internal/middleware_logger/middleware_logger.go

package middleware_logger //nolint:staticcheck

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

	"gitlab.com/gitlab-org/gitlab-zoekt-indexer/internal/dev_debug"
)

func SlogMiddleware(logger *slog.Logger) func(next http.Handler) http.Handler {
	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			start := time.Now()

			// Wrap the ResponseWriter to capture the status and any potential errors
			ww := &enhancedWriter{ResponseWriter: w, status: http.StatusOK}

			// Process the request
			next.ServeHTTP(ww, r)

			// Log the request details
			duration := time.Since(start)
			logFields := []any{
				"method", r.Method,
				"path", r.URL.Path,
				"host", r.Host,
				"status", ww.status,
				"duration_ms", duration.Milliseconds(),
			}

			// Include error message if available
			if ww.errMessage != "" {
				logFields = append(logFields, "error", ww.errMessage)
				logger.Error("HTTP request", logFields...)
				return
			}

			logger.Info("HTTP request", logFields...)
		})
	}
}

func SetUpLogger() *slog.Logger {
	level := slog.LevelInfo

	if dev_debug.IsEnabled() {
		level = slog.LevelDebug
	}

	logger := slog.New(slog.NewJSONHandler(os.Stdout, &slog.HandlerOptions{Level: level}))
	slog.SetDefault(logger)
	return logger
}

// enhancedWriter wraps http.ResponseWriter to capture the HTTP status code and any error messages.
type enhancedWriter struct {
	http.ResponseWriter
	status     int
	errMessage string
}

func (w *enhancedWriter) WriteHeader(code int) {
	w.status = code
	if code >= 400 { // Capture error status codes
		w.errMessage = http.StatusText(code)
	}
	w.ResponseWriter.WriteHeader(code)
}

// Use Write to capture error messages written directly to the response body
func (w *enhancedWriter) Write(b []byte) (int, error) {
	if w.status >= 400 && w.errMessage == "" {
		w.errMessage = string(b) // Capture body content as error message
	}
	return w.ResponseWriter.Write(b)
}