implab/implabjs-djx Commit - r124:fbe158a5752a

added while, until methods to the observable interface....

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djx/src/test/ts/state-tests.ts created 644 +27 0

			@@ -0,0 +1,27
		1	import { observe, stateful } from "./observable";
		2	import * as t from "tap";
		3
		4	interface CounterState {
		5	count: number;
		6
		7	label: "low" \| "mid" \| "high"
		8	}
		9
		10	let set: (v: CounterState) => void = () => void (0);
		11	const initial: CounterState = { count: 0, label: "low" };
		12	let value = initial;
		13
		14	const obs = observe(stateful<CounterState>(({ next }) => {
		15	next(initial);
		16	set = next;
		17	}));
		18
		19	set({ count: 10, label: "mid" });
		20
		21	obs.subscribe({
		22	next: v => value = v
		23	});
		24
		25	t.equal(value.count, 10, "State should update");
		26
		27	set({ count: 20, label: "high" });

djx/src/main/ts/observable.ts +138 -7

              import { Cancellation } from "@implab/core-amd/Cancellation";
              import { ICancellation } from "@implab/core-amd/interfaces";
              /**
               * 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 isUnsubscribable = (v: unknown): v is Unsubscribable =>
                  v !== null && v !== undefined && typeof (v as Unsubscribable).unsubscribe === "function";
              export const isSubscribable = <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;
              }
              export type AccumulatorFn<T, A> = (acc: A, value: T) => A;
+             export type OperatorFn<T, U> = (source: Observable<T>) => Producer<U>;
              /** 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>;
+                 /** Completes the sequence once the condition is met.
+                  * @param predicate The condition which should be met to complete the sequence
+                  */
+                 until(predicate: (value: T) => boolean): Observable<T>;
+                 /** Keeps the sequence running while elements satisfy the condition.
+                  *
+                  * @param predicate The condition which should be met to continue.
+                  */
+                 while(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: AccumulatorFn<T, A>, initial: A): Observable<A>;
                  scan(accumulator: AccumulatorFn<T, T>): Observable<T>;
                  /** Applies accumulator to each value in the sequence and
                   * emits the accumulated value at the end of the sequence
                   *
                   * @param accumulator
                   * @param initial
                   */
                  reduce<A>(accumulator: AccumulatorFn<T, A>, initial: A): Observable<A>;
                  reduce(accumulator: AccumulatorFn<T, T>): Observable<T>;
                  /** Concatenates the specified sequences with this observable
                   *
                   * @param seq sequences to concatenate with the current observable
+                  *
+                  * The concatenation doesn't accumulate values from the specified sequences,
+                  * The result of the concatenation is the new observable which will switch
+                  * to the next observable after the previous one completes. Values emitted
+                  * before the next observable being active are lost.
                   */
                  cat(...seq: Subscribable<T>[]): Observable<T>;
                  /** Pipes the specified operator to produce the new observable
-                  * @param op The operator which consumes this observable and produces a new one
+                  * @param op The operator consumes this observable and produces a new one
+                  *
+                  * The operator is a higher order function which takes a source observable
+                  * and returns a producer for the new observable.
+                  *
+                  * This function can be used to create a complex mapping between source and
+                  * resulting observables. The operator may have a state (or a side effect)
+                  * and can be connected to multiple observables.
                   */
-                 pipe<U>(op: (source: Observable<T>) => Producer<U>): Observable<U>;
+                 pipe<U>(op: OperatorFn<T, U>): Observable<U>;
                  /** Waits for the next event to occur and returns a promise for the next value
                   * @param ct Cancellation token to
                  */
                  next(ct?: ICancellation): Promise<T>;
              }
              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 _fin0 = () => done ? void (0) : (done = true, cleanup());
                  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);
+                 return done ? cleanup() : _fin0;
              };
              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
                      })
                  ),
+                 until: predicate => _observe(({ next, complete, ...rest }) =>
+                     producer({
+                         next: v => predicate(v) ? complete() : next(v),
+                         complete,
+                         ...rest
+                     })
+                 ),
+                 while: predicate => _observe(({ next, complete, ...rest }) =>
+                     producer({
+                         next: v => predicate(v) ? next(v) : complete(),
+                         complete,
+                         ...rest
+                     })
+                 ),
                  scan: <A>(...args: [AccumulatorFn<T, A>, A] | [AccumulatorFn<T, T>]) => _observe<T | A>(({ next, ...rest }) => {
                      if (args.length === 1) {
                          const [accumulator] = args;
                          let _acc: T;
                          let index = 0;
                          return producer({
                              next: next !== noop ? (v: T) => next(index++ === 0 ? _acc = v : _acc = accumulator(_acc, v)) : noop,
                              ...rest
                          });
                      } else {
                          const [accumulator, initial] = args;
                          let _acc = initial;
                          return producer({
                              next: next !== noop ? (v: T) => next(_acc = accumulator(_acc, v)) : noop,
                              ...rest
                          });
                      }
                  }),
                  reduce: <A>(...args: [AccumulatorFn<T, A>, A] | [AccumulatorFn<T, T>]) => _observe<T | A>(({ next, complete, error, ...rest }) => {
                      if (args.length === 1) {
                          const [accumulator] = args;
                          let _acc: T;
                          let index = 0;
                          return producer({
                              next: next !== noop ? (v: T) => {
                                  _acc = index++ === 0 ? v : accumulator(_acc, v);
                              } : noop,
                              complete: () => {
                                  if (index === 0) {
                                      error(new Error("The sequence can't be empty"));
                                  } else {
                                      next(_acc);
                                      complete();
                                  }
                              },
                              error,
                              ...rest
                          });
                      } else {
                          const [accumulator, initial] = args;
                          let _acc = initial;
                          return producer({
                              next: next !== noop ? (v: T) => {
                                  _acc = accumulator(_acc, v);
                              } : noop,
                              complete: () => {
                                  next(_acc);
                                  complete();
                              },
                              error,
                              ...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>(op: (source: Observable<T>) => Producer<U>) => observe(op(_observe(producer))),
                  next: (ct?: ICancellation) => {
                      const _ct = ct ?? Cancellation.none;
                      return new Promise<T>((resolve, reject) => {
                          // wrap the producer to handle only single event
                          const once = fuse<T>(({ next, complete, error, isClosed }) => {
                              const h = _ct.register(error);
                              // is the _ct fires it will call error() and isClosed() will return true
                              const cleanup = !isClosed() ?
                                  producer({
                                      next: v => (next(v), complete()),
                                      complete: () => error(new Error("The sequence is empty")),
                                      error,
                                      isClosed
                                  }) ?? noop :
                                  noop;
                              return () => {
                                  h.destroy();
                                  cleanup();
                              };
                          });
                          once({
                              next: resolve,
                              error: reject,
                              complete: noop,
                              isClosed: () => false
                          });
                      });
                  }
              });
              export const observe = <T>(producer: Producer<T>) => _observe(fuse(producer));
              export const streamArray = <T>(items: T[]) => _observe<T>(
                  ({ next, complete }) => (
                      items.forEach(next),
                      complete()
                  )
              );
              export const streamPromise = <T>(promise: PromiseLike<T>) => observe<T>(
-                 ({next, error, complete}) => void promise.then(v => (next(v), complete()), error)
+                 ({ next, error, complete }) => void promise.then(
+                     v => (next(v), complete()),
+                     error
+                 )
              );
              export const of = <T>(...items: T[]) => _observe<T>(
                  ({ next, complete }) => (
                      items.forEach(next),
                      complete()
                  )
              );
-             export const empty = _observe<never>(({ complete }) => complete());
  No newline at end of file
+             export const empty = _observe<never>(({ complete }) => complete());
+             /**
+              * Creates a mutable state and the observable for the stored value.
+              *
+              * @param value The initial value for the state
+              * @returns an array of three elements `[observable, setter, getter]`
+              *
+              * The returned observable keeps the actual value and will emit it as the next
+              * element each time a consumer subscribes the observable.
+              *
+              * Calling the setter will update the stored value in the observable and notify
+              * all consumers.
+              */
+             export const stateful = <T>(producer: Producer<T>): Producer<T> => {
+                 const fusedProducer = fuse(producer);
+                 type Status = "active" | "complete" | "error";
+                 let lastValue: T;
+                 let hasValue = false;
+                 let status: Status = "active";
+                 let lastError: unknown;
+                 let subscribers: Sink<T>[] = [];
+                 const sink: Sink<T> = {
+                     isClosed: () => status !== "active",
+                     complete: () => {
+                         if (status === "active") {
+                             status = "complete";
+                             const _subscribers = subscribers;
+                             subscribers = [];
+                             _subscribers.forEach(s => s.complete());
+                         }
+                     },
+                     error: e => {
+                         if (status === "active") {
+                             status = "error";
+                             lastError = e;
+                             const _subscribers = subscribers;
+                             subscribers = [];
+                             _subscribers.forEach(s => s.error(e));
+                         }
+                     },
+                     next: v => {
+                         if (status === "active") {
+                             hasValue = true;
+                             lastValue = v;
+                             const _subscribers = subscribers;
+                             _subscribers.forEach(s => s.next(v));
+                         }
+                     }
+                 };
+                 fusedProducer(sink);
+                 return (s: Sink<T>) => {
+                     const _subscribers = subscribers;
+                     switch (status) {
+                         case "active":
+                             if (hasValue)
+                                 s.next(lastValue); // if hasValue is true,
+                                                    // lastValue has a valid value
+                             subscribers.push(s);
+                             return () => {
+                                 if (_subscribers === subscribers) {
+                                     const pos = subscribers.indexOf(s);
+                                     if (pos >= 0)
+                                         subscribers.splice(pos, 1);
+                                 }
+                             };
+                         case "complete":
+                             s.complete();
+                             break;
+                         case "error":
+                             s.error(lastError);
+                             break;
+                     }
+                 };
+             };
+             const subject = <T>(producer: Producer<T>): Producer<T> => {
+                 const fusedProducer = fuse(producer);
+                 return () => {
+                 };
+             };
  No newline at end of file

djx/src/test/ts/plan.ts +2 -1

		@@ -1,2 +1,3
1	1	import "./declare-tests";
2		import "./observable-tests"; No newline at end of file
	2	import "./observable-tests";
	3	import "./state-tests"; No newline at end of file

playground/package-lock.json 0 0

	1		NO CONTENT: modified file
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