feat: support displaying highlights in replies

src/lib/event-metadata.ts

@@ -403,3 +403,34 @@ export function getPinnedEventHexIdSetFromPinListEvent(event?: Event | null): Se
       .slice(0, MAX_PINNED_NOTES) ?? []
   )
 }
+
+export function getHighlightSourceTag(event: Event) {
+  let sourceTag: string[] | undefined
+  for (const tag of event.tags) {
+    // Highest priority: 'source' tag
+    if (tag[2] === 'source') {
+      sourceTag = tag
+      break
+    }
+
+    // Give 'e' tags highest priority
+    if (tag[0] === 'e') {
+      sourceTag = tag
+      continue
+    }
+
+    // Give 'a' tags second priority over 'e' tags
+    if (tag[0] === 'a' && (!sourceTag || sourceTag[0] !== 'e')) {
+      sourceTag = tag
+      continue
+    }
+
+    // Give 'r' tags lowest priority
+    if (tag[0] === 'r' && (!sourceTag || sourceTag[0] === 'r')) {
+      sourceTag = tag
+      continue
+    }
+  }
+
+  return sourceTag
+}