Add ffi value notifier, to be able to re-use session model across UI …

…components

desktop/app/app.go

@@ -88,6 +88,9 @@ type App struct {
 	// should not be called. In short, this slice and its elements should be treated as read-only.
 	proxies     []balancer.Dialer
 	proxiesLock sync.RWMutex
+
+	selectedTab Tab
+	selectedTabMu sync.Mutex
 }
 
 // NewApp creates a new desktop app that initializes the app and acts as a moderator between all desktop components.
@@ -98,6 +101,7 @@ func NewApp(flags flashlight.Flags, configDir string, settings *Settings) *App {
 		exited: eventual.NewValue(),
 		settings:              settings,
 		analyticsSession:      analyticsSession,
+		selectedTab:           AccountTab,
 		statsTracker:          NewStatsTracker(),
 		ws:                    ws.NewUIChannel(),
 	}
@@ -117,6 +121,17 @@ func newAnalyticsSession(settings *Settings) analytics.Session {
 	}
 }
 
+func (app *App) SelectedTab() Tab {
+	app.selectedTabMu.Lock()
+	defer app.selectedTabMu.Unlock()
+	return app.selectedTab
+}
+
+func (app *App) SetSelectedTab(selectedTab Tab) {
+	app.selectedTabMu.Lock()
+	defer app.selectedTabMu.Unlock()
+	app.selectedTab = selectedTab
+}
 
 func (app *App) GetDebugHttpHandlers() []server.PathHandler {
 	return []server.PathHandler{{

desktop/app/tab.go

@@ -0,0 +1,27 @@
+package app
+
+import (
+	"errors"
+	"strings"
+)
+
+var (
+	ErrMissingTab         = errors.New("missing tab")
+	AccountTab = Tab("account")
+	DeveloperTab = Tab("developer")
+	VPNTab = Tab("vpn")
+	UnknownTab = Tab("")
+)
+
+// Identifies a specific tab in the desktop app
+type Tab string
+
+// Parse the given string into a Tab
+func ParseTab(s string) (Tab, error) {
+	normalized := strings.ToLower(strings.TrimSpace(s))
+	if normalized == "" {
+		// leave currency empty
+		return UnknownTab, ErrMissingTab
+	}
+	return Tab(normalized), nil
+}

desktop/lib.go

@@ -10,7 +10,6 @@ import (
 	"runtime"
 	"runtime/debug"
 	"strconv"
-	"sync"
 
 	"github.com/getlantern/appdir"
 	"github.com/getlantern/android-lantern/desktop/app"
@@ -24,8 +23,8 @@ import "C"
 
 var (
 	log = golog.LoggerFor("lantern-desktop.main")
-	selectedTab = "account"
-	selectedTabMu sync.Mutex
+	a *app.App
+
 	proClient *pro.ProClient
 	settings *app.Settings 
 )
@@ -43,7 +42,7 @@ func Start() *C.char {
 	cdir := configDir(&flags)
 	settings = loadSettings(cdir)
 	proClient = pro.New()
-	a := app.NewApp(flags, cdir, settings)
+	a = app.NewApp(flags, cdir, settings)
 	log.Debug("Running headless")
 	go func() { 
 		runApp(a)
@@ -89,17 +88,17 @@ func sendError(err error) *C.char {
 
 //export SelectedTab
 func SelectedTab() *C.char {
-	selectedTabMu.Lock()
-	defer selectedTabMu.Unlock()
-	return C.CString(selectedTab)
+	return C.CString(string(a.SelectedTab()))
 }
 
 //export SetSelectTab
 func SetSelectTab(ttab *C.char) {
-	tab := C.GoString(ttab)
-	selectedTabMu.Lock()
-	defer selectedTabMu.Unlock()
-	selectedTab = tab
+	tab, err := app.ParseTab(C.GoString(ttab))
+	if err != nil {
+		log.Error(err)
+		return
+	}
+	a.SetSelectedTab(tab)
 }
 
 //export Plans
@@ -124,6 +123,11 @@ func UserData() *C.char {
 	return C.CString(string(b))
 }
 
+//export EmailAddress
+func EmailAddress() *C.char {
+	return C.CString("")
+}
+
 // loadSettings loads the initial settings at startup, either from disk or using defaults.
 func loadSettings(configDir string) *app.Settings {
 	path := filepath.Join(configDir, "settings.yaml")

lib/common/common_desktop.dart

@@ -0,0 +1,6 @@
+export 'dart:convert';
+export 'dart:ffi'; // For FFI
+
+export 'package:lantern/desktop/ffi.dart';
+export 'package:ffi/ffi.dart';
+export 'package:ffi/src/utf8.dart';

lib/common/ffi_subscriber.dart

@@ -0,0 +1,72 @@
+import 'common.dart';
+import 'common_desktop.dart';
+
+
+class FfiValueNotifier<T> extends SubscribedNotifier<T?> {
+  FfiValueNotifier(
+    Pointer<Utf8> Function() ffiFunction,
+    T? defaultValue,
+    void Function() removeFromCache, {
+    bool details = false,
+    T Function(Uint8List serialized)? deserialize,
+  }) : super(defaultValue, removeFromCache) {
+    value = ffiFunction().toDartString() as T?;
+  }
+}
+
+/// A ValueListenableBuilder that obtains its single value by subscribing to a
+/// path in the database.
+class FfiValueBuilder<T> extends ValueListenableBuilder<T?> {
+  FfiValueBuilder(
+    String path,
+    ValueNotifier<T?> notifier,
+    ValueWidgetBuilder<T> builder,
+  ) : super(
+          valueListenable: notifier,
+          builder: (BuildContext context, T? value, Widget? child) =>
+              value == null ? const SizedBox() : builder(context, value, child),
+        );
+
+  @override
+  _FfiValueBuilderState createState() =>
+      _FfiValueBuilderState<T>();
+}
+
+class _FfiValueBuilderState<T>
+    extends State<ValueListenableBuilder<T?>> {
+  T? value;
+
+  @override
+  void initState() {
+    super.initState();
+    value = widget.valueListenable.value;
+    widget.valueListenable.addListener(_valueChanged);
+  }
+
+  @override
+  void didUpdateWidget(ValueListenableBuilder<T?> oldWidget) {
+    if (oldWidget.valueListenable != widget.valueListenable) {
+      oldWidget.valueListenable.removeListener(_valueChanged);
+      value = widget.valueListenable.value;
+      widget.valueListenable.addListener(_valueChanged);
+    }
+    super.didUpdateWidget(oldWidget);
+  }
+
+  @override
+  void dispose() {
+    widget.valueListenable.removeListener(_valueChanged);
+    super.dispose();
+  }
+
+  void _valueChanged() {
+    setState(() {
+      value = widget.valueListenable.value;
+    });
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return widget.builder(context, value, widget.child);
+  }
+}

lib/common/model.dart

@@ -1,12 +1,16 @@
 import 'dart:collection';
 
+import 'package:lantern/common/ffi_subscriber.dart';
 import 'package:lantern/messaging/messaging.dart';
+import 'common_desktop.dart';
 
 abstract class Model {
   late MethodChannel methodChannel;
   late ModelEventChannel _updatesChannel;
   final Map<String, SubscribedSingleValueNotifier> _singleValueNotifierCache =
       HashMap();
+  final Map<String, FfiValueNotifier> _ffiValueNotifierCache =
+      HashMap();
   final Map<String, SubscribedListNotifier> _listNotifierCache = HashMap();
   Event? event;
 
@@ -45,6 +49,24 @@ abstract class Model {
     return result;
   }
 
+  ValueListenableBuilder<T?> ffiValueBuilder<T>(
+    String path, 
+    Pointer<Utf8> Function() ffiFunction, {
+    T? defaultValue,
+    required ValueWidgetBuilder<T> builder,
+    bool details = false,
+    T Function(Uint8List serialized)? deserialize,
+  }) {
+    var notifier = ffiValueNotifier(
+      ffiFunction,
+      path,
+      defaultValue,
+      details: details,
+      deserialize: deserialize,
+    );
+    return FfiValueBuilder<T>(path, notifier, builder);
+  }
+
   ValueListenableBuilder<T?> subscribedSingleValueBuilder<T>(
     String path, {
     T? defaultValue,
@@ -61,6 +83,29 @@ abstract class Model {
     return SubscribedSingleValueBuilder<T>(path, notifier, builder);
   }
 
+  ValueNotifier<T?> ffiValueNotifier<T>(
+    Pointer<Utf8> Function() ffiFunction,
+    String path,
+    T? defaultValue, {
+      bool details = false,
+      T Function(Uint8List serialized)? deserialize,      
+  }) {
+    var result =
+        _ffiValueNotifierCache[path] as FfiValueNotifier<T>?;
+    if (result == null) {
+      result = FfiValueNotifier(
+        ffiFunction,
+        defaultValue,
+        () {
+          _ffiValueNotifierCache.remove(path);
+        },
+      );
+      _ffiValueNotifierCache[path] = result;
+    }
+    return result;
+  }
+
+
   ValueNotifier<T?> singleValueNotifier<T>(
     String path,
     T? defaultValue, {

lib/common/session_model.dart

@@ -1,6 +1,8 @@
 import 'package:lantern/replica/common.dart';
 
 import 'common.dart';
+import 'common_desktop.dart';
+
 
 final sessionModel = SessionModel();
 
@@ -120,8 +122,15 @@ class SessionModel extends Model {
   }
 
   Widget emailAddress(ValueWidgetBuilder<String> builder) {
-    return subscribedSingleValueBuilder<String>(
+    if (Platform.isAndroid) {
+      return subscribedSingleValueBuilder<String>(
+        'emailAddress',
+        builder: builder,
+      );
+    }
+    return ffiValueBuilder<String>(
       'emailAddress',
+      ffiEmailAddress,
       builder: builder,
     );
   }

lib/desktop/ffi.dart

@@ -37,6 +37,7 @@ final SelectedTab selectedTab =
 
 final ProFunc getPlans = dylib.lookup<ffi.NativeFunction<pro_func>>('Plans').asFunction();
 final ProFunc getUserData = dylib.lookup<ffi.NativeFunction<pro_func>>('UserData').asFunction();
+final ProFunc ffiEmailAddress = dylib.lookup<ffi.NativeFunction<pro_func>>('EmailAddress').asFunction();
 
 void loadLibrary() {
   start();