message-mixer.js

// Import the functions from encryptors.js here.
const {caesarCipher, symbolCipher, reverseCipher} = require("./encryptors");

  // User Input / Output Logic
  /////////////////////////////////////////////
  
  const encryptionMethod = getEncryptionMethod();
  process.stdin.on('data', (userInput) => {
    displayEncryptedMessage(encryptionMethod, userInput);
  });
  
  /* Helper function for determining which cipher method
  the user chose when they ran the program. */
  function getEncryptionMethod() {
    let encryptionMethod;
    
    const encryptionType = process.argv[2];  
    if (encryptionType === 'symbol') {
      encryptionMethod = symbolCipher;
    } else if (encryptionType === 'reverse') {
      encryptionMethod = reverseCipher;
    } else if (encryptionType === 'caesar') {
      let amount = Number(process.argv[3]);
      if (Number.isNaN(amount)) {
        process.stdout.write(`Try again with a valid amount argument. \n`)
        process.exit();  
      }
      encryptionMethod = (str) => caesarCipher(str, amount);
    } 
    else {
      process.stdout.write(`Try again with a valid encryption type. \n`)
      process.exit();
    }
  
    process.stdout.write('Enter the message you would like to encrypt...\n> ');
    return encryptionMethod;
  }
  
  /* Helper function for displaying the encrypted message to the user. */
  function displayEncryptedMessage(encryptionMethod, userInput) {
    let str = userInput.toString().trim();    
    let output = encryptionMethod(str);
    process.stdout.write(`\nHere is your encrypted message:\n> ${output}\n`)
    process.exit();
  }