/**
 * 速率限制中间件
 * 使用内存存储（生产环境建议使用Redis）
 */

interface RateLimitStore {
  [key: string]: {
    count: number;
    resetTime: number;
  };
}

class RateLimiter {
  private store: RateLimitStore = {};
  private windowMs: number;
  private maxRequests: number;

  constructor(windowMs: number = 60000, maxRequests: number = 100) {
    this.windowMs = windowMs;
    this.maxRequests = maxRequests;
    
    // 定期清理过期记录
    setInterval(() => this.cleanup(), this.windowMs);
  }

  /**
   * 检查是否超过速率限制
   */
  check(identifier: string): { allowed: boolean; remaining: number; resetTime: number } {
    const now = Date.now();
    const record = this.store[identifier];

    if (!record || now > record.resetTime) {
      // 创建新记录
      this.store[identifier] = {
        count: 1,
        resetTime: now + this.windowMs,
      };
      return {
        allowed: true,
        remaining: this.maxRequests - 1,
        resetTime: now + this.windowMs,
      };
    }

    if (record.count >= this.maxRequests) {
      return {
        allowed: false,
        remaining: 0,
        resetTime: record.resetTime,
      };
    }

    record.count++;
    return {
      allowed: true,
      remaining: this.maxRequests - record.count,
      resetTime: record.resetTime,
    };
  }

  /**
   * 清理过期记录
   */
  private cleanup(): void {
    const now = Date.now();
    for (const key in this.store) {
      if (this.store[key].resetTime < now) {
        delete this.store[key];
      }
    }
  }
}

// 创建不同级别的速率限制器
export const rateLimiters = {
  // 通用API限制：每分钟100次请求
  api: new RateLimiter(60000, 100),
  
  // 严格限制：每分钟10次请求（用于敏感操作）
  strict: new RateLimiter(60000, 10),
  
  // 登录限制：每分钟5次请求
  auth: new RateLimiter(60000, 5),
  
  // IP限制：每分钟50次请求
  ip: new RateLimiter(60000, 50),
};

/**
 * 获取客户端标识符（IP地址）
 */
export function getClientIdentifier(request: Request): string {
  // 优先使用x-forwarded-for（考虑代理）
  const forwarded = request.headers.get("x-forwarded-for");
  if (forwarded) {
    return forwarded.split(",")[0].trim();
  }
  
  // 使用x-real-ip
  const realIP = request.headers.get("x-real-ip");
  if (realIP) {
    return realIP;
  }
  
  // 降级到unknown
  return "unknown";
}

/**
 * 速率限制检查函数
 */
export function checkRateLimit(
  request: Request,
  limiter: RateLimiter = rateLimiters.api
): { allowed: boolean; remaining: number; resetTime: number } {
  const identifier = getClientIdentifier(request);
  return limiter.check(identifier);
}