import 'package:flutter/material.dart';
import 'package:lucide_icons/lucide_icons.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:go_router/go_router.dart';

import '../../providers/knowledge_provider.dart';
import '../../widgets/knowledge_item_card.dart';

// Type tab configuration: (label, noteType filter value)
const _kTabs = [
  (label: 'All', type: null),
  (label: 'Notes', type: 'note'),
  (label: 'People', type: 'person'),
  (label: 'Places', type: 'place'),
  (label: 'Lists', type: 'list'),
  (label: 'Tasks', type: 'task'),
];

class KnowledgeScreen extends ConsumerStatefulWidget {
  const KnowledgeScreen({super.key});

  @override
  ConsumerState<KnowledgeScreen> createState() => _KnowledgeScreenState();
}

class _KnowledgeScreenState extends ConsumerState<KnowledgeScreen>
    with SingleTickerProviderStateMixin {
  late final TabController _tabController;
  late final ScrollController _scrollController;
  bool _searchActive = false;
  final _searchController = TextEditingController();
  var _debounce = DateTime.now();

  @override
  void initState() {
    super.initState();
    _tabController = TabController(length: _kTabs.length, vsync: this);
    _scrollController = ScrollController();
    _scrollController.addListener(_onScroll);
    // Trigger initial load
    WidgetsBinding.instance.addPostFrameCallback((_) {
      ref.read(knowledgeProvider.notifier).refresh();
    });
    _tabController.addListener(_onTabChanged);
  }

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

  void _onTabChanged() {
    if (!_tabController.indexIsChanging) return;
    final newType = _kTabs[_tabController.index].type;
    ref.read(knowledgeProvider.notifier).setTypeFilter(newType);
  }

  void _onScroll() {
    final pos = _scrollController.position;
    if (pos.pixels >= pos.maxScrollExtent - 300) {
      ref.read(knowledgeProvider.notifier).hydrateNext();
    }
  }

  void _onSearchChanged(String q) {
    final now = DateTime.now();
    _debounce = now;
    Future.delayed(const Duration(milliseconds: 400), () {
      if (_debounce == now && mounted) {
        ref.read(knowledgeProvider.notifier).setSearch(q);
      }
    });
  }

  String _tabLabel(int index) => _kTabs[index].label;

  @override
  Widget build(BuildContext context) {
    final state = ref.watch(knowledgeProvider);

    return Scaffold(
      appBar: AppBar(
        title: _searchActive
            ? TextField(
                controller: _searchController,
                autofocus: true,
                decoration: const InputDecoration(
                  hintText: 'Search knowledge…',
                  border: InputBorder.none,
                ),
                onChanged: _onSearchChanged,
              )
            : const Text('Knowledge'),
        actions: [
          IconButton(
            icon: Icon(_searchActive ? LucideIcons.x : LucideIcons.search),
            onPressed: () {
              setState(() => _searchActive = !_searchActive);
              if (!_searchActive) {
                _searchController.clear();
                ref.read(knowledgeProvider.notifier).setSearch(null);
              }
            },
          ),
        ],
        bottom: TabBar(
          controller: _tabController,
          isScrollable: true,
          tabAlignment: TabAlignment.start,
          tabs: List.generate(
            _kTabs.length,
            (i) => Tab(text: _tabLabel(i)),
          ),
        ),
      ),
      body: Column(
        children: [
          // Tag filter chips
          if (state.availableTags.isNotEmpty)
            SizedBox(
              height: 48,
              child: ListView.separated(
                scrollDirection: Axis.horizontal,
                padding:
                    const EdgeInsets.symmetric(horizontal: 12, vertical: 8),
                itemCount: state.availableTags.length,
                separatorBuilder: (_, _) => const SizedBox(width: 6),
                itemBuilder: (_, i) {
                  final tag = state.availableTags[i];
                  final active = state.activeTags.contains(tag);
                  return FilterChip(
                    label: Text(tag),
                    selected: active,
                    onSelected: (_) =>
                        ref.read(knowledgeProvider.notifier).toggleTag(tag),
                    visualDensity: VisualDensity.compact,
                  );
                },
              ),
            ),
          // Main list
          Expanded(
            child: _buildList(state),
          ),
        ],
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () => _onFabTapped(context),
        tooltip: 'New',
        child: const Icon(LucideIcons.pencil),
      ),
    );
  }

  Widget _buildList(KnowledgeState state) {
    if (state.isLoadingIds && state.ids.isEmpty) {
      return const Center(child: CircularProgressIndicator());
    }
    if (state.error != null && state.ids.isEmpty) {
      return Center(
        child: Column(
          mainAxisSize: MainAxisSize.min,
          children: [
            Text('Failed to load',
                style: Theme.of(context).textTheme.bodyLarge),
            const SizedBox(height: 8),
            TextButton(
              onPressed: () =>
                  ref.read(knowledgeProvider.notifier).refresh(),
              child: const Text('Retry'),
            ),
          ],
        ),
      );
    }
    final items = state.orderedItems;
    if (items.isEmpty && !state.isLoadingIds && !state.isLoadingBatch) {
      return Center(
        child: Text(
          'No ${_kTabs[_tabController.index].label.toLowerCase()} yet.',
          style: Theme.of(context).textTheme.bodyLarge,
        ),
      );
    }
    return RefreshIndicator(
      onRefresh: () => ref.read(knowledgeProvider.notifier).refresh(),
      child: LayoutBuilder(
        builder: (context, constraints) {
          final cols = constraints.maxWidth >= 900
              ? 3
              : constraints.maxWidth >= 600
                  ? 2
                  : 1;
          if (cols == 1) {
            return ListView.separated(
              controller: _scrollController,
              itemCount: items.length + (state.isLoadingBatch ? 1 : 0),
              separatorBuilder: (_, _) => const Divider(height: 1),
              itemBuilder: (_, i) {
                if (i >= items.length) {
                  return const Padding(
                    padding: EdgeInsets.all(16),
                    child: Center(child: CircularProgressIndicator()),
                  );
                }
                return KnowledgeItemCard(item: items[i]);
              },
            );
          }
          return CustomScrollView(
            controller: _scrollController,
            slivers: [
              SliverPadding(
                padding: const EdgeInsets.all(8),
                sliver: SliverGrid(
                  gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
                    crossAxisCount: cols,
                    crossAxisSpacing: 8,
                    mainAxisSpacing: 8,
                    childAspectRatio: 1.8,
                  ),
                  delegate: SliverChildBuilderDelegate(
                    (_, i) {
                      if (i >= items.length) {
                        return const Center(
                            child: CircularProgressIndicator());
                      }
                      return KnowledgeItemCard(item: items[i])
                          .buildGridCard(context);
                    },
                    childCount:
                        items.length + (state.isLoadingBatch ? 1 : 0),
                  ),
                ),
              ),
            ],
          );
        },
      ),
    );
  }

  void _onFabTapped(BuildContext context) {
    final currentType = _kTabs[_tabController.index].type;
    if (currentType == 'task') {
      context.push('/tasks/new');
      return;
    }
    _showTypePicker(context);
  }

  void _showTypePicker(BuildContext context) {
    showModalBottomSheet<void>(
      context: context,
      builder: (sheetContext) => SafeArea(
        child: Column(
          mainAxisSize: MainAxisSize.min,
          children: [
            _TypePickerRow(
              icon: LucideIcons.fileText,
              label: 'Note',
              description: 'General note or document',
              onTap: () {
                Navigator.pop(sheetContext);
                context.push('/notes/new', extra: {'noteType': 'note'});
              },
            ),
            _TypePickerRow(
              icon: LucideIcons.user,
              label: 'Person',
              description: 'Contact, colleague, or reference person',
              onTap: () {
                Navigator.pop(sheetContext);
                context.push('/notes/new', extra: {'noteType': 'person'});
              },
            ),
            _TypePickerRow(
              icon: LucideIcons.mapPin,
              label: 'Place',
              description: 'Location, venue, or place of interest',
              onTap: () {
                Navigator.pop(sheetContext);
                context.push('/notes/new', extra: {'noteType': 'place'});
              },
            ),
            _TypePickerRow(
              icon: LucideIcons.listChecks,
              label: 'List',
              description: 'Checklist or structured list',
              onTap: () {
                Navigator.pop(sheetContext);
                context.push('/notes/new', extra: {'noteType': 'list'});
              },
            ),
          ],
        ),
      ),
    );
  }
}

class _TypePickerRow extends StatelessWidget {
  final IconData icon;
  final String label;
  final String description;
  final VoidCallback onTap;

  const _TypePickerRow({
    required this.icon,
    required this.label,
    required this.description,
    required this.onTap,
  });

  @override
  Widget build(BuildContext context) {
    return ListTile(
      leading: Icon(icon),
      title: Text(label),
      subtitle: Text(description),
      onTap: onTap,
    );
  }
}