export function rot13(text: string): string {
  const MIN_VALUE = 97 // a
  const MAX_VALUE = 122 // z

  const ALPHABET_SIZE = MAX_VALUE - MIN_VALUE + 1 // 26
  const ALPHABET_SHIFT = 13

  let result = ''

  for (const char of text) {
    const lowerChar = char.toLowerCase()
    const charCode = lowerChar.charCodeAt(0)

    const inRange =
      charCode >= MIN_VALUE && charCode <= MAX_VALUE

    if (!inRange) {
      result += char
      continue
    }

    const isUpper = char !== lowerChar

    const newChar =
      ((charCode - MIN_VALUE + ALPHABET_SHIFT) % ALPHABET_SIZE) + MIN_VALUE

    const transformedChar = String.fromCharCode(newChar)

    result += isUpper
      ? transformedChar.toUpperCase()
      : transformedChar
  }

  return result
}