gomcp/internal/infrastructure/logging/middleware.go

package logging

import (
	"context"
	"crypto/rand"
	"fmt"
	"log/slog"
	"net/http"
	"time"
)

type contextKey string

const requestIDKey contextKey = "request_id"

// RequestID generates a short unique request ID.
func RequestID() string {
	b := make([]byte, 8)
	rand.Read(b)
	return fmt.Sprintf("%x", b)
}

// WithRequestID returns a context with a request ID attached.
func WithRequestID(ctx context.Context, id string) context.Context {
	return context.WithValue(ctx, requestIDKey, id)
}

// GetRequestID extracts the request ID from context (empty if not set).
func GetRequestID(ctx context.Context) string {
	if id, ok := ctx.Value(requestIDKey).(string); ok {
		return id
	}
	return ""
}

// RequestIDMiddleware injects a unique request ID into each request context
// and logs request start/end with duration.
func RequestIDMiddleware(logger *slog.Logger, next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		reqID := r.Header.Get("X-Request-ID")
		if reqID == "" {
			reqID = RequestID()
		}
		w.Header().Set("X-Request-ID", reqID)

		ctx := WithRequestID(r.Context(), reqID)
		r = r.WithContext(ctx)

		start := time.Now()
		wrapped := &statusWriter{ResponseWriter: w, status: 200}
		next.ServeHTTP(wrapped, r)
		dur := time.Since(start)

		logger.Info("http_request",
			"method", r.Method,
			"path", r.URL.Path,
			"status", wrapped.status,
			"duration_ms", dur.Milliseconds(),
			"request_id", reqID,
		)
	})
}

// statusWriter wraps ResponseWriter to capture status code.
type statusWriter struct {
	http.ResponseWriter
	status int
}

func (w *statusWriter) WriteHeader(code int) {
	w.status = code
	w.ResponseWriter.WriteHeader(code)
}