import { listenerKey, senderKey } from './constant';
import { createTransport } from './createTransport';
import type { ListenerOptions } from './interface';
import { Transport } from './transport';

/**
 * Merge multiple transports into one transport
 */
export const merge = (
  first: Transport,
  seconds: Transport,
  ..._args: Transport[]
) => {
  const args = [first, seconds, ..._args] as Transport[];
  if (typeof first === 'undefined' || typeof seconds === 'undefined') {
    throw new Error(`Only more than one transports can be merged.`);
  }
  return createTransport('Base', {
    listener: (callback) => {
      const handler = (data: ListenerOptions) => {
        callback(data);
      };
      const disposers = args.map((transport) =>
        transport[listenerKey](handler)
      );
      return () => {
        disposers.forEach((dispose) => dispose && dispose());
      };
    },
    sender: (message) => {
      args.forEach((transport) => {
        transport[senderKey](message);
      });
    },
  });
};