import 'dart:async';
import 'package:flutter/material.dart';
import '../../../core/network/api_client.dart';
import '../../../core/theme/app_theme.dart';
import '../models/news_article_model.dart';
import '../repositories/news_repository.dart';
import '../widgets/news_card_item.dart';
import '../widgets/advanced_news_filter_bar.dart';

/// Paginated Infinite Scroll Daily News Feed screen with sentiment toggle filters, real-time update handling, and clean navigation.
class NewsFeedScreen extends StatefulWidget {
  final ApiClient apiClient;
  final NewsRepository? repository;

  const NewsFeedScreen({super.key, required this.apiClient, this.repository});

  @override
  State<NewsFeedScreen> createState() => _NewsFeedScreenState();
}

class _NewsFeedScreenState extends State<NewsFeedScreen> {
  late final NewsRepository _repository;
  final ScrollController _scrollController = ScrollController();
  final List<NewsArticleModel> _newsItems = [];
  int _currentPage = 1;
  static const int _pageSize = 20;
  bool _isLoading = false;
  bool _hasMore = true;

  // Filter States
  String? _searchQuery;
  DateTime? _selectedDate;
  String? _selectedIsin;
  bool _hasSentimentOnly = false;
  String? _selectedSentimentFilter; // null, 'POSITIVE', 'NEUTRAL', 'NEGATIVE'

  Timer? _debounceTimer;

  @override
  void initState() {
    super.initState();
    _repository = widget.repository ?? NewsRepository(apiClient: widget.apiClient, backendUrl: ApiClient.baseUrl);
    _loadNews(refresh: true);
    _scrollController.addListener(() {
      if (_scrollController.position.pixels >= _scrollController.position.maxScrollExtent - 200) {
        _loadNews();
      }
    });
  }

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

  Future<void> _loadNews({bool refresh = false}) async {
    if (_isLoading) return;
    if (refresh) {
      _currentPage = 1;
      _hasMore = true;
      _newsItems.clear();
    }
    if (!_hasMore) return;

    setState(() => _isLoading = true);

    try {
      final fetched = await _repository.fetchNews(
        page: _currentPage,
        pageSize: _pageSize,
        date: _selectedDate?.toIso8601String().substring(0, 10),
        query: _searchQuery?.trim(),
        isin: _selectedIsin?.trim(),
        hasSentiment: _hasSentimentOnly || _selectedSentimentFilter != null,
      );

      setState(() {
        final existingIds = _newsItems.map((e) => e.id).where((id) => id.isNotEmpty).toSet();
        for (final item in fetched) {
          if (item.id.isEmpty || !existingIds.contains(item.id)) {
            _newsItems.add(item);
            if (item.id.isNotEmpty) existingIds.add(item.id);
          }
        }

        _newsItems.sort((a, b) => b.publishedAt.compareTo(a.publishedAt));

        _currentPage++;
        if (fetched.length < _pageSize) {
          _hasMore = false;
        }
      });

      // If a sentiment filter is active and no items matched yet on this page, automatically load the next page
      if (_filteredNewsItems.isEmpty && _hasMore && _selectedSentimentFilter != null) {
        _loadNews();
      }
    } catch (_) {
    } finally {
      setState(() => _isLoading = false);
    }
  }

  List<NewsArticleModel> get _filteredNewsItems {
    if (_selectedSentimentFilter == null) return _newsItems;
    final target = _selectedSentimentFilter!.toUpperCase();
    return _newsItems.where((item) {
      final s = item.sentiment.toUpperCase();
      if (target == 'POSITIVE') return s.contains('POS');
      if (target == 'NEGATIVE') return s.contains('NEG');
      if (target == 'NEUTRAL') return s.contains('NEU');
      return s == target;
    }).toList();
  }

  void _onArticleUpdated(NewsArticleModel updated) {
    setState(() {
      final idx = _newsItems.indexWhere((e) => e.id == updated.id);
      if (idx != -1) {
        _newsItems[idx] = updated;
      }
    });
  }

  void _onSearchChanged(String? val) {
    _searchQuery = val;
    _debounceTimer?.cancel();
    _debounceTimer = Timer(const Duration(milliseconds: 600), () {
      _loadNews(refresh: true);
    });
  }

  void _onIsinChanged(String? val) {
    _selectedIsin = val;
    _debounceTimer?.cancel();
    _debounceTimer = Timer(const Duration(milliseconds: 600), () {
      _loadNews(refresh: true);
    });
  }

  void _resetFilters() {
    _debounceTimer?.cancel();
    setState(() {
      _searchQuery = null;
      _selectedDate = null;
      _selectedIsin = null;
      _hasSentimentOnly = false;
      _selectedSentimentFilter = null;
    });
    _loadNews(refresh: true);
  }

  @override
  Widget build(BuildContext context) {
    final displayedItems = _filteredNewsItems;

    return Scaffold(
      body: Padding(
        padding: const EdgeInsets.all(20),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            Row(
              mainAxisAlignment: MainAxisAlignment.spaceBetween,
              children: [
                const Text('Marktnachrichten & Feed', style: TextStyle(fontSize: 20, fontWeight: FontWeight.bold)),
                if (_newsItems.isNotEmpty)
                  Text(
                    '${displayedItems.length} Artikel angezeigt',
                    style: TextStyle(color: AppTheme.textMuted, fontSize: 12),
                  ),
              ],
            ),
            const SizedBox(height: 12),
            AdvancedNewsFilterBar(
              searchQuery: _searchQuery,
              selectedDate: _selectedDate,
              selectedIsin: _selectedIsin,
              hasSentimentOnly: _hasSentimentOnly,
              selectedSentimentFilter: _selectedSentimentFilter,
              onSearchChanged: _onSearchChanged,
              onIsinChanged: _onIsinChanged,
              onDateChanged: (val) {
                setState(() => _selectedDate = val);
                _loadNews(refresh: true);
              },
              onSentimentToggleChanged: (val) {
                setState(() {
                  _hasSentimentOnly = val;
                  if (!val) {
                    _selectedSentimentFilter = null;
                  }
                });
                _loadNews(refresh: true);
              },
              onSentimentFilterChanged: (val) {
                setState(() {
                  _selectedSentimentFilter = val;
                  if (val != null) {
                    _hasSentimentOnly = true;
                  }
                });
                _loadNews(refresh: true);
              },
              onResetFilters: _resetFilters,
            ),
            const SizedBox(height: 16),
            Expanded(
              child: displayedItems.isEmpty && !_isLoading
                  ? Center(
                      child: Column(
                        mainAxisAlignment: MainAxisAlignment.center,
                        children: [
                          Icon(Icons.feed_outlined, size: 40, color: AppTheme.textMuted),
                          const SizedBox(height: 8),
                          Text('Keine Nachrichten für diese Filterkriterien gefunden.', style: TextStyle(color: AppTheme.textMuted, fontSize: 13)),
                          const SizedBox(height: 10),
                          TextButton(
                            onPressed: _resetFilters,
                            child: Text('Filter zurücksetzen', style: TextStyle(color: AppTheme.accentCyan)),
                          ),
                        ],
                      ),
                    )
                  : ListView.builder(
                      controller: _scrollController,
                      itemCount: displayedItems.length + (_hasMore ? 1 : 0),
                      itemBuilder: (context, index) {
                        if (index == displayedItems.length) {
                          return Center(
                            child: Padding(
                              padding: const EdgeInsets.all(16),
                              child: CircularProgressIndicator(color: AppTheme.primaryEmerald, strokeWidth: 2),
                            ),
                          );
                        }
                        return NewsCardItem(
                          item: displayedItems[index],
                          apiClient: widget.apiClient,
                          onArticleUpdated: _onArticleUpdated,
                        );
                      },
                    ),
            ),
          ],
        ),
      ),
    );
  }
}