fin-tracker/app/lib/features/transactions/providers.dart

import 'package:dio/dio.dart';
import 'package:fintracker_api/fintracker_api.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';

import '../../core/api/api_client.dart';

class TransactionsFilter {
  const TransactionsFilter({
    this.q,
    this.from,
    this.to,
    this.accountId,
    this.categoryId,
    this.flowType,
  });

  final String? q;
  final DateTime? from;
  final DateTime? to;
  final int? accountId;
  final int? categoryId;
  final FlowType? flowType;

  bool get isEmpty =>
      q == null && from == null && to == null && accountId == null && categoryId == null && flowType == null;

  TransactionsFilter copyWith({
    String? Function()? q,
    DateTime? Function()? from,
    DateTime? Function()? to,
    int? Function()? accountId,
    int? Function()? categoryId,
    FlowType? Function()? flowType,
  }) {
    return TransactionsFilter(
      q: q != null ? q() : this.q,
      from: from != null ? from() : this.from,
      to: to != null ? to() : this.to,
      accountId: accountId != null ? accountId() : this.accountId,
      categoryId: categoryId != null ? categoryId() : this.categoryId,
      flowType: flowType != null ? flowType() : this.flowType,
    );
  }
}

class TransactionsState {
  const TransactionsState({
    this.items = const [],
    this.page = 1,
    this.pageSize = 50,
    this.total = 0,
    this.loading = false,
    this.loadingMore = false,
    this.error,
  });

  final List<TransactionOut> items;
  final int page;
  final int pageSize;
  final int total;
  final bool loading;
  final bool loadingMore;
  final Object? error;

  bool get hasMore => items.length < total;

  TransactionsState copyWith({
    List<TransactionOut>? items,
    int? page,
    int? pageSize,
    int? total,
    bool? loading,
    bool? loadingMore,
    Object? error,
    bool clearError = false,
  }) {
    return TransactionsState(
      items: items ?? this.items,
      page: page ?? this.page,
      pageSize: pageSize ?? this.pageSize,
      total: total ?? this.total,
      loading: loading ?? this.loading,
      loadingMore: loadingMore ?? this.loadingMore,
      error: clearError ? null : (error ?? this.error),
    );
  }
}

/// Filters + paginated results for Операции. `refresh()` restarts from page 1
/// (called on build and on every filter change); `loadMore()` appends the
/// next page for infinite scroll / the "ещё" button.
class TransactionsController extends Notifier<TransactionsState> {
  TransactionsFilter filter = const TransactionsFilter();

  @override
  TransactionsState build() {
    Future.microtask(refresh);
    return const TransactionsState(loading: true);
  }

  Future<void> setFilter(TransactionsFilter Function(TransactionsFilter) update) {
    filter = update(filter);
    return refresh();
  }

  Future<void> refresh() async {
    state = state.copyWith(loading: true, clearError: true);
    try {
      final r = await ref.read(apiProvider).getTransactionsApi().transactionsList(
            from: filter.from,
            to: filter.to,
            accountId: filter.accountId,
            categoryId: filter.categoryId,
            flowType: filter.flowType,
            q: (filter.q == null || filter.q!.isEmpty) ? null : filter.q,
            page: 1,
            pageSize: state.pageSize,
          );
      final page = r.data!;
      state = TransactionsState(
        items: page.items,
        page: page.page,
        pageSize: page.pageSize,
        total: page.total,
      );
    } on DioException catch (e) {
      state = state.copyWith(loading: false, error: e);
    }
  }

  Future<void> loadMore() async {
    if (state.loading || state.loadingMore || !state.hasMore) return;
    state = state.copyWith(loadingMore: true, clearError: true);
    try {
      final next = state.page + 1;
      final r = await ref.read(apiProvider).getTransactionsApi().transactionsList(
            from: filter.from,
            to: filter.to,
            accountId: filter.accountId,
            categoryId: filter.categoryId,
            flowType: filter.flowType,
            q: (filter.q == null || filter.q!.isEmpty) ? null : filter.q,
            page: next,
            pageSize: state.pageSize,
          );
      final page = r.data!;
      state = state.copyWith(
        items: [...state.items, ...page.items],
        page: page.page,
        total: page.total,
        loadingMore: false,
      );
    } on DioException catch (e) {
      state = state.copyWith(loadingMore: false, error: e);
    }
  }
}

final transactionsControllerProvider =
    NotifierProvider<TransactionsController, TransactionsState>(TransactionsController.new);