見積書画面簡素化\n\n- database_helper.dart の重複 API 削除\n- estimate_screen.dart の Estimate モデル依存排除（Map データ保存）\n- showModal → showDialog 修正\n- Duration(inDays:...) → Duration(days:) 修正\n- TextButton の child パラメータ追加\n- ビルド成功 (49.4MB APK)

lib/screens/estimate_screen.dart

@@ -1,6 +1,9 @@
-// Version: 1.5 - 見積書画面（簡易実装）
+// Version: 1.9 - 見積書画面（簡素版）
 import 'package:flutter/material.dart';
+import 'package:intl/intl.dart';
 import '../models/customer.dart';
+import '../models/product.dart';
+import '../services/database_helper.dart';
 
 /// 見積書作成画面
 class EstimateScreen extends StatefulWidget {
@@ -10,78 +13,411 @@ class EstimateScreen extends StatefulWidget {
   State<EstimateScreen> createState() => _EstimateScreenState();
 }
 
-class _EstimateScreenState extends State<EstimateScreen> {
+class _EstimateScreenState extends State<EstimateScreen> with SingleTickerProviderStateMixin {
   Customer? _selectedCustomer;
   List<Customer> _customers = [];
   DateTime? _expiryDate;
+  
+  // 商品リスト状態
+  List<Product> _products = [];
+  List<_EstimateItem> _estimateItems = <_EstimateItem>[];
+  double _totalAmount = 0.0;
+  String _estimateNumber = '';
 
   @override
   void initState() {
     super.initState();
     _loadCustomers();
+    _generateEstimateNumber();
+    _loadProducts();
   }
 
   Future<void> _loadCustomers() async {
-    // TODO: DatabaseHelper.instance.getCustomers() を使用
+    try {
-    setState(() => _customers = []);
+      final customers = await DatabaseHelper.instance.getCustomers();
+      if (mounted) setState(() => _customers = customers ?? const <Customer>[]);
+    } catch (e) {}
   }
 
-  /// 見積有効期限を設定（簡易）
+  /// 見積書番号を自動生成（YMM-0001 形式）
-  void setExpiryDate(DateTime date) {
+  void _generateEstimateNumber() {
-    setState(() => _expiryDate = date);
+    final now = DateTime.now();
+    final yearMonth = '${now.year}${now.month.toString().padLeft(2, '0')}';
+    if (mounted) setState(() => _estimateNumber = '$yearMonth-0001');
+  }
+
+  Future<void> _loadProducts() async {
+    try {
+      final ps = await DatabaseHelper.instance.getProducts();
+      if (mounted) setState(() => _products = ps ?? const <Product>[]);
+    } catch (e) {}
+  }
+
+  /// 商品を検索して見積項目に追加
+  Future<void> searchProduct(String keyword) async {
+    if (!mounted || keyword.isEmpty || keyword.contains(' ')) return;
+    
+    final keywordLower = keyword.toLowerCase();
+    final matchedProducts = _products.where((p) =>
+        (p.name?.toLowerCase() ?? '').contains(keywordLower) ||
+        (p.productCode ?? '').contains(keyword)).toList();
+
+    if (matchedProducts.isEmpty) return;
+    
+    // 最初の一致する商品を追加
+    final product = matchedProducts.first;
+    final existingItemIndex = _estimateItems.indexWhere((item) => item.productId == product.id);
+    
+    setState(() {
+      if (existingItemIndex == -1 || _estimateItems[existingItemIndex].quantity < 50) {
+        _estimateItems.add(_EstimateItem(
+          productId: product.id ?? 0,
+          productName: product.name ?? '',
+          productCode: product.productCode ?? '',
+          unitPrice: product.unitPrice ?? 0.0,
+          quantity: 1,
+          totalAmount: (product.unitPrice ?? 0.0),
+        ));
+      } else if (existingItemIndex != -1) {
+        _estimateItems[existingItemIndex].quantity += 1;
+        _estimateItems[existingItemIndex].totalAmount = 
+            _estimateItems[existingItemIndex].unitPrice * _estimateItems[existingItemIndex].quantity;
+      }
+      calculateTotal();
+    });
+  }
+
+  void removeItem(int index) {
+    if (index >= 0 && index < _estimateItems.length) {
+      _estimateItems.removeAt(index);
+      calculateTotal();
+    }
+  }
+
+  void increaseQuantity(int index) {
+    if (index >= 0 && index < _estimateItems.length) {
+      final item = _estimateItems[index];
+      if (item.quantity < 50) { // 1 セルで最大 50 件
+        item.quantity += 1;
+        item.totalAmount = item.unitPrice * item.quantity;
+        calculateTotal();
+      }
+    }
+  }
+
+  void decreaseQuantity(int index) {
+    if (index >= 0 && index < _estimateItems.length && _estimateItems[index].quantity > 1) {
+      _estimateItems[index].quantity -= 1;
+      _estimateItems[index].totalAmount = _estimateItems[index].unitPrice * _estimateItems[index].quantity;
+      calculateTotal();
+    }
+  }
+
+  void calculateTotal() {
+    final items = _estimateItems.map((item) => item.totalAmount).toList();
+    if (mounted) setState(() => _totalAmount = items.fold(0.0, (sum, val) => sum + val));
+  }
+
+  Future<void> saveEstimate() async {
+    if (_estimateItems.isEmpty || !_selectedCustomer!.customerCode.isNotEmpty) return;
+
+    try {
+      // Map にデータ構築
+      final estimateData = <String, dynamic>{
+        'customer_code': _selectedCustomer!.customerCode,
+        'estimate_number': _estimateNumber,
+        'expiry_date': _expiryDate != null ? DateFormat('yyyy-MM-dd').format(_expiryDate!) : null,
+        'total_amount': _totalAmount.round(),
+        'tax_rate': _selectedCustomer!.taxRate ?? 8,
+        'product_items': _estimateItems.map((item) {
+          return <String, dynamic>{
+            'productId': item.productId,
+            'productName': item.productName,
+            'unitPrice': item.unitPrice.round(),
+            'quantity': item.quantity,
+          };
+        }).toList(),
+      };
+
+      await DatabaseHelper.instance.insertEstimate(estimateData);
+
+      if (mounted) ScaffoldMessenger.of(context).showSnackBar(
+        const SnackBar(content: Text('見積書保存完了'), duration: Duration(seconds: 2)),
+      );
+    } catch (e) {
+      if (mounted) ScaffoldMessenger.of(context).showSnackBar(
+        SnackBar(content: Text('保存エラー：$e'), backgroundColor: Colors.red),
+      );
+    }
   }
 
   @override
   Widget build(BuildContext context) {
     return Scaffold(
-      appBar: AppBar(title: const Text('見積書')),
+      appBar: AppBar(
-      body: _selectedCustomer == null
+        title: const Text('見積書'),
-          ? const Center(child: Text('得意先を選択してください'))
+        actions: [
+          IconButton(
+            icon: const Icon(Icons.save),
+            onPressed: _selectedCustomer != null ? saveEstimate : null,
+          ),
+        ],
+      ),
+      body: _selectedCustomer == null || _estimateItems.isEmpty
+          ? Center(child: Text('得意先を選択し、商品を検索して見積書を作成'))
           : SingleChildScrollView(
-              child: Padding(
+              padding: const EdgeInsets.all(16),
-                padding: const EdgeInsets.all(16),
+              child: Column(
-                child: Column(
+                crossAxisAlignment: CrossAxisAlignment.stretch,
-                  crossAxisAlignment: CrossAxisAlignment.stretch,
+                children: [
-                  children: [
+                  // 見積書番号表示
-                    // 見積有効期限設定エリア（簡易）
+                  ListTile(
-                    ListTile(
+                    contentPadding: EdgeInsets.zero,
+                    title: const Text('見積書番号'),
+                    subtitle: Text(_estimateNumber),
+                  ),
+
+                  const Divider(height: 24),
+
+                  // 得意先情報表示
+                  Card(
+                    child: ListTile(
                       contentPadding: EdgeInsets.zero,
-                      title: const Text('見積有効期限'),
+                      title: const Text('得意先'),
-                      subtitle: _expiryDate != null ? Text('${_expiryDate!.day}/${_expiryDate!.month}') : const Text('-'),
+                      subtitle: Text(_selectedCustomer!.name),
-                      trailing: IconButton(icon: const Icon(Icons.calendar_today), onPressed: () {
+                      trailing: IconButton(icon: const Icon(Icons.person), onPressed: () => _showCustomerSelector()),
-                        // TODO: デイティピッカーの実装
-                      }),
                     ),
+                  ),
 
-                    const Divider(),
+                  const SizedBox(height: 16),
 
-                    // 合計金額表示（簡易）
+                  // 有効期限設定
-                    Card(
+                  Card(
-                      child: ListTile(
+                    child: ListTile(
-                        contentPadding: EdgeInsets.zero,
+                      contentPadding: EdgeInsets.zero,
-                        title: const Text('見積書合計'),
+                      title: Text(_expiryDate != null ? '見積有効期限' : '見積有効期限（未設定）'),
-                        subtitle: const Text('¥0.00'),
+                      subtitle: _expiryDate != null 
-                        trailing: IconButton(icon: const Icon(Icons.edit), onPressed: () {}),
+                          ? Text(DateFormat('yyyy/MM/dd').format(_expiryDate!))
+                          : const Text('-'),
+                      trailing: IconButton(icon: const Icon(Icons.calendar_today), onPressed: () => _showDatePicker()),
+                    ),
+                  ),
+
+                  const SizedBox(height: 16),
+
+                  // 商品検索エリア
+                  Padding(
+                    padding: const EdgeInsets.only(bottom: 8),
+                    child: TextField(
+                      decoration: InputDecoration(
+                        labelText: '商品検索',
+                        hintText: '商品名または JAN コードを入力',
+                        prefixIcon: const Icon(Icons.search),
+                        suffixIcon: IconButton(icon: const Icon(Icons.clear), onPressed: () => searchProduct('')),
                       ),
+                      onChanged: searchProduct,
                     ),
+                  ),
 
-                    const SizedBox(height: 16),
+                  // 見積項目一覧
+                  Card(
+                    child: _estimateItems.isEmpty 
+                        ? Padding(
+                            padding: const EdgeInsets.all(24),
+                            child: Center(child: Text('商品を登録して見積書を作成')),
+                          )
+                        : ListView.separated(
+                            shrinkWrap: true,
+                            physics: const NeverScrollableScrollPhysics(),
+                            itemCount: _estimateItems.length,
+                            itemBuilder: (context, index) {
+                              final item = _estimateItems[index];
+                              return ListTile(
+                                title: Text(item.productName),
+                                subtitle: Text('コード：${item.productCode} / ¥${item.totalAmount.toStringAsFixed(2)} × ${item.quantity}'),
+                                trailing: Row(
+                                  mainAxisSize: MainAxisSize.min,
+                                  children: [
+                                    IconButton(icon: const Icon(Icons.remove_circle), onPressed: () => decreaseQuantity(index),),
+                                    IconButton(icon: const Icon(Icons.add_circle), onPressed: () => increaseQuantity(index),),
+                                  ],
+                                ),
+                              );
+                            },
+                            separatorBuilder: (_, __) => const Divider(),
+                          ),
+                  ),
 
-                    // PDF 帳票出力ボタン（簡易）
+                  const SizedBox(height: 24),
-                    TextButton.icon(
+
-                      onPressed: () {
+                  // 合計金額表示
-                        ScaffoldMessenger.of(context).showSnackBar(
+                  Card(
-                          const SnackBar(content: Text('PDF 帳票生成中...')),
+                    color: Colors.blue.shade50,
-                        );
+                    child: ListTile(
-                      },
+                      contentPadding: EdgeInsets.zero,
-                      icon: const Icon(Icons.download),
+                      title: const Text('見積書合計'),
-                      label: const Text('PDF をダウンロード'),
+                      subtitle: Text('¥${_totalAmount.toStringAsFixed(2)}', style: const TextStyle(fontSize: 18, fontWeight: FontWeight.bold)),
                     ),
-                  ],
+                  ),
-                ),
+
+                  const SizedBox(height: 24),
+
+                  // 保存ボタン
+                  ElevatedButton.icon(
+                    onPressed: _selectedCustomer != null ? saveEstimate : null,
+                    icon: const Icon(Icons.save),
+                    label: const Text('見積書を保存'),
+                    style: ElevatedButton.styleFrom(padding: const EdgeInsets.all(16)),
+                  ),
+
+                  const SizedBox(height: 12),
+
+                  // 詳細表示ボタン（簡易版）
+                  OutlinedButton.icon(
+                    onPressed: _estimateItems.isNotEmpty ? () => _showSummary() : null,
+                    icon: const Icon(Icons.info),
+                    label: const Text('見積内容を確認'),
+                  ),
+                ],
               ),
             ),
     );
   }
 
+  void _showCustomerSelector() {
+    showDialog(
+      context: context,
+      builder: (context) => StatefulBuilder(
+        builder: (context, setStateDialog) => AlertDialog(
+          title: const Text('得意先を選択'),
+          content: SizedBox(
+            width: double.maxFinite,
+            child: ListView.builder(
+              shrinkWrap: true,
+              itemCount: _customers.length,
+              itemBuilder: (context, index) {
+                final customer = _customers[index];
+                return ListTile(
+                  title: Text(customer.name),
+                  subtitle: Text('${customer.customerCode} / TEL:${customer.phoneNumber}'),
+                  onTap: () {
+                    setState(() {
+                      _selectedCustomer = customer;
+                      if (_expiryDate != null) {
+                        final yearMonth = '${_expiryDate!.year}${_expiryDate!.month.toString().padLeft(2, '0')}';
+                        _estimateNumber = '$yearMonth-0001';
+                      }
+                    });
+                    Navigator.pop(context);
+                  },
+                );
+              },
+            ),
+          ),
+          actions: [TextButton(onPressed: () => Navigator.pop(context), child: const Text('キャンセル'))],
+        ),
+      ),
+    );
+  }
+
+  void _showDatePicker() {
+    showDialog<bool>(
+      context: context,
+      builder: (context) => DatePickerDialog(initialDate: _expiryDate ?? DateTime.now().add(const Duration(days: 30))),
+    );
+  }
+
+  void _showSummary() {
+    if (_estimateItems.isEmpty) return;
+
+    showDialog(
+      context: context,
+      builder: (context) => AlertDialog(
+        title: const Text('見積書概要'),
+        content: Column(
+          mainAxisSize: MainAxisSize.min,
+          crossAxisAlignment: CrossAxisAlignment.start,
+          children: [
+            Text('見積書番号：$_estimateNumber'),
+            const SizedBox(height: 8),
+            Text('得意先：${_selectedCustomer?.name ?? '未指定'}'),
+            const SizedBox(height: 8),
+            Text('合計金額：¥${_totalAmount.toStringAsFixed(2)}'),
+            if (_expiryDate != null) Text('有効期限：${DateFormat('yyyy/MM/dd').format(_expiryDate!)}'),
+          ],
+        ),
+        actions: [TextButton(onPressed: () => Navigator.pop(context), child: const Text('閉じる'))],
+      ),
+    );
+  }
+}
+
+class _EstimateItem {
+  final int productId;
+  final String productName;
+  final String productCode;
+  double unitPrice;
+  int quantity;
+  double totalAmount;
+
+  _EstimateItem({
+    required this.productId,
+    required this.productName,
+    required this.productCode,
+    required this.unitPrice,
+    required this.quantity,
+    required this.totalAmount,
+  });
+}
+
+/// デイティピッカーダイアログ（簡易）
+class DatePickerDialog extends StatefulWidget {
+  final DateTime initialDate;
+  const DatePickerDialog({super.key, required this.initialDate});
+
+  @override
+  State<DatePickerDialog> createState() => _DatePickerDialogState();
+}
+
+class _DatePickerDialogState extends State<DatePickerDialog> {
+  DateTime _selectedDate = DateTime.now();
+
+  void _selectDate(DateTime date) {
+    setState(() => _selectedDate = date);
+    Navigator.pop(context, true);
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return AlertDialog(
+      title: const Text('見積有効期限を選択'),
+      content: Column(
+        mainAxisSize: MainAxisSize.min,
+        children: [
+          ListTile(
+            leading: const Icon(Icons.calendar_today),
+            title: const Text('今日から 30 日後'),
+            onTap: () => _selectDate(DateTime.now().add(const Duration(days: 30))),
+          ),
+          ListTile(
+            leading: const Icon(Icons.access_time),
+            title: const Text('1 ヶ月後（約 30 日）'),
+            onTap: () => _selectDate(DateTime.now().add(const Duration(days: 30))),
+          ),
+          ListTile(
+            leading: const Icon(Icons.info_outline),
+            title: const Text('カスタム日付（簡易：未実装）'),
+            subtitle: const Text('デフォルト：30 日後'),
+          ),
+        ],
+      ),
+      actions: [
+        TextButton(onPressed: () => Navigator.pop(context, false), child: const Text('キャンセル')),
+        ElevatedButton(
+          onPressed: () => _selectDate(DateTime.now().add(const Duration(days: 30))),
+          child: const Text('標準（30 日後）'),
+        ),
+      ],
+    );
+  }
 }

lib/services/database_helper.dart

@@ -1,7 +1,9 @@
 import 'package:sqflite/sqflite.dart';
 import 'package:path/path.dart';
+import 'dart:convert';
 import '../models/customer.dart';
 import '../models/product.dart';
+import '../models/estimate.dart';
 
 class DatabaseHelper {
   static final DatabaseHelper instance = DatabaseHelper._init();
@@ -32,11 +34,13 @@ class DatabaseHelper {
     await db.execute('CREATE TABLE suppliers (id INTEGER PRIMARY KEY AUTOINCREMENT, name TEXT NOT NULL, address TEXT, phone_number TEXT, created_at TEXT NOT NULL, updated_at TEXT NOT NULL)');
     await db.execute('CREATE TABLE products (id INTEGER PRIMARY KEY AUTOINCREMENT, product_code TEXT NOT NULL, name TEXT NOT NULL, unit_price INTEGER NOT NULL, quantity INTEGER DEFAULT 0, stock INTEGER DEFAULT 0, created_at TEXT NOT NULL, updated_at TEXT NOT NULL)');
     await db.execute('CREATE TABLE sales (id INTEGER PRIMARY KEY AUTOINCREMENT, customer_id INTEGER NOT NULL, sale_date TEXT NOT NULL, total_amount INTEGER NOT NULL, tax_rate INTEGER DEFAULT 8, product_items TEXT, created_at TEXT NOT NULL, updated_at TEXT NOT NULL)');
-    await db.execute('CREATE TABLE estimates (id INTEGER PRIMARY KEY AUTOINCREMENT, customer_id INTEGER NOT NULL, estimate_number TEXT NOT NULL, product_items TEXT, total_amount INTEGER NOT NULL, tax_rate INTEGER DEFAULT 8, status TEXT DEFAULT "open", expiry_date TEXT, created_at TEXT NOT NULL, updated_at TEXT NOT NULL)');
+    await db.execute('CREATE TABLE estimates (id INTEGER PRIMARY KEY AUTOINCREMENT, customer_code TEXT NOT NULL, estimate_number TEXT NOT NULL, product_items TEXT, total_amount INTEGER NOT NULL, tax_rate INTEGER DEFAULT 8, status TEXT DEFAULT "open", expiry_date TEXT, created_at TEXT NOT NULL, updated_at TEXT NOT NULL)');
     await db.execute('CREATE TABLE inventory (id INTEGER PRIMARY KEY AUTOINCREMENT, product_code TEXT UNIQUE NOT NULL, name TEXT NOT NULL, unit_price INTEGER NOT NULL, stock INTEGER DEFAULT 0, min_stock INTEGER DEFAULT 0, max_stock INTEGER DEFAULT 1000, supplier_name TEXT, created_at TEXT NOT NULL, updated_at TEXT NOT NULL)');
+    await db.execute('CREATE TABLE invoices (id INTEGER PRIMARY KEY AUTOINCREMENT, customer_code TEXT NOT NULL, invoice_number TEXT NOT NULL, sale_date TEXT NOT NULL, total_amount INTEGER NOT NULL, tax_rate INTEGER DEFAULT 8, status TEXT DEFAULT "paid", product_items TEXT, created_at TEXT NOT NULL, updated_at TEXT NOT NULL)');
     print('Database created with version: 1');
   }
 
+  // Customer API
   Future<int> insertCustomer(Customer customer) async {
     final db = await database;
     return await db.insert('customers', customer.toMap());
@@ -57,12 +61,7 @@ class DatabaseHelper {
 
   Future<int> updateCustomer(Customer customer) async {
     final db = await database;
-    return await db.update(
+    return await db.update('customers', customer.toMap(), where: 'id = ?', whereArgs: [customer.id]);
-      'customers',
-      customer.toMap(),
-      where: 'id = ?',
-      whereArgs: [customer.id],
-    );
   }
 
   Future<int> deleteCustomer(int id) async {
@@ -70,6 +69,7 @@ class DatabaseHelper {
     return await db.delete('customers', where: 'id = ?', whereArgs: [id]);
   }
 
+  // Product API
   Future<int> insertProduct(Product product) async {
     final db = await database;
     return await db.insert('products', product.toMap());
@@ -90,12 +90,7 @@ class DatabaseHelper {
 
   Future<int> updateProduct(Product product) async {
     final db = await database;
-    return await db.update(
+    return await db.update('products', product.toMap(), where: 'id = ?', whereArgs: [product.id]);
-      'products',
-      product.toMap(),
-      where: 'id = ?',
-      whereArgs: [product.id],
-    );
   }
 
   Future<int> deleteProduct(int id) async {
@@ -103,37 +98,9 @@ class DatabaseHelper {
     return await db.delete('products', where: 'id = ?', whereArgs: [id]);
   }
 
-  String encodeToJson(Object? data) {
+  // Sales API
-    try {
-      if (data == null) return '';
-      if (data is String) return data;
-      final json = StringBuffer('{');
-      var first = true;
-      if (data is Map) {
-        for (var key in data.keys) {
-          if (!first) json.write(',');
-          first = false;
-          json.write('"${key}":"${data[key]}"');
-        }
-      } else if (data is List) {
-        for (var item in data) {
-          if (!first) json.write(',');
-          first = false;
-          json.write('{"val":"$item"}');
-        }
-      }
-      json.write('}');
-      return json.toString();
-    } catch (e) {
-      return '';
-    }
-  }
-
   Future<int> insertSales(Map<String, dynamic> salesData) async {
     final db = await database;
-    if (salesData['product_items'] != null && salesData['product_items'] is List) {
-      salesData['product_items'] = encodeToJson(salesData['product_items']);
-    }
     return await db.insert('sales', salesData);
   }
 
@@ -144,15 +111,7 @@ class DatabaseHelper {
 
   Future<int> updateSales(Map<String, dynamic> salesData) async {
     final db = await database;
-    if (salesData['product_items'] != null && salesData['product_items'] is List) {
+    return await db.update('sales', salesData, where: 'id = ?', whereArgs: [salesData['id'] as int]);
-      salesData['product_items'] = encodeToJson(salesData['product_items']);
-    }
-    return await db.update(
-      'sales',
-      salesData,
-      where: 'id = ?',
-      whereArgs: [salesData['id'] as int],
-    );
   }
 
   Future<int> deleteSales(int id) async {
@@ -160,11 +119,9 @@ class DatabaseHelper {
     return await db.delete('sales', where: 'id = ?', whereArgs: [id]);
   }
 
+  // Estimate API（単純化）
   Future<int> insertEstimate(Map<String, dynamic> estimateData) async {
     final db = await database;
-    if (estimateData['product_items'] != null && estimateData['product_items'] is List) {
-      estimateData['product_items'] = encodeToJson(estimateData['product_items']);
-    }
     return await db.insert('estimates', estimateData);
   }
 
@@ -175,15 +132,7 @@ class DatabaseHelper {
 
   Future<int> updateEstimate(Map<String, dynamic> estimateData) async {
     final db = await database;
-    if (estimateData['product_items'] != null && estimateData['product_items'] is List) {
+    return await db.update('estimates', estimateData, where: 'id = ?', whereArgs: [estimateData['id'] as int]);
-      estimateData['product_items'] = encodeToJson(estimateData['product_items']);
-    }
-    return await db.update(
-      'estimates',
-      estimateData,
-      where: 'id = ?',
-      whereArgs: [estimateData['id'] as int],
-    );
   }
 
   Future<int> deleteEstimate(int id) async {
@@ -191,6 +140,28 @@ class DatabaseHelper {
     return await db.delete('estimates', where: 'id = ?', whereArgs: [id]);
   }
 
+  // Invoice API
+  Future<int> insertInvoice(Map<String, dynamic> invoiceData) async {
+    final db = await database;
+    return await db.insert('invoices', invoiceData);
+  }
+
+  Future<List<Map<String, dynamic>>> getInvoices() async {
+    final db = await database;
+    return await db.query('invoices');
+  }
+
+  Future<int> updateInvoice(Map<String, dynamic> invoiceData) async {
+    final db = await database;
+    return await db.update('invoices', invoiceData, where: 'id = ?', whereArgs: [invoiceData['id'] as int]);
+  }
+
+  Future<int> deleteInvoice(int id) async {
+    final db = await database;
+    return await db.delete('invoices', where: 'id = ?', whereArgs: [id]);
+  }
+
+  // Inventory API
   Future<int> insertInventory(Map<String, dynamic> inventoryData) async {
     final db = await database;
     return await db.insert('inventory', inventoryData);
@@ -203,12 +174,7 @@ class DatabaseHelper {
 
   Future<int> updateInventory(Map<String, dynamic> inventoryData) async {
     final db = await database;
-    return await db.update(
+    return await db.update('inventory', inventoryData, where: 'id = ?', whereArgs: [inventoryData['id'] as int]);
-      'inventory',
-      inventoryData,
-      where: 'id = ?',
-      whereArgs: [inventoryData['id'] as int],
-    );
   }
 
   Future<int> deleteInventory(int id) async {
@@ -216,6 +182,7 @@ class DatabaseHelper {
     return await db.delete('inventory', where: 'id = ?', whereArgs: [id]);
   }
 
+  // Employee API
   Future<int> insertEmployee(Map<String, dynamic> employeeData) async {
     final db = await database;
     return await db.insert('employees', employeeData);
@@ -228,12 +195,7 @@ class DatabaseHelper {
 
   Future<int> updateEmployee(Map<String, dynamic> employeeData) async {
     final db = await database;
-    return await db.update(
+    return await db.update('employees', employeeData, where: 'id = ?', whereArgs: [employeeData['id'] as int]);
-      'employees',
-      employeeData,
-      where: 'id = ?',
-      whereArgs: [employeeData['id'] as int],
-    );
   }
 
   Future<int> deleteEmployee(int id) async {
@@ -241,6 +203,7 @@ class DatabaseHelper {
     return await db.delete('employees', where: 'id = ?', whereArgs: [id]);
   }
 
+  // Warehouse API
   Future<int> insertWarehouse(Map<String, dynamic> warehouseData) async {
     final db = await database;
     return await db.insert('warehouses', warehouseData);
@@ -253,12 +216,7 @@ class DatabaseHelper {
 
   Future<int> updateWarehouse(Map<String, dynamic> warehouseData) async {
     final db = await database;
-    return await db.update(
+    return await db.update('warehouses', warehouseData, where: 'id = ?', whereArgs: [warehouseData['id'] as int]);
-      'warehouses',
-      warehouseData,
-      where: 'id = ?',
-      whereArgs: [warehouseData['id'] as int],
-    );
   }
 
   Future<int> deleteWarehouse(int id) async {
@@ -266,6 +224,7 @@ class DatabaseHelper {
     return await db.delete('warehouses', where: 'id = ?', whereArgs: [id]);
   }
 
+  // Supplier API
   Future<int> insertSupplier(Map<String, dynamic> supplierData) async {
     final db = await database;
     return await db.insert('suppliers', supplierData);
@@ -278,12 +237,7 @@ class DatabaseHelper {
 
   Future<int> updateSupplier(Map<String, dynamic> supplierData) async {
     final db = await database;
-    return await db.update(
+    return await db.update('suppliers', supplierData, where: 'id = ?', whereArgs: [supplierData['id'] as int]);
-      'suppliers',
-      supplierData,
-      where: 'id = ?',
-      whereArgs: [supplierData['id'] as int],
-    );
   }
 
   Future<int> deleteSupplier(int id) async {