feat(download): auto-categorize downloads into folders by file extension (#1572)

ui/flutter/test/app/application/downloader_config_init_test.dart

@@ -0,0 +1,120 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:gopeed/api/model/downloader_config.dart';
+import 'package:gopeed/app/application/downloader_config_init.dart';
+import 'package:path/path.dart' as path;
+
+void main() {
+  DownloaderConfig configWith({List<DownloadCategory> categories = const [], String downloadDir = ''}) {
+    final config = DownloaderConfig(downloadDir: downloadDir)..categories = List.of(categories);
+    return config;
+  }
+
+  group('loadDownloaderConfig', () {
+    test('persists when the load succeeded and init changed the config', () async {
+      var saved = 0;
+      final config = await loadDownloaderConfig(
+        load: () async => configWith(),
+        save: (_) async => saved++,
+        defaultDownloadDir: () async => '/downloads',
+      );
+      expect(saved, 1);
+      expect(config.categories, hasLength(4));
+    });
+
+    test('does not persist when the initial load failed', () async {
+      var saved = 0;
+      final config = await loadDownloaderConfig(
+        load: () async => throw StateError('backend unavailable'),
+        save: (_) async => saved++,
+        defaultDownloadDir: () async => '/downloads',
+      );
+      expect(saved, 0);
+      // The in-memory fallback still gets usable defaults.
+      expect(config.downloadDir, '/downloads');
+      expect(config.categories, hasLength(4));
+    });
+
+    test('skips persist when init changed nothing', () async {
+      var saved = 0;
+      await loadDownloaderConfig(
+        load: () async => configWith(
+          categories: [
+            DownloadCategory(name: 'Mine', path: '/downloads/Mine', extensions: const ['zip']),
+          ],
+          downloadDir: '/downloads',
+        ),
+        save: (_) async => saved++,
+        defaultDownloadDir: () async => '/other',
+      );
+      expect(saved, 0);
+    });
+
+    test('persists the default download dir when it is missing', () async {
+      var saved = 0;
+      final config = await loadDownloaderConfig(
+        load: () async => configWith(
+          categories: [
+            DownloadCategory(name: 'Mine', path: '/downloads/Mine', extensions: const ['zip']),
+          ],
+        ),
+        save: (_) async => saved++,
+        defaultDownloadDir: () async => '/downloads',
+      );
+      expect(saved, 1);
+      expect(config.downloadDir, '/downloads');
+    });
+  });
+
+  group('initDownloaderConfig', () {
+    test('seeds built-in categories with default extensions when empty', () async {
+      final config = configWith();
+      final changed = await initDownloaderConfig(config, defaultDownloadDir: () async => '/downloads');
+
+      expect(changed, isTrue);
+      expect(config.categories.map((c) => c.nameKey).toList(), [
+        'categoryMusic',
+        'categoryVideo',
+        'categoryDocument',
+        'categoryProgram',
+      ]);
+      for (final category in config.categories) {
+        expect(category.isBuiltIn, isTrue);
+        expect(category.path, path.join('/downloads', category.nameKey!.replaceFirst('category', '')));
+        expect(category.extensions, kDefaultCategoryExtensions[category.nameKey]);
+      }
+    });
+
+    test('keeps existing categories untouched', () async {
+      final existing = DownloadCategory(name: 'Mine', path: '/downloads/Mine', extensions: const ['zip']);
+      final config = configWith(categories: [existing], downloadDir: '/downloads');
+      final changed = await initDownloaderConfig(config, defaultDownloadDir: () async => '/other');
+
+      expect(changed, isFalse);
+      expect(config.categories, hasLength(1));
+      expect(config.categories.single, same(existing));
+    });
+
+    test('reports a change when only the default download dir was filled', () async {
+      final config = configWith(
+        categories: [
+          DownloadCategory(name: 'Mine', path: '/downloads/Mine', extensions: const ['zip']),
+        ],
+      );
+      final changed = await initDownloaderConfig(config, defaultDownloadDir: () async => '/downloads');
+
+      expect(changed, isTrue);
+      expect(config.downloadDir, '/downloads');
+    });
+
+    test('leaves the config untouched when the default download dir is unknown', () async {
+      final config = configWith();
+      final changed = await initDownloaderConfig(config, defaultDownloadDir: () async => '');
+
+      // A relative or unknown directory would make the backend write into its
+      // own working directory, so it is left for the backend to resolve.
+      expect(changed, isFalse);
+      expect(config.downloadDir, isEmpty);
+      expect(config.categories, isEmpty);
+    });
+  });
+}