/**
 * Generic Event Emitter class following a subscribe/publish paradigm.
 */

type cbFn = (...args: any[]) => any;

interface ISubscriber {
  /**
   * Callback function that will be run when an event is emitted
   */
  cb: cbFn;

  /**
   * Name/identifier for this subscriber
   */
  id: string;
}

function uuidv4(): string {
  return "xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx".replace(/[xy]/g, function (c) {
    const r = (Math.random() * 16) | 0,
      v = c == "x" ? r : (r & 0x3) | 0x8;
    return v.toString(16);
  });
}

export class EventEmitter<T extends any[]> {
  subscribers: { [key: string]: (...args: [...T]) => void | undefined } = {};

  subscribe(s: (...args: [...T]) => void): () => void {
    let uuid = uuidv4();
    while (this.subscribers[uuid] !== undefined) uuid = uuidv4();
    this.subscribers[uuid] = s;

    return () => {
      delete this.subscribers[uuid];
    };
  }

  emit(...args: [...T]): void {
    for (const s in this.subscribers) {
      const sub = this.subscribers[s];
      if (sub === undefined) continue;

      sub(...args);
    }
  }
}