chess/planning/implementation/code-templates/js/utils/EventBus.js

/**
 * @file EventBus.js
 * @description Simple event bus for component communication
 * @author Implementation Team
 */

/**
 * @class EventBus
 * @description Facilitates publish-subscribe pattern for loose coupling between components
 *
 * @example
 * const eventBus = new EventBus();
 * eventBus.subscribe('piece:moved', (data) => console.log(data));
 * eventBus.publish('piece:moved', {from: 'e2', to: 'e4'});
 */
class EventBus {
  constructor() {
    /**
     * @property {Map} _subscribers - Map of event names to arrays of callbacks
     */
    this._subscribers = new Map();
  }

  /**
   * Subscribe to an event
   *
   * @param {string} event - Event name
   * @param {Function} callback - Function to call when event is published
   * @returns {Function} Unsubscribe function
   *
   * @example
   * const unsubscribe = eventBus.subscribe('game:check', handleCheck);
   * // Later: unsubscribe()
   */
  subscribe(event, callback) {
    // TODO: Implement subscription
    // 1. Check if event exists in _subscribers
    // 2. If not, create new array for this event
    // 3. Add callback to array
    // 4. Return unsubscribe function that removes this callback

    // Return unsubscribe function
    return () => {
      // TODO: Implement unsubscribe logic
    };
  }

  /**
   * Publish an event with data
   *
   * @param {string} event - Event name
   * @param {*} data - Data to pass to subscribers
   *
   * @example
   * eventBus.publish('piece:moved', {
   *   piece: pawn,
   *   from: {row: 6, col: 4},
   *   to: {row: 4, col: 4}
   * });
   */
  publish(event, data) {
    // TODO: Implement publishing
    // 1. Get all subscribers for this event
    // 2. Call each callback with the data
    // 3. Handle any errors in callbacks (try-catch)
  }

  /**
   * Unsubscribe a specific callback from an event
   *
   * @param {string} event - Event name
   * @param {Function} callback - Callback to remove
   *
   * @example
   * eventBus.unsubscribe('game:check', handleCheck);
   */
  unsubscribe(event, callback) {
    // TODO: Implement unsubscribe
    // 1. Get subscribers for event
    // 2. Find and remove the callback
  }

  /**
   * Remove all subscribers for an event
   *
   * @param {string} event - Event name
   *
   * @example
   * eventBus.clear('game:over');
   */
  clear(event) {
    // TODO: Implement clear
    // Remove all subscribers for the event
  }

  /**
   * Remove all subscribers for all events
   *
   * @example
   * eventBus.clearAll();
   */
  clearAll() {
    // TODO: Implement clear all
    this._subscribers.clear();
  }

  /**
   * Get count of subscribers for an event
   *
   * @param {string} event - Event name
   * @returns {number} Number of subscribers
   *
   * @example
   * const count = eventBus.getSubscriberCount('piece:moved');
   */
  getSubscriberCount(event) {
    // TODO: Implement subscriber count
    return 0; // Replace with actual logic
  }

  /**
   * Check if an event has any subscribers
   *
   * @param {string} event - Event name
   * @returns {boolean} True if event has subscribers
   *
   * @example
   * if (eventBus.hasSubscribers('game:over')) {
   *   // Do something
   * }
   */
  hasSubscribers(event) {
    // TODO: Implement has subscribers check
    return false; // Replace with actual logic
  }
}

// Export singleton instance
export default new EventBus();