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Maven plugin for generating graphql clients

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/**
 * Copyright (c) 2015-present, Facebook, Inc.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * @flow strict
 */

import isPromise from './isPromise';
import type { MaybePromise } from './MaybePromise';

/**
 * Similar to Array.prototype.reduce(), however the reducing callback may return
 * a Promise, in which case reduction will continue after each promise resolves.
 *
 * If the callback does not return a Promise, then this function will also not
 * return a Promise.
 */
export default function promiseReduce(
  values: $ReadOnlyArray,
  callback: (U, T) => MaybePromise,
  initialValue: MaybePromise,
): MaybePromise {
  return values.reduce(
    (previous, value) =>
      isPromise(previous)
        ? previous.then(resolved => callback(resolved, value))
        : callback(previous, value),
    initialValue,
  );
}