--wip-- [skip ci]

internal/components/gallery/image.go

@@ -12,6 +12,7 @@ import (
 	"time"
 
 	"git.schreifuchs.ch/schreifuchs/schreifuchs.ch/internal/components/images"
+	"git.schreifuchs.ch/schreifuchs/schreifuchs.ch/internal/handlers/rest"
 	"github.com/valkey-io/valkey-go"
 )
 
@@ -124,3 +125,32 @@ func (s *Service) GetImages(ctx context.Context) (images []Image, err error) {
 	err = s.cache.Do(ctx, s.cache.B().Get().Key(imagesKey).Build()).DecodeJSON(&images)
 	return
 }
+
+func (s *Service) GetPrevAndNext(ctx context.Context, uid string) (previous *Image, next *Image, err error) {
+	imgs, err := s.GetImages(ctx)
+	if err != nil {
+		return
+	}
+
+	for i := range imgs {
+		if imgs[i].UID != uid {
+			continue
+		}
+
+		if i-1 >= 0 {
+			previous = &imgs[i-1]
+		}
+		if i+1 >= len(imgs) {
+			next = &imgs[i+1]
+		}
+
+		return
+	}
+
+	err = &rest.Error{
+		Type:    rest.ErrorTypeNotFound,
+		Message: "could not find image with uid",
+	}
+
+	return
+}