refactor: introduce SnapModel

lib/snapd.dart

@@ -1,4 +1,4 @@
 export 'src/snapd/snap_launcher.dart';
-export 'src/snapd/snap_provider.dart';
+export 'src/snapd/snap_model.dart';
 export 'src/snapd/snapd_service.dart';
 export 'src/snapd/snapx.dart';

lib/src/detail/detail_page.dart

@@ -23,78 +23,60 @@ class DetailPage extends ConsumerWidget {
 
   @override
   Widget build(BuildContext context, WidgetRef ref) {
-    final storeState = ref.watch(storeSnapProvider(snapName));
-    return storeState.when(
-      data: (storeSnap) {
-        final localState = ref.watch(localSnapProvider(snapName));
-        return localState.when(
-          data: (localSnap) => _SnapView(
-            storeSnap: storeSnap,
-            localSnap: localSnap,
-          ),
-          error: (error, __) => _SnapView(
-            storeSnap: storeSnap,
-          ),
-          loading: () => _SnapView(storeSnap: storeSnap, busy: true),
-        );
-      },
+    final model = ref.watch(snapModelProvider(snapName));
+    return model.state.when(
+      data: (_) => _SnapView(model: model),
       error: (error, stackTrace) => ErrorWidget(error),
       loading: () => const Center(child: YaruCircularProgressIndicator()),
     );
   }
 }
 
 class _SnapView extends ConsumerWidget {
-  const _SnapView({
-    this.storeSnap,
-    this.localSnap,
-    this.busy = false,
-  });
+  const _SnapView({required this.model});
 
-  final Snap? storeSnap;
-  final Snap? localSnap;
-  final bool busy;
+  final SnapModel model;
 
   @override
   Widget build(BuildContext context, WidgetRef ref) {
     final l10n = AppLocalizations.of(context);
 
-    final channels = storeSnap?.channels.keys;
-    final selectedChannel = storeSnap != null
-        ? ref.watch(selectedChannelProvider(storeSnap!.name))
-        : null;
+    final channels = model.availableChannels;
+    final selectedChannel = model.selectedChannel;
 
-    final channelInfo =
-        selectedChannel != null ? storeSnap?.channels[selectedChannel] : null;
+    final channelInfo = selectedChannel != null
+        ? model.storeSnap?.channels[selectedChannel]
+        : null;
 
+    // TODO: move logic into view model, once app page UI is settled
     final snapInfos = <SnapInfo>[
       (
         label: l10n.detailPageVersionLabel,
         value: channelInfo?.version ??
-            storeSnap?.version ??
-            localSnap?.version ??
+            model.storeSnap?.version ??
+            model.localSnap?.version ??
             '',
       ),
       (
         label: l10n.detailPageConfinementLabel,
         value: channelInfo?.confinement.name ??
-            storeSnap?.confinement.name ??
-            localSnap?.confinement.name ??
+            model.storeSnap?.confinement.name ??
+            model.localSnap?.confinement.name ??
             '',
       ),
-      if (storeSnap?.downloadSize != null)
+      if (model.storeSnap?.downloadSize != null)
         (
           label: l10n.detailPageDownloadSizeLabel,
-          value: context
-              .formatByteSize(channelInfo?.size ?? storeSnap!.downloadSize!)
+          value: context.formatByteSize(
+              channelInfo?.size ?? model.storeSnap!.downloadSize!)
         ),
       (
         label: l10n.detailPageLicenseLabel,
-        value: storeSnap?.license ?? localSnap?.license ?? '',
+        value: model.storeSnap?.license ?? model.localSnap?.license ?? '',
       ),
       (
         label: l10n.detailPageWebsiteLabel,
-        value: storeSnap?.website ?? localSnap?.website ?? '',
+        value: model.storeSnap?.website ?? model.localSnap?.website ?? '',
       ),
     ];
 
@@ -104,7 +86,7 @@ class _SnapView extends ConsumerWidget {
         crossAxisAlignment: CrossAxisAlignment.start,
         children: [
           const YaruBackButton(),
-          _Header(snap: storeSnap ?? localSnap),
+          _Header(snap: model.storeSnap ?? model.localSnap),
           const SizedBox(height: kPagePadding),
           Row(
             children: [
@@ -118,19 +100,13 @@ class _SnapView extends ConsumerWidget {
                   itemBuilder: (_) => channels
                       .map((e) => PopupMenuItem(value: e, child: Text(e)))
                       .toList(),
-                  onSelected: (value) => ref
-                      .read(selectedChannelProvider(storeSnap!.name).notifier)
-                      .state = value,
-                  enabled: !busy,
+                  onSelected: (value) => model.selectedChannel = value,
+                  enabled: model.activeChanges.isEmpty,
                   child: Text(selectedChannel),
                 ),
               const SizedBox(width: 16),
               Flexible(
-                child: _SnapActionButtons(
-                  busy: busy,
-                  localSnap: localSnap,
-                  storeSnap: storeSnap,
-                ),
+                child: _SnapActionButtons(model: model),
               )
             ],
           ),
@@ -155,14 +131,16 @@ class _SnapView extends ConsumerWidget {
             child: SizedBox(
               width: double.infinity,
               child: MarkdownBody(
-                data: storeSnap?.description ?? localSnap?.description ?? '',
+                data: model.storeSnap?.description ??
+                    model.localSnap?.description ??
+                    '',
               ),
             ),
           ),
-          if (storeSnap != null)
+          if (model.storeSnap != null)
             _Section(
               header: const Text('Gallery'),
-              child: SnapScreenshotGallery(snap: storeSnap!),
+              child: SnapScreenshotGallery(snap: model.storeSnap!),
             ),
         ],
       ),
@@ -172,42 +150,33 @@ class _SnapView extends ConsumerWidget {
 
 class _SnapActionButtons extends ConsumerWidget {
   const _SnapActionButtons({
-    required this.busy,
-    this.localSnap,
-    this.storeSnap,
-  }) : assert(localSnap != null || storeSnap != null);
+    required this.model,
+  });
 
-  final bool busy;
-  final Snap? localSnap;
-  final Snap? storeSnap;
+  final SnapModel model;
 
   @override
   Widget build(BuildContext context, WidgetRef ref) {
     final l10n = AppLocalizations.of(context);
-
-    final localSnapNotifier = ref
-        .read(localSnapProvider(storeSnap?.name ?? localSnap!.name).notifier);
-    final snapLauncher =
-        localSnap != null ? ref.watch(launchProvider(localSnap!)) : null;
-    final refreshableSnaps = ref.watch(refreshProvider);
-    final selectedChannel = storeSnap != null
-        ? ref.watch(selectedChannelProvider(storeSnap!.name))
+    final snapLauncher = model.localSnap != null
+        ? ref.watch(launchProvider(model.localSnap!))
         : null;
-    final canRefresh = localSnap == null
+    final refreshableSnaps = ref.watch(refreshProvider);
+    final canRefresh = model.localSnap == null
         ? false
         : refreshableSnaps.whenOrNull(
                     data: (snaps) => snaps.singleWhereOrNull(
-                        (snap) => snap.name == localSnap!.name)) !=
+                        (snap) => snap.name == model.localSnap!.name)) !=
                 null ||
-            selectedChannel != localSnap!.trackingChannel;
+            model.selectedChannel != model.localSnap!.trackingChannel;
 
     final installRemoveButton = PushButton.elevated(
-      onPressed: busy
+      onPressed: model.activeChanges.isNotEmpty
           ? null
-          : localSnap != null
-              ? localSnapNotifier.remove
-              : () => localSnapNotifier.install(channel: selectedChannel),
-      child: busy
+          : model.localSnap != null
+              ? model.remove
+              : () => model.install(),
+      child: model.activeChanges.isNotEmpty
           ? Center(
               child: SizedBox.square(
                 dimension: IconTheme.of(context).size,
@@ -217,15 +186,14 @@ class _SnapActionButtons extends ConsumerWidget {
               ),
             )
           : Text(
-              localSnap != null
+              model.localSnap != null
                   ? l10n.detailPageRemoveLabel
                   : l10n.detailPageInstallLabel,
             ),
     );
     final refreshButton = canRefresh
         ? PushButton.elevated(
-            onPressed: () =>
-                localSnapNotifier.refresh(channel: selectedChannel),
+            onPressed: () => model.refresh(),
             child: Text(l10n.detailPageUpdateLabel),
           )
         : null;

lib/src/snapd/snap_model.dart

@@ -0,0 +1,104 @@
+import 'dart:async';
+
+import 'package:collection/collection.dart';
+import 'package:flutter/widgets.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:snapd/snapd.dart';
+import 'package:ubuntu_service/ubuntu_service.dart';
+
+import '/snapd.dart';
+
+final snapModelProvider = ChangeNotifierProvider.family<SnapModel, String>(
+    (ref, snapName) => SnapModel(getService<SnapdService>(), snapName)..init());
+
+class SnapModel extends ChangeNotifier {
+  SnapModel(this.snapd, this.snapName) : _state = const AsyncValue.loading();
+  final SnapdService snapd;
+  final String snapName;
+
+  final List<String> activeChanges = [];
+
+  AsyncValue<void> get state => _state;
+  AsyncValue<void> _state;
+
+  Snap? localSnap;
+  Snap? storeSnap;
+
+  String? get selectedChannel => _selectedChannel;
+  String? _selectedChannel;
+  set selectedChannel(String? channel) {
+    if (channel == _selectedChannel) return;
+    _selectedChannel = channel;
+    notifyListeners();
+  }
+
+  List<String>? get availableChannels => storeSnap?.channels.keys.toList();
+
+  StreamSubscription? storeSnapSubscription;
+
+  Future<void> init() async {
+    storeSnapSubscription = snapd.getStoreSnap(snapName).listen((snap) {
+      _setStoreSnap(snap);
+      _setDefaultSelectedChannel();
+      notifyListeners();
+    });
+    _state = await AsyncValue.guard(() async {
+      await _getLocalSnap();
+      _setDefaultSelectedChannel();
+      notifyListeners();
+    });
+  }
+
+  @override
+  Future<void> dispose() async {
+    await storeSnapSubscription?.cancel();
+    storeSnapSubscription = null;
+    super.dispose();
+  }
+
+  void _setStoreSnap(Snap? newStoreSnap) {
+    if (newStoreSnap == storeSnap) return;
+    storeSnap = newStoreSnap;
+  }
+
+  Future<void> _getLocalSnap() async {
+    try {
+      localSnap = await snapd.getSnap(snapName);
+    } on SnapdException catch (e) {
+      if (e.kind != 'snap-not-found') rethrow;
+      localSnap = null;
+    }
+  }
+
+  void _setDefaultSelectedChannel() {
+    final channels = storeSnap?.channels.keys;
+    final localChannel = localSnap?.trackingChannel;
+    if (localChannel != null && (channels?.contains(localChannel) ?? false)) {
+      _selectedChannel = localChannel;
+    } else if (channels?.contains('latest/stable') ?? false) {
+      _selectedChannel = 'latest/stable';
+    } else {
+      _selectedChannel =
+          channels?.firstWhereOrNull((c) => c.contains('stable')) ??
+              channels?.firstOrNull;
+    }
+  }
+
+  Future<void> _snapAction(Future<String> Function() action) async {
+    final changeId = await action.call();
+    activeChanges.add(changeId);
+    notifyListeners();
+    await snapd.waitChange(changeId);
+    activeChanges.removeWhere((id) => id == changeId);
+    await _getLocalSnap();
+    notifyListeners();
+  }
+
+  Future<void> install() =>
+      _snapAction(() => snapd.install(snapName, channel: selectedChannel));
+
+  Future<void> refresh() =>
+      _snapAction(() => snapd.refresh(snapName, channel: selectedChannel));
+
+  Future<void> remove() => _snapAction(() => snapd.remove(snapName));
+}