mobile: Update to new client API

The settings screen was refactored too.

mobile/lib/settings.dart

@@ -0,0 +1,102 @@
+import 'package:flutter/services.dart';
+import 'package:meta/meta.dart';
+import 'package:rxdart/rxdart.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+
+/// Settings concerning the Musicus server to connect to.
+///
+/// We don't support setting a scheme here, because there may be password being
+/// submitted in the future, so we default to HTTPS.
+class ServerSettings {
+  static const defaultHost = 'musicus.johrpan.de';
+  static const defaultPort = 1833;
+  static const defaultBasePath = '/api';
+
+  /// Host to connect to, e.g. 'musicus.johrpan.de';
+  final String host;
+
+  /// Port to connect to.
+  final int port;
+
+  /// Path to the API.
+  ///
+  /// This should be null, if the API is at the root of the host.
+  final String basePath;
+
+  ServerSettings({
+    @required this.host,
+    @required this.port,
+    @required this.basePath,
+  });
+}
+
+/// Manager for all settings that are persisted.
+class Settings {
+  static const defaultHost = 'musicus.johrpan.de';
+  static const defaultPort = 443;
+  static const defaultBasePath = '/api';
+
+  static const _platform = MethodChannel('de.johrpan.musicus/platform');
+
+  /// The tree storage access framework tree URI of the music library.
+  final musicLibraryUri = BehaviorSubject<String>();
+
+  /// Musicus server to connect to.
+  final server = BehaviorSubject<ServerSettings>();
+
+  SharedPreferences _shPref;
+
+  /// Initialize the settings.
+  Future<void> load() async {
+    _shPref = await SharedPreferences.getInstance();
+
+    final uri = _shPref.getString('musicLibraryUri');
+    if (uri != null) {
+      musicLibraryUri.add(uri);
+    }
+
+    final host = _shPref.getString('serverHost') ?? defaultHost;
+    final port = _shPref.getInt('serverPort') ?? defaultPort;
+    final basePath = _shPref.getString('serverBasePath') ?? defaultBasePath;
+
+    server.add(ServerSettings(
+      host: host,
+      port: port,
+      basePath: basePath,
+    ));
+  }
+
+  /// Open the system picker to select a new music library URI.
+  Future<void> chooseMusicLibraryUri() async {
+    final uri = await _platform.invokeMethod<String>('openTree');
+
+    if (uri != null) {
+      musicLibraryUri.add(uri);
+      await _shPref.setString('musicLibraryUri', uri);
+    }
+  }
+
+  /// Change the Musicus server settings.
+  Future<void> setServerSettings(ServerSettings settings) async {
+    await _shPref.setString('serverHost', settings.host);
+    await _shPref.setInt('serverPort', settings.port);
+    await _shPref.setString('serverBasePath', settings.basePath);
+
+    server.add(settings);
+  }
+
+  /// Reset the server settings to their defaults.
+  Future<void> resetServerSettings() async {
+    await setServerSettings(ServerSettings(
+      host: defaultHost,
+      port: defaultPort,
+      basePath: defaultBasePath,
+    ));
+  }
+
+  /// Tidy up.
+  void dispose() {
+    musicLibraryUri.close();
+    server.close();
+  }
+}