fix(mobile): hide empty mobile reply backlink wrapper (#1060)

getRenderableMobileBacklinks() now filters mobile backlinks down to replies that can actually render, so ReplyBacklinks only mounts mobileReplyBacklinks when there is visible content. This adds a regression test for the gap where a newly published reply exists before it receives its post number.

src/lib/utils/reply-backlink-utils.ts

@@ -0,0 +1,44 @@
+import type { Comment } from '@bitsocialnet/bitsocial-react-hooks';
+
+interface GetRenderableMobileBacklinksArgs {
+  cid?: string;
+  parentCid?: string;
+  quotedByMap?: Map<string, Comment[]>;
+  directRepliesByParentCid?: Map<string, Comment[]>;
+}
+
+interface RenderableMobileBacklinks {
+  opBacklinks: Comment[];
+  directReplyBacklinks: Comment[];
+  quotedReplyBacklinks: Comment[];
+}
+
+const isRenderableBacklinkReply = (reply?: Comment) => Boolean(reply?.cid && typeof reply.number === 'number' && !(reply.deleted || reply.removed));
+
+export const getRenderableMobileBacklinks = ({ cid, parentCid, quotedByMap, directRepliesByParentCid }: GetRenderableMobileBacklinksArgs): RenderableMobileBacklinks => {
+  if (!cid) {
+    return {
+      opBacklinks: [],
+      directReplyBacklinks: [],
+      quotedReplyBacklinks: [],
+    };
+  }
+
+  const quotedReplies = quotedByMap?.get(cid) ?? [];
+
+  if (!parentCid) {
+    return {
+      opBacklinks: quotedReplies.filter(isRenderableBacklinkReply),
+      directReplyBacklinks: [],
+      quotedReplyBacklinks: [],
+    };
+  }
+
+  const directReplies = directRepliesByParentCid?.get(cid) ?? [];
+
+  return {
+    opBacklinks: [],
+    directReplyBacklinks: directReplies.filter((reply) => reply?.parentCid === cid && isRenderableBacklinkReply(reply)),
+    quotedReplyBacklinks: quotedReplies.filter((reply) => reply?.parentCid !== cid && isRenderableBacklinkReply(reply)),
+  };
+};