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import { isPromise } from "@implab/core-amd/safe";
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import { Unsubscribable, Producer, FusedSink, Observable, Subscribable } from "./observable/interfaces";
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import { ObservableImpl } from "./observable/ObservableImpl";
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export const isUnsubscribable = (v: unknown): v is Unsubscribable =>
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v !== null && v !== undefined && typeof (v as Unsubscribable).unsubscribe === "function";
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export const isSubscribable = <T = unknown>(v: unknown): v is Subscribable<T> =>
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v !== null && v !== undefined && typeof (v as Subscribable<unknown>).subscribe === "function";
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const noop = () => { };
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/** Wraps the producer to handle tear down logic and subscription management
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*
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* The resulting producer will invoke cleanup logic on error or complete events
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* and will prevent calling of any method from the sink.
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*
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* @param producer The producer to wrap
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* @returns The wrapper producer
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*/
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const fuse = <T>(producer: Producer<T>) => ({ next, error, complete }: FusedSink<T>) => {
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let done = false;
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let cleanup = noop;
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const _fin = <A extends unknown[]>(fn: (...args: A) => void) =>
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(...args: A) => done ?
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void (0) :
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(done = true, cleanup(), fn(...args));
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const _fin0 = () => done ? void (0) : (done = true, cleanup());
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const safeSink = {
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next: (value: T) => { !done && next(value); },
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error: _fin(error),
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complete: _fin(complete),
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isClosed: () => done
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};
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// call the producer
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cleanup = producer(safeSink) ?? noop;
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// if the producer throws exception bypass it to the caller rather then to
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// the sink. This is a feature.
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// if the producer completed the sequence immediately call the cleanup in place
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return done ? cleanup() : _fin0;
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};
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export const observe = <T>(producer: Producer<T>): Observable<T> => new ObservableImpl<T>(fuse(producer));
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/** Converts an array to the observable sequence of its elements. */
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export const ofArray = <T>(items: T[]) => new ObservableImpl<T>(
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({ next, complete }) => (
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items.forEach(next),
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complete()
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)
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);
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/** Converts a subscribable to the observable */
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export const ofSubscribable = <T>(subscribable: Subscribable<T>) =>
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observe<T>(sink => {
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const subscription = subscribable.subscribe(sink);
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return () => subscription.unsubscribe();
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});
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const of1 = <T>(item: T | PromiseLike<T>) => observe<T>(
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({ next, error, complete }) =>
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isPromise(item) ?
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void item.then(
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v => (next(v), complete()),
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error
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) :
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(next(item), complete())
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);
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/** Converts a list of parameter values to the observable sequence. The
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* order of elements in the list will be preserved in the resulting sequence.
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*/
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export const of = <T>(...items: (T | PromiseLike<T>)[]) => items.length === 1 ?
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of1(items[0]) :
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observe<T>(
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({ next, error, complete, isClosed }) => {
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const n = items.length;
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const _next = (start: number) => {
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if (start > 0 && isClosed()) // when resumed
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return;
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for (let i = start; i < n; i++) {
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const r = items[i];
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if (isPromise(r)) {
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r.then(v => (next(v), _next(i + 1)), error);
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return; // suspend
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} else {
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next(r);
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}
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}
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complete();
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};
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_next(0);
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}
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);
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export const empty = new ObservableImpl<never>(({ complete }) => complete());
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export type * from "./observable/interfaces";
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