const jwt = require('jsonwebtoken');
const User = require('../models/User');

function getJwtSecret() {
  const envSecret = process.env.JWT_SECRET;

  if (process.env.NODE_ENV === 'production') {
    if (!envSecret) {
      throw new Error(
        '[致命错误] 生产环境未设置 JWT_SECRET 环境变量！\n' +
        '请在服务器环境变量中设置强密钥（至少32位随机字符）。\n' +
        '生成命令（PowerShell）：-join ((48..57) + (65..90) + (97..122) | Get-Random -Count 64 | ForEach-Object { [char]$_ })'
      );
    }
    if (envSecret.length < 32) {
      throw new Error('[致命错误] 生产环境 JWT_SECRET 长度必须至少32位！当前长度：' + envSecret.length);
    }
    return envSecret;
  }

  if (!envSecret) {
    throw new Error(
      '[错误] JWT_SECRET 未配置，请检查 initConfig.js 是否正确执行'
    );
  }

  return envSecret;
}

const JWT_SECRET = getJwtSecret();
const TOKEN_EXPIRY = process.env.TOKEN_EXPIRY || '24h';

const getBrowserInfo = (userAgent) => {
  let device = 'Desktop';
  let browser = 'Unknown';
  let os = 'Unknown';

  if (/Mobile|Android|iPhone|iPad|iPod/i.test(userAgent)) {
    device = 'Mobile';
    if (/iPad/i.test(userAgent)) device = 'Tablet';
  }

  if (/Firefox/i.test(userAgent)) {
    browser = 'Firefox';
  } else if (/Chrome/i.test(userAgent)) {
    browser = 'Chrome';
  } else if (/Safari/i.test(userAgent)) {
    browser = 'Safari';
  } else if (/Edge/i.test(userAgent)) {
    browser = 'Edge';
  } else if (/MSIE|Trident/i.test(userAgent)) {
    browser = 'IE';
  }

  if (/Windows/i.test(userAgent)) {
    os = 'Windows';
  } else if (/Mac OS/i.test(userAgent)) {
    os = 'macOS';
  } else if (/Linux/i.test(userAgent)) {
    os = 'Linux';
  } else if (/Android/i.test(userAgent)) {
    os = 'Android';
  } else if (/iOS|iPhone|iPad|iPod/i.test(userAgent)) {
    os = 'iOS';
  }

  return { device, browser, os };
};

const generateToken = (user) => {
  return jwt.sign(
    {
      userId: user.userId,
      username: user.username,
      roleId: user.roleId
    },
    JWT_SECRET,
    { expiresIn: TOKEN_EXPIRY }
  );
};

const verifyToken = (token) => {
  try {
    return jwt.verify(token, JWT_SECRET);
  } catch (error) {
    return null;
  }
};

const authMiddleware = async (req, res, next) => {
  try {
    const authHeader = req.headers.authorization;
    
    if (!authHeader || !authHeader.startsWith('Bearer ')) {
      return res.status(401).json({
        success: false,
        message: '未提供认证令牌'
      });
    }

    const token = authHeader.substring(7);
    const decoded = verifyToken(token);

    if (!decoded) {
      return res.status(401).json({
        success: false,
        message: '令牌无效或已过期'
      });
    }

    // 验证用户是否存在，增加详细的错误日志
    let user;
    try {
      user = await User.findByPk(decoded.userId);
    } catch (dbError) {
      // 数据库查询错误
      console.error('[认证中间件] 数据库查询失败:', {
        userId: decoded.userId,
        error: dbError.message,
        stack: dbError.stack,
        timestamp: new Date().toISOString()
      });
      return res.status(500).json({
        success: false,
        message: '数据库查询失败，请稍后重试'
      });
    }
    
    if (!user) {
      console.warn('[认证中间件] 用户不存在:', {
        userId: decoded.userId,
        username: decoded.username,
        timestamp: new Date().toISOString()
      });
      return res.status(401).json({
        success: false,
        message: '用户不存在'
      });
    }

    if (user.status === 'locked') {
      console.warn('[认证中间件] 账户已被锁定:', {
        userId: user.userId,
        username: user.username,
        timestamp: new Date().toISOString()
      });
      return res.status(403).json({
        success: false,
        message: '账户已被锁定'
      });
    }

    if (user.status === 'inactive') {
      console.warn('[认证中间件] 账户已禁用:', {
        userId: user.userId,
        username: user.username,
        timestamp: new Date().toISOString()
      });
      return res.status(403).json({
        success: false,
        message: '账户已禁用'
      });
    }

    req.user = decoded;
    req.userModel = user;
    next();
  } catch (error) {
    // 捕获未预期的错误
    console.error('[认证中间件] 未预期的错误:', {
      error: error.message,
      stack: error.stack,
      url: req?.url,
      method: req?.method,
      ip: req?.ip,
      timestamp: new Date().toISOString()
    });
    return res.status(500).json({
      success: false,
      message: '认证失败，请稍后重试'
    });
  }
};

const optionalAuth = async (req, res, next) => {
  try {
    const authHeader = req.headers.authorization;
    
    if (authHeader && authHeader.startsWith('Bearer ')) {
      const token = authHeader.substring(7);
      const decoded = verifyToken(token);
      
      if (decoded) {
        let user;
        try {
          user = await User.findByPk(decoded.userId);
        } catch (dbError) {
          // 数据库错误时不中断请求，仅记录日志
          console.warn('[可选认证] 数据库查询失败:', {
            userId: decoded.userId,
            error: dbError.message,
            timestamp: new Date().toISOString()
          });
          // 继续执行，不设置用户信息
          next();
          return;
        }
        
        if (user && user.status === 'active') {
          req.user = decoded;
          req.userModel = user;
        }
      }
    }
    
    next();
  } catch (error) {
    // 可选认证失败不影响主流程，仅记录日志
    console.warn('[可选认证] 认证失败（已忽略）:', {
      error: error.message,
      url: req?.url,
      timestamp: new Date().toISOString()
    });
    next();
  }
};

module.exports = {
  generateToken,
  verifyToken,
  authMiddleware,
  optionalAuth,
  JWT_SECRET,
  TOKEN_EXPIRY
};