실생활 앱 (구독 관리)

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

class Subscription {
  const Subscription({
    required this.serverId,
    required this.name,
    required this.price,
    required this.nextBillingDay,
    this.active = true,
    this.verified = false,
  });
  final String serverId;
  final String name;
  final int price;
  final int nextBillingDay;
  final bool active;
  final bool verified;

  Subscription copyWith({String? name, int? price, int? nextBillingDay, bool? active, bool? verified}) {
    return Subscription(
      serverId: serverId,
      name: name ?? this.name,
      price: price ?? this.price,
      nextBillingDay: nextBillingDay ?? this.nextBillingDay,
      active: active ?? this.active,
      verified: verified ?? this.verified,
    );
  }
}

class SubscriptionManagerApp extends StatefulWidget {
  const SubscriptionManagerApp({super.key});

  @override
  State<SubscriptionManagerApp> createState() => _SubscriptionManagerAppState();
}

class _SubscriptionManagerAppState extends State<SubscriptionManagerApp> {
  final nameController = TextEditingController(text: '음악 스트리밍');
  final priceController = TextEditingController(text: '9900');
  var subscriptions = const [
    Subscription(serverId: 'sub_cloud_01', name: '클라우드 저장소', price: 3300, nextBillingDay: 4),
    Subscription(serverId: 'sub_video_02', name: '영상 스트리밍', price: 13500, nextBillingDay: 18),
  ];
  var syncing = false;
  var verifying = false;
  var auditLog = const ['로그인 사용자 확인'];

  int get monthlyTotal {
    return subscriptions
        .where((item) => item.active)
        .fold(0, (sum, item) => sum + item.price);
  }

  void addSubscription() {
    final name = nameController.text.trim();
    final price = int.tryParse(priceController.text) ?? 0;
    if (name.isEmpty || price <= 0) return;
    setState(() {
      subscriptions = [
        ...subscriptions,
        Subscription(serverId: 'local_\${DateTime.now().millisecondsSinceEpoch}', name: name, price: price, nextBillingDay: 12),
      ];
      auditLog = ['구독 추가: $name', ...auditLog];
      nameController.clear();
      priceController.clear();
    });
  }

  Future<void> verifyPayments() async {
    setState(() => verifying = true);
    await Future.delayed(const Duration(seconds: 1));
    setState(() {
      subscriptions = [for (final item in subscriptions) item.copyWith(verified: true)];
      auditLog = ['결제 상태 검증 완료', ...auditLog];
      verifying = false;
    });
  }

  Future<void> syncCloud() async {
    setState(() => syncing = true);
    await Future.delayed(const Duration(seconds: 1));
    setState(() {
      auditLog = ['클라우드 동기화 완료', ...auditLog];
      syncing = false;
    });
  }

  void scheduleRenewalAlerts() {
    final count = subscriptions.where((item) => item.active && item.nextBillingDay <= 7).length;
    setState(() => auditLog = ['갱신 알림 $count건 예약', ...auditLog]);
  }

  void toggleSubscription(int index) {
    setState(() {
      subscriptions = [
        for (var i = 0; i < subscriptions.length; i++)
          i == index ? subscriptions[i].copyWith(active: !subscriptions[i].active) : subscriptions[i],
      ];
    });
  }

  void removeSubscription(int index) {
    setState(() => subscriptions = [...subscriptions]..removeAt(index));
  }

  @override
  Widget build(BuildContext context) {
    return Column(
      children: [
        TextField(controller: nameController),
        TextField(controller: priceController, keyboardType: TextInputType.number),
        ElevatedButton(onPressed: addSubscription, child: const Text('구독 추가')),
        Text('월 구독료: $monthlyTotal원'),
        Wrap(children: [
          ElevatedButton(onPressed: syncCloud, child: Text(syncing ? '동기화 중' : '클라우드 동기화')),
          ElevatedButton(onPressed: verifyPayments, child: Text(verifying ? '검증 중' : '결제 검증')),
          ElevatedButton(onPressed: scheduleRenewalAlerts, child: const Text('갱신 알림 예약')),
        ]),
        ...List.generate(subscriptions.length, (index) {
          final item = subscriptions[index];
          return ListTile(
            title: Text(item.name),
            subtitle: Text(item.active
                ? '\${item.price}원 · D-\${item.nextBillingDay} · \${item.verified ? '검증됨' : '미검증'}'
                : '해지됨'),
            trailing: Wrap(children: [
              Switch(value: item.active, onChanged: (_) => toggleSubscription(index)),
              IconButton(onPressed: () => removeSubscription(index), icon: const Icon(Icons.delete)),
            ]),
          );
        }),
        ...auditLog.map(Text.new),
      ],
    );
  }
}

Card(
  child: Padding(
    padding: const EdgeInsets.all(20),
    child: Column(
      crossAxisAlignment: CrossAxisAlignment.start,
      children: [
        const Text(
          '구독 관리',
          style: TextStyle(fontSize: 22, fontWeight: FontWeight.w900),
        ),
        const SizedBox(height: 16),
        TextField(controller: nameController),
      const SizedBox(height: 12),
      FilledButton(onPressed: addSubscription, child: const Text('구독 추가')),
      Text('월 구독료: ${totalPrice}원'),
      ...subscriptions.map((item) {
        return ListTile(
          title: Text(item.name),
          subtitle: Text('${item.price}원'),
          trailing: Switch(value: item.active, onChanged: (_) => toggleSubscription(item)),
        );
      })
      ],
    ),
  ),
)