import 'package:flutter/material.dart';

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

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

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Navigation Assignment',
      theme: ThemeData(primarySwatch: Colors.blue),
      // Defining routes is necessary for the pushNamed method
      initialRoute: '/',
      routes: {
        '/': (context) => const HomeScreen(),
        '/screenTwo': (context) => const ScreenTwo(),
        '/screenThree': (context) => const ScreenThree(),
        '/screenFour': (context) => const ScreenFour(),
      },
    );
  }
}

// ==========================================
// SCREEN 1: HOME SCREEN
// ==========================================
class HomeScreen extends StatelessWidget {
  const HomeScreen({super.key});

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('Home Screen (Screen 1)'), backgroundColor: Colors.blue),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            const Text('Stack: [Home]', style: TextStyle(fontWeight: FontWeight.bold)),
            const SizedBox(height: 20),
            
            // 1. push
            ElevatedButton(
              onPressed: () {
                Navigator.push(
                  context,
                  MaterialPageRoute(builder: (context) => const ScreenTwo()),
                );
              },
              child: const Text('1. Navigator.push() to Screen 2'),
            ),

            // 7. pushNamed
            ElevatedButton(
              onPressed: () {
                Navigator.pushNamed(context, '/screenTwo');
              },
              style: ElevatedButton.styleFrom(backgroundColor: Colors.purple, foregroundColor: Colors.white),
              child: const Text('7. Navigator.pushNamed() to Screen 2'),
            ),

            // 6. maybePop
            ElevatedButton(
              onPressed: () async {
                // maybePop only pops if there is a previous screen.
                // Since this is the root screen, it will return false and do nothing,
                // preventing the app from accidentally closing.
                bool canPop = await Navigator.maybePop(context);
                if (!canPop) {
                  ScaffoldMessenger.of(context).showSnackBar(
                    const SnackBar(content: Text('maybePop: Cannot pop root screen!')),
                  );
                }
              },
              style: ElevatedButton.styleFrom(backgroundColor: Colors.orange, foregroundColor: Colors.white),
              child: const Text('6. Navigator.maybePop() test'),
            ),
          ],
        ),
      ),
    );
  }
}

// ==========================================
// SCREEN 2
// ==========================================
class ScreenTwo extends StatelessWidget {
  const ScreenTwo({super.key});

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('Screen 2'), backgroundColor: Colors.green),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            const Text('Stack: [Home -> Screen 2]', style: TextStyle(fontWeight: FontWeight.bold)),
            const SizedBox(height: 20),

            // 2. pop
            ElevatedButton(
              onPressed: () {
                Navigator.pop(context);
              },
              style: ElevatedButton.styleFrom(backgroundColor: Colors.red, foregroundColor: Colors.white),
              child: const Text('2. Navigator.pop() back to Home'),
            ),

            // 3. pushReplacement
            ElevatedButton(
              onPressed: () {
                // Replaces Screen 2 with Screen 3 in the stack
                Navigator.pushReplacement(
                  context,
                  MaterialPageRoute(builder: (context) => const ScreenThree()),
                );
              },
              style: ElevatedButton.styleFrom(backgroundColor: Colors.teal, foregroundColor: Colors.white),
              child: const Text('3. Navigator.pushReplacement() to Screen 3'),
            ),

            // Normal push to continue the stack deeply for later tests
            ElevatedButton(
              onPressed: () {
                Navigator.push(
                  context,
                  MaterialPageRoute(builder: (context) => const ScreenThree()),
                );
              },
              child: const Text('Navigator.push() to Screen 3'),
            ),
          ],
        ),
      ),
    );
  }
}

// ==========================================
// SCREEN 3
// ==========================================
class ScreenThree extends StatelessWidget {
  const ScreenThree({super.key});

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('Screen 3'), backgroundColor: Colors.orange),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            const Text('Current Screen: Screen 3', style: TextStyle(fontWeight: FontWeight.bold)),
            const SizedBox(height: 20),

            // Normal push to Screen 4
            ElevatedButton(
              onPressed: () {
                Navigator.push(
                  context,
                  MaterialPageRoute(builder: (context) => const ScreenFour()),
                );
              },
              child: const Text('Navigator.push() to Screen 4'),
            ),

            // 4. pushAndRemoveUntil
            ElevatedButton(
              onPressed: () {
                // Pushes a brand new Home Screen and destroys all previous routes in the stack
                Navigator.pushAndRemoveUntil(
                  context,
                  MaterialPageRoute(builder: (context) => const HomeScreen()),
                  (Route<dynamic> route) => false, // false means remove all existing routes
                );
              },
              style: ElevatedButton.styleFrom(backgroundColor: Colors.brown, foregroundColor: Colors.white),
              child: const Text('4. Navigator.pushAndRemoveUntil() to Home'),
            ),
          ],
        ),
      ),
    );
  }
}

// ==========================================
// SCREEN 4
// ==========================================
class ScreenFour extends StatelessWidget {
  const ScreenFour({super.key});

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('Screen 4'), backgroundColor: Colors.purple),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            const Text('Stack: [Home -> ... -> Screen 4]', style: TextStyle(fontWeight: FontWeight.bold)),
            const SizedBox(height: 20),

            // 5. popUntil
            ElevatedButton(
              onPressed: () {
                // Keep popping screens until we reach the very first route (Home)
                Navigator.popUntil(context, (route) => route.isFirst);
              },
              style: ElevatedButton.styleFrom(backgroundColor: Colors.indigo, foregroundColor: Colors.white),
              child: const Text('5. Navigator.popUntil() back to First Screen'),
            ),
          ],
        ),
      ),
    );
  }
}

⚠️Content was pasted as plain text and auto-formatted as a code block. Use the Code Block button in the editor for proper formatting.