refac: atomic merge, lost-update race, RunPurge cost, duplicated walks

internal/infrastructure/useCases/entrySupport.go

@@ -24,26 +24,18 @@ func typedEntry(owner contenttype.ContentType, record entry.Entry, resolver *med
 
 func ensureMediaExists(images image.Repository, owner contenttype.ContentType, data map[string]any, stored map[string]any) error {
 	storedIDs := entry.MediaIDs(owner.Fields, stored)
-	for _, field := range contenttype.MediaFields(owner.Fields) {
-		id, set := contenttype.MediaID(data[field.Key])
-		if !set {
+	for _, ref := range contenttype.MediaRefs(owner.Fields, data) {
+		unchanged := stored != nil && storedIDs[ref.Field.Key] == ref.ID
+		if unchanged && !ref.Field.Required {
 			continue
 		}
-		unchanged := stored != nil && storedIDs[field.Key] == id
-		if unchanged && !field.Required {
-			continue
-		}
-		exists, err := imageExists(images, id)
+		exists, err := imageExists(images, ref.ID)
 		if err != nil {
 			return err
 		}
-		if exists {
-			continue
+		if !exists {
+			return entry.MissingMedia(ref.Field, unchanged)
 		}
-		if unchanged {
-			return entry.InvalidField(field.Key, entry.RuleRequired)
-		}
-		return entry.InvalidField(field.Key, contenttype.RuleType)
 	}
 	return nil
 }