import 'package:flutter/foundation.dart';
import 'package:miaoji_zhang/shared/api/api_client.dart';
import 'package:miaoji_zhang/shared/services/local_database.dart';
import 'package:miaoji_zhang/shared/services/session_store.dart';

class LedgerInfo {
  final int id;
  final String name;
  final String iconKey;
  final bool isDefault;
  final int transactionCount;

  const LedgerInfo({
    required this.id,
    required this.name,
    required this.iconKey,
    required this.isDefault,
    required this.transactionCount,
  });

  factory LedgerInfo.fromJson(Map<String, dynamic> json) => LedgerInfo(
    id: (json['id'] as num).toInt(),
    name: json['name'] as String,
    iconKey: json['iconKey'] as String? ?? 'wallet',
    isDefault: json['isDefault'] as bool? ?? false,
    transactionCount: (json['txCount'] as num?)?.toInt() ?? 0,
  );
}

class CurrentLedgerStore extends ChangeNotifier {
  CurrentLedgerStore._();

  static final instance = CurrentLedgerStore._();
  final _dio = ApiClient.instance.dio;

  List<LedgerInfo> _ledgers = const [];
  LedgerInfo? _current;
  Future<void>? _loading;

  List<LedgerInfo> get ledgers => List.unmodifiable(_ledgers);
  LedgerInfo? get current => _current;
  int? get currentId => _current?.id;
  String get currentName => _current?.name ?? '账本';

  Future<void> ensureLoaded({bool force = false}) {
    if (!force && _current != null) return Future.value();
    return _loading ??= _load().whenComplete(() => _loading = null);
  }

  Future<void> loadCached({bool force = false}) {
    if (!force && _current != null) return Future.value();
    return _loading ??= _loadCached().whenComplete(() => _loading = null);
  }

  Future<void> refreshRemote() async {
    if (!SessionStore.instance.isAccount ||
        SessionStore.instance.shouldUseLocalOnly) {
      return;
    }
    final response = await _dio.get('/api/ledgers');
    final values = response.data as List;
    LocalDatabase.instance.cacheLedgers(values);
    _apply(values);
  }

  Future<void> _loadCached() async {
    _apply(LocalDatabase.instance.ledgers());
  }

  Future<void> _load() async {
    final session = SessionStore.instance;
    List<dynamic> values;
    if (session.shouldUseLocalOnly) {
      values = LocalDatabase.instance.ledgers();
    } else {
      try {
        final response = await _dio.get('/api/ledgers');
        values = response.data as List;
        LocalDatabase.instance.cacheLedgers(values);
      } catch (error) {
        if (!isConnectivityError(error) || !session.isAccount) rethrow;
        values = LocalDatabase.instance.ledgers();
      }
    }
    _apply(values);
  }

  void _apply(List<dynamic> values) {
    final items = values
        .map((item) => LedgerInfo.fromJson(item as Map<String, dynamic>))
        .toList();
    final current =
        items.where((item) => item.isDefault).firstOrNull ??
        (items.isEmpty ? null : items.first);
    final changed =
        _current?.id != current?.id ||
        _ledgers.length != items.length ||
        Iterable<int>.generate(items.length).any((index) {
          final before = _ledgers[index];
          final after = items[index];
          return before.id != after.id ||
              before.name != after.name ||
              before.iconKey != after.iconKey ||
              before.isDefault != after.isDefault ||
              before.transactionCount != after.transactionCount;
        });
    _ledgers = items;
    _current = current;
    if (changed) notifyListeners();
  }

  Future<void> select(int id) async {
    if (_current?.id == id) return;
    final session = SessionStore.instance;
    if (session.shouldUseLocalOnly || id < 0) {
      LocalDatabase.instance.selectLedger(id);
      if (session.isAccount && session.cloudSyncEnabled) {
        LocalDatabase.instance.enqueueSync('ledger', id, 'select', {'id': id});
      }
      await ensureLoaded(force: true);
      return;
    }
    try {
      await _dio.put('/api/ledgers/$id/default');
    } catch (error) {
      if (!isConnectivityError(error)) rethrow;
      LocalDatabase.instance.selectLedger(id);
      LocalDatabase.instance.enqueueSync('ledger', id, 'select', {'id': id});
    }
    await ensureLoaded(force: true);
  }

  Future<void> create(String name) async {
    final session = SessionStore.instance;
    if (session.shouldUseLocalOnly) {
      final id = LocalDatabase.instance.createLedger(name.trim());
      if (session.isAccount && session.cloudSyncEnabled) {
        LocalDatabase.instance.enqueueSync('ledger', id, 'create', {
          'name': name.trim(),
          'iconKey': 'wallet',
        });
      }
      await ensureLoaded(force: true);
      return;
    }
    try {
      await _dio.post(
        '/api/ledgers',
        data: {'name': name.trim(), 'iconKey': 'wallet'},
      );
    } catch (error) {
      if (!isConnectivityError(error)) rethrow;
      final id = LocalDatabase.instance.createLedger(name.trim());
      LocalDatabase.instance.enqueueSync('ledger', id, 'create', {
        'name': name.trim(),
        'iconKey': 'wallet',
      });
    }
    await ensureLoaded(force: true);
  }

  Future<void> rename(int id, String name, String iconKey) async {
    final session = SessionStore.instance;
    if (session.shouldUseLocalOnly || id < 0) {
      LocalDatabase.instance.renameLedger(id, name.trim(), iconKey);
      if (session.isAccount && session.cloudSyncEnabled) {
        LocalDatabase.instance.enqueueSync('ledger', id, 'update', {
          'name': name.trim(),
          'iconKey': iconKey,
        });
      }
      await ensureLoaded(force: true);
      return;
    }
    try {
      await _dio.put(
        '/api/ledgers/$id',
        data: {'name': name.trim(), 'iconKey': iconKey},
      );
    } catch (error) {
      if (!isConnectivityError(error)) rethrow;
      LocalDatabase.instance.renameLedger(id, name.trim(), iconKey);
      LocalDatabase.instance.enqueueSync('ledger', id, 'update', {
        'name': name.trim(),
        'iconKey': iconKey,
      });
    }
    await ensureLoaded(force: true);
  }

  Future<void> delete(int id) async {
    final session = SessionStore.instance;
    if (session.shouldUseLocalOnly || id < 0) {
      LocalDatabase.instance.deleteLedger(id);
      if (session.isAccount && session.cloudSyncEnabled) {
        LocalDatabase.instance.enqueueSync('ledger', id, 'delete', {'id': id});
      }
      await ensureLoaded(force: true);
      return;
    }
    try {
      await _dio.delete('/api/ledgers/$id');
    } catch (error) {
      if (!isConnectivityError(error)) rethrow;
      LocalDatabase.instance.deleteLedger(id);
      LocalDatabase.instance.enqueueSync('ledger', id, 'delete', {'id': id});
    }
    await ensureLoaded(force: true);
  }

  void clear() {
    _ledgers = const [];
    _current = null;
    notifyListeners();
  }
}