feat(gallery): preload images

internal/handlers/restgallery/controller.go

@@ -1,12 +1,16 @@
 package restgallery
 
 import (
+	"fmt"
 	"log/slog"
 	"net/http"
 
+	"git.schreifuchs.ch/schreifuchs/schreifuchs.ch/internal/pkg/templer"
 	"git.schreifuchs.ch/schreifuchs/schreifuchs.ch/web/pages"
 )
 
+const preloadCount = 6
+
 func (h *Handler) gallery(w http.ResponseWriter, r *http.Request) {
 	imgs, err := h.srv.GetGallerySet(r.Context())
 	if err != nil {
@@ -14,5 +18,14 @@ func (h *Handler) gallery(w http.ResponseWriter, r *http.Request) {
 		w.WriteHeader(http.StatusInternalServerError)
 		return
 	}
-	h.r.Render(r.Context(), w, r, pages.GallerySet(imgs))
+	ctx := r.Context()
+	for i, image := range imgs.LG.Images {
+		if i > preloadCount {
+			break
+		}
+		slog.Info("preloading images", "img", image.UID)
+		ctx = templer.AppendHeader(ctx, fmt.Sprintf(`<link rel="preload" href="%s" as="image" />`, image.URL()))
+	}
+
+	h.r.Render(ctx, w, r, pages.GallerySet(imgs))
 }