feat(collections): add many models to a collection in one call

Add POST /collection/:id/items. Thingport Grab uses it to file a
MakerWorld collection's already-imported models instead of one request
per model, falling back on older instances.

backend/src/routes/collections.ts

@@ -245,6 +245,38 @@ router.post(
   }),
 );
 
+const addItemsSchema = z.object({ print_ids: z.array(z.string()).max(10_000) });
+
+// Many at once, e.g. Thingport Grab filing a provider collection's already-imported models.
+router.post(
+  "/collection/:id/items",
+  asyncHandler(async (req, res) => {
+    if (isSystemCollectionId(req.params.id)) {
+      throw new HttpError(400, "This collection can't be edited");
+    }
+    const body = parseBody(addItemsSchema, req.body);
+    const collection = await prisma.collection.findFirst({ where: { id: req.params.id, userId: req.userId } });
+    if (!collection) throw new HttpError(404, "Collection not found");
+    const prints = await prisma.print.findMany({
+      where: { id: { in: body.print_ids }, userId: req.userId },
+      select: { id: true },
+    });
+    await addPrintsToCollection(
+      collection.id,
+      prints.map((p) => p.id),
+    );
+    res.json({ ok: true });
+    if (prints.length) {
+      void createLog({
+        userId: req.userId!,
+        action: "collection_item_added",
+        targetId: collection.id,
+        details: { name: collection.name, count: prints.length },
+      });
+    }
+  }),
+);
+
 router.post(
   "/collection/:id/bookmark",
   asyncHandler(async (req, res) => {

backend/tests/collections.test.ts

@@ -155,6 +155,34 @@ describe("removing one item from a collection", () => {
   });
 });
 
+describe("adding many items to a collection at once", () => {
+  it("adds the caller's own prints, skipping unknown ids and ones already in it", async () => {
+    const uploads = await Promise.all(
+      ["bulk-add-1", "bulk-add-2"].map((name) =>
+        request(app)
+          .post("/api/upload")
+          .set(auth())
+          .attach("files", tmpFile(`${name}.stl`, `solid ${name} endsolid`)),
+      ),
+    );
+    const [first, second] = uploads.map((res) => res.body.prints[0].id as string);
+    const collection = await request(app).post("/api/collections").set(auth()).send({ name: "Bulk Add" });
+    await addPrintsToCollection(collection.body.id, [first]);
+
+    const res = await request(app)
+      .post(`/api/collection/${collection.body.id}/items`)
+      .set(auth())
+      .send({ print_ids: [first, second, "not-a-print"] });
+    expect(res.status).toBe(200);
+
+    const after = await request(app).get(`/api/collection/${collection.body.id}`).set(auth());
+    expect(after.body.item_count).toBe(2);
+
+    for (const id of [first, second]) await request(app).delete(`/api/print/${id}`).set(auth());
+    await request(app).delete(`/api/collection/${collection.body.id}`).set(auth());
+  });
+});
+
 describe("collection/print deletion cascades", () => {
   it("deleting a collection does not delete the models in it", async () => {
     const uploadRes = await request(app)

extension/src/content/panels/makerworldCollection.ts

@@ -244,9 +244,14 @@ async function startGuidedImport(
         `Adding ${alreadyImported.length} existing model${alreadyImported.length === 1 ? "" : "s"} to your collection…`,
       ),
     );
-    for (const entry of alreadyImported) {
-      if (entry.print_id)
-        await api("POST", `/collection/${collectionId}/items/${entry.print_id}`).catch(() => undefined);
+    const printIds = alreadyImported.flatMap((entry) => (entry.print_id ? [entry.print_id] : []));
+    try {
+      await api("POST", `/collection/${collectionId}/items`, { print_ids: printIds });
+    } catch {
+      // Instances without the bulk endpoint, one model at a time.
+      for (const printId of printIds) {
+        await api("POST", `/collection/${collectionId}/items/${printId}`).catch(() => undefined);
+      }
     }
   }