observable.ts

import { Logger } from './logger';
import { Observer } from './observer';

export abstract class Observable {
  protected abstract logger: Logger;
  protected observers: Record<string, Observer> = {};

  /**
   * @function subscribe
   * @description Subscribe to an event
   * @param type - event type
   * @param listener - event callback
   * @returns {void}
   */
  public subscribe = (type: string, listener: Function): void => {
    this.logger.log(`subscribed to ${type} event`);

    if (!this.observers[type]) {
      this.observers[type] = new Observer({ logger: this.logger });
    }

    this.observers[type].subscribe(listener);
  };

  /**
   * @function unsubscribe
   * @description Unsubscribe from an event
   * @param type - event type
   * @returns {void}
   */
  public unsubscribe = (type: string, callback?: (data: unknown) => void): void => {
    this.logger.log(`unsubscribed from ${type} event`);

    if (!this.observers[type]) return;

    if (!callback) {
      this.observers[type].destroy();
      delete this.observers[type];
      return;
    }

    this.observers[type].unsubscribe(callback);
  };

  /**
   * @function publish
   * @description Publish an event to client
   * @param type - event type
   * @param data - event data
   * @returns {void}
   */
  protected publish = (type: string, data?: unknown): void => {
    const hasListenerRegistered = type in this.observers;

    if (!hasListenerRegistered) return;

    this.observers[type].publish(data);
  };
}