import { EventEmitter } from 'events';
import { expectTypeOf } from 'expect-type';
import { map } from '.';
import { observable } from '../observable';

interface SubscriptionEvents<TOutput> {
  data: (data: TOutput) => void;
}

declare interface CustomEventEmitter<TOutput> {
  on<U extends keyof SubscriptionEvents<TOutput>>(
    event: U,
    listener: SubscriptionEvents<TOutput>[U],
  ): this;

  once<U extends keyof SubscriptionEvents<TOutput>>(
    event: U,
    listener: SubscriptionEvents<TOutput>[U],
  ): this;

  emit<U extends keyof SubscriptionEvents<TOutput>>(
    event: U,
    ...args: Parameters<SubscriptionEvents<TOutput>[U]>
  ): boolean;
}
class CustomEventEmitter<TOutput>
  extends EventEmitter
  implements CustomEventEmitter<TOutput> {}
test('map', () => {
  type EventShape = { num: number };
  const ee = new CustomEventEmitter<EventShape>();
  const eventObservable = observable<EventShape, unknown>((observer) => {
    const callback = (data: EventShape) => {
      observer.next(data);
    };
    ee.on('data', callback);

    return () => {
      ee.off('data', callback);
    };
  });
  const pipeCalls = jest.fn();
  const piped = eventObservable.pipe(
    map((...args) => {
      pipeCalls(...args);
      const [value] = args;
      return value.num;
    }),
  );

  const next = jest.fn();
  const subscription = piped.subscribe({
    next(value) {
      expectTypeOf<number>(value);
      next(value);
    },
  });
  expect(next).not.toHaveBeenCalled();
  ee.emit('data', { num: 1 });
  ee.emit('data', { num: 2 });
  expect(next).toHaveBeenCalledTimes(2);
  expect(next.mock.calls).toMatchInlineSnapshot(`
    Array [
      Array [
        1,
      ],
      Array [
        2,
      ],
    ]
  `);
  expect(pipeCalls.mock.calls).toMatchInlineSnapshot(`
    Array [
      Array [
        Object {
          "num": 1,
        },
        0,
      ],
      Array [
        Object {
          "num": 2,
        },
        1,
      ],
    ]
  `);

  expect(ee.listeners('data')).toHaveLength(1);
  subscription.unsubscribe();
  expect(ee.listeners('data')).toHaveLength(0);
});