fix(stats): hide cards deleted from Anki in episode detail

Filters out noteIds whose Anki note no longer exists, drops card events
that have no surviving noteIds, and shows a muted footer counting hidden
cards. Loading-state guard (noteInfosLoaded) prevents premature filtering
before ankiNotesInfo resolves.

stats/src/components/anime/EpisodeDetail.test.tsx

@@ -0,0 +1,60 @@
+import assert from 'node:assert/strict';
+import test from 'node:test';
+import { filterCardEvents } from './EpisodeDetail';
+import type { EpisodeCardEvent } from '../../types/stats';
+
+function makeEvent(over: Partial<EpisodeCardEvent> & { eventId: number }): EpisodeCardEvent {
+  return {
+    sessionId: 1,
+    tsMs: 0,
+    cardsDelta: 1,
+    noteIds: [],
+    ...over,
+  };
+}
+
+test('filterCardEvents: before load, returns all events unchanged', () => {
+  const ev1 = makeEvent({ eventId: 1, noteIds: [101] });
+  const ev2 = makeEvent({ eventId: 2, noteIds: [102] });
+  const noteInfos = new Map(); // empty — simulates pre-load state
+  const result = filterCardEvents([ev1, ev2], noteInfos, /* noteInfosLoaded */ false);
+  assert.equal(result.length, 2, 'should return both events before load');
+  assert.deepEqual(result[0]?.noteIds, [101]);
+  assert.deepEqual(result[1]?.noteIds, [102]);
+});
+
+test('filterCardEvents: after load, drops noteIds not in noteInfos', () => {
+  const ev1 = makeEvent({ eventId: 1, noteIds: [101] }); // survives
+  const ev2 = makeEvent({ eventId: 2, noteIds: [102] }); // deleted from Anki
+  const noteInfos = new Map([[101, { noteId: 101, expression: '食べる' }]]);
+  const result = filterCardEvents([ev1, ev2], noteInfos, /* noteInfosLoaded */ true);
+  assert.equal(result.length, 1, 'should drop event whose noteId was deleted from Anki');
+  assert.equal(result[0]?.eventId, 1);
+  assert.deepEqual(result[0]?.noteIds, [101]);
+});
+
+test('filterCardEvents: after load, legacy rollup events (empty noteIds, positive cardsDelta) are kept', () => {
+  const rollup = makeEvent({ eventId: 3, noteIds: [], cardsDelta: 5 });
+  const noteInfos = new Map<number, { noteId: number; expression: string }>();
+  const result = filterCardEvents([rollup], noteInfos, true);
+  assert.equal(result.length, 1, 'legacy rollup event should survive filtering');
+  assert.equal(result[0]?.cardsDelta, 5);
+});
+
+test('filterCardEvents: after load, event with multiple noteIds keeps surviving ones', () => {
+  const ev = makeEvent({ eventId: 4, noteIds: [201, 202, 203] });
+  const noteInfos = new Map([
+    [201, { noteId: 201, expression: 'A' }],
+    [203, { noteId: 203, expression: 'C' }],
+  ]);
+  const result = filterCardEvents([ev], noteInfos, true);
+  assert.equal(result.length, 1, 'event with surviving noteIds should be kept');
+  assert.deepEqual(result[0]?.noteIds, [201, 203], 'only surviving noteIds should remain');
+});
+
+test('filterCardEvents: after load, event where all noteIds deleted is dropped', () => {
+  const ev = makeEvent({ eventId: 5, noteIds: [301, 302] });
+  const noteInfos = new Map<number, { noteId: number; expression: string }>();
+  const result = filterCardEvents([ev], noteInfos, true);
+  assert.equal(result.length, 0, 'event with all noteIds deleted should be dropped');
+});

stats/src/components/anime/EpisodeDetail.tsx

@@ -16,10 +16,32 @@ interface NoteInfo {
   expression: string;
 }
 
+export function filterCardEvents(
+  cardEvents: EpisodeDetailData['cardEvents'],
+  noteInfos: Map<number, NoteInfo>,
+  noteInfosLoaded: boolean,
+): EpisodeDetailData['cardEvents'] {
+  if (!noteInfosLoaded) return cardEvents;
+  return cardEvents
+    .map((ev) => {
+      // Legacy rollup events: no noteIds, just a cardsDelta count — keep as-is.
+      if (ev.noteIds.length === 0) return ev;
+      const survivingNoteIds = ev.noteIds.filter((id) => noteInfos.has(id));
+      return { ...ev, noteIds: survivingNoteIds };
+    })
+    .filter((ev, i) => {
+      // If the event originally had noteIds, only keep it if some survived.
+      if ((cardEvents[i]?.noteIds.length ?? 0) > 0) return ev.noteIds.length > 0;
+      // Legacy rollup event (originally no noteIds): keep if it has a positive delta.
+      return ev.cardsDelta > 0;
+    });
+}
+
 export function EpisodeDetail({ videoId, onSessionDeleted }: EpisodeDetailProps) {
   const [data, setData] = useState<EpisodeDetailData | null>(null);
   const [loading, setLoading] = useState(true);
   const [noteInfos, setNoteInfos] = useState<Map<number, NoteInfo>>(new Map());
+  const [noteInfosLoaded, setNoteInfosLoaded] = useState(false);
 
   useEffect(() => {
     let cancelled = false;
@@ -41,8 +63,14 @@ export function EpisodeDetail({ videoId, onSessionDeleted }: EpisodeDetailProps)
                 map.set(note.noteId, { noteId: note.noteId, expression: expr });
               }
               setNoteInfos(map);
+              setNoteInfosLoaded(true);
             })
-            .catch((err) => console.warn('Failed to fetch Anki note info:', err));
+            .catch((err) => {
+              console.warn('Failed to fetch Anki note info:', err);
+              if (!cancelled) setNoteInfosLoaded(true);
+            });
+        } else {
+          if (!cancelled) setNoteInfosLoaded(true);
         }
       })
       .catch(() => {
@@ -72,6 +100,16 @@ export function EpisodeDetail({ videoId, onSessionDeleted }: EpisodeDetailProps)
 
   const { sessions, cardEvents } = data;
 
+  const filteredCardEvents = filterCardEvents(cardEvents, noteInfos, noteInfosLoaded);
+
+  const hiddenCardCount = noteInfosLoaded
+    ? cardEvents.reduce((sum, ev) => {
+        if (ev.noteIds.length === 0) return sum;
+        const surviving = ev.noteIds.filter((id) => noteInfos.has(id));
+        return sum + (ev.noteIds.length - surviving.length);
+      }, 0)
+    : 0;
+
   return (
     <div className="bg-ctp-mantle border border-ctp-surface1 rounded-lg">
       {sessions.length > 0 && (
@@ -106,11 +144,11 @@ export function EpisodeDetail({ videoId, onSessionDeleted }: EpisodeDetailProps)
         </div>
       )}
 
-      {cardEvents.length > 0 && (
+      {filteredCardEvents.length > 0 && (
         <div className="p-3 border-b border-ctp-surface1">
           <h4 className="text-xs font-semibold text-ctp-subtext0 mb-2">Cards Mined</h4>
           <div className="space-y-1.5">
-            {cardEvents.map((ev) => (
+            {filteredCardEvents.map((ev) => (
               <div key={ev.eventId} className="flex items-center gap-2 text-xs">
                 <span className="text-ctp-overlay2 shrink-0">{formatRelativeDate(ev.tsMs)}</span>
                 {ev.noteIds.length > 0 ? (
@@ -144,6 +182,11 @@ export function EpisodeDetail({ videoId, onSessionDeleted }: EpisodeDetailProps)
               </div>
             ))}
           </div>
+          {hiddenCardCount > 0 && (
+            <div className="px-3 pb-3 -mt-1 text-[10px] text-ctp-overlay2 italic">
+              {hiddenCardCount} {hiddenCardCount === 1 ? 'card' : 'cards'} hidden (deleted from Anki)
+            </div>
+          )}
         </div>
       )}