A gist for a session timer

session_timer.dart

// Overview Screen
// [Upcoming, In-Progress, Completed]
// When completed -> show a count down timer

// Trigger

import 'dart:async';
import 'dart:math';

import 'package:bloc/bloc.dart';
import 'package:flutter/material.dart';
import 'package:flutter_bloc/flutter_bloc.dart';

final class _SessionMonitorState {
  const _SessionMonitorState({this.status = SessionStatus.unknown, this.severity = const [], this.message});

  final SessionStatus status;
  final String? message;
  final List<(String, int)> severity;

  _SessionMonitorState copyWith({SessionStatus? status, String? message, List<(String, int)>? severity}) =>
      _SessionMonitorState(
        status: status ?? this.status,
        message: message ?? this.message,
        severity: severity ?? this.severity,
      );
}

enum SessionStatus { live, upcoming, completed, unknown }

final class _SessionMonitorCubit extends Cubit<_SessionMonitorState> {
  _SessionMonitorCubit() : super(const _SessionMonitorState());

  final StreamController<String?> _messages = StreamController();

  StreamSubscription<void>? _subscription;
  Timer? _timer;

  void initialize() async {
    await _subscription?.cancel();
    _timer?.cancel();

    _subscription = _messages.stream.listen((data) {
      emit(state.copyWith(message: data));
    });

    _timer = Timer.periodic(const Duration(seconds: 20), (_) async {
      _messages.add('Remember to drink water');

      await Future.delayed(const Duration(milliseconds: 500));
      _messages.add(null);
    });

    // have this randomised
    final nextBool = Random().nextBool();
    final status = nextBool ? SessionStatus.live : SessionStatus.upcoming;

    emit(state.copyWith(status: status));
  }

  void collectData(int value, String text) {
    final severity = List<(String, int)>.from(state.severity)..add((text, value));
    emit(state.copyWith(severity: severity));
  }

  @override
  Future<void> close() async {
    _timer?.cancel();
    await _subscription?.cancel();
    await _messages.close();
    return super.close();
  }
}

class SessionMonitorWidget extends StatefulWidget {
  const SessionMonitorWidget({super.key});

  @override
  State<SessionMonitorWidget> createState() => _SessionMonitorWidgetState();
}

class _SessionMonitorWidgetState extends State<SessionMonitorWidget> {
  final _controller = TextEditingController();
  final _severities = List.generate(10, (index) => index);
  int? _initialValue;

  void _handleCollectData(BuildContext context) {
    if (_initialValue case final value?) {
      final input = _controller.text.trim();
      context.read<_SessionMonitorCubit>().collectData(value, input);
    }
  }

  @override
  void dispose() {
    _controller.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return BlocProvider<_SessionMonitorCubit>(
      create: (_) => _SessionMonitorCubit()..initialize(),
      child: Scaffold(
        body: SafeArea(
          child: Column(
            children: [
              Expanded(child: BlocBuilder<_SessionMonitorCubit, _SessionMonitorState>(
                builder: (context, state) {
                  if (state.message == null) return const SizedBox.shrink();
                  return Text('${state.message}');
                },
              )),
              Expanded(child: BlocBuilder<_SessionMonitorCubit, _SessionMonitorState>(
                builder: (context, state) {
                  if (state.severity.isEmpty) return const SizedBox.shrink();
                  return ListView.builder(
                    itemBuilder: (_, index) {
                      final result = state.severity[index];
                      return Column(
                        children: [Text('${result.$1} --- ${result.$2}')],
                      );
                    },
                  );
                },
              )),
              Expanded(
                child: Column(
                  children: [
                    TextFormField(
                      decoration: InputDecoration(hintText: 'Description'),
                    ),
                    DropdownButtonFormField<int?>(
                      initialValue: _initialValue,
                      items: [
                        ..._severities.map((value) => DropdownMenuItem<int>(
                              child: Text('$value'),
                              value: value,
                            ))
                      ],
                      onChanged: (int? value) {},
                    ),
                    const SizedBox(height: 10),
                    Builder(
                      builder: (context) {
                        return TextButton(
                          onPressed: () => _handleCollectData(context),
                          child: Text('Collect Data'),
                        );
                      }
                    )
                  ],
                ),
              )
            ],
          ),
        ),
      ),
    );
  }
}