import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:shared_preferences/shared_preferences.dart';
import '../../core/services/card_color_service.dart';
import '../../shared/models/transaction.dart';
import '../../shared/services/storage_service.dart';
import '../settings/provider.dart';

final sharedPreferencesProvider = Provider<SharedPreferences>((ref) {
  throw UnimplementedError('Override in main');
});

final storageServiceProvider = Provider<StorageService>((ref) {
  return StorageService(ref.watch(sharedPreferencesProvider));
});

final transactionsProvider =
    StateNotifierProvider<TransactionsNotifier, List<Transaction>>((ref) {
      final storage = ref.watch(storageServiceProvider);
      return TransactionsNotifier(storage);
    });

class TransactionsNotifier extends StateNotifier<List<Transaction>> {
  final StorageService _storage;

  TransactionsNotifier(this._storage) : super(_storage.loadTransactions());

  Future<void> add(Transaction transaction) async {
    await _storage.addTransaction(transaction);
    state = _storage.loadTransactions();
  }

  Future<void> update(Transaction transaction) async {
    await _storage.updateTransaction(transaction);
    state = _storage.loadTransactions();
  }

  Future<void> delete(String id) async {
    await _storage.deleteTransaction(id);
    state = _storage.loadTransactions();
  }

  void restore(Transaction transaction) {
    state = [...state, transaction];
    _storage.addTransaction(transaction);
  }

  void clearAll() {
    state = [];
    SharedPreferences.getInstance().then(
      (prefs) => prefs.remove('transactions'),
    );
  }
}

final searchQueryProvider = StateProvider<String>((ref) => '');

enum TransactionFilter { all, income, expense }

enum TimeFilter { allTime, lastMonth }

final transactionFilterProvider = StateProvider<TransactionFilter>(
  (ref) => TransactionFilter.all,
);

final timeFilterProvider = StateProvider<TimeFilter>(
  (ref) => TimeFilter.lastMonth,
);

final totalBalanceProvider = Provider<double>((ref) {
  final txs = ref.watch(transactionsProvider);
  final exchangeService = ref.watch(exchangeRateServiceProvider);
  final targetCurrency = ref.watch(currencyProvider).code;

  return txs.fold(0.0, (sum, t) {
    final converted = exchangeService.convert(
      t.amount,
      t.currencyCode,
      targetCurrency,
    );
    return t.type == TransactionType.income ? sum + converted : sum - converted;
  });
});

final totalIncomeProvider = Provider<double>((ref) {
  final txs = ref
      .watch(transactionsProvider)
      .where((t) => t.type == TransactionType.income);
  final exchangeService = ref.watch(exchangeRateServiceProvider);
  final targetCurrency = ref.watch(currencyProvider).code;

  return txs.fold(0.0, (sum, t) {
    return sum +
        exchangeService.convert(t.amount, t.currencyCode, targetCurrency);
  });
});

final totalExpenseProvider = Provider<double>((ref) {
  final txs = ref
      .watch(transactionsProvider)
      .where((t) => t.type == TransactionType.expense);
  final exchangeService = ref.watch(exchangeRateServiceProvider);
  final targetCurrency = ref.watch(currencyProvider).code;

  return txs.fold(0.0, (sum, t) {
    return sum +
        exchangeService.convert(t.amount, t.currencyCode, targetCurrency);
  });
});

final currentMonthExpenseProvider = Provider<double>((ref) {
  final now = DateTime.now();
  final txs = ref
      .watch(transactionsProvider)
      .where(
        (t) =>
            t.type == TransactionType.expense &&
            t.date.year == now.year &&
            t.date.month == now.month,
      );
  final exchangeService = ref.watch(exchangeRateServiceProvider);
  final targetCurrency = ref.watch(currencyProvider).code;

  return txs.fold(0.0, (sum, t) {
    return sum +
        exchangeService.convert(t.amount, t.currencyCode, targetCurrency);
  });
});

final filteredTransactionsProvider = Provider<List<Transaction>>((ref) {
  final txs = ref.watch(transactionsProvider);
  final query = ref.watch(searchQueryProvider).toLowerCase();
  final typeFilter = ref.watch(transactionFilterProvider);
  final timeFilter = ref.watch(timeFilterProvider);

  var filtered = txs;

  if (timeFilter == TimeFilter.lastMonth) {
    final now = DateTime.now();
    final start = DateTime(now.year, now.month, 1);
    final end = DateTime(now.year, now.month + 1, 1);
    filtered = filtered
        .where(
          (t) =>
              t.date.isAfter(start.subtract(const Duration(seconds: 1))) &&
              t.date.isBefore(end),
        )
        .toList();
  }

  if (typeFilter == TransactionFilter.income) {
    filtered = filtered.where((t) => t.type == TransactionType.income).toList();
  } else if (typeFilter == TransactionFilter.expense) {
    filtered = filtered
        .where((t) => t.type == TransactionType.expense)
        .toList();
  }

  if (query.isNotEmpty) {
    filtered = filtered.where((t) {
      final matchesCategory = t.category.toLowerCase().contains(query);
      final matchesNote = t.note?.toLowerCase().contains(query) ?? false;
      return matchesCategory || matchesNote;
    }).toList();
  }

  filtered.sort((a, b) => b.date.compareTo(a.date));
  return filtered;
});

final recentTransactionsProvider = Provider<List<Transaction>>((ref) {
  return ref.watch(filteredTransactionsProvider).take(20).toList();
});

class CardColors {
  final Color primary;
  final Color secondary;
  final GradientType gradientType;

  const CardColors(this.primary, this.secondary, this.gradientType);
}

final cardColorsProvider =
    StateNotifierProvider<CardColorsNotifier, CardColors>((ref) {
      final notifier = CardColorsNotifier();
      notifier.setupThemeListener(ref);
      return notifier;
    });

class CardColorsNotifier extends StateNotifier<CardColors> {
  CardColorsNotifier()
    : super(
        const CardColors(
          CardColorService.defaultPrimary,
          CardColorService.defaultSecondary,
          CardColorService.defaultGradient,
        ),
      ) {
    _load();
  }

  void setupThemeListener(Ref ref) {
    ref.listen<ThemeMode>(themeProvider, (previous, next) {
      if (previous != null) {
        _onThemeChanged(previous, next);
      }
    });
  }

  Future<void> _load() async {
    final (c1, c2, g) = await CardColorService.load();
    state = CardColors(c1, c2, g);
  }

  Future<void> save(
    Color primary,
    Color secondary,
    GradientType gradient,
  ) async {
    state = CardColors(primary, secondary, gradient);
    await CardColorService.save(primary, secondary, gradient);
  }

  Future<void> reset(bool isDark) async {
    final primary = isDark
        ? CardColorService.defaultPrimary
        : CardColorService.defaultPrimaryLight;
    final secondary = isDark
        ? CardColorService.defaultSecondary
        : CardColorService.defaultSecondaryLight;
    state = CardColors(primary, secondary, CardColorService.defaultGradient);
    await CardColorService.save(
      primary,
      secondary,
      CardColorService.defaultGradient,
    );
  }

  void _onThemeChanged(ThemeMode previous, ThemeMode next) {
    final previousBrightness = _resolve(previous);
    final nextBrightness = _resolve(next);

    // No change in actual brightness
    if (previousBrightness == nextBrightness) return;

    final oldDefaults = _defaultsFor(previousBrightness);
    final newDefaults = _defaultsFor(nextBrightness);

    // Check if current colors match old theme defaults
    final isUsingOldDefaults =
        state.primary == oldDefaults.primary &&
        state.secondary == oldDefaults.secondary &&
        state.gradientType == oldDefaults.gradient;

    // Only auto-switch if using default colors
    if (isUsingOldDefaults) {
      state = CardColors(
        newDefaults.primary,
        newDefaults.secondary,
        newDefaults.gradient,
      );
    }
  }

  Brightness _resolve(ThemeMode mode) {
    if (mode == ThemeMode.system) {
      return WidgetsBinding.instance.platformDispatcher.platformBrightness;
    }
    return mode == ThemeMode.dark ? Brightness.dark : Brightness.light;
  }

  ({Color primary, Color secondary, GradientType gradient}) _defaultsFor(
    Brightness brightness,
  ) {
    return brightness == Brightness.dark
        ? (
            primary: CardColorService.defaultPrimary,
            secondary: CardColorService.defaultSecondary,
            gradient: CardColorService.defaultGradient,
          )
        : (
            primary: CardColorService.defaultPrimaryLight,
            secondary: CardColorService.defaultSecondaryLight,
            gradient: CardColorService.defaultGradient,
          );
  }
}