package middleware

import (
	"encoding/json"
	"log/slog"
	"net/http"
	"server/internal/model/common"
	"server/internal/utils"
	"time"

	gonanoid "github.com/matoous/go-nanoid/v2"
)

type LoggerMiddleware struct {
}

type responseWriter struct {
	http.ResponseWriter
	statusCode int
	bytes      int
	errorMsg   string
}

func (rw *responseWriter) WriteHeader(code int) {
	rw.statusCode = code
	rw.ResponseWriter.WriteHeader(code)
}

func generateRequestID() string {
	id, _ := gonanoid.New(16) // 16字符
	return id
}

// extractErrorMessage 从响应体中提取错误信息
func (rw *responseWriter) extractErrorMessage(body []byte) string {
	var resp common.Response
	if err := json.Unmarshal(body, &resp); err == nil && resp.Message != "" {
		return resp.Message
	}
	return string(body)
}

func (rw *responseWriter) Write(b []byte) (int, error) {
	n, err := rw.ResponseWriter.Write(b)
	rw.bytes += n

	// 只在错误状态码且未记录错误时处理
	if rw.statusCode >= 400 && rw.errorMsg == "" && n > 0 {
		rw.errorMsg = rw.extractErrorMessage(b[:n])
	}

	return n, err
}

func NewLoggerMiddleware() *LoggerMiddleware {
	return &LoggerMiddleware{}
}

func (m *LoggerMiddleware) Middleware(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		start := time.Now()

		reqID := generateRequestID()

		wrapped := &responseWriter{
			ResponseWriter: w,
			statusCode:     http.StatusOK,
		}

		next.ServeHTTP(wrapped, r)

		duration := time.Since(start)

		ip := utils.ClientIP(r)

		fullPath := r.URL.Path
		if r.URL.RawQuery != "" {
			fullPath = fullPath + "?" + r.URL.RawQuery
		}

		fields := []any{
			"request_id", reqID,
			"method", r.Method,
			"path", fullPath,
			"status", wrapped.statusCode,
			"duration", duration,
			"client_ip", ip,
		}

		if wrapped.errorMsg != "" {
			fields = append(fields, "error", wrapped.errorMsg)
		}

		switch {
		case wrapped.statusCode >= 500:
			slog.Error("request", fields...)
		case wrapped.statusCode >= 400:
			slog.Warn("request", fields...)
		default:
			slog.Info("request", fields...)
		}
	})
}