auth.html

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Simple Auth System</title>
  <style>
    body {
      font-family: Arial, sans-serif;
      display: flex;
      justify-content: center;
      align-items: center;
      min-height: 100vh;
      background-color: #f3f4f6;
      position: relative;
    }
    .top-right {
      position: absolute;
      top: 10px;
      right: 10px;
    }
    .container {
      background: white;
      padding: 20px;
      border-radius: 10px;
      box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
      width: 300px;
    }
    h2 {
      text-align: center;
    }
    .form-group {
      margin-bottom: 15px;
    }
    label {
      display: block;
      margin-bottom: 5px;
    }
    input {
      width: 100%;
      padding: 8px;
      box-sizing: border-box;
      border: 1px solid #ccc;
      border-radius: 5px;
    }
    button {
      width: 100%;
      padding: 10px;
      background-color: #4caf50;
      color: white;
      border: none;
      border-radius: 5px;
      cursor: pointer;
    }
    button:hover {
      background-color: #45a049;
    }
    .error {
      color: red;
      font-size: 0.9em;
    }
  </style>
</head>
<body>
  <div class="top-right">
    <a href="index.html">Back to Home</a>
  </div>
  <div class="container" id="auth-container">
    <h2>Login</h2>
    <div id="form-container">
      <div class="form-group">
        <label for="email">Email:</label>
        <input type="email" id="email" placeholder="Enter your email">
      </div>
      <div class="form-group">
        <label for="password">Password:</label>
        <input type="password" id="password" placeholder="Enter your password">
      </div>
      <button onclick="handleLogin()">Login</button>
      <p class="error" id="error-msg"></p>
      <p>Don't have an account? <a href="#" onclick="showRegisterForm()">Register here</a></p>
    </div>
  </div>

  <script>
    const USERS_KEY = 'users';

    function getUsers() {
      return JSON.parse(localStorage.getItem(USERS_KEY)) || [];
    }

    function saveUsers(users) {
      localStorage.setItem(USERS_KEY, JSON.stringify(users));
    }

    function handleLogin() {
      const email = document.getElementById('email').value;
      const password = document.getElementById('password').value;
      const errorMsg = document.getElementById('error-msg');
      errorMsg.textContent = '';

      if (!email || !password) {
        errorMsg.textContent = 'Please fill in all fields.';
        return;
      }

      const users = getUsers();
      const user = users.find(u => u.email === email && u.password === password);

      if (user) {
        alert('Login successful!');
      } else {
        errorMsg.textContent = 'Invalid email or password.';
      }
    }

    function handleRegister() {
      const email = document.getElementById('email').value;
      const password = document.getElementById('password').value;
      const errorMsg = document.getElementById('error-msg');
      errorMsg.textContent = '';

      if (!email || !password) {
        errorMsg.textContent = 'Please fill in all fields.';
        return;
      }

      const users = getUsers();
      if (users.some(u => u.email === email)) {
        errorMsg.textContent = 'User already exists.';
        return;
      }

      users.push({ email, password });
      saveUsers(users);
      alert('Registration successful! You can now log in.');
      showLoginForm();
    }

    function showRegisterForm() {
      document.getElementById('auth-container').innerHTML = `
        <h2>Register</h2>
        <div id="form-container">
          <div class="form-group">
            <label for="email">Email:</label>
            <input type="email" id="email" placeholder="Enter your email">
          </div>
          <div class="form-group">
            <label for="password">Password:</label>
            <input type="password" id="password" placeholder="Enter your password">
          </div>
          <button onclick="handleRegister()">Register</button>
          <p class="error" id="error-msg"></p>
          <p>Already have an account? <a href="#" onclick="showLoginForm()">Login here</a></p>
        </div>
      `;
    }

    function showLoginForm() {
      document.getElementById('auth-container').innerHTML = `
        <h2>Login</h2>
        <div id="form-container">
          <div class="form-group">
            <label for="email">Email:</label>
            <input type="email" id="email" placeholder="Enter your email">
          </div>
          <div class="form-group">
            <label for="password">Password:</label>
            <input type="password" id="password" placeholder="Enter your password">
          </div>
          <button onclick="handleLogin()">Login</button>
          <p class="error" id="error-msg"></p>
          <p>Don't have an account? <a href="#" onclick="showRegisterForm()">Register here</a></p>
        </div>
      `;
    }
  </script>
</body>
</html>