feat: allow loading mods without a Steam API key

Add fetchModFromUrl/fetchModFileFromUrl and accept a fileUrl query param on /items routes so the frontend can download saves directly from a search result's file_url, with no key required.

README.md

@@ -61,8 +61,12 @@ parser is the first place to look.
 
 ## Notes
 
-- `STEAM_API_KEY` is only needed for `/items/*` (resolving `file_url`). Search
-  works without it.
+- `STEAM_API_KEY` is optional. Search works without it. The mod page works
+  without it too when you arrive from a search result: the frontend passes the
+  item's `file_url` (already present in search results) to `/items/:id` via a
+  `fileUrl` query param, so the proxy downloads the save directly instead of
+  calling the Steam API. Without a key *and* without a `fileUrl` (e.g. a
+  deep-linked mod page), `/items/*` returns 500.
 - Each request fetches fresh; there is no caching by design (client-only tool).
 - `packages/extract` has zero runtime dependencies and runs in browser or Node,
   ready for a future frontend.

apps/proxy/src/routes/items.test.ts

@@ -1,5 +1,5 @@
 import { afterEach, describe, expect, it, vi } from 'vitest';
-import { ItemNotFoundError, SteamApiError } from '@tts/tts';
+import { ItemNotFoundError, SteamApiError, TtsError } from '@tts/tts';
 import type { TTSMod } from '@tts/shared';
 import items from './items.js';
 
@@ -16,12 +16,34 @@ describe('items route', () => {
     expect(await res.json()).toEqual({ error: 'Item ID must be a number' });
   });
 
-  it('returns 500 when the API key is missing', async () => {
+  it('returns 500 when the API key is missing and no fileUrl is given', async () => {
+    vi.spyOn(await import('@tts/tts'), 'fetchMod').mockRejectedValue(
+      new TtsError('STEAM_API_KEY is not configured', 500),
+    );
     const res = await items.request('/123', {}, { STEAM_API_KEY: '', PORT: 3000 });
     expect(res.status).toBe(500);
     expect(await res.json()).toEqual({ error: 'STEAM_API_KEY is not configured' });
   });
 
+  it('loads from a fileUrl without an API key', async () => {
+    const mod: TTSMod = {
+      GameMode: 'Tabletop',
+      Date: '2024-01-01',
+      ObjectStates: [],
+    };
+    const fetchModFromUrl = vi
+      .spyOn(await import('@tts/tts'), 'fetchModFromUrl')
+      .mockResolvedValue(mod);
+    const res = await items.request(
+      '/123?fileUrl=https%3A%2F%2Fexample.com%2Fsave.json',
+      {},
+      { STEAM_API_KEY: '', PORT: 3000 },
+    );
+    expect(res.status).toBe(200);
+    expect(await res.json()).toEqual(mod);
+    expect(fetchModFromUrl).toHaveBeenCalledWith('https://example.com/save.json');
+  });
+
   it('returns the parsed mod on success', async () => {
     const mod: TTSMod = {
       GameMode: 'Tabletop',
@@ -75,6 +97,27 @@ describe('items file route', () => {
     expect(await res.arrayBuffer()).toEqual(new Uint8Array([1, 2, 3]).buffer);
   });
 
+  it('serves the raw file from a fileUrl without an API key', async () => {
+    const fetchModFileFromUrl = vi
+      .spyOn(await import('@tts/tts'), 'fetchModFileFromUrl')
+      .mockResolvedValue({
+        data: new Uint8Array([1, 2, 3]).buffer,
+        filename: 'mod.json',
+      });
+    const res = await items.request(
+      '/123/file?fileUrl=https%3A%2F%2Fexample.com%2Fsave.json',
+      {},
+      { STEAM_API_KEY: '', PORT: 3000 },
+    );
+    expect(res.status).toBe(200);
+    expect(res.headers.get('content-disposition')).toBe(
+      'attachment; filename="mod.json"',
+    );
+    expect(fetchModFileFromUrl).toHaveBeenCalledWith(
+      'https://example.com/save.json',
+    );
+  });
+
   it('maps SteamApiError to 502', async () => {
     vi.spyOn(await import('@tts/tts'), 'fetchModFile').mockRejectedValue(
       new SteamApiError('Steam API responded 500'),

apps/proxy/src/routes/items.ts

@@ -1,6 +1,12 @@
 import { Hono } from 'hono';
 import { itemIdSchema, type TTSMod } from '@tts/shared';
-import { fetchMod, fetchModFile, TtsError } from '@tts/tts';
+import {
+  fetchMod,
+  fetchModFile,
+  fetchModFileFromUrl,
+  fetchModFromUrl,
+  TtsError,
+} from '@tts/tts';
 import type { Bindings } from '../env.js';
 
 const app = new Hono<{ Bindings: Bindings }>();
@@ -11,13 +17,13 @@ app.get('/:id', async (c) => {
     return c.json({ error: 'Item ID must be a number' }, 400);
   }
 
-  const apiKey = c.env.STEAM_API_KEY;
-  if (!apiKey) {
-    return c.json({ error: 'STEAM_API_KEY is not configured' }, 500);
-  }
-
   try {
-    const mod = await fetchMod(id, apiKey);
+    const fileUrl = c.req.query('fileUrl');
+    // With no Steam API key, the caller must supply the save URL (e.g. from a
+    // search result). Otherwise resolve it via the Steam API.
+    const mod: TTSMod = fileUrl
+      ? await fetchModFromUrl(fileUrl)
+      : await fetchMod(id, c.env.STEAM_API_KEY ?? '');
     return c.json<TTSMod>(mod);
   } catch (err) {
     if (err instanceof TtsError) {
@@ -33,13 +39,11 @@ app.get('/:id/file', async (c) => {
     return c.json({ error: 'Item ID must be a number' }, 400);
   }
 
-  const apiKey = c.env.STEAM_API_KEY;
-  if (!apiKey) {
-    return c.json({ error: 'STEAM_API_KEY is not configured' }, 500);
-  }
-
   try {
-    const { data, filename } = await fetchModFile(id, apiKey);
+    const fileUrl = c.req.query('fileUrl');
+    const { data, filename } = fileUrl
+      ? await fetchModFileFromUrl(fileUrl)
+      : await fetchModFile(id, c.env.STEAM_API_KEY ?? '');
     return new Response(data, {
       headers: {
         'Content-Type': 'application/octet-stream',

apps/web/src/api.ts

@@ -18,11 +18,17 @@ export function searchWorkshop(q: string, page = 1): Promise<SearchResult> {
 }
 
 /** Fetch a full parsed TTS save. */
-export function fetchMod(id: string): Promise<TTSMod> {
-  return getJson<TTSMod>(`/items/${id}`);
+export function fetchMod(id: string, fileUrl?: string): Promise<TTSMod> {
+  const params = new URLSearchParams();
+  if (fileUrl) params.set('fileUrl', fileUrl);
+  const qs = params.toString();
+  return getJson<TTSMod>(`/items/${id}${qs ? `?${qs}` : ''}`);
 }
 
 /** Build a URL for the raw save file download. */
-export function modFileUrl(id: string): string {
-  return `${BASE}/items/${id}/file`;
+export function modFileUrl(id: string, fileUrl?: string): string {
+  const params = new URLSearchParams();
+  if (fileUrl) params.set('fileUrl', fileUrl);
+  const qs = params.toString();
+  return `/items/${id}/file${qs ? `?${qs}` : ''}`;
 }

apps/web/src/pages/ModPage.tsx

@@ -2,15 +2,17 @@ import { useEffect } from 'react';
 import { useParams } from 'react-router-dom';
 import { collectRefs, flattenObjects } from '@tts/extract';
 import { useModStore } from '../stores/modStore';
+import { useSearchStore } from '../stores/searchStore';
 import { modFileUrl } from '../api';
 
 export default function ModPage() {
   const { id } = useParams<{ id: string }>();
   const { mod, loading, error, load } = useModStore();
+  const item = useSearchStore((s) => s.items.find((i) => i.id === id));
 
   useEffect(() => {
-    if (id) load(id);
-  }, [id, load]);
+    if (id) load(id, item?.fileUrl);
+  }, [id, item?.fileUrl, load]);
 
   if (loading) return <p className="text-sm text-zinc-400">Loading mod…</p>;
   if (error) return <p className="text-sm text-red-400">{error}</p>;
@@ -28,7 +30,7 @@ export default function ModPage() {
           asset refs
         </p>
         <a
-          href={modFileUrl(id!)}
+          href={modFileUrl(id!, item?.fileUrl)}
           className="mt-3 inline-block rounded-lg bg-zinc-100 px-4 py-2 text-sm font-medium text-zinc-900 hover:bg-zinc-300"
         >
           Download save file

apps/web/src/stores/modStore.ts

@@ -4,26 +4,28 @@ import { fetchMod } from '../api';
 
 interface ModState {
   id: string | null;
+  fileUrl?: string;
   mod: TTSMod | null;
   loading: boolean;
   error: string | null;
-  load: (id: string) => Promise<void>;
+  load: (id: string, fileUrl?: string) => Promise<void>;
   clear: () => void;
 }
 
 export const useModStore = create<ModState>((set) => ({
   id: null,
+  fileUrl: undefined,
   mod: null,
   loading: false,
   error: null,
-  load: async (id) => {
-    set({ loading: true, error: null, id });
+  load: async (id, fileUrl) => {
+    set({ loading: true, error: null, id, fileUrl });
     try {
-      const mod = await fetchMod(id);
+      const mod = await fetchMod(id, fileUrl);
       set({ mod, loading: false });
     } catch (err) {
       set({ loading: false, error: String(err) });
     }
   },
-  clear: () => set({ id: null, mod: null, error: null, loading: false }),
+  clear: () => set({ id: null, fileUrl: undefined, mod: null, error: null, loading: false }),
 }));

docs/implementation-plan.md

@@ -124,6 +124,10 @@ Low-level fetcher, extracted from the existing scraper.
   - `fetchMod(id: string): Promise<TTSMod>` — Steam API call to
     `ISteamRemoteStorage/GetPublishedFileDetails/v1` to get `file_url`, then
     download + BSON-deserialize into `TTSMod`.
+  - `fetchModFromUrl(fileUrl)` — download + BSON-deserialize from a direct URL
+    (no Steam API call).
+  - `fetchModFile(id, apiKey)` / `fetchModFileFromUrl(fileUrl)` — raw save
+    bytes + derived filename, with and without the Steam API.
   - `getFileName(url: string): Promise<string>` — derive filename from the
     `content-disposition` header.
 - `errors.ts`
@@ -171,8 +175,11 @@ Hono server exposing search + fetch.
     `cheerio`, extract `{ id, title, author, previewImageUrl }` from the result
     grid. Supports `pagenum` pagination. No API key required.
 - `routes/items.ts`
-  - `GET /items/:id` — full parsed `TTSMod`.
-  - `GET /items/:id/file` — raw save bytes, filename from `getFileName`.
+  - `GET /items/:id` — full parsed `TTSMod`. Accepts an optional `fileUrl`
+    query param to download the save directly (no Steam API key needed);
+    otherwise resolves via the Steam API.
+  - `GET /items/:id/file` — raw save bytes, filename from `getFileName`. Also
+    accepts `fileUrl`.
 - `routes/health.ts`
   - `GET /health` — liveness.
 - `env.ts` — zod validation of `STEAM_API_KEY`, `PORT`.
@@ -204,15 +211,20 @@ proxy API and `packages/extract` directly for analysis.
 | ------ | ------------------- | -------------------------------------------- | ---- |
 | GET    | `/health`           | Liveness                                     | —    |
 | GET    | `/search?q=&page=`  | Scrape Workshop browse, return item list     | —    |
-| GET    | `/items/:id`        | Full parsed `TTSMod`                         | key  |
-| GET    | `/items/:id/file`   | Raw save bytes, filename from header         | key  |
+| GET    | `/items/:id`        | Full parsed `TTSMod` (`?fileUrl=` skips key) | key* |
+| GET    | `/items/:id/file`   | Raw save bytes, filename from header         | key* |
+
+\* `STEAM_API_KEY` is optional; `/items/*` works without it when a `fileUrl`
+query param is supplied.
 
 ## Data flow
 
 ```
-/search?q=wingspan  →  scrape browse page  →  list of {id, title, ...}
+/search?q=wingspan  →  scrape browse page  →  list of {id, title, fileUrl, ...}
         ↓
 /items/:id          →  Steam API (needs key)  →  file_url
+        ↓
+        └─ /items/:id?fileUrl=...  →  download directly (no key)
         ↓
                       download BSON → parse → TTSMod
         ↓

packages/tts/src/index.test.ts

@@ -1,11 +1,47 @@
 import { afterEach, describe, expect, it, vi } from 'vitest';
-import { getFileName } from './index.js';
+import { fetchModFileFromUrl, fetchModFromUrl, getFileName } from './index.js';
 import { ItemNotFoundError, NoFileError, SteamApiError, TtsError } from './errors.js';
 
 afterEach(() => {
   vi.unstubAllGlobals();
 });
 
+// A minimal valid BSON document: { GameMode: 'Tabletop' }.
+const bsonBytes = new Uint8Array([
+  28, 0, 0, 0, 2, 71, 97, 109, 101, 77, 111, 100, 101, 0, 9, 0, 0, 0, 84, 97,
+  98, 108, 101, 116, 111, 112, 0, 0,
+]);
+
+function bsonResponse(): Response {
+  return new Response(bsonBytes);
+}
+
+describe('fetchModFromUrl', () => {
+  it('downloads and deserializes a save from a URL', async () => {
+    vi.stubGlobal('fetch', vi.fn().mockResolvedValue(bsonResponse()));
+    const mod = await fetchModFromUrl('https://example.com/save.json');
+    expect(mod.GameMode).toBe('Tabletop');
+  });
+
+  it('throws on a failed download', async () => {
+    vi.stubGlobal('fetch', vi.fn().mockResolvedValue(new Response(null, { status: 404 })));
+    await expect(fetchModFromUrl('https://example.com/save.json')).rejects.toThrow(
+      'Failed to download save file (404)',
+    );
+  });
+});
+
+describe('fetchModFileFromUrl', () => {
+  it('returns bytes and a filename derived from the URL', async () => {
+    vi.stubGlobal('fetch', vi.fn().mockResolvedValue(bsonResponse()));
+    const { data, filename } = await fetchModFileFromUrl(
+      'https://example.com/files/mod.json',
+    );
+    expect(new Uint8Array(data)).toEqual(bsonBytes);
+    expect(filename).toBe('mod.json');
+  });
+});
+
 describe('getFileName', () => {
   it('parses a quoted content-disposition filename', () => {
     expect(

packages/tts/src/index.ts

@@ -33,16 +33,16 @@ interface SteamResponse {
  */
 export async function fetchMod(id: string, apiKey: string): Promise<TTSMod> {
   const fileUrl = await getFileUrl(id, apiKey);
-
-  const saveRes = await fetch(fileUrl);
-  if (!saveRes.ok) {
-    throw new SteamApiError(
-      `Failed to download save file (${saveRes.status})`,
-      502,
-    );
+  return fetchModFromUrl(fileUrl);
 }
 
-  const buffer = await saveRes.arrayBuffer();
+/**
+ * Download a TTS save from a direct URL and BSON-deserialize it.
+ *
+ * @param fileUrl Direct URL to the save file (e.g. from a search result).
+ */
+export async function fetchModFromUrl(fileUrl: string): Promise<TTSMod> {
+  const buffer = await downloadSave(fileUrl);
   return deserialize(new Uint8Array(buffer)) as TTSMod;
 }
 
@@ -70,7 +70,23 @@ export async function fetchModFile(
   apiKey: string,
 ): Promise<{ data: ArrayBuffer; filename: string }> {
   const fileUrl = await getFileUrl(id, apiKey);
+  return fetchModFileFromUrl(fileUrl);
+}
 
+/**
+ * Fetch the raw save file bytes from a direct URL.
+ * Returns the bytes plus a derived filename.
+ */
+export async function fetchModFileFromUrl(
+  fileUrl: string,
+): Promise<{ data: ArrayBuffer; filename: string }> {
+  const data = await downloadSave(fileUrl);
+  const filename = getFileName(fileUrl, null);
+  return { data, filename };
+}
+
+/** Download a save file's bytes from a URL, throwing on failure. */
+async function downloadSave(fileUrl: string): Promise<ArrayBuffer> {
   const res = await fetch(fileUrl);
   if (!res.ok) {
     throw new SteamApiError(
@@ -78,10 +94,7 @@ export async function fetchModFile(
       502,
     );
   }
-
-  const data = await res.arrayBuffer();
-  const filename = getFileName(fileUrl, res.headers.get('content-disposition'));
-  return { data, filename };
+  return res.arrayBuffer();
 }
 
 /** Resolve the `file_url` for a Workshop item via the Steam API. */