feature: Added update notification and download links per platform (#362)

Co-authored-by: PartyDonut <PartyDonut@users.noreply.github.com>

lib/providers/update_provider.dart

@@ -0,0 +1,77 @@
+import 'dart:async';
+
+import 'package:flutter/foundation.dart';
+
+import 'package:collection/collection.dart';
+import 'package:freezed_annotation/freezed_annotation.dart';
+import 'package:riverpod_annotation/riverpod_annotation.dart';
+
+import 'package:fladder/providers/settings/client_settings_provider.dart';
+import 'package:fladder/util/update_checker.dart';
+
+part 'update_provider.freezed.dart';
+part 'update_provider.g.dart';
+
+Set<TargetPlatform> get _directUpdatePlatforms => {
+      TargetPlatform.linux,
+      TargetPlatform.macOS,
+      TargetPlatform.windows,
+    };
+
+final hasNewUpdateProvider = Provider<bool>((ref) {
+  //Disable update notification for platforms that are updated outside of Github.
+  if (!_directUpdatePlatforms.contains(defaultTargetPlatform) || kIsWeb) {
+    return false;
+  }
+  return ref.watch(clientSettingsProvider.select((value) => value.lastViewedUpdate)) !=
+      ref.watch(updateProvider.select((value) => value.latestRelease?.version));
+});
+
+@Riverpod(keepAlive: true)
+class Update extends _$Update {
+  final updateChecker = UpdateChecker();
+
+  Timer? _timer;
+
+  @override
+  UpdatesModel build() {
+    final checkForUpdates = ref.watch(clientSettingsProvider.select((value) => value.checkForUpdates));
+
+    if (!checkForUpdates) {
+      _timer?.cancel();
+      return UpdatesModel();
+    }
+    ref.onDispose(() {
+      _timer?.cancel();
+    });
+
+    _timer?.cancel();
+
+    _timer = Timer.periodic(const Duration(minutes: 30), (timer) {
+      _fetchLatest();
+    });
+
+    _fetchLatest();
+
+    return UpdatesModel();
+  }
+
+  Future<List<ReleaseInfo>> _fetchLatest() async {
+    final latest = await updateChecker.fetchRecentReleases();
+    state = state.copyWith(
+      lastRelease: latest,
+    );
+    return latest;
+  }
+}
+
+@Freezed(toJson: false, fromJson: false)
+class UpdatesModel with _$UpdatesModel {
+  const UpdatesModel._();
+
+  factory UpdatesModel({
+    @Default([]) List<ReleaseInfo> lastRelease,
+  }) = _UpdatesModel;
+
+  ReleaseInfo? get latestRelease => lastRelease.firstWhereOrNull((value) => value.isNewerThanCurrent);
+}