import 'package:cloud_firestore/cloud_firestore.dart';

import '../../core/data/backend.dart';

/// 온보딩 6단계(10/3 통합회신 1항 · 해석 확인 Q-OB-02 A · FR-CMN-03~08)가 서버와 주고받는 것.
abstract interface class OnboardingRepository {
  /// ② 약관 — `fnSignupConsent`. 필수 누락은 서버가 거부한다.
  Future<void> agree(Set<String> agreed, String version);

  /// ③ 프로필 — 닉네임(2~20 · 중복 허용) · 국가 · 표시 언어. 지금 값(있으면)을 돌려준다.
  Future<({String nickname, String? country})> currentProfile();
  Future<void> saveProfile({
    required String nickname,
    required String country,
    required String locale,
  });

  /// ③ 추천인 코드(선택) — `fnReferralAttribute`(10/3 7항 「가입 직후 온보딩에 선택 입력」).
  Future<void> attributeReferral(String code);

  /// ④ 관심 아티스트 — 팬덤 행성/성운 목록. [query] 가 있으면 이름 앞부분으로 찾는다.
  Future<List<OnboardingFandom>> fandoms({String query = ''});

  /// ⑤ 행성 가입 — 고른 순서대로 `fnFandomJoin`. 대표가 없던 계정은 첫 가입이 대표가 된다(C-15).
  Future<void> join(List<String> fandomIds);
}

class OnboardingFandom {
  const OnboardingFandom({
    required this.id,
    required this.name,
    required this.members,
    required this.nebula,
  });

  final String id;
  final String name;
  final int members;

  /// Stage0 성운인가.
  final bool nebula;
}

/// 계정이 온보딩을 거쳐야 하는가 — 서버에 가입 약관 동의(`termsAgreedAt`)가 없으면 그렇다.
/// 트리거가 아직 사용자 문서를 만들지 않았어도(갓 생성된 계정) 그렇다.
Future<bool> needsOnboardingFirestore(String uid) async {
  final snap = await FirebaseFirestore.instance.doc('users/$uid').get();
  return snap.data()?['termsAgreedAt'] == null;
}

class FirestoreOnboardingRepository implements OnboardingRepository {
  FirestoreOnboardingRepository(this._backend);

  final Backend _backend;

  @override
  Future<void> agree(Set<String> agreed, String version) => _backend.call(
    'fnSignupConsent',
    {'agreed': agreed.toList(), 'version': version},
  );

  @override
  Future<({String nickname, String? country})> currentProfile() async {
    final data =
        (await _backend.db.doc('users/${_backend.requireUid}').get()).data() ??
        const <String, dynamic>{};
    final nickname = data['nickname'];
    final country = data['countryCode'];
    return (
      nickname: nickname is String ? nickname : '',
      country: country is String && country.isNotEmpty ? country : null,
    );
  }

  @override
  Future<void> saveProfile({
    required String nickname,
    required String country,
    required String locale,
  }) => _backend.db.doc('users/${_backend.requireUid}').set({
    'nickname': nickname,
    'countryCode': country,
    'locale': locale,
    'updatedAt': FieldValue.serverTimestamp(),
  }, SetOptions(merge: true));

  @override
  Future<void> attributeReferral(String code) => _backend.call(
    'fnReferralAttribute',
    {'referralCode': code, 'channel': 'onboarding'},
  );

  @override
  Future<List<OnboardingFandom>> fandoms({String query = ''}) async {
    final col = _backend.db.collection('fandoms');
    final q = query.trim();
    // 검색은 이름 앞부분 일치(단일 필드 정렬이라 별도 색인이 필요 없다). 목록은 FPI 순.
    // ponytail: 페이지 50 건 — 팬덤이 늘면 스크롤 이어읽기를 붙인다.
    final snap =
        await (q.isEmpty
                ? col.orderBy('fpiScore', descending: true)
                : col
                      .orderBy('name')
                      .where('name', isGreaterThanOrEqualTo: q)
                      .where('name', isLessThan: '$q'))
            .limit(50)
            .get();
    return [
      for (final d in snap.docs)
        OnboardingFandom(
          id: d.id,
          name: (d.data()['name'] as String?) ?? d.id,
          members: (d.data()['memberCount'] as num?)?.toInt() ?? 0,
          nebula: d.data()['stage'] == 0,
        ),
    ];
  }

  @override
  Future<void> join(List<String> fandomIds) async {
    for (final id in fandomIds) {
      await _backend.call('fnFandomJoin', {'fandomId': id});
    }
  }
}

/// 목 모드 · 테스트용. **정책값이 아니다.**
class SampleOnboardingRepository implements OnboardingRepository {
  SampleOnboardingRepository();

  final joined = <String>[];
  Set<String>? agreed;
  String? referral;
  ({String nickname, String country, String locale})? profile;

  @override
  Future<void> agree(Set<String> agreed, String version) async =>
      this.agreed = agreed;

  @override
  Future<({String nickname, String? country})> currentProfile() async =>
      (nickname: '', country: null);

  @override
  Future<void> saveProfile({
    required String nickname,
    required String country,
    required String locale,
  }) async => profile = (nickname: nickname, country: country, locale: locale);

  @override
  Future<void> attributeReferral(String code) async => referral = code;

  @override
  Future<List<OnboardingFandom>> fandoms({String query = ''}) async => [
    for (final f in const [
      OnboardingFandom(id: 'bts', name: 'BTS', members: 12840, nebula: false),
      OnboardingFandom(
        id: 'newjeans',
        name: 'NewJeans',
        members: 11230,
        nebula: false,
      ),
      OnboardingFandom(id: 'aespa', name: 'aespa', members: 8, nebula: true),
    ])
      if (f.name.toLowerCase().startsWith(query.trim().toLowerCase())) f,
  ];

  @override
  Future<void> join(List<String> fandomIds) async => joined.addAll(fandomIds);
}