Function itemsToRegexp

src/utils.js:321–428

(itemsArr)

 * @returns {string} regexp
 */
const itemsToRegexp = (itemsArr) => {
  if (itemsArr.length === 1) {
    return quoteMeta(itemsArr[0]);
  }

  /** @type {string[]} */
  const finishedItems = [];

  // merge single char items: (a|b|c|d|ef) => ([abcd]|ef)
  let countOfSingleCharItems = 0;

  for (const item of itemsArr) {
    if (item.length === 1) {
      countOfSingleCharItems++;
    }
  }

  // special case for only single char items
  if (countOfSingleCharItems === itemsArr.length) {
    return `[${quoteMeta(itemsArr.sort().join(""))}]`;
  }

  const items = new Set(itemsArr.sort());

  if (countOfSingleCharItems > 2) {
    let singleCharItems = "";
    for (const item of items) {
      if (item.length === 1) {
        singleCharItems += item;
        items.delete(item);
      }
    }
    finishedItems.push(`[${quoteMeta(singleCharItems)}]`);
  }

  // special case for 2 items with common prefix/suffix
  if (finishedItems.length === 0 && items.size === 2) {
    const prefix = getCommonPrefix(itemsArr);
    const suffix = getCommonSuffix(
      itemsArr.map((item) => item.slice(prefix.length)),
    );

    if (prefix.length > 0 || suffix.length > 0) {
      return `${quoteMeta(prefix)}${itemsToRegexp(
        itemsArr.map((i) =>
          i.slice(prefix.length, -suffix.length || undefined),
        ),
      )}${quoteMeta(suffix)}`;
    }
  }

  // special case for 2 items with common suffix
  if (finishedItems.length === 0 && items.size === 2) {
    /** @type {Iterator<string>} */
    const it = items[Symbol.iterator]();
    const a = it.next().value;
    const b = it.next().value;
    if (a.length > 0 && b.length > 0 && a.slice(-1) === b.slice(-1)) {