import 'package:flutter_riverpod/flutter_riverpod.dart';

import '../core/network/dio_client.dart';
import '../core/utils/number_format.dart';
import '../data/models/currency_rate.dart';
import 'app_provider.dart';

const _kCurrencyCode = 'currency_code';
const _kCurrencyRate = 'currency_rate';
const _kCurrencySymbol = 'currency_symbol';

// ── State ─────────────────────────────────────────────────

class CurrencyState {
  final List<CurrencyRate> rates;
  final String selectedCode;
  final bool isLoading;

  const CurrencyState({
    required this.rates,
    required this.selectedCode,
    this.isLoading = false,
  });

  CurrencyRate? get selected {
    if (rates.isEmpty) return null;
    try {
      return rates.firstWhere((r) => r.currency == selectedCode);
    } catch (_) {
      return rates.first;
    }
  }

  CurrencyState copyWith({
    List<CurrencyRate>? rates,
    String? selectedCode,
    bool? isLoading,
  }) =>
      CurrencyState(
        rates: rates ?? this.rates,
        selectedCode: selectedCode ?? this.selectedCode,
        isLoading: isLoading ?? this.isLoading,
      );
}

// ── Notifier ──────────────────────────────────────────────

class CurrencyNotifier extends Notifier<CurrencyState> {
  @override
  CurrencyState build() {
    final prefs = ref.read(sharedPreferencesProvider);
    final savedCode = prefs.getString(_kCurrencyCode) ?? 'USD';
    final savedRate = prefs.getDouble(_kCurrencyRate) ?? 1.0;
    final savedSymbol = prefs.getString(_kCurrencySymbol) ?? '\$';

    // 立即应用上次保存的汇率，避免启动时显示错误
    setFiatCurrency(rate: savedRate, symbol: savedSymbol);

    Future.microtask(_loadRates);

    return CurrencyState(rates: const [], selectedCode: savedCode, isLoading: true);
  }

  Future<void> _loadRates() async {
    try {
      final dio = ref.read(dioClientProvider);
      final response = await dio.get<Map<String, dynamic>>('contract/currency/rate');
      final list = (response.data?['data'] as List<dynamic>? ?? [])
          .map((e) => CurrencyRate.fromJson(e as Map<String, dynamic>))
          .toList();

      state = state.copyWith(rates: list, isLoading: false);

      // 用最新汇率更新全局法币设置
      final current = state.selected;
      if (current != null) {
        _applyAndPersist(current);
      }
    } catch (_) {
      // 接口失败时继续使用上次保存的汇率
      state = state.copyWith(isLoading: false);
    }
  }

  void selectCurrency(CurrencyRate rate) {
    state = state.copyWith(selectedCode: rate.currency);
    _applyAndPersist(rate);
  }

  void _applyAndPersist(CurrencyRate rate) {
    setFiatCurrency(rate: rate.rate, symbol: rate.symbol);

    final prefs = ref.read(sharedPreferencesProvider);
    prefs.setString(_kCurrencyCode, rate.currency);
    prefs.setDouble(_kCurrencyRate, rate.rate);
    prefs.setString(_kCurrencySymbol, rate.symbol);
  }
}

// ── Provider ──────────────────────────────────────────────

final currencyProvider = NotifierProvider<CurrencyNotifier, CurrencyState>(
  CurrencyNotifier.new,
);