@downpourdigital/dispatcher/dist/esm/index.js

Async event dispatcher.

class Subscription {
    constructor(observer, subscribable) {
        this.observer = observer;
        this.subscribable = subscribable;
    }
    unsubscribe() {
        this.subscribable.unsubscribe(this);
    }
}

class PassiveSubscription extends Subscription {
    constructor(observer, subscribable) {
        super((cb, payload) => {
            cb();
            observer(payload);
            return null;
        }, subscribable);
    }
}

class Subscribable {
    constructor() {
        this.listeners = [];
    }
    subscribe(observer) {
        const subscription = new Subscription(observer, this);
        this.listeners.push(subscription);
        return subscription;
    }
    subscribePassive(observer) {
        const subscription = new PassiveSubscription(observer, this);
        this.listeners.push(subscription);
        return subscription;
    }
    unsubscribe(subscription) {
        this.listeners.splice(this.listeners.findIndex(s => s === subscription), 1);
    }
}

class PersistentEvent {
    constructor(listeners, payload, mayCancelAfterCallback) {
        this.canceled = false;
        this.isAccumulating = true;
        this.listeners = [];
        this.completedListeners = [];
        this.mayCancelAfterCallback = !!mayCancelAfterCallback;
        this.promise = new Promise((resolve, reject) => {
            this.resolve = resolve;
            this.reject = reject;
        });
        listeners.forEach((s) => {
            const ref = {
                subscription: s,
                cancel: null,
            };
            this.listeners.push(ref);
            const cancel = s.observer(() => { this.completeCallback(s); }, payload) || null;
            ref.cancel = cancel;
        });
        this.isAccumulating = false;
        if (this.listeners.length === 0 && this.resolve)
            this.resolve();
    }
    completeCallback(subscription) {
        if (!this.canceled) {
            const [listener] = this.listeners.splice(this.listeners.findIndex(l => l.subscription === subscription), 1);
            if (this.mayCancelAfterCallback && listener) {
                this.completedListeners.push(listener);
            }
            if (this.listeners.length === 0 && !this.isAccumulating && this.resolve) {
                this.resolve();
            }
        }
    }
    cancel() {
        if (!this.canceled) {
            this.canceled = true;
            this.listeners.forEach((listener) => {
                if (listener.cancel)
                    listener.cancel();
            });
            if (this.mayCancelAfterCallback) {
                this.completedListeners.forEach((listener) => {
                    if (listener.cancel)
                        listener.cancel();
                });
            }
            if (this.reject)
                this.reject();
        }
    }
}

class EventDispatcher extends Subscribable {
    constructor(props = {}) {
        super();
        this.events = [];
        const { mayCancelAfterCallback = true, } = props;
        this.mayCancelAfterCallback = mayCancelAfterCallback;
    }
    dispatchPassive(payload) {
        this.listeners.forEach(s => s.observer(() => { }, payload));
    }
    dispatch(payload) {
        const event = new PersistentEvent(this.listeners, payload, this.mayCancelAfterCallback);
        this.events.push(event);
        event.promise.catch(() => { }).finally(() => {
            this.events.splice(this.events.findIndex(e => e === event), 1);
        });
        return event;
    }
    cancelAll() {
        this.events.forEach(e => e.cancel());
    }
}

export { EventDispatcher, Subscribable };