bind(consumer) : noop,
                      error: error ? error.bind(consumer) : noop,
                      complete: complete ? complete.bind(consumer) : noop,
                      isClosed: () => false
                  };
              };
              /** Wraps the producer to handle tear down logic and subscription management
               *
               * @param producer The producer to wrap
               * @returns The wrapper producer
               */
              const fuse = <T>(producer: Producer<T>) => ({ next, error, complete }: Sink<T>) => {
                  let done = false;
                  let cleanup = noop;
                  const _fin = <A extends unknown[]>(fn: (...args: A) => void) =>
                      (...args: A) => done ?
                          void (0) :
                          (done = true, cleanup(), fn(...args));
                  const safeSink = {
                      next: (value: T) => { !done && next(value); },
                      error: _fin(error),
                      complete: _fin(complete),
                      isClosed: () => done
                  };
                  cleanup = producer(safeSink) ?? noop;
                  return done ?
                      (cleanup(), noop) :
                      _fin(noop);
              };
              const _observe = <T>(producer: Producer<T>): Observable<T> => ({
                  subscribe: (consumer: Partial<Observer<T>>) => ({
                      unsubscribe: producer(sink(consumer)) ?? noop
                  }),
                  map: (mapper) => _observe(({ next, ...rest }) =>
                      producer({
                          next: next !== noop ? (v: T) => next(mapper(v)) : noop,
                          ...rest
                      })
                  ),
                  filter: (predicate) => _observe(({ next, ...rest }) =>
                      producer({
                          next: next !== noop ? (v: T) => predicate(v) ? next(v) : void (0) : noop,
                          ...rest
                      })
                  ),
                  scan: (accumulator, initial) => _observe(({ next, ...rest }) => {
                      let _acc = initial;
                      return producer({
                          next: next !== noop ? (v: T) => next(_acc = accumulator(_acc, v)) : noop,
                          ...rest
                      });
                  }),
                  cat: (...seq) => _observe(({ next, complete: final, ...rest }) => {
                      let cleanup: () => void;
                      const complete = () => {
                          const continuation = seq.shift();
                          if (continuation) {
                              // if we have a next sequence, subscribe to it
                              const subscription = continuation.subscribe({ next, complete, ...rest });
                              cleanup = subscription.unsubscribe.bind(subscription);
                          } else {
                              // otherwise notify the consumer about completion
                              final();
                          }
                      };
                      cleanup = producer({ next, complete, ...rest }) ?? noop;
                      return () => cleanup();
-                 })
+                 }),
+                 pipe: <U>(f: (source: Observable<T>) => Producer<U>) => observe(f(_observe(producer)))
              });
              export interface OrderUpdate<T> {
                  /** The item is being updated */
                  item: T;
                  /** The previous index of the item, -1 in case it is inserted */
                  prevIndex: number;
                  /** The new index of the item, -1 in case it is deleted */
                  newIndex: number;
              }
              interface ObservableResults<T> {
                  /**
                   * Allows observation of results
                   */
                  observe(listener: (object: T, previousIndex: number, newIndex: number) => void, includeUpdates?: boolean): {
                      remove(): void;
                  };
              }
              interface Queryable<T, A extends unknown[]> {
                  query(...args: A): PromiseOrValue<T[]>;
              }
              export const isObservableResults = <T>(v: object): v is ObservableResults<T> =>
                  v && (typeof (v as { observe?: unknown; }).observe === "function");
              export const observe = <T>(producer: Producer<T>) => _observe(fuse(producer));
              export const empty = observe<never>(({ complete }) => complete());
              export const query = <T, A extends unknown[]>(store: Queryable<T, A>) =>
                  (...args: A) => {
                      return observe<OrderUpdate<T>>(({ next, complete, error }) => {
                          try {
                              const results = store.query(...args);
                              if (isPromise(results)) {
                                  results.then(items => items.forEach((item, newIndex) => next({ item, newIndex, prevIndex: -1 })))
                                      .then(undefined, error);
                              } else {
                                  results.forEach((item, newIndex) => next({ item, newIndex, prevIndex: -1 }));
                              }
                              if (isObservableResults<T>(results)) {
                                  const h = results.observe((item, prevIndex, newIndex) => next({ item, prevIndex, newIndex }));
                                  return () => h.remove();
                              } else {
                                  complete();
                              }
                          } catch (err) {
                              error(err);
                          }
                      });
                  };

djx/src/test/ts/observable-tests.ts +30 0

              import { observe } from "./observable";
              import * as t from "tap";
              const subj1 = observe<number>(({ next, complete }) => {
                  next(1);
                  complete();
                  next(2);
              });
              const consumer1 = {
                  sum: 0,
                  next(v: number) {
                      this.sum += v;
                  }
              };
              subj1.subscribe(consumer1);
              t.equal(consumer1.sum, 1, "Should get only one value");
              subj1.subscribe(consumer1);
              t.equal(consumer1.sum, 2, "Should get the value again");
              const consumer2 = {
                  value: 0,
                  completed: false,
                  next(v: number) { this.value = v; },
                  complete() { this.completed = true; }
              };
              let maps = 0;
              subj1
                  .map(v => {
                      t.comment(`map1: ${v * 2}`);
                      maps++;
                      return v * 2;
                  })
-                 .map (v => {
                      t.comment(`map2: ${v * 2}`);
                      maps++;
                      return v * 2;
                  })
                  .map(v => {
                      t.comment(`map3: ${v * 2}`);
                      maps++;
                      return v * 2;
                  })
                  .subscribe(consumer2);
              t.equal(consumer2.value, 8, "Should map");
              t.equal(maps, 3, "The map chain should not be executed after completion");
              t.ok(consumer2.completed, "The completion signal should pass through");
+             const subj2 = observe<number>(({ next, complete }) => {
+                 [1, 2, 3, 4, 5].forEach(next);
+                 complete();
+             }).pipe<string>(self => ({ next, complete, error }) => {
+                 t.comment("subj2: subscribe");
+                 const h = self.subscribe({
+                     next: val => {
+                         if (val % 2 === 0)
+                             next("odd");
+                         else
+                             next("even");
+                     },
+                     complete,
+                     error
+                 });
+                 return () =>{
+                     t.comment("subj2: unsubscribe");
+                     h.unsubscribe();
+                 };
+             });
+             subj2.subscribe({
+                 next: val => t.comment("subj2: ", val),
+                 complete: () => t.comment("subj2: complete")
+             });
+             subj2.subscribe({
+                 next: val => t.comment("subj2: ", val),
+                 complete: () => t.comment("subj2: complete")
+             });
  No newline at end of file

playground/package-lock.json 0 0

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