/**
 * Copyright (c) Facebook, Inc. and its affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * @format
 * @flow strict
 * @emails oncall+draft_js
 */
'use strict';

import type { EntityRange } from "./EntityRange";

const UnicodeUtils = require("fbjs/lib/UnicodeUtils");

const {
  substr
} = UnicodeUtils;
/**
 * Convert to native JavaScript string lengths to determine ranges.
 */

function decodeEntityRanges(text: string, ranges: Array<EntityRange>): Array<?string> {
  const entities = Array(text.length).fill(null);

  if (ranges) {
    ranges.forEach(range => {
      // Using Unicode-enabled substrings converted to JavaScript lengths,
      // fill the output array with entity keys.
      const start = substr(text, 0, range.offset).length;
      const end = start + substr(text, range.offset, range.length).length;

      for (let ii = start; ii < end; ii++) {
        entities[ii] = range.key;
      }
    });
  }

  return entities;
}

module.exports = decodeEntityRanges;