/**
 * 管理员认证中间件
 * Session/Cookie 保护 /dashboard 和 /api/stats
 */
import cookieParser from 'cookie-parser';

// Session 存储（生产环境应使用 Redis）
const SESSIONS: Map<string, { user: string; expires: number }> = new Map();

// Session 有效期 24 小时
const SESSION_EXPIRY = 24 * 60 * 60 * 1000;

// 环境变量凭证
const ADMIN_USER = process.env.ADMIN_USER || 'admin';
const ADMIN_PASS = process.env.ADMIN_PASS || '';

// Session Secret（用于签名）
const SESSION_SECRET = process.env.SESSION_SECRET || 'default-secret-change-me';

/**
 * 初始化 Cookie Parser
 */
export function initCookieParser() {
  return cookieParser();
}

/**
 * 生成 Session Token
 */
function generateSessionToken(): string {
  const randomBytes = new Uint8Array(32);
  crypto.getRandomValues(randomBytes);
  return Array.from(randomBytes).map(b => b.toString(16).padStart(2, '0')).join('');
}

/**
 * 验证凭证并创建 Session
 */
export function createSession(user: string, pass: string): { success: boolean; token?: string; error?: string } {
  // 检查凭证
  if (user !== ADMIN_USER || pass !== ADMIN_PASS) {
    return { success: false, error: 'Invalid credentials' };
  }

  // 检查是否配置了密码
  if (!ADMIN_PASS) {
    return { success: false, error: 'Admin password not configured' };
  }

  // 创建 Session
  const token = generateSessionToken();
  const expires = Date.now() + SESSION_EXPIRY;

  SESSIONS.set(token, { user, expires });

  console.log('[Auth] Session created for user:', user);

  return { success: true, token };
}

/**
 * 验证 Session Token
 */
export function validateSession(token: string): { valid: boolean; user?: string } {
  const session = SESSIONS.get(token);

  if (!session) {
    return { valid: false };
  }

  if (session.expires < Date.now()) {
    SESSIONS.delete(token);
    return { valid: false };
  }

  return { valid: true, user: session.user };
}

/**
 * 删除 Session（注销）
 */
export function destroySession(token: string): void {
  SESSIONS.delete(token);
  console.log('[Auth] Session destroyed');
}

/**
 * 路由保护中间件
 * 检查 Session Cookie，未登录重定向到 /login
 */
export function requireAdmin(req: any, res: any, next: any): void {
  const session = req.cookies?.admin_session;

  if (!session) {
    return res.redirect('/login');
  }

  const validation = validateSession(session);

  if (!validation.valid) {
    return res.redirect('/login');
  }

  // 设置用户信息到请求对象
  req.user = validation.user;
  next();
}

/**
 * API 保护中间件
 * 检查 Session，返回 401 JSON 响应
 */
export function requireAdminApi(req: any, res: any, next: any): void {
  const session = req.cookies?.admin_session;

  if (!session) {
    return res.status(401).json({ error: 'Unauthorized' });
  }

  const validation = validateSession(session);

  if (!validation.valid) {
    return res.status(401).json({ error: 'Session expired' });
  }

  req.user = validation.user;
  next();
}

/**
 * 清理过期 Session（可定期调用）
 */
export function cleanupExpiredSessions(): number {
  const now = Date.now();
  let cleaned = 0;

  for (const [token, session] of SESSIONS.entries()) {
    if (session.expires < now) {
      SESSIONS.delete(token);
      cleaned++;
    }
  }

  if (cleaned > 0) {
    console.log('[Auth] Cleaned', cleaned, 'expired sessions');
  }

  return cleaned;
}