core/src/util/events.ts

import { logger } from '../core';

/**
 * Event emitter that can be scoped by plugin name or core.
 */
export class ScopedEventEmitter {
  protected listeners: {[key: string]: any[]};

  /**
   * Add an event listener on `name` scope for event `event`. Alias of `on`.
   * @param name Event scope
   * @param event Event name
   * @param func Listener
   * @param once Listen once
   * @see on
   */
  public addEventListener = this.on;

  constructor() {
    this.listeners = {};
  }

  /**
   * Add an event listener on `name` scope for event `event`.
   * @param name Event scope
   * @param event Event name
   * @param func Listener
   * @param once Listen once
   */
  public on(name: string, event: string, func: any, once = false): void {
    if (!func || !event || !name) {
      throw new Error('missing arguments');
    }

    if (!this.listeners[name]) {
      this.listeners[name] = [];
    }

    this.listeners[name].push({
      event, func, name, once,
    });
  }

  /**
   * Add an one-off event listener on `name` scope for event `event`.
   * @param name Event scope
   * @param event Event name
   * @param func Listener
   */
  public once(name: string, event: string, func: any): void {
    this.on(name, event, func, true);
  }

  /**
   * Emit an event `event` to all listeners in all scopes.
   * @param event Event name
   * @param args Data
   */
  public emit(event: string, ...args: any[]): void {
    for (const name in this.listeners) {
      for (const i in this.listeners[name]) {
        if (!this.listeners[name]) {
          break;
        }
        const listener = this.listeners[name][i];

        if (listener.event === event && listener.func) {
          try {
            listener.func(...args);
          } catch (e: any) {
            logger.error('An error occured in one of the listeners for "%s":',
              event, e.stack);
          }

          if (listener.once) {
            this.listeners[name].splice(parseInt(i, 10), 1);
          }
        }
      }
    }
  }

  /**
   * Emit an event `event` to listeners listening for scope `name`.
   * @param name Scope name
   * @param event Event name
   * @param args Data
   */
  public emitTo(name: string, event: string, ...args: any[]): void {
    if (!this.listeners[name]) {
      return;
    }

    for (const i in this.listeners[name]) {
      if (!this.listeners[name]) {
        break;
      }

      const listener = this.listeners[name][i];

      if (listener.event === event && listener.func) {
        try {
          listener.func(...args);
        } catch (e: any) {
          logger.error('An error occured in one of the listeners for "%s", stream "%s":',
            event, name, e.stack);
        }

        if (listener.once) {
          this.listeners[name].splice(parseInt(i, 10), 1);
        }
      }
    }
  }

  /**
   * Remove all listeners for scope `name`.
   * @param name Scope name
   */
  public removeName(name: string): void {
    if (this.listeners[name]) {
      delete this.listeners[name];
    }
  }
}