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added pipe method to observable
added pipe method to observable
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r114:e9a9ed6d7647 v1.5.0 default
r114:e9a9ed6d7647 v1.5.0 default
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observable.ts
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/ djx / src / main / ts / observable.ts
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cin
corrected tear down logic handling in observables. Added support for observable query results
 r110 import { PromiseOrValue } from "@implab/core-amd/interfaces";
import { isPromise } from "@implab/core-amd/safe";
cin
`Subscribable` is made compatible with rxjs, added map, filter and scan...
 r102 /**
* 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;
cin
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 r96
cin
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 r102 /**
* Called once when the error occurs in the sequence.
*/
cin
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 r96 error: (e: unknown) => void;
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 r102
/**
* Called once at the end of the sequence.
*/
cin
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 r96 complete: () => void;
}
cin
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 r102 /**
cin
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 r110 * The group of functions to feed an observable. These methods are provided to
cin
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 r102 * the producer to generate a stream of events.
*/
export type Sink<T> = {
cin
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 r110 /**
* 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;
cin
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 r102 };
cin
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export type Producer<T> = (sink: Sink<T>) => (void | (() => void));
cin
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 r102 export interface Unsubscribable {
unsubscribe(): void;
}
export const isUnsubsribable = (v: unknown): v is Unsubscribable =>
v !== null && v !== undefined && typeof (v as Unsubscribable).unsubscribe === "function";
cin
Working on WatchForRendition
 r107 export const isSubsribable = <T = unknown>(v: unknown): v is Subscribable<T> =>
cin
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 r102 v !== null && v !== undefined && typeof (v as Subscribable<unknown>).subscribe === "function";
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cin
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 r102 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>;
cin
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 r96
cin
`Subscribable` is made compatible with rxjs, added map, filter and scan...
 r102 /** 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>;
cin
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cin
`Subscribable` is made compatible with rxjs, added map, filter and scan...
 r102 /** 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>;
cin
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 r110
cat(...seq: Subscribable<T>[]): Observable<T>;
cin
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pipe<U>(f: (source: Observable<T>) => Producer<U>): Observable<U>;
cin
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 r102 }
const noop = () => { };
const sink = <T>(consumer: Partial<Observer<T>>) => {
const { next, error, complete } = consumer;
cin
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 r96 return {
cin
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 r102 next: next ? next.bind(consumer) : noop,
error: error ? error.bind(consumer) : noop,
cin
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 r110 complete: complete ? complete.bind(consumer) : noop,
isClosed: () => false
cin
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 r109 };
cin
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 r102 };
cin
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 r110 /** 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>) => {
cin
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 r102 let done = false;
cin
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 r110 let cleanup = noop;
const _fin = <A extends unknown[]>(fn: (...args: A) => void) =>
(...args: A) => done ?
void (0) :
(done = true, cleanup(), fn(...args));
const safeSink = {
cin
linting
 r109 next: (value: T) => { !done && next(value); },
cin
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 r110 error: _fin(error),
complete: _fin(complete),
isClosed: () => done
cin
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 r109 };
cin
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 r110 cleanup = producer(safeSink) ?? noop;
return done ?
(cleanup(), noop) :
_fin(noop);
cin
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 r109 };
cin
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 r96
cin
`Subscribable` is made compatible with rxjs, added map, filter and scan...
 r102 const _observe = <T>(producer: Producer<T>): Observable<T> => ({
subscribe: (consumer: Partial<Observer<T>>) => ({
unsubscribe: producer(sink(consumer)) ?? noop
}),
cin
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 r110 map: (mapper) => _observe(({ next, ...rest }) =>
cin
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 r102 producer({
next: next !== noop ? (v: T) => next(mapper(v)) : noop,
cin
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 r110 ...rest
})
),
filter: (predicate) => _observe(({ next, ...rest }) =>
producer({
next: next !== noop ? (v: T) => predicate(v) ? next(v) : void (0) : noop,
...rest
cin
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 r102 })
),
cin
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 r110 scan: (accumulator, initial) => _observe(({ next, ...rest }) => {
cin
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 r102 let _acc = initial;
return producer({
cin
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 r110 next: next !== noop ? (v: T) => next(_acc = accumulator(_acc, v)) : noop,
...rest
cin
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 r102 });
cin
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 r110 }),
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();
cin
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 r114 }),
pipe: <U>(f: (source: Observable<T>) => Producer<U>) => observe(f(_observe(producer)))
cin
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 r96 });
cin
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 r102
cin
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 r110 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);
}
});
};