feat(cache): add SimpleCacheManager and cache formatted rates/amounts in exchange and currency services

2025-09-08 14:31:44 +09:00
parent eb6691ce6a
commit b034f60510
3 changed files with 164 additions and 9 deletions
--- a/lib/services/cache_manager.dart
+++ b/lib/services/cache_manager.dart
@@ -0,0 +1,97 @@
+class _CacheEntry<T> {
+  final T value;
+  final DateTime expiresAt;
+  final int size;
+
+  _CacheEntry(
+      {required this.value, required this.expiresAt, required this.size});
+
+  bool get isExpired => DateTime.now().isAfter(expiresAt);
+}
+
+/// 간단한 메모리 기반 캐시 매니저 (TTL/최대 개수/용량 제한)
+class SimpleCacheManager<T> {
+  final int maxEntries;
+  final int maxBytes;
+  final Duration ttl;
+
+  final Map<String, _CacheEntry<T>> _store = <String, _CacheEntry<T>>{};
+  int _currentBytes = 0;
+
+  // 간단한 메트릭
+  int _hits = 0;
+  int _misses = 0;
+  int _puts = 0;
+  int _evictions = 0;
+
+  SimpleCacheManager({
+    this.maxEntries = 128,
+    this.maxBytes = 1024 * 1024, // 1MB
+    this.ttl = const Duration(minutes: 30),
+  });
+
+  T? get(String key) {
+    final entry = _store.remove(key);
+    if (entry == null) return null;
+    if (entry.isExpired) {
+      _currentBytes -= entry.size;
+      _misses++;
+      return null;
+    }
+    // LRU 갱신: 재삽입으로 가장 최근으로 이동
+    _store[key] = entry;
+    _hits++;
+    return entry.value;
+  }
+
+  void set(String key, T value, {int size = 1, Duration? customTtl}) {
+    final expiresAt = DateTime.now().add(customTtl ?? ttl);
+    final existing = _store.remove(key);
+    if (existing != null) {
+      _currentBytes -= existing.size;
+    }
+    _store[key] = _CacheEntry(value: value, expiresAt: expiresAt, size: size);
+    _currentBytes += size;
+    _puts++;
+    _evictIfNeeded();
+  }
+
+  void invalidate(String key) {
+    final removed = _store.remove(key);
+    if (removed != null) {
+      _currentBytes -= removed.size;
+    }
+  }
+
+  void clear() {
+    _store.clear();
+    _currentBytes = 0;
+  }
+
+  void _evictIfNeeded() {
+    // 개수/용량 제한을 넘으면 오래된 것부터 제거
+    while (_store.length > maxEntries || _currentBytes > maxBytes) {
+      if (_store.isEmpty) break;
+      final firstKey = _store.keys.first;
+      final removed = _store.remove(firstKey);
+      if (removed != null) {
+        _currentBytes -= removed.size;
+        _evictions++;
+      }
+    }
+  }
+
+  Map<String, num> dumpMetrics() {
+    final totalGets = _hits + _misses;
+    final hitRate = totalGets == 0 ? 0 : _hits / totalGets;
+    return {
+      'entries': _store.length,
+      'bytes': _currentBytes,
+      'hits': _hits,
+      'misses': _misses,
+      'hitRate': hitRate,
+      'puts': _puts,
+      'evictions': _evictions,
+    };
+  }
+}