feat: add comments count

internal/repository/comment_repo.go

@@ -178,9 +178,10 @@ func (r *CommentRepo) ListReplies(ctx context.Context, parentID, viewerID string
 	return out, total, err
 }
 
-// HydratePinned attaches each post's pinned comment (if any) to
-// Post.PinnedComment in a single query for the page.
-func (r *CommentRepo) HydratePinned(ctx context.Context, viewerID string, posts []*model.Post) error {
+// Hydrate fills each post's comment summary — its pinned comment (if any) and
+// total comment count (top-level + replies) — in two batched queries for the
+// page. Drives the card footer's pinned line and comment count.
+func (r *CommentRepo) Hydrate(ctx context.Context, viewerID string, posts []*model.Post) error {
 	ids := make([]string, 0, len(posts))
 	for _, p := range posts {
 		if p != nil {
@@ -190,27 +191,52 @@ func (r *CommentRepo) HydratePinned(ctx context.Context, viewerID string, posts
 	if len(ids) == 0 {
 		return nil
 	}
+
+	// Pinned comment per post.
 	q := `SELECT ` + commentSelect + commentFrom + `
 		WHERE c.post_id = ANY($1) AND c.pinned_at IS NOT NULL`
 	rows, err := r.pg.Pool.Query(ctx, q, ids, nullUUIDArg(viewerID))
 	if err != nil {
 		return fmt.Errorf("hydrate pinned: %w", err)
 	}
-	list, err := scanComments(rows)
+	list, err := scanComments(rows) // closes rows
 	if err != nil {
 		return err
 	}
-	byPost := make(map[string]*model.Comment, len(list))
+	pinnedByPost := make(map[string]*model.Comment, len(list))
 	for i := range list {
-		byPost[list[i].PostID] = &list[i]
+		pinnedByPost[list[i].PostID] = &list[i]
 	}
+
+	// Total comment count per post (top-level + replies).
+	counts := make(map[string]int, len(ids))
+	crows, err := r.pg.Pool.Query(ctx,
+		`SELECT post_id, count(*) FROM post_comments WHERE post_id = ANY($1) GROUP BY post_id`,
+		ids)
+	if err != nil {
+		return fmt.Errorf("hydrate comment counts: %w", err)
+	}
+	defer crows.Close()
+	for crows.Next() {
+		var id string
+		var n int
+		if err := crows.Scan(&id, &n); err != nil {
+			return fmt.Errorf("scan comment count: %w", err)
+		}
+		counts[id] = n
+	}
+	if err := crows.Err(); err != nil {
+		return err
+	}
+
 	for _, p := range posts {
 		if p == nil {
 			continue
 		}
-		if c, ok := byPost[p.ID]; ok {
+		if c, ok := pinnedByPost[p.ID]; ok {
 			p.PinnedComment = c
 		}
+		p.CommentsCount = counts[p.ID]
 	}
 	return nil
 }