Initial Flutter booru app

lib/core/cache/cache_service.dart

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+import 'package:isar/isar.dart';
+
+import '../database/app_database.dart';
+import '../database/database_service.dart';
+import '../utils/result.dart';
+import '../../backend/models/post.dart';
+
+class CacheService {
+  CacheService(this._databaseService);
+
+  final DatabaseService _databaseService;
+
+  Future<Result<void>> cachePosts(
+    List<Post> posts, {
+    int? maxItems,
+  }) {
+    return _databaseService.safeWrite((isar) async {
+      await isar.cachedPostEntitys.putAll(
+        posts.map((post) => CachedPostEntity.fromModel(post)).toList(),
+      );
+      if (maxItems != null && maxItems > 0) {
+        await _evictOverflow(isar, maxItems);
+      }
+    });
+  }
+
+  Future<Result<List<Post>>> getCachedPosts({
+    Duration maxAge = const Duration(hours: 24),
+  }) {
+    return _databaseService.safeRead((isar) async {
+      final cutoff = DateTime.now().subtract(maxAge);
+      final entities = await isar.cachedPostEntitys
+          .filter()
+          .cachedAtGreaterThan(cutoff)
+          .findAll();
+      entities.sort((a, b) => b.cachedAt.compareTo(a.cachedAt));
+      return entities.map((entity) => entity.toModel()).toList();
+    });
+  }
+
+  Future<Result<void>> prune({
+    Duration? olderThan,
+    int? maxItems,
+  }) {
+    return _databaseService.safeWrite((isar) async {
+      if (olderThan != null) {
+        final cutoff = DateTime.now().subtract(olderThan);
+        await isar.cachedPostEntitys
+            .filter()
+            .cachedAtLessThan(cutoff)
+            .deleteAll();
+      }
+      if (maxItems != null && maxItems > 0) {
+        await _evictOverflow(isar, maxItems);
+      }
+    });
+  }
+
+  Future<Result<void>> clear() {
+    return _databaseService.safeWrite((isar) async {
+      await isar.cachedPostEntitys.clear();
+    });
+  }
+
+  Future<void> _evictOverflow(Isar isar, int maxItems) async {
+    final entities = await isar.cachedPostEntitys.where().findAll();
+    if (entities.length <= maxItems) return;
+    entities.sort((a, b) => b.cachedAt.compareTo(a.cachedAt));
+    final overflowIds =
+        entities.skip(maxItems).map((entity) => entity.isarId).toList();
+    await isar.cachedPostEntitys.deleteAll(overflowIds);
+  }
+}

lib/core/cache/image_cache_service.dart

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+import '../../backend/models/post.dart';
+
+class ImageCacheService {
+  String previewCacheKey(Post post) => 'preview:${post.providerId}:${post.id}';
+  String sampleCacheKey(Post post) => 'sample:${post.providerId}:${post.id}';
+  String fileCacheKey(Post post) => 'file:${post.providerId}:${post.id}';
+}