Vigenère cipher test

Vigenere.ts

class VigenereCipher {
  table: string[];

  constructor(table: string[]) {
    this.table = table;
  }

  encrypt(plaintext: string, key: string): string {
    let ciphertext = "";
    key = key
      .repeat(Math.ceil(plaintext.length / key.length))
      .slice(0, plaintext.length);

    for (let i = 0; i < plaintext.length; i++) {
      const pIndex = this.table[0].indexOf(plaintext[i]);
      const kIndex = this.table[0].indexOf(key[i]);
      if (pIndex !== -1 && kIndex !== -1) {
        ciphertext += this.table[pIndex][kIndex];
      } else {
        ciphertext += plaintext[i]; // Non-alphabetic characters are added as-is
      }
    }
    return ciphertext;
  }

  decrypt(ciphertext: string, key: string): string {
    let plaintext = "";
    key = key
      .repeat(Math.ceil(ciphertext.length / key.length))
      .slice(0, ciphertext.length);

    for (let i = 0; i < ciphertext.length; i++) {
      const kIndex = this.table[0].indexOf(key[i]);
      if (kIndex !== -1) {
        const row = this.table[kIndex];
        const cIndex = row.indexOf(ciphertext[i]);
        if (cIndex !== -1) {
          plaintext += this.table[0][cIndex];
        } else {
          plaintext += ciphertext[i]; // Non-alphabetic characters are added as-is
        }
      } else {
        plaintext += ciphertext[i]; // Non-alphabetic characters are added as-is
      }
    }
    return plaintext;
  }

  prettyPrintTable(): void {
    for (const row of this.table) {
      console.log(row.split("").join(" "));
    }
  }
}

function generateAlphabet(key: string = "") {
  let alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
  const keySet = new Set(key.toUpperCase());
  // ie. key="KRYPTOS" -> alphabet="KRYPTOSABCDEFGHIJLMNQUVWXZ"
  for (const char of keySet) {
    alphabet = alphabet.replace(char, "");
  }
  alphabet = key + alphabet;
  return alphabet;
}

// Example usage
const alphabet = generateAlphabet("KRYPTOS");
console.log("Alphabet:", alphabet);
const table: string[] = [];

// Generating the Vigenere table
for (let i = 0; i < alphabet.length; i++) {
  table.push(alphabet.slice(i) + alphabet.slice(0, i));
}

const cipher = new VigenereCipher(table);

const plaintext =
  "IT WAS TOTALLY INVISIBLE HOWS THAT POSSIBLE ? THEY USED THE EARTHS MAGNETIC FIELD X THE INFORMATION WAS GATHERED AND TRANSMITTED UNDERGRUUND TO AN UNKNOWN LOCATION X DOES LANGLEY KNOW ABOUT THIS ? THEY SHOULD ITS BURIED OUT THERE SOMEWHERE X WHO KNOWS THE EXACT LOCATION ? ONLY WW THIS WAS HIS LAST MESSAGE X THIRTY EIGHT DEGREES FIFTY SEVEN MINUTES SIX POINT FIVE SECONDS NORTH SEVENTY SEVEN DEGREES EIGHT MINUTES FORTY FOUR SECONDS WEST X LAYER TWO";
const key = "ABSCISSA";
const encrypted = cipher.encrypt(plaintext, key);
const decrypted = cipher.decrypt(encrypted, key);

console.log("Table:");
cipher.prettyPrintTable();
console.log("--------------------");
console.log("Key:", key);
console.log("--------------------");

console.log("Plaintext:", plaintext);
console.log("--------------------");

console.log("Encrypted:", encrypted);
console.log("--------------------");