feat: v0.4.1 — untrack map-asset pack (~100 MB): compose volume mount + runtime fallback to remote OFM styles

lib/mapStyles.test.ts

@@ -1,5 +1,5 @@
-import { describe, expect, it } from 'vitest';
-import { DEFAULT_STYLE_ID, STYLES, isStyleId, rewriteStyle, styleUrl } from './mapStyles';
+import { afterEach, describe, expect, it, vi } from 'vitest';
+import { DEFAULT_STYLE_ID, REMOTE_STYLE_BASE, STYLES, isStyleId, rewriteStyle, styleUrl, styleUrlFor } from './mapStyles';
 
 // Mirrors the real OFM style JSONs (verified against tiles.openfreemap.org): same
 // glyphs/sprite values and source shapes, no attribution anywhere.
@@ -76,3 +76,49 @@ describe('rewriteStyle', () => {
     expect(JSON.stringify(RAW_OFM_STYLE)).toBe(before);
   });
 });
+
+describe('styleUrlFor', () => {
+  it('points at the local style file when the asset pack is available', () => {
+    for (const s of STYLES) {
+      expect(styleUrlFor(s.id, true)).toBe(`/styles/${s.id}.json`);
+    }
+  });
+
+  it('points at the exact remote OFM style url otherwise', () => {
+    for (const s of STYLES) {
+      expect(styleUrlFor(s.id, false)).toBe(`${REMOTE_STYLE_BASE}/${s.id}`);
+      expect(styleUrlFor(s.id, false)).toBe(`https://tiles.openfreemap.org/styles/${s.id}`);
+    }
+  });
+});
+
+describe('localAssetsAvailable', () => {
+  // The probe caches its promise at module level, so each test gets a fresh module
+  // instance (resetModules + dynamic import) with its own stubbed fetch.
+  afterEach(() => {
+    vi.unstubAllGlobals();
+    vi.resetModules();
+  });
+
+  it('resolves false on non-200 responses', async () => {
+    vi.stubGlobal('fetch', vi.fn().mockResolvedValue({ ok: false, status: 404 }));
+    const mod = await import('./mapStyles');
+    await expect(mod.localAssetsAvailable()).resolves.toBe(false);
+  });
+
+  it('resolves true on 200 and caches the probe (one fetch across awaits)', async () => {
+    const fetchMock = vi.fn().mockResolvedValue({ ok: true, status: 200 });
+    vi.stubGlobal('fetch', fetchMock);
+    const mod = await import('./mapStyles');
+    const [a, b] = await Promise.all([mod.localAssetsAvailable(), mod.localAssetsAvailable()]);
+    expect(a).toBe(true);
+    expect(b).toBe(true);
+    expect(fetchMock).toHaveBeenCalledTimes(1);
+  });
+
+  it('resolves false on network errors', async () => {
+    vi.stubGlobal('fetch', vi.fn().mockRejectedValue(new Error('offline')));
+    const mod = await import('./mapStyles');
+    await expect(mod.localAssetsAvailable()).resolves.toBe(false);
+  });
+});

lib/mapStyles.ts

@@ -38,6 +38,33 @@ export function styleUrl(id: string): string {
   return `/styles/${id}.json`;
 }
 
+// Remote fallback base for styles when the local asset pack is absent (fresh clone
+// without `npm run assets:download` / no volume mount). The raw OFM styles already
+// point glyphs/sprites at remote URLs, so they work as-is — only vector tiles were
+// ever remote. A future self-hosted tile pack plugs into the same availability
+// mechanism below (the manifest describes the whole local asset set).
+export const REMOTE_STYLE_BASE = 'https://tiles.openfreemap.org/styles';
+
+export function styleUrlFor(id: string, localAssetsAvailable: boolean): string {
+  return localAssetsAvailable ? `/styles/${id}.json` : `${REMOTE_STYLE_BASE}/${id}`;
+}
+
+// The manifest is written LAST by scripts/download-map-assets.mjs, so its presence
+// means the whole pack (styles + fonts + sprites — and any future asset class) is in
+// place. Probed once per page life via a module-level cached promise: any non-200 or
+// network error → false (fall back to remote styles).
+const MANIFEST_URL = '/map-assets-manifest.json';
+let assetsProbePromise: Promise<boolean> | null = null;
+
+export function localAssetsAvailable(): Promise<boolean> {
+  if (!assetsProbePromise) {
+    assetsProbePromise = fetch(MANIFEST_URL, { cache: 'no-store' })
+      .then((res) => res.ok)
+      .catch(() => false);
+  }
+  return assetsProbePromise;
+}
+
 type Source = Record<string, unknown>;
 
 // Takes a raw OFM style object and returns a new one with glyphs/sprite pointed at the