import 'package:flutter/material.dart';
import 'package:go_router/go_router.dart';
import '../../core/theme/app_theme.dart';
import '../../core/widgets/step_indicator.dart';
import '../../data/models/models.dart';
import '../../data/services/order_service.dart';

class PickingScreen extends StatefulWidget {
  final int orderId;
  final int segmentId;

  const PickingScreen({super.key, required this.orderId, required this.segmentId});

  @override
  State<PickingScreen> createState() => _PickingScreenState();
}

class _PickingScreenState extends State<PickingScreen> {
  final _service = MockOrderService();
  Order? _order;
  OrderSegment? _segment;
  int _currentItemIndex = 0;
  bool _loading = true;

  @override
  void initState() {
    super.initState();
    _load();
  }

  Future<void> _load() async {
    final order = await _service.getOrderDetail(widget.orderId);
    final segment = order.segments.firstWhere((s) => s.id == widget.segmentId);
    final firstUndone = segment.items.indexWhere((i) => !i.isCompleted);
    if (mounted) {
      setState(() {
        _order = order;
        _segment = segment;
        _currentItemIndex = firstUndone >= 0 ? firstUndone : 0;
        _loading = false;
      });
    }
  }

  OrderItem? get _currentItem => _segment?.items.elementAtOrNull(_currentItemIndex);

  void _onItemDone() {
    final items = _segment!.items;
    final next = items.indexWhere((i) => !i.isCompleted, _currentItemIndex + 1);
    if (next >= 0) {
      setState(() => _currentItemIndex = next);
    } else {
      // Segment done — go back to order detail
      context.pop();
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(_order?.orderNumber ?? ''),
        leading: IconButton(icon: const Icon(Icons.arrow_back), onPressed: () => context.pop()),
        actions: [
          Padding(
            padding: const EdgeInsets.only(right: 16),
            child: Center(
              child: Text(
                '${_segment?.pickedCount ?? 0}/${_segment?.totalCount ?? 0}',
                style: const TextStyle(fontWeight: FontWeight.bold, fontSize: 16),
              ),
            ),
          ),
        ],
      ),
      body: _loading || _currentItem == null
          ? const Center(child: CircularProgressIndicator())
          : Column(
              children: [
                const StepIndicator(currentStep: BatchStep.picking),
                Expanded(
                  child: _ItemCard(
                    item: _currentItem!,
                    service: _service,
                    onDone: () {
                      setState(() {});
                      _onItemDone();
                    },
                  ),
                ),
              ],
            ),
    );
  }
}

class _ItemCard extends StatefulWidget {
  final OrderItem item;
  final OrderService service;
  final VoidCallback onDone;

  const _ItemCard({required this.item, required this.service, required this.onDone});

  @override
  State<_ItemCard> createState() => _ItemCardState();
}

class _ItemCardState extends State<_ItemCard> {
  final _qtyController = TextEditingController();
  bool _loading = false;
  bool _showSubstitutes = false;

  @override
  void initState() {
    super.initState();
    _qtyController.text = widget.item.planQty.toString();
  }

  Color get _cardColor {
    switch (widget.item.type) {
      case ItemType.cold: return AppColors.itemCold;
      case ItemType.frozen: return AppColors.itemFrozen;
      case ItemType.alcohol: return AppColors.itemAlcohol;
      case ItemType.clarify: return AppColors.itemClarify;
      case ItemType.normal: return AppColors.itemNormal;
    }
  }

  String get _typeLabel {
    switch (widget.item.type) {
      case ItemType.cold: return '❄️ Холодне';
      case ItemType.frozen: return '🧊 Морозилка';
      case ItemType.alcohol: return '🍷 Алкоголь';
      case ItemType.clarify: return '❓ Уточнення';
      case ItemType.normal: return '';
    }
  }

  Future<void> _markPicked() async {
    setState(() => _loading = true);
    final qty = double.tryParse(_qtyController.text) ?? widget.item.planQty;
    await widget.service.markItemPicked(widget.item.id, qty);
    widget.item.status = ItemStatus.picked;
    widget.item.actualQty = qty;
    if (mounted) setState(() => _loading = false);
    widget.onDone();
  }

  Future<void> _markNotFound() async {
    setState(() => _loading = true);
    await widget.service.markItemNotFound(widget.item.id);
    widget.item.status = ItemStatus.notFound;
    if (mounted) setState(() => _loading = false);
    widget.onDone();
  }

  Future<void> _replaceWith(OrderItemSubstitute sub) async {
    setState(() => _loading = true);
    final qty = double.tryParse(_qtyController.text) ?? widget.item.planQty;
    await widget.service.replaceItem(widget.item.id, sub.sku, qty);
    widget.item.status = ItemStatus.replaced;
    if (mounted) setState(() => _loading = false);
    widget.onDone();
  }

  @override
  Widget build(BuildContext context) {
    final item = widget.item;
    return Container(
      color: _cardColor,
      child: SingleChildScrollView(
        padding: const EdgeInsets.all(16),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            if (_typeLabel.isNotEmpty)
              Padding(
                padding: const EdgeInsets.only(bottom: 8),
                child: Text(_typeLabel, style: const TextStyle(fontSize: 14, fontWeight: FontWeight.w600)),
              ),
            // Product image + name
            Row(
              crossAxisAlignment: CrossAxisAlignment.start,
              children: [
                ClipRRect(
                  borderRadius: BorderRadius.circular(8),
                  child: Container(
                    width: 80,
                    height: 80,
                    color: AppColors.divider,
                    child: item.imageUrl != null
                        ? Image.network(item.imageUrl!, fit: BoxFit.cover,
                            errorBuilder: (_, __, ___) => const Icon(Icons.image_not_supported, size: 40))
                        : const Icon(Icons.shopping_bag_outlined, size: 40, color: AppColors.textSecondary),
                  ),
                ),
                const SizedBox(width: 12),
                Expanded(
                  child: Column(
                    crossAxisAlignment: CrossAxisAlignment.start,
                    children: [
                      Text(item.name,
                          style: const TextStyle(fontSize: 18, fontWeight: FontWeight.bold),
                          maxLines: 3,
                          overflow: TextOverflow.ellipsis),
                      const SizedBox(height: 4),
                      Text(item.category,
                          style: const TextStyle(fontSize: 13, color: AppColors.textSecondary)),
                      const SizedBox(height: 4),
                      Text('${item.price.toStringAsFixed(2)} грн',
                          style: const TextStyle(fontSize: 15, fontWeight: FontWeight.w600, color: AppColors.primary)),
                    ],
                  ),
                ),
              ],
            ),
            const SizedBox(height: 20),
            // Plan / Actual
            Row(
              children: [
                Expanded(
                  child: Column(
                    children: [
                      const Text('Потрібно', style: TextStyle(fontSize: 12, color: AppColors.textSecondary)),
                      const SizedBox(height: 4),
                      Text('${item.planQty}',
                          style: const TextStyle(fontSize: 32, fontWeight: FontWeight.bold, color: AppColors.primary)),
                    ],
                  ),
                ),
                const VerticalDivider(width: 1),
                Expanded(
                  child: Column(
                    children: [
                      const Text('Зібрано', style: TextStyle(fontSize: 12, color: AppColors.textSecondary)),
                      const SizedBox(height: 4),
                      SizedBox(
                        width: 100,
                        child: TextField(
                          controller: _qtyController,
                          keyboardType: const TextInputType.numberWithOptions(decimal: true),
                          textAlign: TextAlign.center,
                          style: const TextStyle(fontSize: 32, fontWeight: FontWeight.bold),
                          decoration: const InputDecoration(border: UnderlineInputBorder(), contentPadding: EdgeInsets.zero),
                        ),
                      ),
                    ],
                  ),
                ),
              ],
            ),
            const SizedBox(height: 24),
            // Actions
            ElevatedButton.icon(
              onPressed: _loading ? null : _markPicked,
              icon: const Icon(Icons.check),
              label: const Text('Зібрано'),
            ),
            const SizedBox(height: 10),
            OutlinedButton.icon(
              onPressed: _loading ? null : () => setState(() => _showSubstitutes = !_showSubstitutes),
              icon: const Icon(Icons.swap_horiz),
              label: const Text('Замінити'),
              style: OutlinedButton.styleFrom(
                minimumSize: const Size(double.infinity, 52),
                side: const BorderSide(color: AppColors.warning),
                foregroundColor: AppColors.warning,
              ),
            ),
            const SizedBox(height: 10),
            TextButton.icon(
              onPressed: _loading ? null : _markNotFound,
              icon: const Icon(Icons.remove_circle_outline, color: AppColors.error),
              label: const Text('Немає товару', style: TextStyle(color: AppColors.error)),
              style: TextButton.styleFrom(minimumSize: const Size(double.infinity, 52)),
            ),
            // Substitutes
            if (_showSubstitutes && item.substitutes.isNotEmpty) ...[
              const Divider(),
              const Text('Замінити на:', style: TextStyle(fontWeight: FontWeight.w600)),
              const SizedBox(height: 8),
              ...item.substitutes.map((sub) => Card(
                    child: ListTile(
                      title: Text(sub.name),
                      subtitle: Text(sub.sku),
                      trailing: const Icon(Icons.arrow_forward_ios, size: 16),
                      onTap: _loading ? null : () => _replaceWith(sub),
                    ),
                  )),
            ],
            if (_showSubstitutes && item.substitutes.isEmpty)
              const Padding(
                padding: EdgeInsets.all(8),
                child: Text('Немає доступних замін', style: TextStyle(color: AppColors.textSecondary)),
              ),
          ],
        ),
      ),
    );
  }
}