@fbltd/async/dist/bin/dependency/dependency.js

Miscellaneous async utils

import { PromiseConfiguration } from "../promise-configuration.js";
import { baseComparer } from "./utils.js";
import { symAI } from "../constants.js";
import { observationState } from "./observe.state.js";
export class Dependency {
    _value;
    reactionPromise;
    abortPromise = new PromiseConfiguration();
    config;
    constructor(_value, config = {}) {
        this._value = _value;
        this.config = {
            withCustomEquality: baseComparer,
            withReactionOnSubscribe: false,
            ...config,
        };
    }
    _set(v) {
        if (this.done)
            return;
        if (this.config.withCustomEquality(this._value, v)) {
            return;
        }
        this._value = v;
        if (this.reactionPromise) {
            this.reactionPromise.resolve(v);
            this.reactionPromise = undefined;
        }
    }
    set value(v) {
        this._set(v);
    }
    get value() {
        observationState.setDep(this);
        return this._value;
    }
    get value_unsafe() {
        return this._value;
    }
    get done() {
        return !this.abortPromise || this.abortPromise.isFulfilled;
    }
    [symAI](thisStreamConfig = {}) {
        const externalPromises = [];
        let firstPromise;
        const withReactionOnSubscribe = this.config.withReactionOnSubscribe || thisStreamConfig.withReactionOnSubscribe;
        if (withReactionOnSubscribe) {
            firstPromise = Promise.resolve();
            externalPromises.push(firstPromise);
        }
        const owner = this;
        return {
            owner,
            dispose: owner.dispose.bind(owner),
            get isDisposed() {
                return owner.done;
            },
            next: async () => {
                await Promise.race([
                    owner.next(),
                    ...externalPromises,
                ]);
                if (firstPromise) {
                    firstPromise = undefined;
                    externalPromises.pop();
                }
                if (this.done) {
                    return { done: true };
                }
                return {
                    done: false,
                    get value() {
                        return owner.value;
                    }
                };
            }
        };
    }
    /**
     * One race of value change and dependency dispose
     * for all subscribers
     */
    _race;
    getOrCreateRace() {
        if (!this._race) {
            this.reactionPromise = this.reactionPromise ?? new PromiseConfiguration();
            this._race = Promise.race([
                this.abortPromise.promise,
                this.reactionPromise.promise,
            ]);
        }
        return this._race;
    }
    /**
     * Another subscribe for current race
     */
    async next() {
        const done = { done: true };
        const owner = this;
        if (this.done)
            return done;
        await this.getOrCreateRace();
        this._race = undefined;
        if (this.done)
            return done;
        this.abortPromise = new PromiseConfiguration();
        return {
            done: false,
            get value() {
                return owner.value;
            }
        };
    }
    get disposePromise() {
        return this.abortPromise?.promise ?? Promise.resolve();
    }
    dispose() {
        this.abortPromise?.resolve();
        this.abortPromise = this.reactionPromise = undefined;
    }
}