// Version: 1.0.0
import 'package:flutter/material.dart';
import '../services/database_helper.dart';
import '../models/product.dart';

/// 受注入力画面（Material Design）
class OrderScreen extends StatefulWidget {
  const OrderScreen({super.key});

  @override
  State<OrderScreen> createState() => _OrderScreenState();
}

class _OrderScreenState extends State<OrderScreen> {
  Customer? _selectedCustomer;
  final DatabaseHelper _db = DatabaseHelper.instance;
  List<Product> _products = [];
  List<Customer> _customers = [];
  List<LineItem> _items = [];
  String? _orderDate; // Default: 現在時刻

  @override
  void initState() {
    super.initState();
    _loadProducts();
    _loadCustomers();
  }

  Future<void> _loadProducts() async {
    try {
      final products = await _db.getProducts();
      setState(() => _products = products);
    } catch (e) {
      debugPrint('Product loading failed: $e');
    }
  }

  Future<void> _loadCustomers() async {
    try {
      final customers = await _db.getCustomers();
      setState(() => _customers = customers.where((c) => c.isDeleted == 0).toList());
    } catch (e) {
      debugPrint('Customer loading failed: $e');
    }
  }

  Future<void> _showCustomerPicker() async {
    if (_customers.isEmpty) await _loadCustomers();

    final selected = await showModalBottomSheet<Customer>(
      context: context,
      builder: (ctx) => SizedBox(
        height: MediaQuery.of(context).size.height * 0.4,
        child: ListView.builder(
          padding: const EdgeInsets.all(8),
          itemCount: _customers.length,
          itemBuilder: (ctx, index) => ListTile(
            title: Text(_customers[index].name),
            subtitle: Text('コード：${_customers[index].customerCode}'),
            onTap: () => Navigator.pop(ctx, _customers[index]),
          ),
        ),
      ),
    );

    if (selected is Customer && selected.id != _selectedCustomer?.id) {
      setState(() => _selectedCustomer = selected);
    }
  }

  void _addSelectedProducts() async {
    for (final product in _products) {
      final existingStock = product.stock;
      if (existingStock > 0 && !_items.any((i) => i.productId == product.id)) {
        setState(() => _items.add(LineItem(
          orderId: DateTime.now().millisecondsSinceEpoch,
          productId: product.id,
          productName: product.name,
          unitPrice: product.price,
          quantity: 1,
          total: product.price,
          stockRemaining: existingStock - 1,
        )));
      }
    }
    _showAddDialog();
  }

  void _removeLineItem(int index) {
    setState(() => _items.removeAt(index));
  }

  String? get _orderId => _items.isNotEmpty ? _items.first.orderId.toString() : null;

  int get _totalAmount => _items.fold(0, (sum, item) => sum + item.total);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('受注入力')),
      body: ListView(
        padding: const EdgeInsets.all(16),
        children: [
          _buildCustomerField(),
          const SizedBox(height: 16),
          Row(
            mainAxisAlignment: MainAxisAlignment.spaceBetween,
            children: [
              const Text('発注日'),
              DropdownButton<String>(
                value: _orderDate ?? '',
                items: ['', '2026-03-07'].map((s) => DropdownMenuItem(value: s, child: Text(s))).toList(),
                onChanged: (v) => setState(() => _orderDate = v),
              ),
            ],
          ),
          const SizedBox(height: 8),
          Card(
            margin: EdgeInsets.zero,
            child: ExpansionTile(
              title: const Text('受注商品'),
              children: [
                if (_items.isEmpty) ...[
                  Padding(
                    padding: const EdgeInsets.all(16),
                    child: Column(
                      children: [
                        Icon(Icons.shopping_cart_outlined, size: 48, color: Colors.grey.shade400),
                        const SizedBox(height: 8),
                        Text('商品を追加してください', style: TextStyle(color: Colors.grey.shade600)),
                      ],
                    ),
                  ),
                ] else ...[
                  ListView.builder(
                    shrinkWrap: true,
                    padding: EdgeInsets.zero,
                    itemCount: _items.length,
                    itemBuilder: (context, index) => Card(
                      margin: const EdgeInsets.symmetric(vertical: 4),
                      child: ListTile(
                        leading: CircleAvatar(
                          backgroundColor: Colors.teal.shade100,
                          child: Icon(Icons.shopping_cart, color: Colors.teal),
                        ),
                        title: Text(_items[index].productName),
                        subtitle: Text('数量：${_items[index].quantity} / 単価：¥${_items[index].unitPrice}'),
                        trailing: IconButton(icon: const Icon(Icons.delete, color: Colors.red), onPressed: () => _removeLineItem(index)),
                      ),
                    ),
                  ),
                ],
              ),
            ),
          ),
        ],
      ),
    );
  }

  Widget _buildCustomerField() {
    return TextField(
      decoration: InputDecoration(
        labelText: '得意先',
        hintText: _selectedCustomer != null ? _selectedCustomer.name : '得意先マスタから選択',
        prefixIcon: Icon(Icons.person_search),
        isReadOnly: true,
      ),
      onTap: () => _showCustomerPicker(),
    );
  }

  void _showAddDialog() async {
    final selected = await showModalBottomSheet<Product>(
      context: context,
      builder: (ctx) => ListView.builder(
        padding: EdgeInsets.zero,
        itemCount: _products.length,
        itemBuilder: (ctx, index) => CheckboxListTile(
          title: Text(_products[index].name),
          subtitle: Text('¥${_products[index].price} / 在庫：${_products[index].stock}${_products[index].unit ?? ''}'),
          value: _items.any((i) => i.productId == _products[index].id),
          onChanged: (value) {
            if (value && _products[index].stock > 0) _addSelectedProducts();
          },
        ),
      ),
    );

    if (selected != null && selected.id != null && _products[selected.id]?.stock! > 0 && !_items.any((i) => i.productId == selected.id)) {
      setState(() => _items.add(LineItem(
        orderId: _orderId ?? DateTime.now().millisecondsSinceEpoch,
        productId: selected.id,
        productName: selected.name,
        unitPrice: selected.price,
        quantity: 1,
        total: selected.price,
        stockRemaining: _products[selected.id].stock - 1,
      )));
    }
  }

  void _showSaveDialog() async {
    if (_items.isEmpty) {
      ScaffoldMessenger.of(context).showSnackBar(
        const SnackBar(content: Text('商品を追加してください')),
      );
      return;
    }

    showDialog(
      context: context,
      builder: (ctx) => AlertDialog(
        title: const Text('受注確定'),
        content: SingleChildScrollView(
          child: Column(
            mainAxisSize: MainAxisSize.min,
            children: [
              if (_selectedCustomer != null) ...[
                Padding(
                  padding: const EdgeInsets.symmetric(vertical: 8),
                  child: Text('得意先：${_selectedCustomer!.name}'),
                ),
              ],
              Text('合計：¥${_totalAmount}'),
              if (_items.isNotEmpty) ...[
                Divider(),
                ..._items.map((item) => Padding(
                  padding: const EdgeInsets.symmetric(vertical: 4),
                  child: Row(
                    mainAxisAlignment: MainAxisAlignment.spaceBetween,
                    children: [
                      Text(item.productName),
                      Text('¥${item.unitPrice} × ${item.quantity} = ¥${item.total}'),
                    ],
                  ),
                )),
              ],
            ],
          ),
        ),
        actions: [
          TextButton(
            onPressed: () => Navigator.pop(ctx),
            child: const Text('キャンセル'),
          ),
          ElevatedButton(
            onPressed: () {
              Navigator.pop(ctx);
              ScaffoldMessenger.of(context).showSnackBar(
                const SnackBar(content: Text('受注保存しました'))..behavior: SnackBarBehavior.floating,
              );
            },
            child: const Text('確定'),
          ),
        ],
      ),
    );
  }
}

/// 受注行モデル（在庫振替付き）
class LineItem {
  final String? orderId;
  final int? productId;
  final String productName;
  final int unitPrice;
  int quantity = 1;
  final int stockRemaining; // 追加後の在庫数

  LineItem({this.orderId, required this.productId, required this.productName, required this.unitPrice, this.quantity = 1, required this.stockRemaining});
}