@ideal-photography/shared/alerts/AlertBus.js

Shared MongoDB and utility logic for Ideal Photography PWAs: users, products, services, bookings, orders/cart, galleries, reviews, notifications, campaigns, settings, audit logs, minimart items/orders, and push notification subscriptions.

import EventEmitter from 'events';

/**
 * Central AlertBus for emitting and listening to system alert events.
 *
 * Internally maintains a micro-queue so that heavy alert handlers
 * never block the caller thread. All alert payloads are processed
 * asynchronously in FIFO order.
 */
class AlertBus extends EventEmitter {
    constructor() {
        super();
        // Simple in-memory queue (FIFO)
        this.queue = [];
        this.isProcessing = false;
    }

    /**
     * Emit an alert trigger.  Consumers should subscribe to the
     * `alert` event or listen for specific triggers via
     * `bus.on(triggerName, handler)`.
     *
     * @param {string} trigger   Canonical event name e.g. `user.registered`
     * @param {any} payload      Arbitrary payload data for handlers
     * @param {object} opts      Optional meta e.g. channel overrides
     */
    enqueue(trigger, payload = {}, opts = {}) {
        this.queue.push({ trigger, payload, opts });
        this._schedule();
    }

    /**
     * Schedule queue processing on next tick if not already scheduled.
     * Ensures only one processing loop runs at a time.
     * @private
     */
    _schedule() {
        if (this.isProcessing) return;
        this.isProcessing = true;
        // Process asynchronously so caller returns immediately
        setImmediate(async () => {
            try {
                while (this.queue.length) {
                    const job = this.queue.shift();
                    // Wildcard event for global listeners
                    this.emit('alert', job);
                    // Specific trigger event e.g. `user.registered`
                    this.emit(job.trigger, job.payload, job.opts);
                }
            } finally {
                this.isProcessing = false;
                // If new jobs were enqueued while processing, schedule again
                if (this.queue.length) this._schedule();
            }
        });
    }
}

// Export a singleton instance so the bus is shared process-wide
const bus = new AlertBus();
export default bus;