DefinitelyTyped/types/ee-first/index.d.ts

// Type definitions for ee-first 1.1
// Project: https://github.com/jonathanong/ee-first
// Definitions by: BendingBender <https://github.com/BendingBender>
// Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
// TypeScript Version: 3.0

/// <reference types="node" />

import { EventEmitter } from 'events';

export = first;

/**
 * Get the first event in a set of event emitters and event pairs, then clean up after itself.
 * Invoke `listener` on the first event from the list specified in `eventSpec`.
 *
 * @param eventSpec Array of arrays, with each array in the format `[ee, ...event]`.
 * @param listener Will be called only once, the first time any of the given events are emitted.
 * If `error` is one of the listened events, then if that fires first, the `listener` will be given the `err` argument.
 * `listener`'s arguments:
 * - `err`: the first argument emitted from an error event, if applicable
 * - `ee`: the event emitter that fired
 * - `event`: the string event name that fired
 * - `args`: an array of the arguments that were emitted on the event
 */
declare function first<TEmitter extends EventEmitter>(
    eventSpec: Array<[TEmitter, ...string[]]>,
    listener: first.Listener<TEmitter>
): first.Thunk<TEmitter>;

declare namespace first {
    type Listener<TEmitter extends EventEmitter> = (
        err: any,
        ee: TEmitter,
        event: string[],
        args: any[]
    ) => void;

    interface Thunk<TEmitter extends EventEmitter> {
        (listener: Listener<TEmitter>): void;

        /**
         * The group of listeners can be cancelled before being invoked and have all the event listeners removed
         * from the underlying event emitters.
         */
        cancel(): void;
    }
}