/**
 * Internal dependencies
 */

/** @typedef {import('./types').RichTextValue} RichTextValue */

/**
 * Split a Rich Text value in two at the given `startIndex` and `endIndex`, or
 * split at the given separator. This is similar to `String.prototype.split`.
 * Indices are retrieved from the selection if none are provided.
 *
 * @param {RichTextValue} value
 * @param {number|string} [string] Start index, or string at which to split.
 *
 * @return {Array<RichTextValue>|undefined} An array of new values.
 */
export function split({
  formats,
  replacements,
  text,
  start,
  end
}, string) {
  if (typeof string !== 'string') {
    return splitAtSelection(...arguments);
  }
  let nextStart = 0;
  return text.split(string).map(substring => {
    const startIndex = nextStart;
    const value = {
      formats: formats.slice(startIndex, startIndex + substring.length),
      replacements: replacements.slice(startIndex, startIndex + substring.length),
      text: substring
    };
    nextStart += string.length + substring.length;
    if (start !== undefined && end !== undefined) {
      if (start >= startIndex && start < nextStart) {
        value.start = start - startIndex;
      } else if (start < startIndex && end > startIndex) {
        value.start = 0;
      }
      if (end >= startIndex && end < nextStart) {
        value.end = end - startIndex;
      } else if (start < nextStart && end > nextStart) {
        value.end = substring.length;
      }
    }
    return value;
  });
}
function splitAtSelection({
  formats,
  replacements,
  text,
  start,
  end
}, startIndex = start, endIndex = end) {
  if (start === undefined || end === undefined) {
    return;
  }
  const before = {
    formats: formats.slice(0, startIndex),
    replacements: replacements.slice(0, startIndex),
    text: text.slice(0, startIndex)
  };
  const after = {
    formats: formats.slice(endIndex),
    replacements: replacements.slice(endIndex),
    text: text.slice(endIndex),
    start: 0,
    end: 0
  };
  return [before, after];
}
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