line.dart

import 'package:flutter/material.dart';

Future<void> main() async {
  WidgetsFlutterBinding.ensureInitialized();

  runApp(const App());
}

class App extends StatelessWidget {
  const App({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      themeMode: ThemeMode.system,
      theme: ThemeData(brightness: Brightness.light),
      darkTheme: ThemeData(brightness: Brightness.dark),
      home: const Home(),
    );
  }
}

class Home extends StatefulWidget {
  const Home({Key? key}) : super(key: key);

  @override
  State<Home> createState() => _HomeState();
}

class _HomeState extends State<Home> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('PenguinApp'),
      ),
      body: ListView.builder(
        itemCount: 100,
        itemBuilder: (context, index) {
          return Post(
            title: const Text('My Post Title'),
            content: const Text(
              'Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.',
            ),
            isFirst: index == 0,
            isLast: index == 99,
          );
        },
      ),
    );
  }
}

class Post extends StatelessWidget {
  const Post({
    Key? key,
    this.padding = const EdgeInsets.all(8.0),
    required this.title,
    required this.content,
    this.isFirst = false,
    this.isLast = false,
  }) : super(key: key);

  final bool isFirst;
  final EdgeInsets padding;
  final Widget title;
  final Widget content;
  final bool isLast;

  @override
  Widget build(BuildContext context) {
    return Column(
      mainAxisSize: MainAxisSize.min,
      children: [
        IntrinsicHeight(
          child: Row(
            crossAxisAlignment: CrossAxisAlignment.stretch,
            children: [
              SizedBox(width: padding.left),
              Column(
                crossAxisAlignment: CrossAxisAlignment.center,
                children: [
                  SizedBox(
                    width: 1.0,
                    height: padding.top,
                    child: ColoredBox(
                      color: !isFirst ? Colors.grey : Colors.transparent,
                    ),
                  ),
                  const CircleAvatar(),
                  Expanded(
                    child: SizedBox(
                      width: 1.0,
                      child: ColoredBox(
                        color: !isLast ? Colors.grey : Colors.transparent,
                      ),
                    ),
                  ),
                ],
              ),
              const SizedBox(width: 8.0),
              Expanded(
                child: Column(
                  crossAxisAlignment: CrossAxisAlignment.stretch,
                  children: [
                    SizedBox(height: padding.top),
                    DefaultTextStyle.merge(
                      style: Theme.of(context).textTheme.titleLarge,
                      child: title,
                    ),
                    DefaultTextStyle.merge(
                      style: Theme.of(context).textTheme.bodyMedium,
                      child: content,
                    ),
                    SizedBox(height: padding.bottom),
                  ],
                ),
              ),
              SizedBox(width: padding.right),
            ],
          ),
        ),
      ],
    );
  }
}