fix(stats): address CodeRabbit review on PR #50

- Guard episode deletion against double-submit with an isDeletingRef +
  setIsDeleting pair threaded through buildDeleteEpisodeHandler, and
  disable the MediaHeader delete button while a request is in flight.
- Restore MediaHeader title truncation by adding min-w-0 flex-1 to the
  h2 so long titles shrink instead of pushing the delete button away.
- Normalize the headword in FrequencyRankTable before comparing it to
  the (hiragana-normalized) reading so katakana-only entries like カレー
  no longer render a redundant 【かれー】. Test strengthened to reject
  any bracketed reading, not just the literal.
- Rewrite confirmBucketDelete copy to include the "and all associated
  data" warning and handle singular/plural cleanly.
- Run Prettier across the stats files CI was complaining about
  (EpisodeDetail, WatchTimeChart, SessionsTab + test, FrequencyRankTable
  + test, session-grouping test) to clear the format:check:stats gate.

stats/src/components/anime/EpisodeDetail.tsx

@@ -184,7 +184,8 @@ export function EpisodeDetail({ videoId, onSessionDeleted }: EpisodeDetailProps)
           </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)
+              {hiddenCardCount} {hiddenCardCount === 1 ? 'card' : 'cards'} hidden (deleted from
+              Anki)
             </div>
           )}
         </div>

stats/src/components/library/MediaDetailView.tsx

@@ -1,4 +1,4 @@
-import { useEffect, useState } from 'react';
+import { useEffect, useRef, useState } from 'react';
 import { useMediaDetail } from '../../hooks/useMediaDetail';
 import { apiClient } from '../../lib/api-client';
 import { confirmSessionDelete, confirmEpisodeDelete } from '../../lib/delete-confirm';
@@ -14,17 +14,31 @@ interface DeleteEpisodeHandlerOptions {
   confirmFn: (title: string) => boolean;
   onBack: () => void;
   setDeleteError: (msg: string | null) => void;
+  /**
+   * Ref used to guard against reentrant delete calls synchronously. When set,
+   * a subsequent invocation while the previous request is still pending is
+   * ignored so clicks during the await window can't trigger duplicate deletes.
+   */
+  isDeletingRef?: { current: boolean };
+  /** Optional React state setter so the UI can reflect the pending state. */
+  setIsDeleting?: (value: boolean) => void;
 }
 
 export function buildDeleteEpisodeHandler(opts: DeleteEpisodeHandlerOptions): () => Promise<void> {
   return async () => {
+    if (opts.isDeletingRef?.current) return;
     if (!opts.confirmFn(opts.title)) return;
+    if (opts.isDeletingRef) opts.isDeletingRef.current = true;
+    opts.setIsDeleting?.(true);
     opts.setDeleteError(null);
     try {
       await opts.apiClient.deleteVideo(opts.videoId);
       opts.onBack();
     } catch (err) {
       opts.setDeleteError(err instanceof Error ? err.message : 'Failed to delete episode.');
+    } finally {
+      if (opts.isDeletingRef) opts.isDeletingRef.current = false;
+      opts.setIsDeleting?.(false);
     }
   };
 }
@@ -57,6 +71,8 @@ export function MediaDetailView({
   const [localSessions, setLocalSessions] = useState<SessionSummary[] | null>(null);
   const [deleteError, setDeleteError] = useState<string | null>(null);
   const [deletingSessionId, setDeletingSessionId] = useState<number | null>(null);
+  const [isDeletingEpisode, setIsDeletingEpisode] = useState(false);
+  const isDeletingEpisodeRef = useRef(false);
 
   useEffect(() => {
     setLocalSessions(data?.sessions ?? null);
@@ -108,6 +124,8 @@ export function MediaDetailView({
     confirmFn: confirmEpisodeDelete,
     onBack,
     setDeleteError,
+    isDeletingRef: isDeletingEpisodeRef,
+    setIsDeleting: setIsDeletingEpisode,
   });
 
   return (
@@ -130,7 +148,11 @@ export function MediaDetailView({
           </button>
         ) : null}
       </div>
-      <MediaHeader detail={detail} onDeleteEpisode={handleDeleteEpisode} />
+      <MediaHeader
+        detail={detail}
+        onDeleteEpisode={handleDeleteEpisode}
+        isDeletingEpisode={isDeletingEpisode}
+      />
       {deleteError ? <div className="text-sm text-ctp-red">{deleteError}</div> : null}
       <MediaSessionList
         sessions={sessions}

stats/src/components/library/MediaHeader.tsx

@@ -13,12 +13,14 @@ interface MediaHeaderProps {
     knownWordCount: number;
   } | null;
   onDeleteEpisode?: () => void;
+  isDeletingEpisode?: boolean;
 }
 
 export function MediaHeader({
   detail,
   initialKnownWordsSummary = null,
   onDeleteEpisode,
+  isDeletingEpisode = false,
 }: MediaHeaderProps) {
   const knownTokenRate =
     detail.totalLookupCount > 0 ? detail.totalLookupHits / detail.totalLookupCount : null;
@@ -56,14 +58,17 @@ export function MediaHeader({
       />
       <div className="flex-1 min-w-0">
         <div className="flex items-start justify-between gap-2">
-          <h2 className="text-lg font-bold text-ctp-text truncate">{detail.canonicalTitle}</h2>
+          <h2 className="min-w-0 flex-1 text-lg font-bold text-ctp-text truncate">
+            {detail.canonicalTitle}
+          </h2>
           {onDeleteEpisode != null ? (
             <button
               type="button"
               onClick={onDeleteEpisode}
-              className="shrink-0 text-xs text-ctp-red hover:opacity-75 transition-opacity"
+              disabled={isDeletingEpisode}
+              className="shrink-0 text-xs text-ctp-red hover:opacity-75 transition-opacity disabled:opacity-50 disabled:cursor-not-allowed"
             >
-              Delete Episode
+              {isDeletingEpisode ? 'Deleting...' : 'Delete Episode'}
             </button>
           ) : null}
         </div>

stats/src/components/overview/WatchTimeChart.tsx

@@ -1,13 +1,5 @@
 import { useState } from 'react';
-import {
-  BarChart,
-  Bar,
-  CartesianGrid,
-  XAxis,
-  YAxis,
-  Tooltip,
-  ResponsiveContainer,
-} from 'recharts';
+import { BarChart, Bar, CartesianGrid, XAxis, YAxis, Tooltip, ResponsiveContainer } from 'recharts';
 import { epochDayToDate } from '../../lib/formatters';
 import { CHART_DEFAULTS, CHART_THEME, TOOLTIP_CONTENT_STYLE } from '../../lib/chart-theme';
 import type { DailyRollup } from '../../types/stats';

stats/src/components/sessions/SessionsTab.test.tsx

@@ -75,10 +75,7 @@ test('buildBucketDeleteHandler is a no-op when confirm returns false', async ()
   let deleteCalled = false;
   let successCalled = false;
 
-  const bucket = makeBucket([
-    makeSession({ sessionId: 1 }),
-    makeSession({ sessionId: 2 }),
-  ]);
+  const bucket = makeBucket([makeSession({ sessionId: 1 }), makeSession({ sessionId: 2 })]);
 
   const handler = buildBucketDeleteHandler({
     bucket,
@@ -104,10 +101,7 @@ test('buildBucketDeleteHandler reports errors via onError without calling onSucc
   let errorMessage: string | null = null;
   let successCalled = false;
 
-  const bucket = makeBucket([
-    makeSession({ sessionId: 1 }),
-    makeSession({ sessionId: 2 }),
-  ]);
+  const bucket = makeBucket([makeSession({ sessionId: 1 }), makeSession({ sessionId: 2 })]);
 
   const handler = buildBucketDeleteHandler({
     bucket,

stats/src/components/sessions/SessionsTab.tsx

@@ -269,9 +269,7 @@ export function SessionsTab({
                                 isExpanded={expandedId === s.sessionId}
                                 detailsId={detailsId}
                                 onToggle={() =>
-                                  setExpandedId(
-                                    expandedId === s.sessionId ? null : s.sessionId,
-                                  )
+                                  setExpandedId(expandedId === s.sessionId ? null : s.sessionId)
                                 }
                                 onDelete={() => void handleDeleteSession(s)}
                                 deleteDisabled={deletingSessionId === s.sessionId}

stats/src/components/vocabulary/FrequencyRankTable.test.tsx

@@ -36,5 +36,8 @@ test('omits reading when reading equals headword', () => {
     <FrequencyRankTable words={[entry]} knownWords={new Set()} />,
   );
   assert.ok(markup.includes('カレー'), 'should include the headword');
-  assert.ok(!markup.includes('【カレー】'), 'should not render reading in brackets when equal to headword');
+  assert.ok(
+    !markup.includes('【'),
+    'should not render any bracketed reading when equal to headword',
+  );
 });

stats/src/components/vocabulary/FrequencyRankTable.tsx

@@ -131,11 +131,13 @@ export function FrequencyRankTable({ words, knownWords, onSelectWord }: Frequenc
                       <span className="text-ctp-text font-medium">{w.headword}</span>
                       {(() => {
                         const reading = fullReading(w.headword, w.reading);
-                        if (!reading || reading === w.headword) return null;
+                        // `fullReading` normalizes katakana to hiragana, so we normalize the
+                        // headword the same way before comparing — otherwise katakana-only
+                        // entries like `カレー` would render `【かれー】`.
+                        const normalizedHeadword = fullReading(w.headword, w.headword);
+                        if (!reading || reading === normalizedHeadword) return null;
                         return (
-                          <span className="text-ctp-subtext0 text-xs ml-1.5">
-                            【{reading}】
-                          </span>
+                          <span className="text-ctp-subtext0 text-xs ml-1.5">【{reading}】</span>
                         );
                       })()}
                     </td>

stats/src/lib/delete-confirm.test.ts

@@ -65,16 +65,15 @@ test('confirmBucketDelete asks about merging multiple sessions of the same episo
 
   try {
     assert.equal(confirmBucketDelete('My Episode', 3), true);
-    assert.equal(calls.length, 1);
-    assert.match(calls[0]!, /3/);
-    assert.match(calls[0]!, /My Episode/);
-    assert.match(calls[0]!, /sessions/);
+    assert.deepEqual(calls, [
+      'Delete all 3 sessions of "My Episode" from this day and all associated data?',
+    ]);
   } finally {
     globalThis.confirm = originalConfirm;
   }
 });
 
-test('confirmBucketDelete uses singular for one session', () => {
+test('confirmBucketDelete uses a clean singular form for one session', () => {
   const calls: string[] = [];
   const originalConfirm = globalThis.confirm;
   globalThis.confirm = ((message?: string) => {
@@ -84,7 +83,9 @@ test('confirmBucketDelete uses singular for one session', () => {
 
   try {
     assert.equal(confirmBucketDelete('Solo Episode', 1), false);
-    assert.match(calls[0]!, /1 session of/);
+    assert.deepEqual(calls, [
+      'Delete this session of "Solo Episode" from this day and all associated data?',
+    ]);
   } finally {
     globalThis.confirm = originalConfirm;
   }

stats/src/lib/delete-confirm.ts

@@ -19,7 +19,12 @@ export function confirmEpisodeDelete(title: string): boolean {
 }
 
 export function confirmBucketDelete(title: string, count: number): boolean {
+  if (count === 1) {
+    return globalThis.confirm(
+      `Delete this session of "${title}" from this day and all associated data?`,
+    );
+  }
   return globalThis.confirm(
-    `Delete all ${count} session${count === 1 ? '' : 's'} of "${title}" from this day?`,
+    `Delete all ${count} sessions of "${title}" from this day and all associated data?`,
   );
 }

stats/src/lib/session-grouping.test.ts

@@ -32,8 +32,20 @@ test('empty input returns empty array', () => {
 
 test('two unique videoIds produce 2 singleton buckets', () => {
   const sessions = [
-    makeSession({ sessionId: 1, videoId: 10, startedAtMs: 1000, activeWatchedMs: 100, cardsMined: 2 }),
-    makeSession({ sessionId: 2, videoId: 20, startedAtMs: 2000, activeWatchedMs: 200, cardsMined: 3 }),
+    makeSession({
+      sessionId: 1,
+      videoId: 10,
+      startedAtMs: 1000,
+      activeWatchedMs: 100,
+      cardsMined: 2,
+    }),
+    makeSession({
+      sessionId: 2,
+      videoId: 20,
+      startedAtMs: 2000,
+      activeWatchedMs: 200,
+      cardsMined: 3,
+    }),
   ];
   const buckets = groupSessionsByVideo(sessions);
   assert.equal(buckets.length, 2);
@@ -45,8 +57,20 @@ test('two unique videoIds produce 2 singleton buckets', () => {
 });
 
 test('two sessions sharing a videoId collapse into 1 bucket with summed totals and most-recent representative', () => {
-  const older = makeSession({ sessionId: 1, videoId: 42, startedAtMs: 1000, activeWatchedMs: 300, cardsMined: 5 });
-  const newer = makeSession({ sessionId: 2, videoId: 42, startedAtMs: 9000, activeWatchedMs: 500, cardsMined: 7 });
+  const older = makeSession({
+    sessionId: 1,
+    videoId: 42,
+    startedAtMs: 1000,
+    activeWatchedMs: 300,
+    cardsMined: 5,
+  });
+  const newer = makeSession({
+    sessionId: 2,
+    videoId: 42,
+    startedAtMs: 9000,
+    activeWatchedMs: 500,
+    cardsMined: 7,
+  });
   const buckets = groupSessionsByVideo([older, newer]);
   assert.equal(buckets.length, 1);
   const [bucket] = buckets;