// ignore_for_file: unused_element

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

final router = GoRouter(
  initialLocation: '/page1',
  routes: [
    ShellRoute(
      builder: (context, state, child) {
        return HomePage(child: child);
      },
      routes: [
        GoRoute(
          path: '/page1',
          name: "page1",
          // builder: (context, state) => const Page1(),
          pageBuilder: (context, state) {
            return FadeTransitionPage(key: state.pageKey, child: const Page1());
          },
        ),

        GoRoute(
          path: '/page2',
          name: "page2",
          // builder: (context, state) => const Page2(),
          pageBuilder: (context, state) {
            return FadeTransitionPage(key: state.pageKey, child: const Page2());
          },
        ),

        GoRoute(
          path: '/page3',
          name: "page3",
          // builder: (context, state) => const Page3(),
          pageBuilder: (context, state) {
            return FadeTransitionPage(key: state.pageKey, child: const Page3());
          },
        )
      ], 
    ),
  ]
);

void main() {
  runApp(const MyApp());
}

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

  @override
  Widget build(BuildContext context) {
    return MaterialApp.router(
      title: 'Flutter Demo',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(useMaterial3: true),
      routerConfig: router,
    );
  }
}

class HomePage extends StatefulWidget {
  final Widget child;

  const HomePage({
    super.key,
    required this.child
  });

  @override
  State<HomePage> createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> with SingleTickerProviderStateMixin {
  static const _routes = ["page1", "page2", "page3"];

  int _routeIndex = 0;
  
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Go Router Issue'),
      ),
      body: widget.child,
      bottomNavigationBar: NavigationBar(
        selectedIndex: _routeIndex,
        onDestinationSelected: (index) {
          setState(() => _routeIndex = index);
          context.goNamed(_routes[index]);
        },
        destinations: const [
          NavigationDestination(
            icon: Icon(Icons.looks_one_rounded), 
            label: "Page 1"
          ),

          NavigationDestination(
            icon: Icon(Icons.looks_two_rounded), 
            label: "Page 2"
          ),

          NavigationDestination(
            icon: Icon(Icons.looks_3_rounded), 
            label: "Page 3"
          )
        ],        
      ),
    );
  }
}

class Page1 extends StatelessWidget {
  const Page1({super.key});

  @override
  Widget build(BuildContext context) {
    return const Align(
      alignment: Alignment(0.0, -0.2),
      child: Text('PAGE 1', style: TextStyle(fontSize: 48)),
    );
  }
}

class Page2 extends StatelessWidget {
  const Page2({super.key});

  @override
  Widget build(BuildContext context) {
    return const Align(
      alignment: Alignment(0.0, 0.0),
      child: Text('PAGE 2', style: TextStyle(fontSize: 48)),
    );
  }
}

class Page3 extends StatelessWidget {
  const Page3({super.key});

  @override
  Widget build(BuildContext context) {
    return const Align(
      alignment: Alignment(0.0, 0.2),
      child: Text('PAGE 3', style: TextStyle(fontSize: 48)),
    );
  }
}

class FadeTransitionPage extends CustomTransitionPage {
  const FadeTransitionPage({
    super.key,
    required super.child, 
  }) : super(
    transitionsBuilder: _transitionBuilder,
    transitionDuration: const Duration(milliseconds: 1000),
    reverseTransitionDuration: const Duration(milliseconds: 1000)
  );

  static Widget _transitionBuilder(BuildContext context, Animation<double> animation, Animation<double> secondaryAnimation, Widget child) {
    return _FadePageTransition(animation: animation, secondaryAnimation: secondaryAnimation, child: child);
  }
}


class _FadePageTransition extends StatelessWidget {
  const _FadePageTransition({
    super.key,
    required this.animation,
    required this.secondaryAnimation,
    required this.child,
  });

  final Animation<double> animation;
  final Animation<double> secondaryAnimation;
  final Widget? child;

  @override
  Widget build(BuildContext context) {
    return DualTransitionBuilder(
      animation: animation,
      forwardBuilder: (
        BuildContext context,
        Animation<double> animation,
        Widget? child,
      ) {
        return _FadeEnterTransition(
          animation: animation,
          child: child,
        );
      },
      reverseBuilder: (
        BuildContext context,
        Animation<double> animation,
        Widget? child,
      ) {
        return _FadeExitTransition(
          animation: animation,
          reverse: true,
          child: child,
        );
      },
      child: DualTransitionBuilder(
        animation: ReverseAnimation(secondaryAnimation),
        forwardBuilder: (
          BuildContext context,
          Animation<double> animation,
          Widget? child,
        ) {
          return _FadeEnterTransition(
            animation: animation,
            reverse: true,
            child: child,
          );
        },
        reverseBuilder: (
          BuildContext context,
          Animation<double> animation,
          Widget? child,
        ) {
          return _FadeExitTransition(
            animation: animation,
            child: child,
          );
        },
        child: child,
      ),
    );
  }
}

class _FadeEnterTransition extends StatelessWidget {
  const _FadeEnterTransition({
    super.key,
    required this.animation,
    this.reverse = false,
    required this.child,
  });

  final Animation<double> animation;
  final Widget? child;
  final bool reverse;

  static final Animatable<double> _fadeInTransition = Tween<double>(begin: 0.0, end: 1.00);

  @override
  Widget build(BuildContext context) {
    final Animation<double> fadeTransition = reverse
      ? kAlwaysCompleteAnimation
      : _fadeInTransition.animate(animation);

    return FadeTransition(
      opacity: fadeTransition,
      child: child,
    );
  }
}

class _FadeExitTransition extends StatelessWidget {
  const _FadeExitTransition({
    super.key,
    required this.animation,
    this.reverse = false,
    required this.child,
  });

  final Animation<double> animation;
  final bool reverse;
  final Widget? child;

  static final Animatable<double> _fadeOutTransition = Tween<double>(begin: 1.0, end: 0.0);

  @override
  Widget build(BuildContext context) {
    final Animation<double> fadeTransition = reverse
      ? _fadeOutTransition.animate(animation)
      : kAlwaysCompleteAnimation;

    return FadeTransition(
      opacity: fadeTransition,
      child: child,
    );
  }
}