const alphabet = [
    'A',
    'B',
    'C',
    'D',
    'E',
    'F',
    'G',
    'H',
    'I',
    'J',
    'K',
    'L',
    'M',
    'N',
    'O',
    'P',
    'Q',
    'R',
    'S',
    'T',
    'U',
    'V',
    'W',
    'X',
    'Y',
    'Z'
]
const MAX_ROT = alphabet.length

/**
 * Encrypt text  using spanish Cesar encryption
 * @memberof crypt/cesar
 * @param {string} text - A string to be encrypted
 * @param {number} rot - Scroll numer, can be from 0 to 26
 * @returns {string} - Encrypted text
 */
const encrypt = (text, rot = 3) => {
    if (rot > MAX_ROT || rot < 0) {
        throw Error('rot can be only beetween 0 to 26')
    }

    text = Array.from(text)

    const encryptedText = text.map((char) => {
        const isLower = char.toLowerCase()
        const idx = alphabet.indexOf(char.toUpperCase())

        if (idx === -1) {
            return char
        }

        const encryptedIdx = (idx + rot) % MAX_ROT
        const encryptedChar = alphabet[encryptedIdx]

        return isLower ? encryptedChar.toLowerCase() : encryptedChar
    })

    return encryptedText.join('')
}

/**
 * Decrypt text using spanish Cesar encryption
 * @memberof crypt/cesar
 * @param {string} text - A string to be decrypted
 * @param {number} rot - Scroll numer, can be from 0 to 26
 * @returns {string} - Decrypted text
 */
const decrypt = (text, rot = 3) => {
    if (rot > MAX_ROT || rot < 0) {
        throw Error('rot can be only beetween 0 to 26')
    }

    text = Array.from(text)

    const decryptedText = text.map((char) => {
        const isLower = char.toLowerCase()
        const idx = alphabet.indexOf(char.toUpperCase())

        if (idx === -1) {
            return char
        }

        let decryptedIdx = (idx - rot) % MAX_ROT

        decryptedIdx = decryptedIdx < 0 ? decryptedIdx + MAX_ROT : decryptedIdx

        const decryptedChar = alphabet[decryptedIdx]

        return isLower ? decryptedChar.toLowerCase() : decryptedChar
    })

    return decryptedText.join('')
}

console.log(encrypt('abcxyz', 5))
console.log(decrypt('fghcde', 5))