const originalAlphabet = 'abcdefghijklmnopqrstuvwxyz'
const cipherAlphabet = 'zyxwvutsrqponmlkjihgfedcba'

export function encode(plainText: string): string {
  return plainText
    .toLowerCase()
    .split('')
    .map(c => c.match(/\d/) ? c : cipherAlphabet[originalAlphabet.indexOf(c)])
    .filter(Boolean)
    .map((c, i) =>  (i + 1) % 5 === 0 ? `${c} ` : c)
    .join("")
    .trim()
}

export function decode(cipherText: string): string {
  return cipherText
    .split('')
    .map(c => c.match(/\d/) ? c : originalAlphabet[cipherAlphabet.indexOf(c)])
    .filter(Boolean)
    .join("")
}