react-native-unit-components/lib/module/utils/eventBus/EventBus.js

Unit React Native components

// Type-safe callback that receives the correct data type for the event key

class EventBus {
  debug = false;
  listeners = new Map();
  eventQueue = [];
  isProcessing = false;

  /**
   * Subscribe to an event
   * @returns Unsubscribe function
   */
  on(eventKey, callback) {
    if (!this.listeners.has(eventKey)) {
      this.listeners.set(eventKey, new Set());
    }
    this.listeners.get(eventKey).add(callback);
    if (this.debug) {
      console.log(`[EventBus] Subscribed to: ${eventKey} (${this.listenerCount(eventKey)} listeners)`);
    }

    // Return unsubscribe function
    return () => {
      const callbacks = this.listeners.get(eventKey);
      if (callbacks) {
        callbacks.delete(callback);
        if (callbacks.size === 0) {
          this.listeners.delete(eventKey);
        }
      }
    };
  }

  /**
   * Emit an event - queues it for processing to ensure all events are delivered
   */
  emit(eventKey, data) {
    const event = {
      key: eventKey,
      data
    };
    if (this.debug) {
      console.log(`[EventBus] Emitting: ${eventKey} (${this.listenerCount(eventKey)} listeners)`);
    }
    this.eventQueue.push(event);
    this.processQueue();
  }

  /**
   * Process events from queue sequentially
   * This ensures rapid successive events are all delivered
   */
  processQueue() {
    if (this.isProcessing || this.eventQueue.length === 0) {
      return;
    }
    this.isProcessing = true;

    // Process all queued events synchronously to ensure immediate delivery
    while (this.eventQueue.length > 0) {
      const event = this.eventQueue.shift();
      const callbacks = this.listeners.get(event.key);
      if (callbacks && callbacks.size > 0) {
        // Process all listeners for this event
        callbacks.forEach(callback => {
          try {
            callback(event.data);
          } catch (error) {
            console.error(`Error in event listener for ${event.key}:`, error);
          }
        });
      }
    }
    this.isProcessing = false;
  }

  /**
   * Remove all listeners for an event
   */
  off(eventKey) {
    this.listeners.delete(eventKey);
  }

  /**
   * Get number of listeners for an event (useful for debugging)
   */
  listenerCount(eventKey) {
    return this.listeners.get(eventKey)?.size ?? 0;
  }

  /**
   * Enable or disable debug logging
   */
  setDebug(enabled) {
    this.debug = enabled;
  }
}

// Singleton instance
export const eventBus = new EventBus();
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