import 'dart:collection';

import 'package:swagger_generator_flutter/utils/string_utils.dart';

/// 缓存管理器
/// 提供简单的内存缓存功能
class CacheManager {
  CacheManager();
  static const int _maxMemoryItems = 100;

  // 内存缓存
  final Map<String, _CacheEntry> _memoryCache = {};
  final Queue<String> _accessOrder = Queue<String>();

  /// 从缓存获取数据
  T? get<T>(String key) {
    final entry = _memoryCache[key];
    if (entry != null && !entry.isExpired) {
      _updateAccessOrder(key);
      return entry.value as T?;
    }
    return null;
  }

  /// 存储数据到缓存
  void put<T>(String key, T value, [Duration? ttl]) {
    ttl ??= const Duration(hours: 1);

    // 检查内存缓存大小限制
    if (_memoryCache.length >= _maxMemoryItems) {
      _evictOldestItem();
    }

    final entry = _CacheEntry(
      value: value,
      expiresAt: DateTime.now().add(ttl),
    );

    _memoryCache[key] = entry;
    _updateAccessOrder(key);
  }

  /// 检查是否存在缓存
  bool has(String key) {
    final entry = _memoryCache[key];
    return entry != null && !entry.isExpired;
  }

  /// 删除缓存项
  void remove(String key) {
    _memoryCache.remove(key);
    _accessOrder.removeWhere((k) => k == key);
  }

  /// 清空缓存
  void clear() {
    _memoryCache.clear();
    _accessOrder.clear();
  }

  /// 获取缓存统计信息
  CacheStats getStats() {
    return CacheStats(
      memoryItems: _memoryCache.length,
      diskItems: 0,
      hitRate: 0,
      totalSize: 0,
    );
  }

  /// 更新访问顺序
  void _updateAccessOrder(String key) {
    _accessOrder
      ..removeWhere((k) => k == key)
      ..addLast(key);
  }

  /// 驱逐最旧的项
  void _evictOldestItem() {
    if (_accessOrder.isNotEmpty) {
      final oldestKey = _accessOrder.removeFirst();
      _memoryCache.remove(oldestKey);
    }
  }
}

/// 缓存条目
class _CacheEntry {
  _CacheEntry({
    required this.value,
    required this.expiresAt,
  });
  final dynamic value;
  final DateTime expiresAt;

  bool get isExpired => DateTime.now().isAfter(expiresAt);
}

/// 缓存统计信息
class CacheStats {
  const CacheStats({
    required this.memoryItems,
    required this.diskItems,
    required this.hitRate,
    required this.totalSize,
  });
  final int memoryItems;
  final int diskItems;
  final double hitRate;
  final int totalSize;

  @override
  String toString() {
    return 'CacheStats{'
        'memoryItems: $memoryItems, '
        'diskItems: $diskItems, '
        'hitRate: ${(hitRate * 100).toStringAsFixed(1)}%, '
        'totalSize: ${StringUtils.formatBytes(totalSize)}'
        '}';
  }

  // 已移动到 StringUtils.formatBytes
}