fix(orders): correct page math in backfill endpoint (perPage must equal limit)

src/app/api/v1/orders/backfill-duplicate-checks/route.test.ts

@@ -72,16 +72,16 @@ describe("POST /api/v1/orders/backfill-duplicate-checks", () => {
 
   it("returns done=false and advances nextSkip when more rows remain", async () => {
     const { getAdminPocketBase } = await import("@/lib/server/pocketbase-admin");
-    // Fetch of 100 with limit=2 yields 3 rows (limit+1) — implies
-    // more rows remain after this 2-row chunk.
+    // perPage=limit=2 returns 2 items, totalItems=5 → hasMore=true
+    // (2 items consumed, 3 rows remain after offset 2).
     vi.mocked(getAdminPocketBase).mockResolvedValueOnce({
       autoCancellation: vi.fn(),
       collection: () => ({
         getList: vi.fn().mockResolvedValue({
-          items: [{ id: "a" }, { id: "b" }, { id: "c" }],
-          totalItems: 3,
+          items: [{ id: "a" }, { id: "b" }],
+          totalItems: 5,
           page: 1,
-          perPage: 3,
+          perPage: 2,
         }),
       }),
     } as unknown as Awaited<ReturnType<typeof getAdminPocketBase>>);
@@ -106,7 +106,7 @@ describe("POST /api/v1/orders/backfill-duplicate-checks", () => {
       items: [{ id: "x" }],
       totalItems: 1,
       page: 5,
-      perPage: 3,
+      perPage: 2,
     });
     vi.mocked(getAdminPocketBase).mockResolvedValueOnce({
       autoCancellation: vi.fn(),
@@ -115,8 +115,8 @@ describe("POST /api/v1/orders/backfill-duplicate-checks", () => {
 
     const res = await POST(backfillRequest("?limit=2&skip=8"));
     expect(res.status).toBe(200);
-    // skip=8, limit=2 → page = floor(8/2) + 1 = 5
-    expect(getListSpy).toHaveBeenCalledWith(5, 3, expect.any(Object));
+    // skip=8, limit=2 → page = skip/limit + 1 = 5, perPage = limit = 2
+    expect(getListSpy).toHaveBeenCalledWith(5, 2, expect.any(Object));
     expect((await res.json()).nextSkip).toBe(9);
   });
 

src/app/api/v1/orders/backfill-duplicate-checks/route.ts

@@ -89,22 +89,23 @@ export async function POST(req: NextRequest) {
   const pb = await getAdminPocketBase();
   pb.autoCancellation(false);
 
-  // Convert `skip` to a 1-based page number. PB's getList uses page,
-  // not offset, so we compute `page = floor(skip/limit) + 1`.
-  const page = Math.floor(skip / limit) + 1;
+  // PB pagination: getList(page, perPage) returns items at offsets
+  // [(page-1)*perPage, page*perPage). With perPage = limit and
+  // page = skip/limit + 1, the slice starts exactly at offset `skip`.
+  // `hasMore` is derived from `totalItems` rather than fetching +1.
+  const page = skip / limit + 1;
+  const perPage = limit;
 
-  // Fetch `limit + 1` so we can detect whether more rows remain after
-  // this chunk without a second `count` query.
   const orders = await pb.collection("orders").getList<{ id: string }>(
     page,
-    limit + 1,
+    perPage,
     {
       fields: "id",
       sort: "created",
     },
   );
-  const slice = orders.items.slice(0, limit);
-  const hasMore = orders.items.length > limit;
+  const slice = orders.items;
+  const hasMore = skip + slice.length < orders.totalItems;
 
   let ordersProcessed = 0;
   const failures: Array<{ orderId: string; error: string }> = [];