feat: increase watchlist item limit and prewarm installs (STR-52)

apps/backend/package.json

@@ -28,6 +28,7 @@
     "@hono/zod-validator": "^0.4.3",
     "@stremlist/shared": "workspace:*",
     "@supabase/supabase-js": "^2.95.3",
+    "@vercel/functions": "^3.9.5",
     "@vercel/related-projects": "^1.0.0",
     "hono": "^4.11.9",
     "linkedom": "^0.18.9",

apps/backend/src/__tests__/watchlist-crud.test.ts

@@ -4,6 +4,16 @@ import { describe, it, expect, beforeEach, vi } from "vitest";
 
 import app from "../index.js";
 
+const backgroundMocks = vi.hoisted(() => ({
+  scheduleBackgroundTask: vi.fn(),
+}));
+const prewarmMocks = vi.hoisted(() => ({
+  prewarmWatchlists: vi.fn(),
+}));
+
+vi.mock("../lib/background", () => backgroundMocks);
+vi.mock("../services/watchlist-prewarm", () => prewarmMocks);
+
 vi.mock("../lib/supabase", async () => {
   return await import("./helpers/mock-supabase.js");
 });
@@ -91,6 +101,9 @@ describe("Watchlist CRUD via API", () => {
   beforeEach(() => {
     db.reset();
     seedUser(OWNER);
+    backgroundMocks.scheduleBackgroundTask.mockReset();
+    prewarmMocks.prewarmWatchlists.mockReset();
+    prewarmMocks.prewarmWatchlists.mockResolvedValue(undefined);
   });
 
   // ---- GET /:userId/config ----
@@ -178,6 +191,17 @@ describe("Watchlist CRUD via API", () => {
 
       expect(data.watchlists[0].imdbUserId).toBe(OWNER);
       expect(data.watchlists[1].imdbUserId).toBe(OTHER_IMDB);
+
+      expect(backgroundMocks.scheduleBackgroundTask).toHaveBeenCalledOnce();
+      const task = backgroundMocks.scheduleBackgroundTask.mock.calls[0][0] as
+        | (() => Promise<void>)
+        | undefined;
+      expect(task).toBeTypeOf("function");
+      await task?.();
+      expect(prewarmMocks.prewarmWatchlists).toHaveBeenCalledWith(
+        OWNER,
+        data.watchlists,
+      );
     });
 
     it("preserves IDs when updating sort order", async () => {
@@ -269,6 +293,7 @@ describe("Watchlist CRUD via API", () => {
       expect(res.status).toBe(400);
       const data = await res.json();
       expect(data.error).toContain("unique");
+      expect(backgroundMocks.scheduleBackgroundTask).not.toHaveBeenCalled();
     });
 
     it("rejects empty watchlist array", async () => {

apps/backend/src/lib/__tests__/background.test.ts

@@ -0,0 +1,98 @@
+import { Hono } from "hono";
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+
+const vercelMocks = vi.hoisted(() => ({
+  waitUntil: vi.fn(),
+}));
+
+vi.mock("@vercel/functions", () => vercelMocks);
+
+import { scheduleBackgroundTask } from "../background";
+
+describe("scheduleBackgroundTask", () => {
+  const originalVercel = process.env.VERCEL;
+
+  beforeEach(() => {
+    vercelMocks.waitUntil.mockReset();
+    delete process.env.VERCEL;
+  });
+
+  afterEach(() => {
+    if (originalVercel === undefined) {
+      delete process.env.VERCEL;
+    } else {
+      process.env.VERCEL = originalVercel;
+    }
+  });
+
+  it("registers the task with Vercel so it can finish after the response", async () => {
+    process.env.VERCEL = "1";
+    const task = vi.fn().mockResolvedValue(undefined);
+
+    scheduleBackgroundTask(task);
+
+    expect(vercelMocks.waitUntil).toHaveBeenCalledOnce();
+    const promise = vercelMocks.waitUntil.mock.calls[0][0] as Promise<unknown>;
+    await promise;
+    expect(task).toHaveBeenCalledOnce();
+  });
+
+  it("runs the task locally without registering it with Vercel", async () => {
+    const task = vi.fn().mockResolvedValue(undefined);
+
+    scheduleBackgroundTask(task);
+    await vi.waitFor(() => {
+      expect(task).toHaveBeenCalledOnce();
+    });
+
+    expect(vercelMocks.waitUntil).not.toHaveBeenCalled();
+  });
+
+  it("does not delay the HTTP response while the task is pending", async () => {
+    let finishTask: (() => void) | undefined;
+    const pendingTask = new Promise<void>((resolve) => {
+      finishTask = resolve;
+    });
+    const task = vi.fn(() => pendingTask);
+    const app = new Hono().get("/probe", (c) => {
+      scheduleBackgroundTask(task);
+      return c.json({ ok: true });
+    });
+
+    const response = await app.request("/probe");
+
+    expect(response.status).toBe(200);
+    await expect(response.json()).resolves.toEqual({ ok: true });
+    expect(task).toHaveBeenCalledOnce();
+    expect(vercelMocks.waitUntil).not.toHaveBeenCalled();
+
+    finishTask?.();
+    await pendingTask;
+  });
+
+  it.each([
+    [
+      "synchronous",
+      () => {
+        throw new Error("sync failure");
+      },
+    ],
+    ["asynchronous", () => Promise.reject(new Error("async failure"))],
+  ])(
+    "logs a %s task failure without an unhandled rejection",
+    async (_, task) => {
+      const error = vi
+        .spyOn(console, "error")
+        .mockImplementation(() => undefined);
+
+      scheduleBackgroundTask(task);
+
+      await vi.waitFor(() => {
+        expect(error).toHaveBeenCalledWith(
+          "Background task failed:",
+          expect.any(Error),
+        );
+      });
+    },
+  );
+});

apps/backend/src/lib/background.ts

@@ -0,0 +1,15 @@
+import { waitUntil } from "@vercel/functions";
+
+type BackgroundTask = () => Promise<unknown>;
+
+export function scheduleBackgroundTask(task: BackgroundTask): void {
+  const promise = Promise.resolve()
+    .then(task)
+    .catch((error: unknown) => {
+      console.error("Background task failed:", error);
+    });
+
+  if (process.env.VERCEL) {
+    waitUntil(promise);
+  }
+}

apps/backend/src/routes/api.ts

@@ -9,6 +9,7 @@ import {
 } from "@stremlist/shared";
 import { Hono } from "hono";
 import { z } from "zod";
+import { scheduleBackgroundTask } from "../lib/background";
 import { resend } from "../lib/resend";
 import { supabase } from "../lib/supabase";
 import {
@@ -25,6 +26,7 @@ import {
   setUserRpdbApiKey,
 } from "../services/user";
 import { getWatchlistByConfig } from "../services/watchlist";
+import { prewarmWatchlists } from "../services/watchlist-prewarm";
 
 const REFRESH_COOLDOWN_MS =
   (Number.isFinite(Number(process.env.REFRESH_COOLDOWN_SECONDS))
@@ -190,6 +192,13 @@ const api = new Hono()
         setUserRpdbApiKey(userId, normalizedRpdbApiKey),
       ]);
 
+      // A fresh installation already has a seeded watchlist ID, so an
+      // "ID-less rows only" check would miss its first scrape. Queue every
+      // saved watchlist and let the normal cache-first path skip warm entries.
+      scheduleBackgroundTask(() =>
+        prewarmWatchlists(userId, updatedWatchlists),
+      );
+
       return c.json({ ok: true, watchlists: updatedWatchlists });
     },
   )

apps/backend/src/routes/manifest.ts

@@ -1,4 +1,8 @@
-import { BASE_MANIFEST, ADDON_VERSION } from "@stremlist/shared";
+import {
+  BASE_MANIFEST,
+  ADDON_VERSION,
+  IMDB_USER_ID_PATTERN,
+} from "@stremlist/shared";
 import type { StremioManifest } from "@stremlist/shared";
 import { Hono } from "hono";
 import { buildManifestCatalogs } from "../services/stremio-catalogs";
@@ -30,6 +34,19 @@ manifest.get("/:userId/manifest.json", async (c) => {
   const userId = c.req.param("userId");
   console.log(`Serving user-specific manifest for: ${userId}`);
 
+  if (!IMDB_USER_ID_PATTERN.test(userId)) {
+    return c.json(
+      {
+        ...structuredClone(BASE_MANIFEST),
+        behaviorHints: {
+          configurable: true,
+          configurationRequired: true,
+        },
+      },
+      400,
+    );
+  }
+
   try {
     await ensureUser(userId);
     const savedRpdbApiKey = await getUserRpdbApiKey(userId);