Daily Challenge #42 - Caesar Cipher

f=(s)=>[...Array(26)].map((_,i)=>26-i).map(n=>`key: ${26-n}\ncipher: ${s}\nplain: ${[...s].map(l=>(a=l.charCodeAt(0),String.fromCharCode(a<123&&a>96?97+((a-97+n)%26):a))).join('')}`).join`\n---\n`

f('dwwdfn iurp wkh zrrgv dw gdzq');

"key: 0
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: dwwdfn iurp wkh zrrgv dw gdzq
---
key: 1
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: cvvcem htqo vjg yqqfu cv fcyp
---
key: 2
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: buubdl gspn uif xppet bu ebxo
---
key: 3
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: attack from the woods at dawn
---
key: 4
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: zsszbj eqnl sgd vnncr zs czvm
---
key: 5
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: yrryai dpmk rfc ummbq yr byul
---
key: 6
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: xqqxzh colj qeb tllap xq axtk
---
key: 7
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: wppwyg bnki pda skkzo wp zwsj
---
key: 8
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: voovxf amjh ocz rjjyn vo yvri
---
key: 9
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: unnuwe zlig nby qiixm un xuqh
---
key: 10
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: tmmtvd ykhf max phhwl tm wtpg
---
key: 11
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: sllsuc xjge lzw oggvk sl vsof
---
key: 12
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: rkkrtb wifd kyv nffuj rk urne
---
key: 13
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: qjjqsa vhec jxu meeti qj tqmd
---
key: 14
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: piiprz ugdb iwt lddsh pi splc
---
key: 15
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: ohhoqy tfca hvs kccrg oh rokb
---
key: 16
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: nggnpx sebz gur jbbqf ng qnja
---
key: 17
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: mffmow rday ftq iaape mf pmiz
---
key: 18
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: leelnv qczx esp hzzod le olhy
---
key: 19
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: kddkmu pbyw dro gyync kd nkgx
---
key: 20
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: jccjlt oaxv cqn fxxmb jc mjfw
---
key: 21
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: ibbiks nzwu bpm ewwla ib liev
---
key: 22
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: haahjr myvt aol dvvkz ha khdu
---
key: 23
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: gzzgiq lxus znk cuujy gz jgct
---
key: 24
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: fyyfhp kwtr ymj bttix fy ifbs
---
key: 25
cipher: dwwdfn iurp wkh zrrgv dw gdzq
plain: exxego jvsq xli asshw ex hear"

const cipher = (s, k) => s.toLowerCase()
                          .split('')
                          .map(c => c.charCodeAt(0) < 'a'.charCodeAt(0) || c.charCodeAt(0) > 'z'.charCodeAt(0) 
                                    ? c
                                    : c.charCodeAt(0) > 122 - k
                                      ? String.fromCharCode(97 + (c.charCodeAt(0) + k - 1) % 122)
                                      : String.fromCharCode(c.charCodeAt(0) + k))
                          .join('');

using System;

class MainClass {
  public static void Main (string[] args) {
    var caesarCipher = new CaesarCipher();

    caesarCipher.Encrypt(3, "attack from the woods at dawn");
  }
}

public class CaesarCipher {
  public void Encrypt(int key, string text){

    if(key < 1 || key > 26){
      throw new Exception("Key must be between 1 and 26 inclusive.");
    }

    Console.WriteLine("Plain:");
    Console.WriteLine(text);

    var decText = new char[text.Length];

    for(int i = 0; i < text.Length; i++){
      int dec = (int)text[i];

      if(dec >= 65 && dec <= 90 || dec >= 97 && dec <= 122){
        decText[i] = (char)(dec + key);
      } else {
        decText[i] = (char)dec;
      }
    }

    Console.WriteLine("Encrypted:");
    Console.WriteLine(decText);
  }
}

#include <iostream>

int main(){
    unsigned key = 1;
    std::string toEncrypt = "defend the east wall of the castle";

    if(key < 1 || key > 26){
        std::cout << "Key must be in range of 1-26" << std::endl;
        return 0;
    }

    for(char& c : toEncrypt){
        if(c < 'A' || c > 'z'){
            continue;
        }else if(c + key > 'z'){
            c = 'a' + (c + key) % 122 - 1;
            continue;
        }else if(c + key > 'Z' && c < 'a'){
            c = 'A' + (c + key) % 90 - 1;
            continue;
        }

        c += key;
    }
    std::cout << toEncrypt;
    return 0;
}

const encode = (sentence, key) => sentence.split(' ')
                                          .map((word) => word.split('')
                                          .map((char) => (/[a-z]/i.test(char)) ? String.fromCharCode(char.charCodeAt(0) + key) : char)
                                          .join(''))
                                          .join(' ');

class String
  def cesar_encrypt(key)
    raise ArgumentError, 'Key must be between 1 and 26 inclusive.' if key < 1 || key > 26

    letters_min = ('a'..'z').to_a
    letters_maj = ('A'..'Z').to_a

    result = tr!(letters_min.join, letters_min.rotate(key).join)
    result.tr(letters_maj.join, letters_maj.rotate(key).join)
  end

  def cesar_decrypt(key)
    raise ArgumentError, 'Key must be between 1 and 26 inclusive.' if key < 1 || key > 26

    letters_min = ('a'..'z').to_a
    letters_maj = ('A'..'Z').to_a

    result = tr!(letters_min.join, letters_min.rotate(-key).join)
    result.tr(letters_maj.join, letters_maj.rotate(-key).join)
  end
end

pp 'efgfoe uif fbtu xbmm pg uif dbtumfabAB'.cesar_decrypt(1)
pp 'defend the east wall of the castlezaZA'.cesar_encrypt(1)

// English letter frequency a-z
// source: https://en.wikipedia.org/wiki/Letter_frequency
const ENGLISH_FREQUENCIES = new Float32Array([
  0.0816, 0.0149, 0.0278, 0.0425, 0.1270, 0.0222, 0.0201, 0.0609, 0.0696, 0.0015, 0.0077, 0.0402, 0.0240,
  0.0674, 0.0750, 0.0192, 0.0009, 0.0598, 0.0632, 0.0905, 0.0275, 0.0097, 0.0236, 0.0015, 0.0197, 0.0007,
].map(v => Math.log(v) / Math.LN2));

// Here we are !
const decipher = str =>
  Array.from({ length: 26 }, (_, key) => {
    // Rotate text
    const text = str
      .toLowerCase()
      .replace(/[a-z]/g, $0 =>
        String.fromCharCode(97 + (($0.charCodeAt(0) - 97 + key) % 26))
      );

    // Get entropy information based on Shannon
    // https://en.wikipedia.org/wiki/Entropy_(information_theory)
    const entropy = text
      .match(/[a-z]/g)
      .map(c => ENGLISH_FREQUENCIES[c.charCodeAt(0) - 97])
      .reduce((sum, frequency, _, arr) => sum - frequency / arr.length, 0);

    return { key, text, entropy };
  }).sort((a, b) => a.entropy - b.entropy); // Sort results

console.log(
  decipher("dwwdfn iurp wkh zrrgv dw gdzq")
    .map(({ key, text, entropy }) => `${entropy.toFixed(3)} - ${text} (${key})`)
    .join("\n")
);

// 4.227 - attack from the woods at dawn (23)
// 4.936 - piiprz ugdb iwt lddsh pi splc (12)
// 4.974 - ohhoqy tfca hvs kccrg oh rokb (11)
// 5.098 - tmmtvd ykhf max phhwl tm wtpg (16)

//-----------------------------------------------------------------------
//-----------------------------Caesar Cipher-----------------------------
//-----------------------------------------------------------------------
//a == 97 z == 122
//A == 65 Z == 90

const cypher = function(msg,key)
{
    let inRange = (number, x, y) =>
    {
        if(number >= x && number <= y)
        {
            return true;
        }
        return false;
    }
    let newMsg = "";
    for(let i = 0; i < msg.length; i++)
    {
        let charUnicode = msg.codePointAt(i);
        if(inRange(charUnicode, 97, 122) || inRange(charUnicode, 65, 90))
        {
            newMsg += String.fromCodePoint(charUnicode + key);
        }else
        {
            newMsg += msg[i];
        }
    }
    return newMsg;
}

let message = "This took hella lotta time !";
console.log(cypher(message, 4));

def decrypt_caesar_cipher(s, shift)
  decrypter = (?a..?z).cycle.lazy.then { @1.zip(@1.drop(26 - shift)).take(26).to_h }
  decrypter.default_proc = -> { @1.fetch(@2.downcase, nil)&.upcase || @2 }
  s.each_char.inject('') { @1 + decrypter[@2] }
end

def brute_force_caesar_cipher(s)
  0...26 |> to_h { [@1, decrypt_caesar_cipher(s, @1)] }
end

p decrypt_caesar_cipher('dwwdfn iurp wkh zrrgv dw gdzq', 3)
pp brute_force_caesar_cipher('dwwdfn iurp wkh zrrgv dw gdzq')