|
|
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 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;
|
|
|
}
|
|
|
|
|
|
export type AccumulatorFn<T, A> = (acc: A, value: T) => A;
|
|
|
|
|
|
/** 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: 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
|
|
|
*/
|
|
|
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
|
|
|
*/
|
|
|
pipe<U>(op: (source: Observable<T>) => Producer<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 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: <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)
|
|
|
);
|
|
|
|
|
|
export const of = <T>(...items: T[]) => _observe<T>(
|
|
|
({ next, complete }) => (
|
|
|
items.forEach(next),
|
|
|
complete()
|
|
|
)
|
|
|
);
|
|
|
|
|
|
export const empty = _observe<never>(({ complete }) => complete());
|
