Add pagination to service catalogue

app/modules/services/services.py

@@ -65,6 +65,13 @@ def get_category(db: Session, category_id: int) -> ServiceCategory | None:
 
 
 def list_catalogue_payload(db: Session, *, q: str = "", category_id: int | None = None, recurrence_type: str = "", engagement_type: str = "", page: int = 1, per_page: int = 20):
+    # Keep catalogue paging predictable and prevent invalid/very large requests.
+    page = max(1, int(page or 1))
+    allowed_page_sizes = {20, 50, 100}
+    per_page = int(per_page or 20)
+    if per_page not in allowed_page_sizes:
+        per_page = 20
+
     query = select(ServiceCatalogue).where(
         ServiceCatalogue.is_active.is_(True)
     ).options(
@@ -90,12 +97,18 @@ def list_catalogue_payload(db: Session, *, q: str = "", category_id: int | None
         query = query.where(ServiceCatalogue.engagement_type == normalize_engagement_type(engagement_type))
 
     total = db.execute(select(func.count()).select_from(query.subquery())).scalar_one()
+    pages = max(1, (total + per_page - 1) // per_page)
+    page = min(page, pages)
+
     rows = db.execute(
         query.order_by(ServiceCatalogue.sort_order.asc(), ServiceCatalogue.service_name.asc())
         .offset((page - 1) * per_page)
         .limit(per_page)
     ).scalars().all()
 
+    start_item = ((page - 1) * per_page + 1) if total else 0
+    end_item = min(page * per_page, total)
+
     return {
         "rows": rows,
         "q": q,
@@ -105,7 +118,9 @@ def list_catalogue_payload(db: Session, *, q: str = "", category_id: int | None
         "page": page,
         "per_page": per_page,
         "total": total,
-        "pages": max(1, (total + per_page - 1) // per_page),
+        "pages": pages,
+        "start_item": start_item,
+        "end_item": end_item,
     }