Label button with '(dis)connect'

This does not yet work but the correct text based on the page is
displayed.

This is based on a state machine based implementation suitable to
implement the state handling cleanly.

2 files changed, 47 insertions, 9 deletions

diff --git a/lib/data.dart b/lib/data.dart
index e660689..53c3d01 100644
--- a/lib/data.dart
+++ b/lib/data.dart
@@ -8,8 +8,27 @@ const String brokerHostname = 'sia.xengineering.eu';
 const int brokerPort = 1883;
 const String topicPrefix = 'sia';
 
+enum MachineState {
+  init,          // user does not want connection MQTT not connected
+  disconnected,  // user wants connection but MQTT not (yet) connected
+}
+
+enum MachineEvent {
+  connect,       // user wants to connect
+  disconnect,    // user does not want an connection anymore
+}
+
 class AppState with ChangeNotifier {
-  bool onConnectionPage = true;
+  static const Map<MachineState, Map<MachineEvent, MachineState>> machine = <MachineState, Map<MachineEvent, MachineState>> {
+    MachineState.init: <MachineEvent, MachineState> {
+      MachineEvent.connect: MachineState.disconnected,
+    },
+    MachineState.disconnected: <MachineEvent, MachineState> {
+      MachineEvent.disconnect: MachineState.init,
+    },
+  };
+  MachineState state = MachineState.init;
+
   Map<String, bool> contacts = <String, bool>{};
   late final MqttServerClient _client;
   bool _brokerConnected = false;
@@ -21,6 +40,21 @@ class AppState with ChangeNotifier {
     _initMqtt();
   }
 
+  void process(MachineEvent event) {
+    Map<MachineEvent, MachineState>? ruleset = machine[state];
+    if (ruleset == null) {
+      return;
+    }
+
+    MachineState? nextMachineState = ruleset[event];
+    if (nextMachineState == null) {
+      return;
+    }
+
+    state = nextMachineState;
+    notifyListeners();
+  }
+
   @override
   void dispose() {
     _client.disconnect();
@@ -123,9 +157,4 @@ class AppState with ChangeNotifier {
         return null;
     }
   }
-
-  void togglePage() {
-    onConnectionPage = !onConnectionPage;
-    notifyListeners();
-  }
 }
diff --git a/lib/ui.dart b/lib/ui.dart
index 73e532a..e14895b 100644
--- a/lib/ui.dart
+++ b/lib/ui.dart
@@ -13,7 +13,7 @@ class Sia extends StatelessWidget {
       child: MaterialApp(
         home: Consumer<AppState>(
           builder: (_, AppState provider, _) {
-            if (provider.onConnectionPage) {
+            if (provider.state == MachineState.init) {
               return const ConnectionPage();
             }
             return const DevicesPage();
@@ -112,6 +112,13 @@ class ConnectionStatus extends StatelessWidget {
             text = const Text('Disconnected');
           }
 
+          MachineEvent event = MachineEvent.disconnect;
+          String action = 'disconnect';
+          if (state.state == MachineState.init) {
+            event = MachineEvent.connect;
+            action = 'connect';
+          }
+
           return Row(
             children: <Widget>[
               Expanded(
@@ -119,8 +126,10 @@ class ConnectionStatus extends StatelessWidget {
                   leading: icon,
                   title: text,
                   trailing: ElevatedButton(
-                    onPressed: state.togglePage,
-                    child: const Text('switch view'),
+                    onPressed: () {
+                      state.process(event);
+                    },
+                    child: Text(action),
                   ),
                 ),
               ),