feat(offline): open entry details from the saved snapshot

Opening an entry while offline needed a request that could not be made. Read it
from the snapshot claimed by the signed-in account instead, re-checking
ownership after the read so a sign-in mid-read cannot surface another account's
data, and let controls marked data-offline-action stay usable in read-only mode.

src/lib/stores/offlineSync.ts

@@ -265,3 +265,27 @@ export function startOfflineSync(getUserId: () => string | null): () => void {
 		window.removeEventListener('online', schedule);
 	};
 }
+
+/** Read details only from the snapshot currently claimed by this account. */
+export async function readOfflineEntry(userId: string, pokedexId: string, entryId: string) {
+	if (typeof window === 'undefined' || !('caches' in window)) return null;
+	const meta = (await readOfflineMeta()) as (OfflineMeta & { dataCache?: string }) | null;
+	if (
+		meta?.userId !== userId ||
+		meta.format !== OFFLINE_META_FORMAT ||
+		!meta.dataCache?.startsWith(`${OFFLINE_CACHE_PREFIX}data-v1-${userId}-`)
+	)
+		return null;
+	const response = await (
+		await caches.open(meta.dataCache)
+	).match(`/__offline/snapshot/${encodeURIComponent(userId)}`);
+	const snapshot = (await response?.json()) as OfflineSnapshot | undefined;
+	const current = await readOfflineMeta();
+	if (current?.userId !== userId || snapshot?.userId !== userId || snapshot.version !== 1)
+		return null;
+	return (
+		snapshot.pokedexes
+			.find((dex) => dex.pokedex._id === pokedexId)
+			?.entries.find((row) => row.pokedexEntry._id === entryId) ?? null
+	);
+}

src/routes/+layout.svelte

@@ -52,6 +52,7 @@
 			if (navigator.onLine) return;
 			const target = event.target instanceof Element ? event.target : null;
 			if (!target?.closest('button, input, textarea, select, form')) return;
+			if (target.closest('[data-offline-action]')) return;
 			event.preventDefault();
 			event.stopImmediatePropagation();
 		};
@@ -313,10 +314,10 @@
 </div>
 
 <style>
-	:global(.offline-readonly button),
-	:global(.offline-readonly input),
-	:global(.offline-readonly textarea),
-	:global(.offline-readonly select) {
+	:global(.offline-readonly button:not([data-offline-action])),
+	:global(.offline-readonly input:not([data-offline-action])),
+	:global(.offline-readonly textarea:not([data-offline-action])),
+	:global(.offline-readonly select:not([data-offline-action])) {
 		pointer-events: none;
 		opacity: 0.65;
 	}

tests/unit/offlineEntry.test.ts

@@ -0,0 +1,58 @@
+import { afterEach, describe, expect, it, vi } from 'vitest';
+vi.mock('$env/static/public', () => ({ PUBLIC_USE_LOCAL_POKEMON_SPRITE_FOLDER: 'true' }));
+import { readOfflineEntry } from '$lib/stores/offlineSync';
+
+describe('offline detail snapshots', () => {
+	const row = {
+		pokedexEntry: { _id: '1', catchInformation: 'Full instructions' },
+		catchRecord: { personalNotes: 'Saved note' }
+	};
+	function snapshot(owner = 'owner', ageMs = 0, includeEntry = true) {
+		const meta = {
+			userId: owner,
+			format: 2,
+			dataCache: `livingdex-offline-data-v1-${owner}-copy`,
+			generatedAt: new Date(Date.now() - ageMs).toISOString()
+		};
+		const cache = {
+			keys: async () => ['livingdex-offline-meta-v1', meta.dataCache],
+			open: async (name: string) => ({
+				match: async () =>
+					new Response(
+						JSON.stringify(
+							name === 'livingdex-offline-meta-v1'
+								? meta
+								: {
+										userId: owner,
+										version: 1,
+										pokedexes: [{ pokedex: { _id: 'dex' }, entries: includeEntry ? [row] : [] }]
+									}
+						)
+					)
+			})
+		};
+		vi.stubGlobal('window', { caches: cache });
+		vi.stubGlobal('caches', cache);
+	}
+	afterEach(() => vi.unstubAllGlobals());
+	it.each([0, 60 * 60 * 1000])(
+		'uses a matching full snapshot offline even when %i ms old',
+		async (age) => {
+			snapshot('owner', age);
+			expect(await readOfflineEntry('owner', 'dex', '1')).toEqual(row);
+		}
+	);
+	it('never reads another account snapshot', async () => {
+		snapshot('other');
+		expect(await readOfflineEntry('owner', 'dex', '1')).toBeNull();
+	});
+	it('reports missing entries and dexes without fabricating details', async () => {
+		snapshot('owner', 0, false);
+		expect(await readOfflineEntry('owner', 'dex', '1')).toBeNull();
+		expect(await readOfflineEntry('owner', 'missing', '1')).toBeNull();
+	});
+	it('works without Cache Storage', async () => {
+		vi.stubGlobal('window', {});
+		expect(await readOfflineEntry('owner', 'dex', '1')).toBeNull();
+	});
+});