feat(stats): add v1 immersion stats dashboard (#19)

stats/src/hooks/useKanjiDetail.ts

@@ -0,0 +1,42 @@
+import { useState, useEffect } from 'react';
+import { getStatsClient } from './useStatsApi';
+import type { KanjiDetailData } from '../types/stats';
+
+export function useKanjiDetail(kanjiId: number | null) {
+  const [data, setData] = useState<KanjiDetailData | null>(null);
+  const [loading, setLoading] = useState(false);
+  const [error, setError] = useState<string | null>(null);
+
+  useEffect(() => {
+    let cancelled = false;
+    if (kanjiId === null) {
+      setData(null);
+      setLoading(false);
+      setError(null);
+      return () => {
+        cancelled = true;
+      };
+    }
+    setLoading(true);
+    setError(null);
+    getStatsClient()
+      .getKanjiDetail(kanjiId)
+      .then((next) => {
+        if (cancelled) return;
+        setData(next);
+      })
+      .catch((err: Error) => {
+        if (cancelled) return;
+        setError(err.message);
+      })
+      .finally(() => {
+        if (cancelled) return;
+        setLoading(false);
+      });
+    return () => {
+      cancelled = true;
+    };
+  }, [kanjiId]);
+
+  return { data, loading, error };
+}