first commit

helper.go

@@ -0,0 +1,107 @@
+package main
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"image/gif"
+	"log/slog"
+	"net/http"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/h2non/bimg"
+)
+
+type contextKey string
+
+const loggerKey contextKey = "logger"
+
+type responseWriter struct {
+	http.ResponseWriter
+	statusCode int
+}
+
+func (rw *responseWriter) WriteHeader(code int) {
+	rw.statusCode = code
+	rw.ResponseWriter.WriteHeader(code)
+}
+
+// loggingMiddleware injects a contextual logger into the request and logs request metrics.
+func loggingMiddleware(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		start := time.Now()
+		requestID := strconv.FormatInt(time.Now().UnixNano(), 36)
+		logger := slog.With(
+			"request_id", requestID,
+			"method", r.Method,
+			"path", r.URL.Path,
+			"remote_addr", r.RemoteAddr,
+		)
+		ctx := context.WithValue(r.Context(), loggerKey, logger)
+		rw := &responseWriter{ResponseWriter: w, statusCode: http.StatusOK}
+		next.ServeHTTP(rw, r.WithContext(ctx))
+
+		statusText := fmt.Sprintf("%d %s", rw.statusCode, http.StatusText(rw.statusCode))
+		logger.Info("Handled request",
+			"status", statusText,
+			"duration", time.Since(start).String(),
+			"user_agent", r.UserAgent(),
+		)
+	})
+}
+
+// isAllowedType performs a categorical check for 'image/*', 'video/*', and 'audio/*'.
+func isAllowedType(mimeType string, allowGeneric bool) bool {
+	mimeType = strings.Split(mimeType, ";")[0]
+	category := strings.Split(mimeType, "/")[0]
+
+	switch category {
+	case "image", "video", "audio":
+		return true
+	}
+
+	// Allow generic binary streams on the initial HEAD request, forcing the
+	// more reliable content sniffing to make the final decision.
+	if allowGeneric && mimeType == "application/octet-stream" {
+		return true
+	}
+	return false
+}
+
+// isAllowedDomain checks if a host is in the configured whitelist.
+func isAllowedDomain(host string, allowedDomains []string) bool {
+	if len(allowedDomains) == 0 {
+		return true
+	}
+	for _, domain := range allowedDomains {
+		if host == domain || strings.HasSuffix(host, "."+domain) {
+			return true
+		}
+	}
+	return false
+}
+
+// isGif checks if the provided byte slice represents an animated GIF.
+func isGif(data []byte) (bool, error) {
+	r := bytes.NewReader(data)
+	g, err := gif.DecodeAll(r)
+	if err != nil {
+		return false, err
+	}
+	return len(g.Image) > 1, nil
+}
+
+// optimizeMedia converts a static image to WebP and applies a quality setting.
+func optimizeMedia(data []byte, quality int) ([]byte, error) {
+	webp, err := bimg.NewImage(data).Convert(bimg.WEBP)
+	if err != nil {
+		return nil, fmt.Errorf("failed to convert image to webp: %w", err)
+	}
+	processed, err := bimg.NewImage(webp).Process(bimg.Options{Quality: quality})
+	if err != nil {
+		return nil, fmt.Errorf("failed to process image quality: %w", err)
+	}
+	return processed, nil
+}