pad/internal/server/middleware_logging.go

package server

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

	chimiddleware "github.com/go-chi/chi/v5/middleware"
)

// StructuredLogger is a chi-compatible request logger that writes structured
// log entries via slog. It replaces chi's default Logger middleware.
func StructuredLogger(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		start := time.Now()
		ww := chimiddleware.NewWrapResponseWriter(w, r.ProtoMajor)

		next.ServeHTTP(ww, r)

		duration := time.Since(start)
		status := ww.Status()

		level := slog.LevelInfo
		if status >= 500 {
			level = slog.LevelError
		} else if status >= 400 {
			level = slog.LevelWarn
		}

		attrs := []slog.Attr{
			slog.String("method", r.Method),
			slog.String("path", r.URL.Path),
			slog.Int("status", status),
			slog.Duration("duration", duration),
			slog.Int("bytes", ww.BytesWritten()),
		}

		if reqID := chimiddleware.GetReqID(r.Context()); reqID != "" {
			attrs = append(attrs, slog.String("request_id", reqID))
		}

		if r.URL.RawQuery != "" {
			attrs = append(attrs, slog.String("query", r.URL.RawQuery))
		}

		slog.LogAttrs(r.Context(), level, "http request", attrs...)
	})
}