lookbook/internal/middleware/logger.go

package middleware

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

// Logging emits structured request logs.
func Logging(logger *slog.Logger) func(http.Handler) http.Handler {
	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			start := time.Now()
			ww := &responseWriter{ResponseWriter: w, status: http.StatusOK}

			next.ServeHTTP(ww, r)

			logger.LogAttrs(r.Context(), slog.LevelInfo, "request",
				slog.String("method", r.Method),
				slog.String("path", r.URL.Path),
				slog.Int("status", ww.status),
				slog.Int("bytes", ww.bytes),
				slog.Duration("latency", time.Since(start)),
			)
		})
	}
}

type responseWriter struct {
	http.ResponseWriter
	status int
	bytes  int
}

func (w *responseWriter) WriteHeader(statusCode int) {
	w.status = statusCode
	w.ResponseWriter.WriteHeader(statusCode)
}

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