Ceasar's Cipher Brute Force

CeasarCipher.swift

// MARK: - Main

var cipherText = "VSRQJHEREVTXDUHSDQWU".lowercased()
let decipheredTexts = decipherText(cipherText)

for (k, s) in decipheredTexts {
    print("Shifts: \(k)\t\(s)")
}

// MARK: - Actions

func decipherText(_ cipher: String) -> [(Int, String)] {
    let alphabet = getEnglishAlphabet()
    var tempDecipher = ""
    var decipheredTexts: [(Int, String)] = []
    var asciiCode: Int = 0
    var shifts = 0

    for i in 0 ... 25 {
        tempDecipher = ""

        for (_, c) in cipher.enumerated() {
            asciiCode = (i + (Int(c.ascii!) - 97)) % 26
            tempDecipher.append(alphabet[asciiCode])
        }

        shifts = 26 - i

        if shifts < 0 {
            shifts =  shifts + 26
        }

        decipheredTexts.insert((shifts, tempDecipher), at: decipheredTexts.startIndex)
    }

    return decipheredTexts
}

func getEnglishAlphabet() -> [String] {
    var alphabet: [String] = []
    for i in 97 ... (97+25) {
        alphabet.append(i.asciiCharacter!)
    }

    return alphabet
}

// MARK: - Extensions

extension String {
    var ascii: [UInt32] {
        return unicodeScalars.compactMap{
            $0.isASCII ? $0.value : nil
        }
    }
}

extension Character {
    var ascii: UInt32? {
        return String(self).ascii.first
    }
}

extension Int {
    var asciiCharacter: String? {
        guard let asciiCode = UnicodeScalar(self) else {
            return nil
        }
        return String(asciiCode)
    }
}