@johngw/stream/dist/es/sinks/ForkableReplaySink.js

Reactive programming tools using the WHATWG Streams API.

import { ForkableSink } from '@johngw/stream/sinks/ForkableSink';
/**
 * An extension to the {@link ForkableSink:class} that immediately
 * queues the entire contents of whatever has been previously consumed.
 *
 * @group Sinks
 * @see {@link ForkableReplayStream:class}
 * @example
 * ```
 * const forkable = new ForkableReplayStream<number>()
 * const writable = new WritableStream(forkable)
 * await fromCollection([1, 2, 3, 4, 5, 6, 7]).pipeTo(writable)
 * ```
 *
 * Now the stream has finished, if we fork from it we'll
 * receive the entire events that were published to it.
 *
 * ```
 * await forkable.fork().pipeTo(write(console.info))
 * // 1
 * // 2
 * // 3
 * // 4
 * // 5
 * // 6
 * // 7
 * ```
 */
export class ForkableReplaySink extends ForkableSink {
    #chunks = [];
    #maxReplaySize = Number.MAX_SAFE_INTEGER;
    constructor(maxReplaySize = Number.MAX_SAFE_INTEGER) {
        super();
        this.#maxReplaySize = maxReplaySize;
    }
    write(chunk) {
        if (this.#chunks.length === this.#maxReplaySize)
            this.#chunks.shift();
        this.#chunks.push(chunk);
        return super.write(chunk);
    }
    _addController(underlyingSource, queuingStrategy) {
        const [controller, stream] = super._addController(underlyingSource, queuingStrategy);
        for (const chunk of this.#chunks)
            controller.enqueue(chunk);
        return [controller, stream];
    }
    clear() {
        this.#chunks = [];
    }
}
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