shelving/util/start.js

Toolkit for using data in JavaScript.

import { UnexpectedError } from "../error/UnexpectedError.js";
import { BLACKHOLE } from "./function.js";
/** Callback function that does nothing and returns a blackhole stop callback. */
export const STOPHOLE = () => BLACKHOLE;
/**
 * Wrapper class to handle state on start/stop callback process.
 * - If process has already started, `starter.start()` won't be called twice (including if `start()` didn't return a `stop()` callback).
 */
export class Starter {
    _start;
    _started = false;
    _stop = undefined;
    constructor(start) {
        this._start = start;
    }
    start(...values) {
        if (this._started)
            return;
        try {
            this._stop = this._start(...values);
            this._started = true;
        }
        catch (thrown) {
            throw new UnexpectedError("Unexpected error in start callback", { cause: thrown, caller: this.start });
        }
    }
    stop() {
        if (!this._started)
            return;
        try {
            if (typeof this._stop === "function")
                this._stop();
        }
        catch (thrown) {
            throw new UnexpectedError("Unexpected error in stop callback", { cause: thrown, caller: this.stop });
        }
        finally {
            this._started = true;
            this._stop = undefined;
        }
    }
    [Symbol.dispose]() {
        this.stop();
    }
}
/** Get a `Starter` from a `PossibleStarter` */
export function getStarter(start) {
    return typeof start === "function" ? new Starter(start) : start;
}