content.js

chrome.runtime.onMessage.addListener((request, sender, sendResponse) => {
  const activeElement = document.activeElement;
  generatePassword(request, activeElement);
});

function generateSecurePassword(length = 20) {
  const lowercaseChars = 'abcdefghijklmnopqrstuvwxyz';
  const uppercaseChars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
  const digitChars = '0123456789';
  const specialChars = '!@#$%^&*()_+-=[]{}|;:,.<>?';

  const lowerArray = lowercaseChars.split('');
  const upperArray = uppercaseChars.split('');
  const digitArray = digitChars.split('');
  const specialArray = specialChars.split('');

  const allChars = [...lowerArray, ...upperArray, ...digitArray, ...specialArray];

  length = Math.max(length, 8);

  const passwordArray = [
    randomCharFrom(lowerArray),
    randomCharFrom(lowerArray),
    randomCharFrom(upperArray),
    randomCharFrom(upperArray),
    randomCharFrom(digitArray),
    randomCharFrom(digitArray),
    randomCharFrom(specialArray),
    randomCharFrom(specialArray),
  ];

  const rest = length - 8;
  const randomBytes = new Uint8Array(rest);
  crypto.getRandomValues(randomBytes);

  for (let i = 0; i < rest; i++) {
    passwordArray.push(allChars[randomBytes[i] % allChars.length]);
  }

  shuffleArray(passwordArray);

  return passwordArray.join('');
}

function randomCharFrom(array) {
  const [rand] = crypto.getRandomValues(new Uint8Array(1));
  return array[rand % array.length];
}

function shuffleArray(arr) {
  for (let i = arr.length - 1; i > 0; i--) {
    const [rand] = crypto.getRandomValues(new Uint8Array(1));
    const j = rand % (i + 1);
    [arr[i], arr[j]] = [arr[j], arr[i]];
  }
}

function generatePassword(request, activeElement) {
  if (request.action === 'generatePassword') {
    const password = generateSecurePassword();
    activeElement.value = password;
  }
}