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

/// Paginated Infinite Scroll Daily News Feed screen with deduplication and strict chronological sorting.
class NewsFeedScreen extends StatefulWidget {
  final ApiClient apiClient;

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

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

class _NewsFeedScreenState extends State<NewsFeedScreen> {
  final ScrollController _scrollController = ScrollController();
  final List<dynamic> _newsItems = [];
  int _currentPage = 1;
  static const int _pageSize = 15;
  bool _isLoading = false;
  bool _hasMore = true;

  // Filter States
  String? _searchQuery;
  DateTime? _selectedDate;
  String? _selectedIsin;
  bool _hasSentimentOnly = false;
  
  Timer? _debounceTimer;

  @override
  void initState() {
    super.initState();
    _loadNews(refresh: true);
    _scrollController.addListener(() {
      if (_scrollController.position.pixels >= _scrollController.position.maxScrollExtent - 200) {
        _loadNews();
      }
    });
  }

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

  DateTime _parseDateTime(dynamic val) {
    if (val == null) return DateTime.fromMillisecondsSinceEpoch(0);
    final str = val.toString().trim();
    if (str.isEmpty) return DateTime.fromMillisecondsSinceEpoch(0);
    try {
      return DateTime.parse(str).toUtc();
    } catch (_) {
      return DateTime.fromMillisecondsSinceEpoch(0);
    }
  }

  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 queryParams = <String, dynamic>{
        'page': _currentPage,
        'pageSize': _pageSize,
      };

      if (_selectedDate != null) {
        queryParams['date'] = _selectedDate!.toIso8601String().substring(0, 10);
      }
      if (_searchQuery != null && _searchQuery!.trim().isNotEmpty) {
        queryParams['query'] = _searchQuery!.trim();
      }
      if (_selectedIsin != null && _selectedIsin!.trim().isNotEmpty) {
        queryParams['isin'] = _selectedIsin!.trim();
      }
      if (_hasSentimentOnly) {
        queryParams['hasSentiment'] = true;
      }

      final res = await widget.apiClient.get('/api/v1/news', queryParameters: queryParams);

      if (res.statusCode == 200 && res.data != null && res.data is List) {
        final List fetched = res.data as List;
        setState(() {
          // Deduplicate by ID
          final existingIds = _newsItems.map((e) => e['id'] ?? e['Id']).where((id) => id != null).toSet();
          for (final item in fetched) {
            final id = item['id'] ?? item['Id'];
            if (id == null || !existingIds.contains(id)) {
              _newsItems.add(item);
              if (id != null) existingIds.add(id);
            }
          }

          // Re-sort strictly by publication timestamp descending (newest articles at the top)
          _newsItems.sort((a, b) {
            final dtA = _parseDateTime(a['publishedAt'] ?? a['PublishedAt'] ?? a['scrapedAt'] ?? a['ScrapedAt']);
            final dtB = _parseDateTime(b['publishedAt'] ?? b['PublishedAt'] ?? b['scrapedAt'] ?? b['ScrapedAt']);
            return dtB.compareTo(dtA);
          });

          _currentPage++;
          if (fetched.length < _pageSize) {
            _hasMore = false;
          }
        });
      }
    } catch (_) {
      // Handle error visually if necessary, currently silent fallback
    } finally {
      setState(() => _isLoading = false);
    }
  }

  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;
    });
    _loadNews(refresh: true);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Padding(
        padding: const EdgeInsets.all(20),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            const Text('Marktnachrichten & Feed', style: TextStyle(fontSize: 20, fontWeight: FontWeight.bold)),
            const SizedBox(height: 12),
            AdvancedNewsFilterBar(
              searchQuery: _searchQuery,
              selectedDate: _selectedDate,
              selectedIsin: _selectedIsin,
              hasSentimentOnly: _hasSentimentOnly,
              onSearchChanged: _onSearchChanged,
              onIsinChanged: _onIsinChanged,
              onDateChanged: (val) {
                setState(() => _selectedDate = val);
                _loadNews(refresh: true);
              },
              onSentimentToggleChanged: (val) {
                setState(() => _hasSentimentOnly = val);
                _loadNews(refresh: true);
              },
              onResetFilters: _resetFilters,
            ),
            const SizedBox(height: 16),
            Expanded(
              child: _newsItems.isEmpty && !_isLoading
                  ? Center(
                      child: Text('Keine Nachrichten für diese Filterkriterien gefunden.', style: TextStyle(color: AppTheme.textMuted)),
                    )
                  : ListView.builder(
                      controller: _scrollController,
                      itemCount: _newsItems.length + (_hasMore ? 1 : 0),
                      itemBuilder: (context, index) {
                        if (index == _newsItems.length) {
                          return Center(
                            child: Padding(
                              padding: const EdgeInsets.all(16),
                              child: CircularProgressIndicator(color: AppTheme.primaryEmerald),
                            ),
                          );
                        }
                        return NewsCardItem(item: _newsItems[index], apiClient: widget.apiClient);
                      },
                    ),
            ),
          ],
        ),
      ),
    );
  }
}