main.dart

import 'package:flutter/material.dart';

final books = [
  const Book(id: '3160', name: 'The Odyssey', author: 'Homer'),
  const Book(id: '8795', name: 'The Divine Comedy', author: 'Dante Alighieri'),
];

void main() {
  final betterRoutes = BetterRouter(routes: {
    '/': (_) => const HomeScreen(),
    '/books': (_) => const BooksScreen(),
    r"\/books\/(?<id>.+)": (_) => const BookScreen(),
    '-matchAll': (_) => const Text('not found page'),
  });

  runApp(MaterialApp(onGenerateRoute: betterRoutes));
}

class HomeScreen extends StatelessWidget {
  const HomeScreen({super.key});

  @override
  Widget build(BuildContext context) {
    return AppShell(
        title: const Text("Welcome"),
        body: TextButton(
            onPressed: () => Navigator.pushNamed(context, "/books"),
            child: const Text("Go to books")));
  }
}

class Book {
  final String id;
  final String name;
  final String author;

  const Book({required this.id, required this.name, required this.author});
}

class BooksScreen extends StatelessWidget {
  const BooksScreen({super.key});

  @override
  Widget build(BuildContext context) {
    return AppShell(
        title: const Text("Books"),
        body: Column(children: [
          for (var i = 0; i < books.length; i++)
            TextButton(
                onPressed: () =>
                    Navigator.pushNamed(context, "/books/${books[i].id}"),
                child: Text(books[i].name))
        ]));
  }
}

class BookScreen extends StatelessWidget {
  const BookScreen({super.key});

  @override
  Widget build(BuildContext context) {
    final params =
        ModalRoute.of(context)!.settings.arguments as Map<String, String?>;
    final book = books.firstWhere((b) => b.id == params["id"]!);

    return AppShell(
        title: Text(book.name),
        body: Column(
          children: [Text("By ${book.author}"), Text("ID: ${params['id']}")],
        ));
  }
}

class AppShell extends StatelessWidget {
  final Widget body;
  final Widget title;

  const AppShell({super.key, required this.body, required this.title});

  @override
  Widget build(BuildContext context) {
    return Scaffold(appBar: AppBar(title: title), body: body);
  }
}

class RouteInfo {
  final String path;
  final Map<String, String?> data;

  RouteInfo({required this.path, required this.data});
}

class Matcher {
  final String path;
  final RegExp matcher;

  const Matcher(this.path, this.matcher);

  RouteInfo? matchWith(expPath) {
    final match = matcher.firstMatch(expPath);

    if (match == null) {
      return null;
    }

    final values =
        List.generate(match.groupCount, (index) => match.group(index + 1));
    final data = Map.fromIterables(match.groupNames, values);

    return RouteInfo(path: path, data: data);
  }
}

class BetterRouter {
  final Map<String, WidgetBuilder> routes;

  BetterRouter({required this.routes}) : assert(routes['-matchAll'] != null);

  pageRouteBuilder<T>(RouteSettings settings, WidgetBuilder builder) {
    return MaterialPageRoute<T>(settings: settings, builder: builder);
  }

  Route<dynamic>? call(RouteSettings settings) {
    final String path = settings.name!;

    RouteInfo routeInfo = _routeInfo(path);

    final WidgetBuilder pageContentBuilder = routes[routeInfo.path]!;

    final Route<dynamic> route = pageRouteBuilder<dynamic>(
      settings.copyWith(arguments: routeInfo.data),
      pageContentBuilder,
    );

    return route;
  }

  Iterable<Matcher> get _mapper =>
      routes.keys.map((path) => Matcher(path, RegExp("^$path\$")));

  final _mapped = <String, RouteInfo>{};

  RouteInfo _routeInfo(path) => _mapped.putIfAbsent(
      path,
      () => _mapper.map((m) => m.matchWith(path)).lastWhere(
            (element) => element != null,
            orElse: () => RouteInfo(path: "-matchAll", data: {}),
          )!);
}