forma-embedded-view-sdk/dist/internal/queued-pub-sub.js

The Forma Embedded View SDK is a JavaScript library for creating custom extensions in Autodesk Forma (previously Spacemaker).

/**
 * A pub/sub implementation that queues events until a subscriber is added.
 * There is no event name/type, so all events are of the same type.
 *
 * The first subscriber will receive any previously queued events.
 */
export class QueuedPubSub {
    #eventTarget = new EventTarget();
    #queued = [];
    #subscribers = new Set();
    subscribe(handler) {
        const internalHandler = (_event) => {
            const event = _event;
            handler(event.detail);
        };
        const subscriber = Symbol();
        this.#subscribers.add(subscriber);
        this.#eventTarget.addEventListener("event", internalHandler);
        if (this.#queued.length > 0) {
            const queued = this.#queued;
            this.#queued = [];
            for (const data of queued) {
                this.#dispatch(data);
            }
        }
        return () => {
            this.#subscribers.delete(subscriber);
            this.#eventTarget.removeEventListener("event", internalHandler);
        };
    }
    publish(data) {
        if (this.#subscribers.size === 0) {
            this.#queued.push(data);
        }
        else {
            this.#dispatch(data);
        }
    }
    #dispatch(data) {
        this.#eventTarget.dispatchEvent(new CustomEvent("event", {
            detail: data,
        }));
    }
}