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 deduplication and strict chronological sorting.
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 = 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();
    _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,
      );

      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;
        }
      });
    } catch (_) {
    } 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);
                      },
                    ),
            ),
          ],
        ),
      ),
    );
  }
}