typed-emitter/rxjs/index.d.ts

Strictly typed event emitter interface for TypeScript 3.

/**
 * devanshj/rxjs-from-emitter#4 - typed-emitter compatibility
 *
 * @see https://github.com/devanshj/rxjs-from-emitter/issues/4#issuecomment-665104646
 */
/* eslint-disable no-use-before-define */
import {
  fromEvent as rxFromEvent,
  Observable,
} from 'rxjs'
import type { default as BaseTypedEmitter, EventMap } from '../index'

type ObservedValue<A extends unknown[]> =
  A['length'] extends 0 ? void :
  A['length'] extends 1 ? A[0] :
  A

interface FromTypedEvent {
  <   Emitter extends TypedEmitter<any>
    , EventName extends keyof Events
    , Events = Emitter extends TypedEmitter<infer T> ? T : never
  >(emitter: Emitter, event: EventName): Observable<ObservedValue<Events[EventName] extends (...args: infer A) => any ? A : never>>
}

export type FromEvent = FromTypedEvent & typeof rxFromEvent

interface TypedEmitter<Events extends EventMap> extends BaseTypedEmitter<Events> {
  /**
   * required by `FromEvent`
   * @see https://github.com/devanshj/rxjs-from-emitter/issues/4#issuecomment-665104646
   */
   __events: Events
}

export default TypedEmitter