flutter-freaccess-hub/lib/shared/widgets/enhanced_list_view.dart

part of 'widgets.dart';

/// [TypeDefs]

typedef EnhancedListViewKey<B, H, F>
    = GlobalKey<EnhancedListViewState<B, H, F>>;

typedef PaginatedListViewHeaderBuilder<H> = Widget Function(
    Future<List<H?>> Function() headerItems);
typedef PaginatedListViewBodyBuilder<T> = Widget Function(
    BuildContext context, T item, int index);
typedef PaginatedListViewFooterBuilder<F> = Widget Function(
    Future<List<F?>> Function() footerItems);

typedef Query<T> = T?;

typedef BodyItemsBuilder<T> = Future<List<T?>> Function(
    int page, int pageSize, Query query);
typedef HeaderItemsBuilder<H> = Future<List<H?>> Function();
typedef FooterItemsBuilder<F> = Future<List<F?>> Function();

/// [Extensions]
extension PaginatedListMergeExtensions<T>
    on Stream<Result<EnhancedPaginatedList<T>>> {
  Stream<EnhancedPaginatedList<T>> mergeWithPaginatedList(
      BehaviorSubject<EnhancedPaginatedList<T>> currentList) {
    return map(
      (result) {
        final current = currentList.value;
        if (result is ResultSuccess<EnhancedPaginatedList<T>>) {
          final newPaginated = result.data;
          return current.items.isEmpty
              ? newPaginated
              : current.copyWith(
                  list: [...current.items, ...newPaginated.items],
                  currentPage: newPaginated.currentPage,
                  totalCount: newPaginated.totalCount,
                  error: newPaginated.error,
                );
        } else if (result is ResultError<EnhancedPaginatedList<T>>) {
          return current.copyWith(error: result.error);
        } else {
          return current;
        }
      },
    );
  }
}

extension PublishSubjectExtensions<T> on PublishSubject<T> {
  Stream<T> startWith(T initial) => Rx.concat([Stream.value(initial), this]);
}

extension StreamStartWithExtension<T> on Stream<T> {
  Stream<T> startWith(T initial) => Rx.concat([Stream.value(initial), this]);
}

extension QueryBlocStreamExtensions<T> on Stream<bool> {
  Stream<Result<EnhancedPaginatedList<T>>> fetchData(
    EnhancedListViewRepository<T> repository,
    PaginatedListViewBodyBuilder<T> builder,
    BehaviorSubject<EnhancedPaginatedList<T>> paginatedList,
  ) =>
      switchMap((reset) {
        if (reset) {
          paginatedList.add(paginatedList.value.resetAll());
        }
        final nextPage = paginatedList.value.currentPage + 1;
        return repository
            .fetchPage(nextPage, paginatedList.value.pageSize, builder)
            .asResultStream();
      });
}

/// [Widgets]

/// [EnhancedListView]

interface class EnhancedPaginatedList<T> extends PaginatedList<T> {
  @override
  final Exception? error;
  final bool isInitialized;
  @override
  final bool isLoading;
  final List<T> items;
  @override
  final int pageSize;
  @override
  final int? totalCount;
  final int currentPage;

  EnhancedPaginatedList({
    required this.items,
    required this.pageSize,
    this.currentPage = 0,
    this.totalCount,
    required this.error,
    required this.isInitialized,
    required this.isLoading,
  }) : super(
          error: error,
          isInitialized: isInitialized,
          isLoading: isLoading,
          list: items,
          pageSize: pageSize,
          totalCount: totalCount,
        );

  EnhancedPaginatedList<T> resetAll() => EnhancedPaginatedList<T>(
        error: null,
        isInitialized: false,
        isLoading: false,
        items: const [],
        pageSize: pageSize,
        totalCount: null,
        currentPage: 0,
      );

  @override
  EnhancedPaginatedList<T> copyWith({
    List<T>? list,
    bool? isLoading,
    int? totalCount,
    Exception? error,
    int? pageSize,
    bool? isInitialized,
    int? currentPage,
  }) =>
      EnhancedPaginatedList<T>(
        error: error ?? this.error,
        isInitialized: isInitialized ?? this.isInitialized,
        isLoading: isLoading ?? this.isLoading,
        items: list ?? this.items,
        pageSize: pageSize ?? this.pageSize,
        totalCount: totalCount ?? this.totalCount,
        currentPage: currentPage ?? this.currentPage,
      );

  @override
  int get itemCount => items.length;

  @override
  T? getItem(int index) => index < items.length ? items[index] : null;

  Future<void> awaitLoad() async => Future.value();
}

abstract interface class EnhancedListViewBase<T, H, F> extends StatefulWidget {
  const EnhancedListViewBase({super.key});
}

abstract interface class EnhancedListViewBaseState<T>
    extends State<EnhancedListViewBase> {}

// ignore: must_be_immutable
class EnhancedListView<BodyType, HeaderType, FooterType>
    extends EnhancedListViewBase<BodyType, HeaderType, FooterType> {
  BodyItemsBuilder<BodyType> bodyItems;
  PaginatedListViewBodyBuilder<BodyType> bodyBuilder;
  HeaderItemsBuilder<HeaderType>? headerItems;
  PaginatedListViewHeaderBuilder<HeaderType>? headerBuilder;
  FooterItemsBuilder<FooterType>? footerItems;
  PaginatedListViewFooterBuilder<FooterType>? footerBuilder;

  EnhancedListView({
    Key? key,
    required this.bodyItems,
    required this.bodyBuilder,
    this.headerItems,
    this.headerBuilder,
    this.footerItems,
    this.footerBuilder,
  }) : super(key: key);

  @override
  EnhancedListViewState<BodyType, HeaderType, FooterType> createState() =>
      EnhancedListViewState<BodyType, HeaderType, FooterType>();
}

class EnhancedListViewState<ItemType, HeaderType, FooterType>
    extends State<EnhancedListView<ItemType, HeaderType, FooterType>> {
  final ScrollController _scrollController = ScrollController();
  bool _isLoadingMore = false;
  List<ItemType?> items = [];
  List<HeaderType?> headerItems = [];
  List<FooterType?> footerItems = [];
  int currentPage = 1;
  Query<ItemType> query;

  @override
  void initState() {
    super.initState();
    _scrollController.addListener(_onScroll);
    _loadBodyItems();
    _loadHeaderItems();
    _loadFooterItems();
  }

  void _onScroll() {
    if (_scrollController.position.pixels ==
            _scrollController.position.maxScrollExtent &&
        !_isLoadingMore) {
      _loadMoreBodyItems();
    }
  }

  Future<void> _loadBodyItems() async {
    log('loadInitialItems');
    final newItems = await widget.bodyItems(1, 10, query);
    setState(() {
      items = newItems;
    });
  }

  Future<void> _loadMoreBodyItems() async {
    log('loadMoreItems');
    setState(() {
      _isLoadingMore = true;
    });
    final newItems = await widget.bodyItems(currentPage + 1, 10, query);
    setState(() {
      _isLoadingMore = false;
      if (newItems.isNotEmpty) {
        items.addAll(newItems);
        currentPage++;
      }
    });
  }

  Future<void> _loadHeaderItems() async {
    if (widget.headerItems != null) {
      log('loadHeaderItems');
      final newHeaderItems = await widget.headerItems!();
      setState(() {
        headerItems = newHeaderItems;
      });
    }
  }

  Future<void> _loadFooterItems() async {
    if (widget.footerItems != null) {
      log('loadFooterItems');
      final newFooterItems = await widget.footerItems!();
      setState(() {
        footerItems = newFooterItems;
      });
    }
  }

  Future<void> filterBodyItems(Query<ItemType> newQuery) async {
    log('filterItems B: ${newQuery.toString()}');
    setState(() {
      query = newQuery;
      items = [];
      currentPage = 1;
    });
    await _loadBodyItems();
  }

  @override
  Widget build(BuildContext context) {
    log('key: ${widget.key}');
    return ListView.builder(
      controller: _scrollController,
      itemCount: items.length +
          (headerItems.isNotEmpty ? 1 : 0) +
          (footerItems.isNotEmpty ? 1 : 0) +
          (_isLoadingMore ? 1 : 0),
      itemBuilder: (context, index) {
        if (headerItems.isNotEmpty && index == 0) {
          return widget.headerBuilder!(() => Future.value(headerItems));
        }
        if (footerItems.isNotEmpty &&
            index == items.length + (headerItems.isNotEmpty ? 1 : 0)) {
          return widget.footerBuilder!(() => Future.value(footerItems));
        }
        if (_isLoadingMore &&
            index ==
                items.length +
                    (headerItems.isNotEmpty ? 1 : 0) +
                    (footerItems.isNotEmpty ? 1 : 0)) {
          return const EnhancedProgressIndicator();
        }
        final item = items[index - (headerItems.isNotEmpty ? 1 : 0)];
        return widget.bodyBuilder(context, item as ItemType, index);
      },
    );
  }

  @override
  void dispose() {
    _scrollController.dispose();
    super.dispose();
  }
}

/// [Utils]

class EnhancedListTile<T extends Widget> extends StatelessWidget {
  const EnhancedListTile(
      {required this.leading, required this.title, super.key});

  final T leading;
  final T title;

  @override
  Widget build(BuildContext context) {
    return Card(
      child: ListTile(
        leading: leading,
        title: title,
      ),
    );
  }
}

class EnhancedErrorWidget extends StatelessWidget {
  final Object? error;
  const EnhancedErrorWidget({required this.error, super.key});

  @override
  Widget build(BuildContext context) {
    log('error: $error');
    return Padding(
      padding: const EdgeInsets.all(16.0),
      child: Text(
        error.toString(),
        style: const TextStyle(color: Colors.red),
      ),
    );
  }
}

class EnhancedProgressIndicator extends StatelessWidget {
  const EnhancedProgressIndicator({super.key});

  @override
  Widget build(BuildContext context) => const Center(
        child: Padding(
          padding: EdgeInsets.symmetric(vertical: 12),
          child: CircularProgressIndicator(),
        ),
      );
}

class NetworkError implements Exception {
  final String message;
  NetworkError(this.message);
}

class ParsingError implements Exception {
  final String message;
  ParsingError(this.message);
}

class AuthorizationError implements Exception {
  final String message;
  AuthorizationError(this.message);
}

/// [State Managment]
Stream<bool> get loadingState => Stream<bool>.empty();
Stream<Exception> get errorState => Stream<Exception>.empty();

abstract class EnhancedListViewRepository<T> {
  Future<EnhancedPaginatedList<T>> fetchPage(
      int page, int pageSize, PaginatedListViewBodyBuilder<T> builder);
}

abstract class EnhancedListViewBlocStates<T> {
  Stream<bool> get isLoading;
  Stream<String> get errors;
  Stream<EnhancedPaginatedList<T>> get paginatedList;

  @RxBlocIgnoreState()
  Future<void> get refreshDone;
}

abstract class EnhancedListViewEvents<T> {
  void loadPage({bool reset = false});
}

abstract class EnhancedListViewBlocType<T> extends RxBlocTypeBase {
  EnhancedListViewEvents<T> get events;
  EnhancedListViewBlocStates<T> get states;
}

abstract class $EnhancedListViewBloc<T> extends RxBlocBase
    implements
        EnhancedListViewEvents<T>,
        EnhancedListViewBlocStates<T>,
        EnhancedListViewBlocType<T> {
  final _compositeSubscription = CompositeSubscription();

  final _$loadPageEvent = PublishSubject<bool>();

  late final Stream<bool> _isLoadingState = _mapToIsLoadingState();
  late final Stream<String> _errorsState = _mapToErrorsState();
  late final Stream<EnhancedPaginatedList<T>> _paginatedListState =
      _mapToPaginatedListState();

  @override
  void loadPage({bool reset = false}) => _$loadPageEvent.add(reset);

  @override
  Stream<bool> get isLoading => _isLoadingState;
  @override
  Stream<String> get errors => _errorsState;
  @override
  Stream<EnhancedPaginatedList<T>> get paginatedList => _paginatedListState;

  Stream<bool> _mapToIsLoadingState();
  Stream<String> _mapToErrorsState();
  Stream<EnhancedPaginatedList<T>> _mapToPaginatedListState();

  @override
  EnhancedListViewEvents<T> get events => this;
  @override
  EnhancedListViewBlocStates<T> get states => this;

  @override
  void dispose() {
    _$loadPageEvent.close();
    _compositeSubscription.dispose();
    super.dispose();
  }
}

class EnhancedListViewBloc<T> extends $EnhancedListViewBloc<T> {
  EnhancedListViewBloc({
    required EnhancedListViewRepository<T> repository,
    required PaginatedListViewBodyBuilder<T> builder,
    required T item,
    int initialPageSize = 50,
  }) {
    _$loadPageEvent
        .startWith(true)
        .fetchData(
          repository,
          (context, item, index) => builder(context, item, index),
          _paginatedList,
        )
        .setResultStateHandler(this)
        .mergeWithPaginatedList(_paginatedList)
        .bind(_paginatedList)
        .addTo(_compositeSubscription);
  }

  final _paginatedList = BehaviorSubject<EnhancedPaginatedList<T>>.seeded(
    EnhancedPaginatedList<T>(
      items: [],
      pageSize: 1,
      currentPage: 1,
      error: Exception(),
      isInitialized: true,
      isLoading: false,
      totalCount: 0,
    ),
  );

  @override
  Future<void> get refreshDone async => _paginatedList.value.awaitLoad();

  @override
  Stream<EnhancedPaginatedList<T>> _mapToPaginatedListState() => _paginatedList;
  @override
  Stream<String> _mapToErrorsState() =>
      errorState.map((error) => error.toString());
  @override
  Stream<bool> _mapToIsLoadingState() => loadingState;

  @override
  void dispose() {
    _paginatedList.close();
    super.dispose();
  }
}