@bemedev/rx-add-ons/lib/pausable.js

A collection of RxJS operators and utilities to enhance reactive programming capabilities.

import { Subject } from 'rxjs/internal/Subject';
import { EMPTY } from 'rxjs/internal/observable/empty';
import { scan } from 'rxjs/internal/operators/scan';
import { startWith } from 'rxjs/internal/operators/startWith';
import { switchMap } from 'rxjs/internal/operators/switchMap';

const createPausable = (source$, observer) => {
    // Control Subject for start, stop, pause, and resume
    const control$ = new Subject();
    // State management for the observable
    const controlled$ = control$.pipe(startWith('stop'), // Start in "stopped" state
    scan((state, action) => {
        if (action === 'start' && state !== 'running')
            return 'running';
        if (action === 'stop')
            return 'stopped';
        if (action === 'pause' && state === 'running')
            return 'paused';
        if (action === 'resume' && state === 'paused')
            return 'running';
        return state; // Ignore invalid transitions
    }, 'stopped'), switchMap(state => {
        if (state === 'running')
            return source$; // Emit values when running
        return EMPTY; // Emit nothing when paused or stopped
    }));
    // Subscribe to the controlled Observable
    controlled$.subscribe(observer);
    return {
        start: () => control$.next('start'),
        stop: () => control$.next('stop'),
        pause: () => control$.next('pause'),
        resume: () => control$.next('resume'),
        command: (action) => control$.next(action),
    };
};

export { createPausable };
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