import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';
import '../main.dart';
import '../scanner_screen.dart';
import '../services/collection_service.dart';
import '../services/main_collection_sync.dart';
import '../theme/app_colors.dart';
import '../utils/preferences_utils.dart';

class ScanTab extends StatefulWidget {
  const ScanTab({super.key});

  @override
  State<ScanTab> createState() => ScanTabState();
}

class ScanTabState extends State<ScanTab> {
  static const _duplicateCooldown = Duration(seconds: 2);

  bool _isBusy = false;
  List<Collection> _collections = [];
  Collection? _selectedCollection;
  bool _loadingCollections = true;
  String? _lastProcessedHwId;
  DateTime? _lastProcessedAt;

  bool get _canAddToSelectedCollection =>
      (_selectedCollection?.canModifyCars ?? false);

  @override
  void initState() {
    super.initState();
    MainCollectionSync.changeToken.addListener(_handleMainCollectionChanged);
    _loadCollections();
  }

  @override
  void dispose() {
    MainCollectionSync.changeToken.removeListener(_handleMainCollectionChanged);
    super.dispose();
  }

  void refresh() => _loadCollections();

  void _handleMainCollectionChanged() {
    if (!mounted) return;
    _loadCollections();
  }

  Future<void> _loadCollections() async {
    try {
      final list = await CollectionService.getMyCollections();
      final userId = supabase.auth.currentUser?.id;
      if (userId == null) {
        throw Exception('You must be signed in to load collections.');
      }

      final prefs = await SharedPreferences.getInstance();
      final persistedId = await readActiveCollectionId(prefs, userId: userId);

      Collection? selected;
      if (persistedId != null) {
        final matching = list.where((c) => c.id == persistedId);
        if (matching.isNotEmpty) {
          selected = matching.first;
        }
      }

      selected ??= list.isNotEmpty ? list.first : null;

      if (!mounted) return;
      setState(() {
        _collections = list;
        _selectedCollection = selected;
        _loadingCollections = false;
      });

      if (selected != null) {
        await writeActiveCollectionId(
          prefs,
          userId: userId,
          collectionId: selected.id,
        );
      }
    } catch (e) {
      if (!mounted) return;
      setState(() => _loadingCollections = false);
      showGlobalError(
        e,
        fallback: 'Failed to load collections. Please try again.',
      );
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: SafeArea(
        child: Padding(
          padding: const EdgeInsets.symmetric(horizontal: 24),
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: [
              Container(
                width: 120,
                height: 120,
                decoration: BoxDecoration(
                  gradient: AppColors.brandGradientSoft,
                  shape: BoxShape.circle,
                ),
                child: const Icon(
                  Icons.qr_code_scanner,
                  size: 56,
                  color: AppColors.orange,
                ),
              ),
              const SizedBox(height: 28),
              const Text(
                'Scan a Hot Wheels Car',
                style: TextStyle(fontSize: 22, fontWeight: FontWeight.w700),
              ),
              const SizedBox(height: 10),
              const Text(
                'Point your camera at the model ID and add cars\ninstantly to your selected collection.',
                textAlign: TextAlign.center,
                style: TextStyle(
                  fontSize: 14,
                  color: AppColors.textSecondary,
                  height: 1.5,
                ),
              ),
              const SizedBox(height: 24),
              if (_loadingCollections)
                const Padding(
                  padding: EdgeInsets.symmetric(vertical: 8),
                  child: SizedBox(
                    width: 20,
                    height: 20,
                    child: CircularProgressIndicator(strokeWidth: 2),
                  ),
                )
              else if (_collections.isEmpty)
                const Text(
                  'Create a collection first!',
                  style: TextStyle(color: AppColors.error),
                )
              else
                Container(
                  width: double.infinity,
                  padding: const EdgeInsets.symmetric(horizontal: 16),
                  decoration: BoxDecoration(
                    borderRadius: BorderRadius.circular(14),
                    border: Border.all(
                      color: AppColors.orange.withValues(alpha: 0.4),
                    ),
                  ),
                  child: DropdownButtonHideUnderline(
                    child: DropdownButton<String>(
                      isExpanded: true,
                      value: _selectedCollection?.id,
                      icon: const Icon(Icons.arrow_drop_down,
                          color: AppColors.orange),
                      items: _collections
                          .map((c) => DropdownMenuItem(
                                value: c.id,
                                child: Row(
                                  children: [
                                    Icon(
                                      c.isOwner
                                          ? Icons.collections_bookmark
                                          : Icons.group,
                                      size: 18,
                                      color: AppColors.orange,
                                    ),
                                    const SizedBox(width: 8),
                                    Expanded(
                                      child: Text(
                                        c.name,
                                        overflow: TextOverflow.ellipsis,
                                      ),
                                    ),
                                  ],
                                ),
                              ))
                          .toList(),
                      onChanged: (id) {
                        _setSelectedCollection(id);
                      },
                    ),
                  ),
                ),
              const SizedBox(height: 24),
              if (_selectedCollection?.isViewer == true)
                const Padding(
                  padding: EdgeInsets.only(bottom: 12),
                  child: Text(
                    'Viewer role is read-only. Choose an owner/member collection to add cars.',
                    textAlign: TextAlign.center,
                    style: TextStyle(color: AppColors.textSecondary),
                  ),
                ),
              SizedBox(
                width: double.infinity,
                height: 56,
                child: DecoratedBox(
                  decoration: BoxDecoration(
                    gradient: AppColors.brandGradient,
                    borderRadius: BorderRadius.circular(50),
                    boxShadow: [
                      BoxShadow(
                        color: AppColors.orange.withValues(alpha: 0.35),
                        blurRadius: 14,
                        offset: const Offset(0, 5),
                      ),
                    ],
                  ),
                  child: ElevatedButton.icon(
                    onPressed: _isBusy || !_canAddToSelectedCollection
                        ? null
                        : _openScanner,
                    icon: _isBusy
                        ? const SizedBox(
                            width: 22,
                            height: 22,
                            child: CircularProgressIndicator(
                              strokeWidth: 2.5,
                              color: Colors.white,
                            ),
                          )
                        : const Icon(Icons.camera_alt, color: Colors.white),
                    label: Text(
                      _isBusy ? 'Processing…' : 'Open Scanner',
                      style: const TextStyle(
                        fontSize: 16,
                        fontWeight: FontWeight.w600,
                        color: Colors.white,
                      ),
                    ),
                    style: ElevatedButton.styleFrom(
                      backgroundColor: Colors.transparent,
                      shadowColor: Colors.transparent,
                      shape: RoundedRectangleBorder(
                        borderRadius: BorderRadius.circular(50),
                      ),
                    ),
                  ),
                ),
              ),
              const SizedBox(height: 16),
              SizedBox(
                width: double.infinity,
                child: OutlinedButton.icon(
                  onPressed: _isBusy || !_canAddToSelectedCollection
                      ? null
                      : _manualEntry,
                  icon: const Icon(Icons.keyboard),
                  label: const Text('Enter ID Manually'),
                ),
              ),
            ],
          ),
        ),
      ),
    );
  }

  void _setSelectedCollection(String? id) {
    if (id == null) return;
    final matching = _collections.where((c) => c.id == id);
    if (matching.isEmpty) return;

    setState(() => _selectedCollection = matching.first);
  }

  Future<void> _openScanner() async {
    await navigatorKey.currentState!.push<void>(
      MaterialPageRoute(
        builder: (_) => ScannerScreen(
          collections: _collections,
          activeCollectionId: _selectedCollection?.id,
          onCollectionChanged: _setSelectedCollection,
          onDetected: (hwId) => _processHwId(hwId),
        ),
      ),
    );
  }

  Future<void> _manualEntry() async {
    final controller = TextEditingController();
    final result = await showDialog<String>(
      context: context,
      builder: (_) => AlertDialog(
        title: const Text('Enter HW ID'),
        content: TextField(
          controller: controller,
          autofocus: true,
          textCapitalization: TextCapitalization.characters,
          decoration: const InputDecoration(hintText: 'e.g. JKF21'),
          onSubmitted: (v) {
            final val = v.trim().toUpperCase();
            if (val.isNotEmpty) Navigator.pop(context, val);
          },
        ),
        actions: [
          TextButton(
            onPressed: () => Navigator.pop(context),
            child: const Text('Cancel'),
          ),
          ElevatedButton(
            onPressed: () {
              final val = controller.text.trim().toUpperCase();
              if (val.isNotEmpty) Navigator.pop(context, val);
            },
            child: const Text('OK'),
          ),
        ],
      ),
    );

    if (result == null || !mounted) return;
    await _processHwId(result);
  }

  Future<bool> _processHwId(String hwId) async {
    final now = DateTime.now();
    if (_lastProcessedHwId == hwId &&
        _lastProcessedAt != null &&
        now.difference(_lastProcessedAt!) < _duplicateCooldown) {
      return true;
    }
    _lastProcessedHwId = hwId;
    _lastProcessedAt = now;

    final collection = _selectedCollection;
    if (collection == null) return false;

    setState(() => _isBusy = true);

    try {
      final existing = await supabase
          .from('hotwheels')
          .select('id')
          .eq('hw_id', hwId)
          .eq('collection_id', collection.id)
          .maybeSingle();

      if (existing != null) {
        if (!mounted) return false;
        setState(() => _isBusy = false);
        await showDialog(
          context: navigatorKey.currentContext ?? context,
          builder: (_) => AlertDialog(
            icon: const Icon(Icons.check_circle,
                color: AppColors.success, size: 48),
            title: const Text('Already in Collection!'),
            content: Text('$hwId is already in "${collection.name}".'),
            actions: [
              ElevatedButton(
                onPressed: () => Navigator.pop(context),
                child: const Text('Got it'),
              ),
            ],
          ),
        );
        return true;
      }

      final globalCar = await supabase
          .from('global_cars')
          .select('hw_id, name, series, year, color, is_verified, confirmation_count')
          .eq('hw_id', hwId)
          .maybeSingle();

      if (!mounted) return false;
      setState(() => _isBusy = false);

      if (globalCar != null) {
        final addConfirmed = await showModalBottomSheet<bool>(
          context: navigatorKey.currentContext ?? context,
          isScrollControlled: true,
          shape: const RoundedRectangleBorder(
            borderRadius: BorderRadius.vertical(top: Radius.circular(24)),
          ),
          builder: (_) => _FoundCarSheet(
            collectionName: collection.name,
            car: globalCar,
          ),
        );

        if (addConfirmed == true) {
          await _addToCollection(collection.id, hwId);
          await _ensureValidationVote(hwId);
          if (!mounted) return false;
          showGlobalSuccess('$hwId added to "${collection.name}"! 🎉');
        }
      } else {
        final discovery = await showModalBottomSheet<_NewDiscoveryData>(
          context: navigatorKey.currentContext ?? context,
          isScrollControlled: true,
          shape: const RoundedRectangleBorder(
            borderRadius: BorderRadius.vertical(top: Radius.circular(24)),
          ),
          builder: (_) => _NewDiscoverySheet(
            hwId: hwId,
            collectionName: collection.name,
          ),
        );

        if (discovery != null) {
          await _createGlobalCarAndVote(
            hwId: hwId,
            name: discovery.name,
            series: discovery.series,
            year: discovery.year,
          );
          await _addToCollection(collection.id, hwId, notes: discovery.notes);
          if (!mounted) return false;
          showGlobalSuccess('$hwId added to "${collection.name}"! 🎉');
        }
      }
      return true;
    } catch (e) {
      if (mounted) setState(() => _isBusy = false);
      showGlobalError(
        e,
        fallback: 'Could not save this car right now. Please try again.',
      );
      return true;
    }
  }

  Future<void> _addToCollection(
    String collectionId,
    String hwId, {
    String? notes,
  }) async {
    final userId = supabase.auth.currentUser?.id;
    if (userId == null) {
      throw Exception('You must be signed in to add cars.');
    }

    await supabase.from('hotwheels').insert({
      'hw_id': hwId,
      'user_id': userId,
      'collection_id': collectionId,
      if (notes != null && notes.trim().isNotEmpty) 'notes': notes.trim(),
    });
  }

  Future<void> _createGlobalCarAndVote({
    required String hwId,
    required String name,
    String? series,
    int? year,
  }) async {
    final userId = supabase.auth.currentUser?.id;
    if (userId == null) {
      throw Exception('You must be signed in to create catalog entries.');
    }

    final cleanedSeries = series?.trim();
    final payload = <String, dynamic>{
      'hw_id': hwId,
      'name': name,
      'series': (cleanedSeries?.isNotEmpty ?? false) ? cleanedSeries : null,
      'year': year,
    }..removeWhere((key, value) => value == null);

    await supabase.from('global_cars').insert(payload);

    await supabase.from('car_votes').insert({
      'hw_id': hwId,
      'user_id': userId,
    });
  }

  Future<void> _ensureValidationVote(String hwId) async {
    final userId = supabase.auth.currentUser?.id;
    if (userId == null) {
      throw Exception('You must be signed in to validate entries.');
    }
    final existingVote = await supabase
        .from('car_votes')
        .select('id')
        .eq('hw_id', hwId)
        .eq('user_id', userId)
        .maybeSingle();

    if (existingVote != null) return;

    await supabase.from('car_votes').insert({
      'hw_id': hwId,
      'user_id': userId,
    });
  }
}

class _FoundCarSheet extends StatelessWidget {
  final String collectionName;
  final Map<String, dynamic> car;

  const _FoundCarSheet({required this.collectionName, required this.car});

  @override
  Widget build(BuildContext context) {
    final hwId = car['hw_id'] as String? ?? '???';
    final name = car['name'] as String? ?? 'Unknown model';
    final series = car['series'] as String?;
    final year = car['year'];
    final verified = car['is_verified'] == true;
    final confirmations = (car['confirmation_count'] as num?)?.toInt() ?? 0;

    return Padding(
      padding: EdgeInsets.only(
        left: 20,
        right: 20,
        top: 20,
        bottom: MediaQuery.of(context).viewInsets.bottom + 20,
      ),
      child: Column(
        mainAxisSize: MainAxisSize.min,
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          Text(
            'Found in Catalog',
            style: Theme.of(context).textTheme.titleLarge?.copyWith(
                  fontWeight: FontWeight.w700,
                ),
          ),
          const SizedBox(height: 8),
          Text('$name ($hwId)', style: const TextStyle(fontWeight: FontWeight.w600)),
          if (series != null && series.isNotEmpty) ...[
            const SizedBox(height: 4),
            Text('Series: $series'),
          ],
          if (year != null) ...[
            const SizedBox(height: 4),
            Text('Year: $year'),
          ],
          const SizedBox(height: 6),
          Text(
            verified ? 'Verified by community' : 'Unverified catalog entry',
            style: TextStyle(
              color: verified ? AppColors.success : AppColors.textSecondary,
              fontSize: 12,
            ),
          ),
          const SizedBox(height: 4),
          Text(
            '$confirmations confirmation${confirmations == 1 ? '' : 's'}',
            style: const TextStyle(
              color: AppColors.textHint,
              fontSize: 12,
            ),
          ),
          const SizedBox(height: 16),
          SizedBox(
            width: double.infinity,
            child: ElevatedButton.icon(
              onPressed: () => Navigator.pop(context, true),
              icon: const Icon(Icons.add),
              label: Text('Add to "$collectionName"'),
            ),
          ),
          const SizedBox(height: 8),
          SizedBox(
            width: double.infinity,
            child: TextButton(
              onPressed: () => Navigator.pop(context, false),
              child: const Text('Cancel'),
            ),
          ),
        ],
      ),
    );
  }
}

class _NewDiscoveryData {
  final String name;
  final String? series;
  final int? year;
  final String? notes;

  const _NewDiscoveryData({
    required this.name,
    this.series,
    this.year,
    this.notes,
  });
}

class _NewDiscoverySheet extends StatefulWidget {
  final String hwId;
  final String collectionName;

  const _NewDiscoverySheet({
    required this.hwId,
    required this.collectionName,
  });

  @override
  State<_NewDiscoverySheet> createState() => _NewDiscoverySheetState();
}

class _NewDiscoverySheetState extends State<_NewDiscoverySheet> {
  final _nameController = TextEditingController();
  final _seriesController = TextEditingController();
  final _yearController = TextEditingController();
  final _notesController = TextEditingController();
  bool _isSaving = false;

  @override
  void dispose() {
    _nameController.dispose();
    _seriesController.dispose();
    _yearController.dispose();
    _notesController.dispose();
    super.dispose();
  }

  void _save() {
    final name = _nameController.text.trim();
    if (name.isEmpty) {
      showGlobalSnackBar('Name is required for a new discovery.', isError: true);
      return;
    }

    setState(() => _isSaving = true);

    Navigator.pop(
      context,
      _NewDiscoveryData(
        name: name,
        series: _seriesController.text.trim().isEmpty
            ? null
            : _seriesController.text.trim(),
        year: int.tryParse(_yearController.text.trim()),
        notes: _notesController.text.trim().isEmpty
            ? null
            : _notesController.text.trim(),
      ),
    );
  }

  @override
  Widget build(BuildContext context) {
    return Padding(
      padding: EdgeInsets.only(
        left: 20,
        right: 20,
        top: 20,
        bottom: MediaQuery.of(context).viewInsets.bottom + 20,
      ),
      child: Column(
        mainAxisSize: MainAxisSize.min,
        children: [
          Text(
            'New Discovery: ${widget.hwId}',
            style: Theme.of(context).textTheme.titleLarge?.copyWith(
                  fontWeight: FontWeight.w700,
                ),
          ),
          const SizedBox(height: 14),
          TextField(
            controller: _nameController,
            autofocus: true,
            decoration: const InputDecoration(
              labelText: 'Name *',
              hintText: "e.g. '70 Dodge Charger",
            ),
          ),
          const SizedBox(height: 10),
          TextField(
            controller: _seriesController,
            decoration: const InputDecoration(labelText: 'Series'),
          ),
          const SizedBox(height: 10),
          TextField(
            controller: _yearController,
            keyboardType: TextInputType.number,
            decoration: const InputDecoration(labelText: 'Year'),
          ),
          const SizedBox(height: 10),
          TextField(
            controller: _notesController,
            maxLines: 2,
            decoration: const InputDecoration(
              labelText: 'Notes (for your garage entry)',
            ),
          ),
          const SizedBox(height: 16),
          SizedBox(
            width: double.infinity,
            child: ElevatedButton.icon(
              onPressed: _isSaving ? null : _save,
              icon: const Icon(Icons.save_outlined),
              label: Text('Save & Add to "${widget.collectionName}"'),
            ),
          ),
          const SizedBox(height: 8),
          SizedBox(
            width: double.infinity,
            child: TextButton(
              onPressed: _isSaving ? null : () => Navigator.pop(context),
              child: const Text('Cancel'),
            ),
          ),
        ],
      ),
    );
  }
}