import 'package:flutter/material.dart';

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

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

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
        useMaterial3: true,
      ),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key, required this.title});
  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        backgroundColor: Theme.of(context).colorScheme.inversePrimary,
        title: Text(widget.title),
      ),
      body: Column(
        children: [
          Padding(
            padding: const EdgeInsets.all(20.0),
            child: Row(
              mainAxisAlignment: MainAxisAlignment.center,
              children: [
                Builder(
                  builder: (context) {
                    final child = Container(
                      width: 200,
                      height: 125,
                      color: Colors.green,
                    );

                    return Draggable<String>(
                      data: "data",
                      feedback: child,
                      childWhenDragging: Opacity(opacity: 0.5, child: child),
                      child: child,
                    );
                  },
                ),
              ],
            ),
          ),
          Expanded(
            child: Stack(
              children: [
                Center(
                  child: DragTarget(
                    onWillAccept: (_) => true,
                    builder: (context, candidates, _) => Container(
                      color: Colors.yellow,
                      width: 250,
                      height: 250,
                      alignment: Alignment.center,
                      child: candidates.isNotEmpty
                          ? const Icon(Icons.check, size: 48)
                          : null,
                    ),
                  ),
                ),
                Positioned.fill(
                  child: DragTarget(
                    onWillAccept: (_) => false,
                    builder: (context, candidates, rejected) {
                      return IgnorePointer(
                        child: Container(
                          alignment: Alignment.topLeft,
                          padding: const EdgeInsets.all(10),
                          decoration: BoxDecoration(
                            border: Border.all(
                              color: rejected.isEmpty
                                  ? Colors.blue
                                  : Colors.purple,
                              width: 5,
                            ),
                          ),
                          child: Text(
                            "Entered: ${rejected.length}",
                            style: Theme.of(context).textTheme.headlineSmall,
                          ),
                        ),
                      );
                    },
                  ),
                ),
              ],
            ),
          ),
        ],
      ),
    );
  }
}