import 'package:flutter/material.dart';

import '../../core/data/backend.dart' show BackendException;
import '../../core/i18n/app_locale.dart';
import '../../core/push/push_messaging.dart';
import '../../core/theme/tokens.dart';
import '../../core/ui/app_icons.dart';
import '../../core/ui/sheet_route.dart';
import '../home/coach_mark.dart';
import '../home/home_data.dart';
import '../home/nebula_create_screen.dart';
import '../my/my_data.dart'
    show nicknameMaxLength, nicknameMinLength, nicknameReserved;
import '../planet/planet_data.dart' show countryName;
import 'auth_repository.dart';
import 'onboarding_data.dart';
import 'signup_screens.dart';

/// 온보딩 ① 소개 3장 — FR-CMN-03 「소개는 3장으로 고정 · 건너뛰기를 눌러도 로그인 화면으로」.
///
/// 앱 Figma 사본에 소개 화면이 없다(해석 확인 Q-OB-02 A 「사본의 컴포넌트 · 색 · 글꼴 · 화면 틀로
/// 구성」). 문구 · 이미지는 발주사 제공본이 오면 바꾼다(해석 확인 요청 E-Q7).
class IntroScreen extends StatefulWidget {
  const IntroScreen({super.key, required this.onDone});

  final VoidCallback onDone;

  @override
  State<IntroScreen> createState() => _IntroScreenState();
}

class _IntroScreenState extends State<IntroScreen> {
  final _pages = PageController();
  int _page = 0;

  @override
  void dispose() {
    _pages.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    final l10n = context.l10n;
    final slides = [
      (l10n.onbIntro1Title, l10n.onbIntro1Body),
      (l10n.onbIntro2Title, l10n.onbIntro2Body),
      (l10n.onbIntro3Title, l10n.onbIntro3Body),
    ];
    final last = _page == slides.length - 1;
    return Scaffold(
      body: SafeArea(
        child: Column(
          children: [
            Align(
              alignment: Alignment.centerRight,
              child: TextButton(
                onPressed: widget.onDone,
                child: Text(l10n.onbSkip),
              ),
            ),
            Expanded(
              child: PageView(
                controller: _pages,
                onPageChanged: (i) => setState(() => _page = i),
                children: [
                  for (final (title, body) in slides)
                    Padding(
                      padding: const EdgeInsets.all(AppSpace.s6),
                      child: Column(
                        mainAxisAlignment: MainAxisAlignment.center,
                        children: [
                          const SizedBox.square(
                            dimension: 120,
                            child: DecoratedBox(
                              decoration: BoxDecoration(
                                color: AppColors.cosmicAccent,
                                shape: BoxShape.circle,
                              ),
                            ),
                          ),
                          const SizedBox(height: AppSpace.s6),
                          Text(
                            title,
                            textAlign: TextAlign.center,
                            style: _title,
                          ),
                          const SizedBox(height: AppSpace.s3),
                          Text(body, textAlign: TextAlign.center, style: _body),
                        ],
                      ),
                    ),
                ],
              ),
            ),
            Row(
              mainAxisAlignment: MainAxisAlignment.center,
              children: [
                for (var i = 0; i < slides.length; i++)
                  Container(
                    margin: const EdgeInsets.all(4),
                    width: 8,
                    height: 8,
                    decoration: BoxDecoration(
                      shape: BoxShape.circle,
                      color: i == _page
                          ? AppColors.cosmicAccent
                          : AppColors.onCosmicMuted,
                    ),
                  ),
              ],
            ),
            Padding(
              padding: const EdgeInsets.all(AppSpace.s4),
              child: _PrimaryButton(
                label: last ? l10n.commonStart : l10n.commonNext,
                onPressed: last
                    ? widget.onDone
                    : () => _pages.nextPage(
                        duration: const Duration(milliseconds: 250),
                        curve: Curves.easeOut,
                      ),
              ),
            ),
          ],
        ),
      ),
    );
  }
}

enum _Step { terms, profile, artist, planet, permissions }

/// 온보딩 ②~⑥ — 로그인(가입 · 로그인 버튼 구분 없이) 뒤 서버에 약관 동의가 없으면 여기로 온다.
///
/// 순서는 10/3 통합회신 1항 그대로: 약관 → 프로필 → 관심 아티스트/Primary → 행성 가입 또는 성운
/// 생성 → 권한 안내. 약관을 기록한 뒤 앱을 닫으면 다음 실행은 HOME(`홈_초기사용자`)으로 간다
/// (Q-OB-02 A 「`홈_초기사용자` — 가입 흐름을 마치기 전에 앱을 닫은 사용자에게 사본대로」).
class OnboardingFlow extends StatefulWidget {
  const OnboardingFlow({
    super.key,
    required this.auth,
    required this.repository,
    required this.home,
    this.push,
  });

  final AuthRepository auth;
  final OnboardingRepository repository;

  /// 성운 생성(`홈/성운 생성` 사본 화면)이 쓰는 저장소.
  final HomeRepository home;

  /// 권한 안내의 OS 알림 팝업. 목 모드에서는 null.
  final PushMessaging? push;

  @override
  State<OnboardingFlow> createState() => _OnboardingFlowState();
}

class _OnboardingFlowState extends State<OnboardingFlow> {
  _Step _step = _Step.terms;
  bool _busy = false;

  /// ② 에서 서버에 기록한 동의 항목. ③ 에서 뒤로 오면 이 상태로 체크해 보여 준다.
  Set<String>? _agreed;

  /// ③ 에서 서버에 귀속한 추천인 코드. ④ 에서 뒤로 와 다시 「다음」이면 또 부르지 않는다
  /// (서버는 1인 1회라 두 번째 호출을 거절한다).
  String? _referred;

  /// ④ 에서 고른 팬덤 — 고른 순서. 첫 번째가 대표(Primary).
  final _picked = <OnboardingFandom>[];

  @override
  void initState() {
    super.initState();
    // 가입 모드는 제공자 인증 전에 약관을 받았다 — 다시 묻지 않고 기록만 한다.
    final pending = widget.auth.pendingConsent;
    if (pending != null) _agree(pending);
  }

  Future<void> _run(Future<void> Function() task) async {
    setState(() => _busy = true);
    try {
      await task();
    } on BackendException catch (e) {
      _toast(e.message);
    } catch (_) {
      if (mounted) _toast(context.l10n.commonRequestFailed);
    } finally {
      if (mounted) setState(() => _busy = false);
    }
  }

  void _toast(String message) => ScaffoldMessenger.maybeOf(context)
    ?..hideCurrentSnackBar()
    ..showSnackBar(SnackBar(content: Text(message)));

  void _agree(Set<String> agreed) {
    if (_busy) return;
    // ③ 에서 뒤로 왔다가 그대로 「완료」면 기록을 다시 남기지 않는다(서버 동의 기록 유지).
    final prev = _agreed;
    if (prev != null &&
        prev.length == agreed.length &&
        prev.containsAll(agreed)) {
      setState(() => _step = _Step.profile);
      return;
    }
    _run(() async {
      await widget.repository.agree(agreed, signupTermsVersion);
      _agreed = agreed;
      if (mounted) setState(() => _step = _Step.profile);
    });
  }

  void _back() => setState(
    () => _step = switch (_step) {
      // 명세 `511:86825` 「상단 뒤로가기 — 이전 화면」. 이전 = ② 약관(동의 체크 유지).
      _Step.profile => _Step.terms,
      _Step.artist => _Step.profile,
      _Step.planet => _Step.artist,
      final s => s,
    },
  );

  Future<void> _finish() async {
    try {
      await widget.push?.requestPermission();
    } catch (_) {
      // 거부 · 플러그인 오류여도 다음으로 간다(FR-CMN-08).
    }
    await armCoachMark();
    widget.auth.completeOnboarding();
  }

  @override
  Widget build(BuildContext context) {
    final body = switch (_step) {
      _Step.terms => TermsScreen(
        key: ValueKey(_agreed),
        initial: _agreed ?? const {},
        onAgreed: _agree,
        onBack: widget.auth.signOut,
      ),
      _Step.profile => _ProfileStep(
        repository: widget.repository,
        referred: _referred,
        onReferred: (code) => _referred = code,
        onBack: _back,
        onDone: () => setState(() => _step = _Step.artist),
      ),
      _Step.artist => _ArtistStep(
        repository: widget.repository,
        picked: _picked,
        onNext: () => setState(() => _step = _Step.planet),
        onBack: _back,
      ),
      _Step.planet => _PlanetStep(
        picked: _picked,
        busy: _busy,
        onBack: _back,
        onJoin: () => _run(() async {
          await widget.repository.join([for (final f in _picked) f.id]);
          if (mounted) setState(() => _step = _Step.permissions);
        }),
        onCreateNebula: () async {
          final created = await Navigator.of(context).push<String>(
            SheetRoute(
              builder: (_) => NebulaCreateScreen(repository: widget.home),
            ),
          );
          if (created != null && mounted) {
            setState(() => _step = _Step.permissions);
          }
        },
      ),
      _Step.permissions => _PermissionStep(onContinue: _finish),
    };
    return PopScope(
      canPop: false,
      onPopInvokedWithResult: (didPop, _) {
        if (!didPop) _back();
      },
      child: body,
    );
  }
}

/// ③ 프로필 — 닉네임 2~20(중복 허용 · B-52) · 국가/지역 · 표시 언어 · 추천인 코드(선택).
/// 사본 `MY/프로필 설정` 구성을 따른다. 국가 기본값은 기기 지역(Figma `554:24126` 「앱 기동 단계에서
/// 조회된 국가/언어를 디폴트」).
class _ProfileStep extends StatefulWidget {
  const _ProfileStep({
    required this.repository,
    required this.referred,
    required this.onReferred,
    required this.onDone,
    required this.onBack,
  });

  final OnboardingRepository repository;

  /// 이미 귀속한 추천인 코드(뒤로 왔을 때 채워 보여 준다).
  final String? referred;
  final ValueChanged<String> onReferred;
  final VoidCallback onDone;
  final VoidCallback onBack;

  @override
  State<_ProfileStep> createState() => _ProfileStepState();
}

class _ProfileStepState extends State<_ProfileStep> {
  final _nickname = TextEditingController();
  late final _referral = TextEditingController(text: widget.referred);
  String? _country = _deviceCountry();
  Locale? _locale;
  String? _nicknameError;
  String? _referralError;
  bool _busy = false;

  /// 기기 지역. 없으면 비워 두고 사용자가 고르게 한다(임의 국가로 채우지 않는다).
  static String? _deviceCountry() {
    final code = WidgetsBinding.instance.platformDispatcher.locale.countryCode
        ?.toUpperCase();
    return code != null && isoCountries.contains(code) ? code : null;
  }

  @override
  void initState() {
    super.initState();
    _nickname.addListener(() => setState(() => _nicknameError = null));
    widget.repository.currentProfile().then((p) {
      if (!mounted) return;
      setState(() {
        if (_nickname.text.isEmpty) _nickname.text = p.nickname;
        if (p.country != null && isoCountries.contains(p.country)) {
          _country = p.country!;
        }
      });
    }, onError: (_) {});
  }

  @override
  void dispose() {
    _nickname.dispose();
    _referral.dispose();
    super.dispose();
  }

  bool get _valid {
    final n = _nickname.text.trim().characters.length;
    return n >= nicknameMinLength && n <= nicknameMaxLength && _country != null;
  }

  Future<void> _save() async {
    final l10n = context.l10n;
    final nickname = _nickname.text.trim();
    if (nicknameReserved(nickname)) {
      setState(() => _nicknameError = l10n.nicknameReserved);
      return;
    }
    final scope = LocaleScope.maybeOf(context);
    final locale = _locale ?? scope?.locale ?? fallbackLocale;
    setState(() => _busy = true);
    try {
      await widget.repository.saveProfile(
        nickname: nickname,
        country: _country!,
        locale: localeTag(locale),
      );
      if (_locale != null) await scope?.select(_locale!);
      final code = _referral.text.trim().toUpperCase();
      if (code.isNotEmpty && code != widget.referred) {
        try {
          await widget.repository.attributeReferral(code);
          widget.onReferred(code);
        } on BackendException catch (e) {
          // 거절 사유(형식 · 없는 코드 · 본인 · 상호 · 이미 등록 · 7일 경과)는 Figma `511:86845`
          // 문구 하나로 보인다(C-119 「오류 문구 재사용」). 통신 실패만 서버 문구 그대로.
          if (mounted) {
            setState(
              () => _referralError = e.code == 'E-SYS-01'
                  ? e.message
                  : l10n.onbReferralInvalid,
            );
          }
          return;
        }
      }
      widget.onDone();
    } on BackendException catch (e) {
      if (mounted) setState(() => _nicknameError = e.message);
    } finally {
      if (mounted) setState(() => _busy = false);
    }
  }

  Future<void> _pickCountry() async {
    final picked = await showModalBottomSheet<String>(
      context: context,
      isScrollControlled: true,
      backgroundColor: const Color(0xFF101010),
      // 사본 `178:23489` 상단 손잡이.
      showDragHandle: true,
      builder: (_) => _CountrySheet(current: _country),
    );
    if (picked != null && mounted) setState(() => _country = picked);
  }

  @override
  Widget build(BuildContext context) {
    final l10n = context.l10n;
    final current = _locale ?? LocaleScope.maybeOf(context)?.locale;
    // Figma `511:86825` — 머리줄 「<」 좌측 · 타이틀 중앙(사본 `178:23489` 「회원가입」), 본문 큰 제목 없음.
    // 입력란은 사본처럼 테두리 상자(`511:86809`).
    return _StepScaffold(
      barTitle: l10n.authSignup,
      onBack: widget.onBack,
      boxedInputs: true,
      action: _PrimaryButton(
        label: l10n.commonNext,
        onPressed: _valid && !_busy ? _save : null,
      ),
      children: [
        TextField(
          controller: _nickname,
          maxLength: nicknameMaxLength,
          decoration: InputDecoration(
            labelText: l10n.settingsNickname,
            helperText: l10n.onbNicknameHint,
            errorText: _nicknameError,
          ),
        ),
        const SizedBox(height: AppSpace.s3),
        // 사본 국가 리스트 모달 `178:23489`(명세 `511:86786` · `511:86796`) — 국기 · 국가명 ·
        // 단수 선택 체크, 「선택」을 눌러야 적용하고 닫힌다.
        InkWell(
          onTap: _pickCountry,
          child: InputDecorator(
            decoration: InputDecoration(
              labelText: l10n.onbCountry,
              suffixIcon: const Icon(Icons.expand_more),
            ),
            isEmpty: _country == null,
            child: _country == null
                ? null
                : Text('${countryFlag(_country!)}  ${countryName(_country!)}'),
          ),
        ),
        const SizedBox(height: AppSpace.s3),
        DropdownButtonFormField<Locale>(
          initialValue: appLocales.contains(current) ? current : null,
          isExpanded: true,
          decoration: InputDecoration(labelText: l10n.onbLanguage),
          items: [
            for (final l in appLocales)
              DropdownMenuItem(value: l, child: Text(languageName(l))),
          ],
          onChanged: (v) => setState(() => _locale = v),
        ),
        const SizedBox(height: AppSpace.s3),
        // 추천인 코드 입력칸 — Figma 이메일 가입 `333:18620`(입력칸) · `511:86845`(오류) ·
        // `511:86809`(선택 입력). 10/3 통합회신 7항으로 가입 직후 온보딩에 둔다(C-119).
        TextField(
          controller: _referral,
          textCapitalization: TextCapitalization.characters,
          maxLength: 10,
          onChanged: (_) => setState(() => _referralError = null),
          decoration: InputDecoration(
            labelText: l10n.onbReferral,
            errorText: _referralError,
          ),
        ),
      ],
    );
  }
}

/// 국가 리스트 모달 — 사본 `178:23489`.
///
/// 명세 `511:86762` 타이틀 좌측 · 닫기 우측(누르면 모달 종료) / `511:86786` 국기 좌측 · 국가명 ·
/// 선택한 국가에만 오른쪽 체크(단수) / `511:86796` 국가를 골라야 「선택」이 켜지고, 누르면 적용 후 닫힘.
class _CountrySheet extends StatefulWidget {
  const _CountrySheet({required this.current});

  final String? current;

  @override
  State<_CountrySheet> createState() => _CountrySheetState();
}

class _CountrySheetState extends State<_CountrySheet> {
  late String? _picked = widget.current;

  @override
  Widget build(BuildContext context) => SafeArea(
    child: SizedBox(
      height: MediaQuery.sizeOf(context).height * 0.8,
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.stretch,
        children: [
          Padding(
            padding: const EdgeInsets.fromLTRB(16, 0, 4, 0),
            child: Row(
              children: [
                Expanded(
                  child: Text(context.l10n.onbCountrySheetTitle, style: _title),
                ),
                IconButton(
                  tooltip: context.l10n.commonClose,
                  onPressed: () => Navigator.of(context).pop(),
                  icon: const ImageIcon(AppIcons.x, size: 24),
                ),
              ],
            ),
          ),
          Expanded(
            child: ListView(
              children: [
                for (final c in sortedCountries())
                  ListTile(
                    onTap: () => setState(() => _picked = c),
                    leading: Text(
                      countryFlag(c),
                      style: const TextStyle(fontSize: 22),
                    ),
                    title: Text(countryName(c)),
                    trailing: c == _picked
                        ? const Icon(
                            Icons.check_circle_outline,
                            color: AppColors.cosmicAccent,
                          )
                        : null,
                  ),
              ],
            ),
          ),
          Padding(
            padding: const EdgeInsets.all(AppSpace.s4),
            child: _PrimaryButton(
              label: context.l10n.commonSelect,
              onPressed: _picked == null
                  ? null
                  : () => Navigator.of(context).pop(_picked),
            ),
          ),
        ],
      ),
    ),
  );
}

/// ④ 관심 아티스트 / Primary Fandom — 최소 1개(FR-CMN-06). 처음 고른 팬덤이 대표가 된다.
/// 찾는 아티스트가 없으면 ⑤ 에서 성운을 만든다.
class _ArtistStep extends StatefulWidget {
  const _ArtistStep({
    required this.repository,
    required this.picked,
    required this.onNext,
    required this.onBack,
  });

  final OnboardingRepository repository;
  final List<OnboardingFandom> picked;
  final VoidCallback onNext;
  final VoidCallback onBack;

  @override
  State<_ArtistStep> createState() => _ArtistStepState();
}

class _ArtistStepState extends State<_ArtistStep> {
  late Future<List<OnboardingFandom>> _list = widget.repository.fandoms();
  final _query = TextEditingController();

  @override
  void dispose() {
    _query.dispose();
    super.dispose();
  }

  void _toggle(OnboardingFandom f) => setState(() {
    final i = widget.picked.indexWhere((p) => p.id == f.id);
    i >= 0 ? widget.picked.removeAt(i) : widget.picked.add(f);
  });

  @override
  Widget build(BuildContext context) {
    final l10n = context.l10n;
    final picked = widget.picked;
    return _StepScaffold(
      title: l10n.onbArtistTitle,
      subtitle: l10n.onbArtistBody,
      onBack: widget.onBack,
      action: Column(
        crossAxisAlignment: CrossAxisAlignment.stretch,
        children: [
          _PrimaryButton(
            label: l10n.commonNext,
            onPressed: picked.isEmpty ? null : widget.onNext,
          ),
          TextButton(
            onPressed: () {
              picked.clear();
              widget.onNext();
            },
            child: Text(l10n.onbArtistNone),
          ),
        ],
      ),
      children: [
        TextField(
          controller: _query,
          textInputAction: TextInputAction.search,
          decoration: InputDecoration(
            hintText: l10n.onbArtistSearch,
            prefixIcon: const Icon(Icons.search),
          ),
          onSubmitted: (q) =>
              setState(() => _list = widget.repository.fandoms(query: q)),
        ),
        const SizedBox(height: AppSpace.s3),
        FutureBuilder<List<OnboardingFandom>>(
          future: _list,
          builder: (context, snap) {
            if (snap.hasError) {
              return TextButton(
                onPressed: () => setState(
                  () => _list = widget.repository.fandoms(query: _query.text),
                ),
                child: Text(l10n.commonRetry),
              );
            }
            final list = snap.data;
            if (list == null) {
              return const Center(child: CircularProgressIndicator());
            }
            if (list.isEmpty) return Text(l10n.commonNoResults);
            return Column(
              children: [
                for (final f in list)
                  CheckboxListTile(
                    value: picked.any((p) => p.id == f.id),
                    onChanged: (_) => _toggle(f),
                    title: Text(f.name),
                    subtitle: Text(
                      [
                        if (f.nebula) l10n.onbNebulaTag,
                        l10n.onbMembers('${f.members}'),
                      ].join(' · '),
                    ),
                    secondary: picked.isNotEmpty && picked.first.id == f.id
                        ? Chip(label: Text(l10n.onbPrimary))
                        : null,
                  ),
              ],
            );
          },
        ),
      ],
    );
  }
}

/// ⑤ 행성 가입 또는 성운 생성 — 성운 생성은 사본 `홈/성운 생성`(`340:75466`) 그대로.
class _PlanetStep extends StatelessWidget {
  const _PlanetStep({
    required this.picked,
    required this.busy,
    required this.onBack,
    required this.onJoin,
    required this.onCreateNebula,
  });

  final List<OnboardingFandom> picked;
  final bool busy;
  final VoidCallback onBack;
  final VoidCallback onJoin;
  final VoidCallback onCreateNebula;

  @override
  Widget build(BuildContext context) {
    final l10n = context.l10n;
    return _StepScaffold(
      title: l10n.onbPlanetTitle,
      onBack: onBack,
      action: Column(
        crossAxisAlignment: CrossAxisAlignment.stretch,
        children: [
          if (picked.isNotEmpty)
            _PrimaryButton(
              label: l10n.onbPlanetJoin,
              onPressed: busy ? null : onJoin,
            ),
          const SizedBox(height: AppSpace.s2),
          OutlinedButton(
            onPressed: busy ? null : onCreateNebula,
            child: Text(l10n.onbPlanetCreate),
          ),
        ],
      ),
      children: [
        for (final (i, f) in picked.indexed)
          ListTile(
            title: Text(f.name),
            trailing: i == 0 ? Chip(label: Text(l10n.onbPrimary)) : null,
          ),
      ],
    );
  }
}

/// ⑥ 권한 안내 — 한 화면에서 쓰임을 설명하고 OS 팝업은 알림만(FR-CMN-08 · C-84). 건강은 걷기 Quest,
/// 위치는 위치 Quest 에 처음 들어갈 때 요청한다. 거부해도 다음으로 간다.
class _PermissionStep extends StatefulWidget {
  const _PermissionStep({required this.onContinue});

  final Future<void> Function() onContinue;

  @override
  State<_PermissionStep> createState() => _PermissionStepState();
}

class _PermissionStepState extends State<_PermissionStep> {
  bool _busy = false;

  @override
  Widget build(BuildContext context) {
    final l10n = context.l10n;
    return _StepScaffold(
      title: l10n.onbPermTitle,
      subtitle: l10n.onbPermBody,
      action: _PrimaryButton(
        label: l10n.onbPermContinue,
        onPressed: _busy
            ? null
            : () async {
                setState(() => _busy = true);
                await widget.onContinue();
              },
      ),
      children: [
        for (final (icon, title, desc) in [
          (
            Icons.notifications_outlined,
            l10n.onbPermPush,
            l10n.onbPermPushDesc,
          ),
          (Icons.directions_walk, l10n.onbPermHealth, l10n.onbPermHealthDesc),
          (
            Icons.place_outlined,
            l10n.onbPermLocation,
            l10n.onbPermLocationDesc,
          ),
        ])
          ListTile(
            leading: Icon(icon, color: AppColors.cosmicAccent),
            title: Text(title),
            subtitle: Text(desc),
          ),
      ],
    );
  }
}

/// 단계 화면 틀 — 사본 가입 화면과 같은 코스믹 다크 · 하단 고정 버튼.
class _StepScaffold extends StatelessWidget {
  const _StepScaffold({
    this.title,
    required this.action,
    required this.children,
    this.subtitle,
    this.onBack,
    this.barTitle,
    this.boxedInputs = false,
  });

  final String? title;
  final String? barTitle;
  final bool boxedInputs;
  final String? subtitle;
  final Widget action;
  final List<Widget> children;
  final VoidCallback? onBack;

  @override
  Widget build(BuildContext context) => Scaffold(
    appBar: AppBar(
      automaticallyImplyLeading: false,
      leading: onBack == null ? null : BackButton(onPressed: onBack),
      title: barTitle == null ? null : Text(barTitle!),
      centerTitle: true,
    ),
    body: SafeArea(
      top: false,
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.stretch,
        children: [
          Expanded(
            child: _boxed(
              context,
              ListView(
                padding: const EdgeInsets.all(AppSpace.s4),
                children: [
                  if (title != null) ...[
                    Text(title!, style: _title),
                    if (subtitle != null) ...[
                      const SizedBox(height: AppSpace.s2),
                      Text(subtitle!, style: _body),
                    ],
                    const SizedBox(height: AppSpace.s5),
                  ],
                  ...children,
                ],
              ),
            ),
          ),
          Padding(padding: const EdgeInsets.all(AppSpace.s4), child: action),
        ],
      ),
    ),
  );

  /// 사본 가입 화면 입력란 — 회색 테두리 상자(약관 상자와 같은 선 · 모서리 8).
  Widget _boxed(BuildContext context, Widget child) {
    if (!boxedInputs) return child;
    OutlineInputBorder line(Color c, [double w = 1]) => OutlineInputBorder(
      borderRadius: BorderRadius.circular(AppRadius.sm),
      borderSide: BorderSide(color: c, width: w),
    );
    final theme = Theme.of(context);
    return Theme(
      data: theme.copyWith(
        inputDecorationTheme: theme.inputDecorationTheme.copyWith(
          border: line(_stroke),
          enabledBorder: line(_stroke),
          focusedBorder: line(AppColors.cosmicAccent, 2),
          errorBorder: line(AppColors.error),
          focusedErrorBorder: line(AppColors.error, 2),
        ),
      ),
      child: child,
    );
  }
}

class _PrimaryButton extends StatelessWidget {
  const _PrimaryButton({required this.label, required this.onPressed});

  final String label;
  final VoidCallback? onPressed;

  @override
  Widget build(BuildContext context) => FilledButton(
    onPressed: onPressed,
    style: FilledButton.styleFrom(
      backgroundColor: AppColors.cosmicAccent,
      foregroundColor: AppColors.onCosmicAccent,
      disabledBackgroundColor: const Color(0xFF333333),
      disabledForegroundColor: const Color(0xFF777777),
    ),
    child: Text(label),
  );
}

/// 사본 입력란 테두리 — 약관 상자(`signup_screens.dart`)와 같은 값.
const _stroke = Color(0xFF545454);

const _title = TextStyle(
  fontFamily: AppFonts.body,
  fontSize: 20,
  fontWeight: FontWeight.w600,
  height: 1.4,
  color: AppColors.onCosmic,
);

const _body = TextStyle(
  fontFamily: AppFonts.body,
  fontSize: 14,
  height: 1.6,
  color: Color(0xFFCDCDCD),
);

/// 국기 이모지 — 지역 표시 기호 두 글자.
String countryFlag(String code) =>
    String.fromCharCodes(code.codeUnits.map((c) => c - 0x41 + 0x1F1E6));

/// 국가 시트 순서 — 기기 OS 정렬([platformCountryNames] 순서)을 따르고, OS 가 모르는 코드는 표시명 순으로 뒤에 둔다.
/// 사본 `178:23489` 목록은 (첫 줄 독일을 빼면) 국가명 가나다순이고 검색 칸이 없다. 범위는 Q-E10 회신 대기.
List<String> sortedCountries() {
  final rest = isoCountries.toSet();
  final ordered = [
    for (final c in platformCountryNames.keys)
      if (rest.remove(c)) c,
  ];
  return ordered..addAll(
    rest.toList()..sort((a, b) => countryName(a).compareTo(countryName(b))),
  );
}

/// ISO 3166-1 alpha-2 전체. 랭킹 집계 · Admin 사용자 일람의 「거주 국가/지역」 값이다.
final List<String> isoCountries =
    ('AD AE AF AG AI AL AM AO AQ AR AS AT AU AW AX AZ BA BB BD BE BF BG BH BI BJ BL BM BN BO BQ '
            'BR BS BT BV BW BY BZ CA CC CD CF CG CH CI CK CL CM CN CO CR CU CV CW CX CY CZ DE DJ DK '
            'DM DO DZ EC EE EG EH ER ES ET FI FJ FK FM FO FR GA GB GD GE GF GG GH GI GL GM GN GP GQ '
            'GR GS GT GU GW GY HK HM HN HR HT HU ID IE IL IM IN IO IQ IR IS IT JE JM JO JP KE KG KH '
            'KI KM KN KP KR KW KY KZ LA LB LC LI LK LR LS LT LU LV LY MA MC MD ME MF MG MH MK ML MM '
            'MN MO MP MQ MR MS MT MU MV MW MX MY MZ NA NC NE NF NG NI NL NO NP NR NU NZ OM PA PE PF '
            'PG PH PK PL PM PN PR PS PT PW PY QA RE RO RS RU RW SA SB SC SD SE SG SH SI SJ SK SL SM '
            'SN SO SR SS ST SV SX SY SZ TC TD TF TG TH TJ TK TL TM TN TO TR TT TV TW TZ UA UG UM US '
            'UY UZ VA VC VE VG VI VN VU WF WS YE YT ZA ZM ZW')
        .split(' ');