didvan-app/lib/views/news/news.dart

import 'dart:async';
import 'dart:math';

import 'package:didvan/constants/app_icons.dart';
import 'package:didvan/models/enums.dart';
import 'package:didvan/models/requests/news.dart';
import 'package:didvan/models/view/action_sheet_data.dart';
import 'package:didvan/utils/action_sheet.dart';
import 'package:didvan/views/news/news_state.dart';
import 'package:didvan/views/widgets/date_picker_button.dart';
import 'package:didvan/views/widgets/didvan/scaffold.dart';
import 'package:didvan/views/widgets/home_app_bar.dart';
import 'package:didvan/views/widgets/item_title.dart';
import 'package:didvan/views/widgets/overview/news.dart';
import 'package:didvan/views/widgets/state_handlers/empty_result.dart';
import 'package:didvan/views/widgets/state_handlers/sliver_state_handler.dart';
import 'package:flutter/material.dart';
import 'package:flutter_svg/flutter_svg.dart';
import 'package:provider/provider.dart';

class News extends StatefulWidget {
  const News({Key? key}) : super(key: key);

  @override
  State<News> createState() => _NewsState();
}

class _NewsState extends State<News> {
  Timer? _timer;
  final _focusNode = FocusNode();
  @override
  void initState() {
    context.read<NewsState>().init();
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    final state = context.watch<NewsState>();
    final theme = Theme.of(context);
    final colorScheme = theme.colorScheme;

    return DidvanScaffold(
      padding: EdgeInsets.zero,
      appBarData: null,
      slivers: [
        SliverToBoxAdapter(
          child: Padding(
            padding: const EdgeInsets.only(top: 12.0),
            child: HomeAppBar(
              showBackButton: false,
              showSearchField: state.appState != AppState.failed,
              onSearchChanged: _onChanged,
              onFilterPressed: _showFilterBottomSheet,
              searchFocusNode: _focusNode,
              isFiltered: state.isFiltering,
              searchValue: state.search,
            ),
          ),
        ),
        SliverAppBar(
          pinned: true,
          automaticallyImplyLeading: false,
          backgroundColor: colorScheme.surface,
          elevation: 0,
          centerTitle: false,
          titleSpacing: 16,
          title: Text(
            'دنیای فولاد',
            style: theme.textTheme.headlineSmall?.copyWith(
              color: const Color.fromARGB(255, 0, 53, 70),
              fontWeight: FontWeight.bold,
              fontSize: 19
            ),
          ),
          actions: [
            IconButton(
              onPressed: () => Navigator.of(context).pop(),
              icon: SvgPicture.asset(
                'lib/assets/icons/arrow-left.svg',
                width: 30,
                height: 30,
                colorFilter: const ColorFilter.mode(
                    Color.fromARGB(255, 102, 102, 102), BlendMode.srcIn),
              ),
            ),
            const SizedBox(width: 8),
          ],
        ),
        const SliverToBoxAdapter(
          child: SizedBox(
            height: 16,
          ),
        ),
        SliverStateHandler<NewsState>(
          centerEmptyState: false,
          onRetry: () => state.getNews(page: state.page),
          state: state,
          childCount: min(state.visibleCount, state.news.length) +
              (_hasMoreItems(state) ? 1 : 0),
          builder: (context, state, index) {
            final currentDisplayCount = min(state.visibleCount, state.news.length);

            if (index == currentDisplayCount && _hasMoreItems(state)) {
              return _buildLoadMoreButton(context, state);
            }

            if (index >= state.news.length) {
              return NewsOverview.placeholder;
            }

            final news = state.news[index];
            return NewsOverview(
              news: news,
              onMarkChanged: state.onMarkChanged,
              newsRequestArgs: NewsRequestArgs(
                page: state.page,
                endDate: state.endDate,
                startDate: state.startDate,
                search: state.search,
              ),
              onLikedChanged: state.onLikedChanged,
            );
          },
          enableEmptyState: state.news.isEmpty && state.appState != AppState.busy,
          emptyState: EmptyResult(
            onNewSearch: () => _focusNode.requestFocus(),
          ),
          itemPadding: const EdgeInsets.only(left: 16, right: 16, bottom: 16),
          placeholder: NewsOverview.placeholder,
        ),
      ],
    );
  }

  bool _hasMoreItems(NewsState state) {
    return state.news.length > state.visibleCount || state.page < state.lastPage;
  }

  Widget _buildLoadMoreButton(BuildContext context, NewsState state) {
    if (state.appState == AppState.busy && state.news.length <= state.visibleCount) {
       return const Padding(
        padding: EdgeInsets.all(16.0),
        child: Center(child: CircularProgressIndicator()),
      );
    }
  
    return Padding(
      padding: const EdgeInsets.symmetric(vertical: 16.0, horizontal: 16.0),
      child: Center(
        child: GestureDetector(
          onTap: () {
            state.loadMore();
          },
          child: Container(
            padding: const EdgeInsets.symmetric(
              horizontal: 50.0,
              vertical: 12.0,
            ),
            decoration: BoxDecoration(
              color: const Color.fromARGB(255, 0, 126, 167),
              borderRadius: BorderRadius.circular(15),
            ),
            child: Row(
              mainAxisSize: MainAxisSize.min,
              children: [
                SvgPicture.asset(
                  'lib/assets/icons/element-plus.svg',
                  colorFilter: const ColorFilter.mode(Colors.white, BlendMode.srcIn),
                  width: 20,
                ),
                const SizedBox(width: 8),
                const Text(
                  'بارگذاری بیشتر',
                  style: TextStyle(
                    color: Colors.white,
                    fontSize: 14,
                    fontWeight: FontWeight.bold,
                  ),
                ),
              ],
            ),
          ),
        ),
      ),
    );
  }

  void _onChanged(String value) {
    final state = context.read<NewsState>();
    if (value.length < 3 && value.isNotEmpty || state.lastSearch == value) {
      return;
    }
    _timer?.cancel();
    _timer = Timer(const Duration(seconds: 1), () {
      state.search = value;
      state.getNews(page: 1);
    });
  }

  Future<void> _showFilterBottomSheet() async {
    final state = context.read<NewsState>();
    await ActionSheetUtils(context).showBottomSheet(
      data: ActionSheetData(
        title: 'فیلتر جستجو',
        smallDismissButton: true,
        titleIcon: DidvanIcons.filter_regular,
        dismissTitle: 'حذف فیلتر',
        confrimTitle: 'نمایش نتایج',
        onDismissed: state.resetFilters,
        onConfirmed: () => state.getNews(page: 1),
        content: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            ItemTitle(
              title: 'تاریخ خبر',
              style: Theme.of(context).textTheme.bodyMedium,
              icon: DidvanIcons.calendar_range_regular,
            ),
            const SizedBox(height: 8),
            StatefulBuilder(
              builder: (context, setState) => Row(
                children: [
                  DatePickerButton(
                    initialValue: state.startDate,
                    emptyText: 'از تاریخ',
                    onPicked: (date) {
                      setState(() => state.startDate = date);
                    },
                    lastDate: state.endDate,
                  ),
                  const SizedBox(width: 8),
                  DatePickerButton(
                    initialValue: state.endDate,
                    emptyText: 'تا تاریخ',
                    onPicked: (date) => setState(() => state.endDate = date),
                    firstDate: state.startDate,
                  ),
                ],
              ),
            ),
          ],
        ),
      ),
    );
  }
}