/*
middleware.go - 中间件
实现了各种HTTP中间件功能
*/

package server

import (
	"log"
	"net/http"
	"runtime/debug"
	"time"
)

// LoggingMiddleware 日志记录中间件
func LoggingMiddleware(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		start := time.Now()

		// 创建响应记录器来捕获状态码
		recorder := &responseRecorder{
			ResponseWriter: w,
			statusCode:     http.StatusOK,
		}

		// 调用下一个处理器
		next.ServeHTTP(recorder, r)

		// 记录请求日志
		duration := time.Since(start)
		log.Printf("[%s] %s %s %d %v",
			r.Method,
			r.RequestURI,
			r.RemoteAddr,
			recorder.statusCode,
			duration,
		)
	})
}

// responseRecorder 响应记录器
type responseRecorder struct {
	http.ResponseWriter
	statusCode int
}

// WriteHeader 记录状态码
func (rr *responseRecorder) WriteHeader(code int) {
	rr.statusCode = code
	rr.ResponseWriter.WriteHeader(code)
}

// CORSMiddleware CORS中间件
func CORSMiddleware(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		// 设置CORS头
		w.Header().Set("Access-Control-Allow-Origin", "*")
		w.Header().Set("Access-Control-Allow-Methods", "GET, POST, PUT, DELETE, OPTIONS")
		w.Header().Set("Access-Control-Allow-Headers", "Content-Type, Authorization")

		// 处理预检请求
		if r.Method == "OPTIONS" {
			w.WriteHeader(http.StatusOK)
			return
		}

		// 调用下一个处理器
		next.ServeHTTP(w, r)
	})
}

// RecoveryMiddleware 恢复中间件（处理panic）
func RecoveryMiddleware(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		defer func() {
			if err := recover(); err != nil {
				// 记录panic信息
				log.Printf("❌ Panic recovered: %v\n%s", err, debug.Stack())

				// 返回500错误
				http.Error(w, "Internal Server Error", http.StatusInternalServerError)
			}
		}()

		// 调用下一个处理器
		next.ServeHTTP(w, r)
	})
}

// AuthMiddleware 认证中间件（示例）
func AuthMiddleware(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		// 检查Authorization头
		token := r.Header.Get("Authorization")
		if token == "" {
			http.Error(w, "Unauthorized", http.StatusUnauthorized)
			return
		}

		// 这里可以添加实际的token验证逻辑
		// 为了演示，我们简单检查token是否为"Bearer valid-token"
		if token != "Bearer valid-token" {
			http.Error(w, "Invalid token", http.StatusUnauthorized)
			return
		}

		// 调用下一个处理器
		next.ServeHTTP(w, r)
	})
}

// RateLimitMiddleware 限流中间件（简化版）
func RateLimitMiddleware(next http.Handler) http.Handler {
	// 这里可以实现基于IP的限流逻辑
	// 为了简化，我们只是一个示例框架
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		// 实际实现中，这里会检查请求频率
		// 如果超过限制，返回429状态码

		// 调用下一个处理器
		next.ServeHTTP(w, r)
	})
}

// ContentTypeMiddleware 内容类型中间件
func ContentTypeMiddleware(contentType string) func(http.Handler) http.Handler {
	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			w.Header().Set("Content-Type", contentType)
			next.ServeHTTP(w, r)
		})
	}
}

// SecurityMiddleware 安全头中间件
func SecurityMiddleware(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		// 设置安全相关的HTTP头
		w.Header().Set("X-Content-Type-Options", "nosniff")
		w.Header().Set("X-Frame-Options", "DENY")
		w.Header().Set("X-XSS-Protection", "1; mode=block")
		w.Header().Set("Strict-Transport-Security", "max-age=31536000; includeSubDomains")

		// 调用下一个处理器
		next.ServeHTTP(w, r)
	})
}