<?php
session_start();
if ($_SERVER['REQUEST_METHOD'] === 'POST') {
    $username = $_POST['username'] ?? '';
    $password = $_POST['password'] ?? '';
    
    // 默认账号密码设置：admin / admin123
    // 后续建议移动到环境变量或数据库加密存储
    if ($username === 'admin' && $password === 'admin123') { 
        $_SESSION['loggedin'] = true;
        $_SESSION['username'] = $username;
        header('Location: admin.php');
        exit;
    } else {
        $error = '账号或密码错误';
    }
}
?>
<!doctype html>
<html lang="zh-CN">
<head>
  <meta charset="utf-8">
  <title>登录 - 管理后台</title>
  <link href="https://cdn.jsdelivr.net/npm/bootstrap@5.3.2/dist/css/bootstrap.min.css" rel="stylesheet">
  <style>
    body { height: 100vh; display: flex; align-items: center; justify-content: center; background-color: #f8f9fa; }
    .login-card { width: 100%; max-width: 400px; padding: 20px; background: white; border-radius: 8px; box-shadow: 0 2px 10px rgba(0,0,0,0.1); }
  </style>
</head>
<body>
  <div class="login-card">
    <h4 class="mb-3">后台登录</h4>
    <?php if (isset($error)): ?><div class="alert alert-danger"><?= htmlspecialchars($error) ?></div><?php endif; ?>
    <form method="POST">
      <div class="mb-3">
        <label class="form-label">账号</label>
        <input type="text" name="username" class="form-control" required>
      </div>
      <div class="mb-3">
        <label class="form-label">密码</label>
        <input type="password" name="password" class="form-control" required>
      </div>
      <button type="submit" class="btn btn-primary w-100">登入</button>
    </form>
  </div>
</body>
</html>