res_levis_backend/internal/pkg/api/middleware/logging.go

package middleware

import (
	"log/slog"
	"net/http"
	"time"
)

// responseWriter wraps http.ResponseWriter to capture status and bytes written.
type responseWriter struct {
	http.ResponseWriter
	status int
	bytes  int
}

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

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

// Logging logs each request with method, path, status, duration, and bytes written.
func Logging(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		start := time.Now()
		wrap := &responseWriter{ResponseWriter: w, status: http.StatusOK}
		next.ServeHTTP(wrap, r)
		slog.Info("request",
			"method", r.Method,
			"path", r.URL.Path,
			"status", wrap.status,
			"duration_ms", time.Since(start).Milliseconds(),
			"bytes", wrap.bytes,
		)
	})
}