/**
 * Copyright (c) 2013-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 *
 * @providesModule findRangesImmutable
 * @format
 * @flow
 */

'use strict';

import type { List } from 'immutable';

/**
 * Search through an array to find contiguous stretches of elements that
 * match a specified filter function.
 *
 * When ranges are found, execute a specified `found` function to supply
 * the values to the caller.
 */
function findRangesImmutable<T>(haystack: List<T>, areEqualFn: (a: T, b: T) => boolean, filterFn: (value: T) => boolean, foundFn: (start: number, end: number) => void): void {
  if (!haystack.size) {
    return;
  }

  var cursor: number = 0;

  haystack.reduce((value: T, nextValue, nextIndex) => {
    if (!areEqualFn(value, nextValue)) {
      if (filterFn(value)) {
        foundFn(cursor, nextIndex);
      }
      cursor = nextIndex;
    }
    return nextValue;
  });

  filterFn(haystack.last()) && foundFn(cursor, haystack.count());
}

module.exports = findRangesImmutable;