feat(stats): speed up session maintenance and improve stats UI (#111)

stats/src/lib/cover-images.test.ts

@@ -0,0 +1,52 @@
+import assert from 'node:assert/strict';
+import test from 'node:test';
+import {
+  buildCoverImageRequestKey,
+  collectSessionCoverRequests,
+  getCoverImageKey,
+} from './cover-images';
+import type { SessionSummary } from '../types/stats';
+
+function makeSession(overrides: Partial<SessionSummary> & { sessionId: number }): SessionSummary {
+  const { sessionId, ...rest } = overrides;
+  return {
+    sessionId,
+    canonicalTitle: null,
+    videoId: null,
+    animeId: null,
+    animeTitle: null,
+    startedAtMs: 0,
+    endedAtMs: null,
+    totalWatchedMs: 0,
+    activeWatchedMs: 0,
+    linesSeen: 0,
+    tokensSeen: 0,
+    cardsMined: 0,
+    lookupCount: 0,
+    lookupHits: 0,
+    yomitanLookupCount: 0,
+    knownWordsSeen: 0,
+    knownWordRate: 0,
+    ...rest,
+  };
+}
+
+test('collectSessionCoverRequests dedupes anime ids and only requests media for ungrouped sessions', () => {
+  const requests = collectSessionCoverRequests([
+    makeSession({ sessionId: 1, animeId: 10, videoId: 100 }),
+    makeSession({ sessionId: 2, animeId: 10, videoId: 101 }),
+    makeSession({ sessionId: 3, animeId: null, videoId: 200 }),
+    makeSession({ sessionId: 4, animeId: null, videoId: 200 }),
+  ]);
+
+  assert.deepEqual(requests, { animeIds: [10], videoIds: [200] });
+});
+
+test('getCoverImageKey separates anime and media ids', () => {
+  assert.equal(getCoverImageKey('anime', 1), 'anime:1');
+  assert.equal(getCoverImageKey('media', 1), 'media:1');
+});
+
+test('buildCoverImageRequestKey changes when callers force a cover refresh', () => {
+  assert.notEqual(buildCoverImageRequestKey([10], [], 0), buildCoverImageRequestKey([10], [], 1));
+});