logging.go

package api

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

// responseRecorder wraps http.ResponseWriter to capture the status code and size.
type responseRecorder struct {
	http.ResponseWriter
	status int
	size   int
}

func (r *responseRecorder) WriteHeader(code int) {
	r.status = code
	r.ResponseWriter.WriteHeader(code)
}

func (r *responseRecorder) Write(b []byte) (int, error) {
	n, err := r.ResponseWriter.Write(b)
	r.size += n
	return n, err
}

// Unwrap returns the underlying ResponseWriter (supports http.ResponseController).
func (r *responseRecorder) Unwrap() http.ResponseWriter {
	return r.ResponseWriter
}

// Logger returns middleware that logs each request using the provided slog.Logger.
func Logger(logger *slog.Logger) Middleware {
	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			start := time.Now()
			rec := &responseRecorder{ResponseWriter: w, status: http.StatusOK}
			next.ServeHTTP(rec, r)

			attrs := []slog.Attr{
				slog.String("method", r.Method),
				slog.String("path", r.URL.Path),
				slog.Int("status", rec.status),
				slog.Duration("latency", time.Since(start)),
				slog.Int("size", rec.size),
				slog.String("remote", r.RemoteAddr),
			}

			if id := GetRequestID(r); id != "" {
				attrs = append(attrs, slog.String("request_id", id))
			}

			args := make([]any, len(attrs))
			for i, a := range attrs {
				args[i] = a
			}

			logger.LogAttrs(r.Context(), slog.LevelInfo, "request", attrs...)
		})
	}
}