refactor: manage local library in local tracks tab

This also refactors the list to use slivers instead. That's the
easiest way to have multiple scrolling lists here...

The console keeps getting spammed with some intermediate layout
error but I can't hold it long enough to figure out what's causing
it.

Signed-off-by: Blake Leonard <me@blakes.dev>

lib/components/library/user_local_tracks.dart

@@ -1,8 +1,11 @@
 import 'dart:io';
 
 import 'package:catcher_2/catcher_2.dart';
+import 'package:file_picker/file_picker.dart';
+import 'package:file_selector/file_selector.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
+import 'package:flutter_desktop_tools/flutter_desktop_tools.dart';
 import 'package:flutter_hooks/flutter_hooks.dart';
 import 'package:collection/collection.dart';
 import 'package:fuzzywuzzy/fuzzywuzzy.dart';
@@ -59,29 +62,29 @@ enum SortBy {
   album,
 }
 
-final localTracksProvider = FutureProvider<List<LocalTrack>>((ref) async {
+final localTracksProvider = FutureProvider<Map<String, List<LocalTrack>>>((ref) async {
   try {
-    if (kIsWeb) return [];
+    if (kIsWeb) return {};
+    final Map<String, List<LocalTrack>> tracks = {};
+
     final downloadLocation = ref.watch(
       userPreferencesProvider.select((s) => s.downloadLocation),
     );
-    if (downloadLocation.isEmpty) return [];
     final downloadDir = Directory(downloadLocation);
     if (!await downloadDir.exists()) {
       await downloadDir.create(recursive: true);
-      return [];
     }
-    final entities = downloadDir.listSync(recursive: true);
-
     final localLibraryLocations = ref.watch(
       userPreferencesProvider.select((s) => s.localLibraryLocation),
     );
-    for (final location in localLibraryLocations) {
+
+    for (var location in [downloadLocation, ...localLibraryLocations]) {
+      if (location.isEmpty) continue;
+      final entities = <FileSystemEntity>[];
       final dir = Directory(location);
       if (await Directory(location).exists()) {
         entities.addAll(Directory(location).listSync(recursive: true));
       }
-    }
 
       final filesWithMetadata = (await Future.wait(
         entities.map((e) => File(e.path)).where((file) {
@@ -120,7 +123,8 @@ final localTracksProvider = FutureProvider<List<LocalTrack>>((ref) async {
           .where((e) => e.isNotEmpty)
           .toList();
 
-    final tracks = filesWithMetadata
+      // ignore: no_leading_underscores_for_local_identifiers
+      final _tracks = filesWithMetadata
           .map(
             (fileWithMetadata) => LocalTrack.fromTrack(
               track: Track().fromFile(
@@ -133,10 +137,12 @@ final localTracksProvider = FutureProvider<List<LocalTrack>>((ref) async {
           )
           .toList();
 
+      tracks[location] = _tracks;
+    }
     return tracks;
   } catch (e, stack) {
     Catcher2.reportCheckedError(e, stack);
-    return [];
+    return {};
   }
 });
 
@@ -171,7 +177,7 @@ class UserLocalTracks extends HookConsumerWidget {
     final playlist = ref.watch(proxyPlaylistProvider);
     final trackSnapshot = ref.watch(localTracksProvider);
     final isPlaylistPlaying =
-        playlist.containsTracks(trackSnapshot.asData?.value ?? []);
+        playlist.containsTracks(trackSnapshot.asData?.value.values.flattened.toList() ?? []);
 
     final searchController = useTextEditingController();
     useValueListenable(searchController);
@@ -179,6 +185,31 @@ class UserLocalTracks extends HookConsumerWidget {
     final isFiltering = useState(false);
 
     final controller = useScrollController();
+    final preferencesNotifier = ref.watch(userPreferencesProvider.notifier);
+    final preferences = ref.watch(userPreferencesProvider);
+    
+    final addLocalLibraryLocation = useCallback(() async {
+      if (DesktopTools.platform.isMobile || DesktopTools.platform.isMacOS) {
+        final dirStr = await FilePicker.platform.getDirectoryPath(
+          initialDirectory: preferences.downloadLocation,
+        );
+        if (dirStr == null) return;
+        if (preferences.localLibraryLocation.contains(dirStr)) return;
+        preferencesNotifier.setLocalLibraryLocation([...preferences.localLibraryLocation, dirStr]);
+      } else {
+        String? dirStr = await getDirectoryPath(
+          initialDirectory: preferences.downloadLocation,
+        );
+        if (dirStr == null) return;
+        if (preferences.localLibraryLocation.contains(dirStr)) return;
+        preferencesNotifier.setLocalLibraryLocation([...preferences.localLibraryLocation, dirStr]);
+      }
+    }, [preferences.localLibraryLocation]);
+
+    final removeLocalLibraryLocation = useCallback((String location) {
+      if (!preferences.localLibraryLocation.contains(location)) return;
+      preferencesNotifier.setLocalLibraryLocation([...preferences.localLibraryLocation]..remove(location));
+    }, [preferences.localLibraryLocation]);
 
     return Column(
       children: [
@@ -194,7 +225,7 @@ class UserLocalTracks extends HookConsumerWidget {
                           if (!isPlaylistPlaying) {
                             await playLocalTracks(
                               ref,
-                              trackSnapshot.asData!.value,
+                              trackSnapshot.asData!.value.values.flattened.toList(),
                             );
                           }
                         }
@@ -222,6 +253,16 @@ class UserLocalTracks extends HookConsumerWidget {
                   sortBy.value = value;
                 },
               ),
+              if (!kIsWeb) ...[
+                const SizedBox(width: 10),
+                Tooltip(
+                  message: context.l10n.add_library_location,
+                  child: IconButton(
+                    onPressed: addLocalLibraryLocation,
+                    icon: const Icon(SpotubeIcons.folder), // TODO: use a "folder add" icon
+                  ),
+                ),
+              ],
               const SizedBox(width: 5),
               FilledButton(
                 child: const Icon(SpotubeIcons.refresh),
@@ -239,7 +280,42 @@ class UserLocalTracks extends HookConsumerWidget {
           onChangeFiltering: (value) => isFiltering.value = value,
         ),
         trackSnapshot.when(
-          data: (tracks) {
+          data: (groups) => Expanded(
+            child: RefreshIndicator(
+              onRefresh: () async {
+                ref.invalidate(localTracksProvider);
+              },
+              child: Expanded(
+                child: InterScrollbar(
+                  controller: controller,
+                  child: CustomScrollView(
+                    controller: controller,
+                    physics: const AlwaysScrollableScrollPhysics(),
+                    slivers: [
+                      for (var MapEntry(key: location, value: tracks) in groups.entries) ...[
+                        SliverPadding(
+                          padding: const EdgeInsets.symmetric(horizontal: 8, vertical: 4),
+                          sliver: SliverToBoxAdapter(
+                            child: Row(
+                              children: [
+                                Text(preferences.downloadLocation == location ? context.l10n.downloads : location,
+                                  style: Theme.of(context).textTheme.titleLarge
+                                ),
+                                const Expanded(child: SizedBox()),
+                                Tooltip(
+                                  message: context.l10n.remove_library_location,
+                                  child: IconButton(
+                                    icon: Icon(SpotubeIcons.trash, color: Colors.red[400]),
+                                    onPressed: () => removeLocalLibraryLocation(location),
+                                  ),
+                                ),
+                              ],
+                            ),
+                          ),
+                        ),
+                        HookBuilder(
+                          key: ValueKey("LocalTracks\$$location"),
+                          builder: (context) {
                             final sortedTracks = useMemoized(() {
                               return ServiceUtils.sortTracks(tracks, sortBy.value);
                             }, [sortBy.value, tracks]);
@@ -267,26 +343,16 @@ class UserLocalTracks extends HookConsumerWidget {
                             }, [searchController.text, sortedTracks]);
                       
                             if (!trackSnapshot.isLoading && filteredTracks.isEmpty) {
-              return const Expanded(
+                              return const SliverFillRemaining(
                                 child: Row(
                                   mainAxisAlignment: MainAxisAlignment.center,
                                   children: [NotFound()],
                                 ),
                               );
                             }
-
+                            return SliverSkeletonizer(
-            return Expanded(
-              child: RefreshIndicator(
-                onRefresh: () async {
-                  ref.invalidate(localTracksProvider);
-                },
-                child: InterScrollbar(
-                  controller: controller,
-                  child: Skeletonizer(
                               enabled: trackSnapshot.isLoading,
-                    child: ListView.builder(
+                              child: SliverList.builder(
-                      controller: controller,
-                      physics: const AlwaysScrollableScrollPhysics(),
                                 itemCount:
                                     trackSnapshot.isLoading ? 5 : filteredTracks.length,
                                 itemBuilder: (context, index) {
@@ -314,11 +380,16 @@ class UserLocalTracks extends HookConsumerWidget {
                                   );
                                 },
                               ),
-                  ),
-                ),
-              ),
                             );
-          },
+                          }
+                        )
+                      ]
+                    ]
+                  )
+                ),
+              ),
+            ),
+          ),
           loading: () => Expanded(
             child: Skeletonizer(
               enabled: true,