Fix thumbnail preview count display

Keep the raw thumbnail preview count in the redirect URL and format it
only while rendering the preview page. This prevents localized values
such as 4,980 from being parsed as 4 after redirect.

Add a regression test covering counts over 999.

Fixes #451

Assisted-by: OpenCode:gpt-5.5

Author: dahlia

CHANGES.md

@@ -6,6 +6,12 @@ Version 0.8.1
 
 To be released.
 
+ -  Fixed thumbnail cleanup preview counts over 999 being truncated after the
+    localized count was passed through the redirect URL.  The preview now keeps
+    the raw count in the URL and formats it only when rendering.  [[#451]]
+
+[#451]: https://github.com/fedify-dev/hollo/issues/451
+
 
 Version 0.8.0
 -------------

src/pages/thumbnail_cleanup.test.ts

@@ -0,0 +1,67 @@
+import { Hono } from "hono";
+import { beforeEach, describe, expect, it, vi } from "vitest";
+
+import { cleanDatabase } from "../../tests/helpers";
+import { getLoginCookie } from "../../tests/helpers/web";
+import { getMediaWithDeletableThumbnails } from "../entities/medium";
+import thumbnailCleanup from "./thumbnail_cleanup";
+
+vi.mock("../entities/medium", () => ({
+  getMediaWithDeletableThumbnails: vi.fn(),
+}));
+
+const app = new Hono();
+app.route("/thumbnail_cleanup", thumbnailCleanup);
+
+type DeletableMedia = Awaited<
+  ReturnType<typeof getMediaWithDeletableThumbnails>
+>;
+
+function createMediaItems(count: number): DeletableMedia {
+  return Array.from({ length: count }, (_, index) => ({
+    created: new Date(Date.UTC(2025, 0, index + 1)),
+  })) as DeletableMedia;
+}
+
+describe.sequential("thumbnail cleanup", () => {
+  beforeEach(async () => {
+    await cleanDatabase();
+    vi.mocked(getMediaWithDeletableThumbnails).mockReset();
+  });
+
+  it("preserves preview counts over 999 across the redirect", async () => {
+    expect.assertions(5);
+
+    vi.mocked(getMediaWithDeletableThumbnails).mockResolvedValue(
+      createMediaItems(4980),
+    );
+
+    const formData = new FormData();
+    formData.append("before", "2026-04-12");
+    const cookie = await getLoginCookie();
+    const response = await app.request("/thumbnail_cleanup/clean_preview", {
+      method: "POST",
+      body: formData,
+      headers: {
+        Cookie: cookie,
+      },
+    });
+
+    expect(response.status).toBe(302);
+
+    const location = response.headers.get("Location");
+    expect(location).not.toBeNull();
+
+    const url = new URL(location!, "http://localhost");
+    expect(url.searchParams.get("fileCount")).toBe("4980");
+
+    const previewResponse = await app.request(url.pathname + url.search, {
+      headers: {
+        Cookie: cookie,
+      },
+    });
+
+    expect(previewResponse.status).toBe(200);
+    expect(await previewResponse.text()).toContain("Number of Items: 4,980");
+  });
+});

src/pages/thumbnail_cleanup.tsx

@@ -27,7 +27,7 @@ data.get("/", async (c) => {
   const done = c.req.query("done");
   const error = c.req.query("error");
   const before = c.req.query("before");
-  const fileCount = Number.parseInt(c.req.query("fileCount") ?? "0");
+  const fileCount = Number(c.req.query("fileCount") ?? "0");
   const firstFile = c.req.query("firstFile");
   const lastFile = c.req.query("lastFile");
   const cleanupDataResult = c.req.query("cleanup-data-result");
@@ -187,7 +187,7 @@ data.get("/", async (c) => {
         {done === "clean_preview" &&
           (fileCount > 0 ? (
             <p>
-              Number of Items: {fileCount}
+              Number of Items: {fileCount.toLocaleString("en")}
               <br />
               First: {firstFile}
               <br />
@@ -356,7 +356,7 @@ data.post("/clean_preview", async (c) => {
         doneUrl.searchParams.set("before", beforeParameter);
         doneUrl.searchParams.set(
           "fileCount",
-          mediaWithThumbnailToClean.length.toLocaleString("en"),
+          String(mediaWithThumbnailToClean.length),
         );
         if (firstItem) {
           doneUrl.searchParams.set(