kaptan/ground-suite/lib/app/app_shell.dart

import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';

import '../features/diagnostics/presentation/diagnostics_page.dart';
import '../features/observability/presentation/observability_controller.dart';
import '../features/overview/presentation/overview_page.dart';

enum _Destination { overview, diagnostics }

class AppShell extends ConsumerStatefulWidget {
  const AppShell({super.key});

  @override
  ConsumerState<AppShell> createState() => _AppShellState();
}

class _AppShellState extends ConsumerState<AppShell> {
  _Destination _destination = _Destination.overview;

  @override
  Widget build(BuildContext context) {
    final state = ref.watch(observabilityControllerProvider);
    const pages = <Widget>[OverviewPage(), DiagnosticsPage()];

    return Scaffold(
      body: SafeArea(
        child: Stack(
          children: [
            LayoutBuilder(
              builder: (context, constraints) {
                final compact = constraints.maxWidth < 760;
                final content = _Workspace(
                  state: state,
                  selectedIndex: _destination.index,
                  pages: pages,
                  compact: compact,
                );
                return compact
                    ? _CompactShell(
                        selectedIndex: _destination.index,
                        onSelected: _selectDestination,
                        content: content,
                      )
                    : _WideShell(
                        selectedIndex: _destination.index,
                        onSelected: _selectDestination,
                        content: content,
                      );
              },
            ),
            if (state.accessibilityAnnouncement case final announcement?)
              _CriticalAnnouncement(message: announcement),
          ],
        ),
      ),
    );
  }

  void _selectDestination(int index) {
    setState(() => _destination = _Destination.values[index]);
  }
}

class _WideShell extends StatelessWidget {
  const _WideShell({
    required this.selectedIndex,
    required this.onSelected,
    required this.content,
  });

  final int selectedIndex;
  final ValueChanged<int> onSelected;
  final Widget content;

  @override
  Widget build(BuildContext context) {
    return Row(
      children: [
        NavigationRail(
          selectedIndex: selectedIndex,
          labelType: NavigationRailLabelType.all,
          onDestinationSelected: onSelected,
          leading: const Padding(
            padding: EdgeInsets.symmetric(vertical: 16),
            child: Icon(Icons.flight_takeoff_outlined, size: 28),
          ),
          destinations: _destinations,
        ),
        const VerticalDivider(width: 1),
        Expanded(child: content),
      ],
    );
  }
}

class _CompactShell extends StatelessWidget {
  const _CompactShell({
    required this.selectedIndex,
    required this.onSelected,
    required this.content,
  });

  final int selectedIndex;
  final ValueChanged<int> onSelected;
  final Widget content;

  @override
  Widget build(BuildContext context) {
    return Column(
      children: [
        Expanded(child: content),
        NavigationBar(
          selectedIndex: selectedIndex,
          onDestinationSelected: onSelected,
          destinations: const [
            NavigationDestination(
              icon: Icon(Icons.space_dashboard_outlined),
              selectedIcon: Icon(Icons.space_dashboard),
              label: 'Overview',
            ),
            NavigationDestination(
              icon: Icon(Icons.receipt_long_outlined),
              selectedIcon: Icon(Icons.receipt_long),
              label: 'Diagnostics',
            ),
          ],
        ),
      ],
    );
  }
}

const _destinations = <NavigationRailDestination>[
  NavigationRailDestination(
    icon: Icon(Icons.space_dashboard_outlined),
    selectedIcon: Icon(Icons.space_dashboard),
    label: Text('Overview'),
  ),
  NavigationRailDestination(
    icon: Icon(Icons.receipt_long_outlined),
    selectedIcon: Icon(Icons.receipt_long),
    label: Text('Diagnostics'),
  ),
];

class _Workspace extends StatelessWidget {
  const _Workspace({
    required this.state,
    required this.selectedIndex,
    required this.pages,
    required this.compact,
  });

  final ObservabilityState state;
  final int selectedIndex;
  final List<Widget> pages;
  final bool compact;

  @override
  Widget build(BuildContext context) {
    return Column(
      children: [
        _ConnectionBar(state: state, compact: compact),
        const Divider(height: 1),
        Expanded(
          child: IndexedStack(index: selectedIndex, children: pages),
        ),
      ],
    );
  }
}

class _ConnectionBar extends StatelessWidget {
  const _ConnectionBar({required this.state, required this.compact});

  final ObservabilityState state;
  final bool compact;

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    final heartbeat = state.lastHeartbeat;
    final peer = heartbeat == null
        ? 'No vehicle identity observed'
        : 'System ${heartbeat.systemId} / component ${heartbeat.componentId}';
    final frameTime = state.lastFrameAt == null
        ? 'No frames received'
        : 'Last frame ${_formatTimestamp(state.lastFrameAt!)}';

    return Semantics(
      label: '${state.status.label}; ${state.sourceLabel}; $peer; $frameTime',
      child: Padding(
        padding: EdgeInsets.symmetric(
          horizontal: compact ? 16 : 24,
          vertical: 12,
        ),
        child: Wrap(
          spacing: 8,
          runSpacing: 8,
          crossAxisAlignment: WrapCrossAlignment.center,
          children: [
            Icon(Icons.visibility_outlined, color: theme.colorScheme.primary),
            Text('Observation only', style: theme.textTheme.titleSmall),
            _StatusChip(label: state.sourceLabel),
            _StatusChip(label: state.status.label),
            Text(peer),
            Text(frameTime),
          ],
        ),
      ),
    );
  }
}

class _CriticalAnnouncement extends StatelessWidget {
  const _CriticalAnnouncement({required this.message});

  final String message;

  @override
  Widget build(BuildContext context) {
    return Semantics(
      container: true,
      liveRegion: true,
      label: message,
      child: const SizedBox.square(dimension: 1),
    );
  }
}

class _StatusChip extends StatelessWidget {
  const _StatusChip({required this.label});

  final String label;

  @override
  Widget build(BuildContext context) {
    return Chip(label: Text(label), visualDensity: VisualDensity.compact);
  }
}

String _formatTimestamp(DateTime value) => value.toIso8601String();