part of 'game_resource_manager.dart';

extension _GameResourceManagerCache on GameResourceManager {
  void _touch(_ImageResourceRecord record) {
    record.lastUsed = ++_accessCounter;
  }

  void _enforceImageBudget() {
    while (_isOverBudget()) {
      final victim = _leastRecentlyUsedEvictableImage();
      if (victim == null || !_removeImageRecord(victim)) {
        return;
      }
    }
  }

  bool _isOverBudget() {
    final maxBytes = _maxCacheBytes;
    final maxEntries = _maxCacheEntries;
    return (maxBytes != null && _cacheBytes > maxBytes) ||
        (maxEntries != null && _readyImageCount > maxEntries);
  }

  int get _readyImageCount => _images.values
      .where((record) => record.state == GameResourceState.ready)
      .length;

  String? _leastRecentlyUsedEvictableImage() {
    String? victimPath;
    _ImageResourceRecord? victim;
    for (final entry in _images.entries) {
      final record = entry.value;
      if (record.state != GameResourceState.ready || record.refCount > 0) {
        continue;
      }
      if (victim == null || record.lastUsed < victim.lastUsed) {
        victim = record;
        victimPath = entry.key;
      }
    }
    return victimPath;
  }

  void _releaseCachedImages() {
    _loadLimiter.clearPending();
    for (final path in _images.keys.toList(growable: false)) {
      _removeImageRecord(path);
    }
  }

  bool _removeImageRecord(String path) {
    final record = _images.remove(path);
    if (record == null) {
      return false;
    }
    record.state = GameResourceState.disposed;
    _cacheBytes -= record.estimatedBytes;
    if (_cacheBytes < 0) {
      _cacheBytes = 0;
    }
    record.image?.dispose();
    record.image = null;
    record.inflight = null;
    return true;
  }
}