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lib/Screens/Sales/provider/sales_cart_provider.dart

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+import 'package:flutter/material.dart';
+import 'package:flutter_easyloading/flutter_easyloading.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:mobile_pos/Provider/profile_provider.dart';
+import 'package:mobile_pos/model/business_info_model.dart';
+
+import '../../Settings/sales settings/model/amount_rounding_dropdown_model.dart';
+import '../../vat_&_tax/model/vat_model.dart';
+import '../../../model/add_to_cart_model.dart';
+
+final cartNotifier = ChangeNotifierProvider((ref) {
+  return CartNotifier(businessInformation: ref.watch(businessInfoProvider).value);
+});
+
+class CartNotifier extends ChangeNotifier {
+  final BusinessInformationModel? businessInformation;
+
+  CartNotifier({required this.businessInformation});
+
+  @override
+  void addListener(VoidCallback listener) {
+    super.addListener(listener);
+    roundedOption = businessInformation?.data?.saleRoundingOption ?? roundingMethods[0].value;
+  }
+
+  List<SaleCartModel> cartItemList = [];
+  TextEditingController discountTextControllerFlat = TextEditingController();
+  TextEditingController vatAmountController = TextEditingController();
+  TextEditingController shippingChargeController = TextEditingController();
+
+  ///_________NEW_________________________________
+  num totalAmount = 0;
+  num discountAmount = 0;
+  num discountPercent = 0;
+  num roundingAmount = 0;
+  num actualTotalAmount = 0;
+  num totalPayableAmount = 0;
+  VatModel? selectedVat;
+  num vatAmount = 0;
+  bool isFullPaid = false;
+  num receiveAmount = 0;
+  num changeAmount = 0;
+  num dueAmount = 0;
+  num finalShippingCharge = 0;
+  String roundedOption = roundingMethods[0].value;
+
+  void changeSelectedVat({VatModel? data}) {
+    if (data != null) {
+      selectedVat = data;
+    } else {
+      selectedVat = null;
+      vatAmount = 0;
+      vatAmountController.clear();
+    }
+
+    calculatePrice();
+  }
+
+  void calculateDiscount({required String value, bool? rebuilding, String? selectedTaxType}) {
+    if (value.isEmpty) {
+      discountAmount = 0;
+      discountPercent = 0;
+      discountTextControllerFlat.clear();
+    } else {
+      num discountValue = num.tryParse(value) ?? 0;
+
+      if (selectedTaxType == null) {
+        EasyLoading.showError('Please select a discount type');
+        discountAmount = 0;
+        discountPercent = 0;
+      } else if (selectedTaxType == "Flat") {
+        discountAmount = discountValue;
+      } else if (selectedTaxType == "Percent") {
+        discountPercent = num.tryParse(discountTextControllerFlat.text) ?? 0.0;
+        discountAmount = (totalAmount * discountValue) / 100;
+
+        if (discountAmount > totalAmount) {
+          discountAmount = totalAmount;
+        }
+      } else {
+        EasyLoading.showError('Invalid discount type selected');
+        discountAmount = 0;
+      }
+
+      if (discountAmount > totalAmount) {
+        discountTextControllerFlat.clear();
+        discountAmount = 0;
+        EasyLoading.showError('Enter a valid discount');
+      }
+    }
+
+    if (rebuilding == false) return;
+    calculatePrice();
+  }
+
+  void updateProduct({required num productId, required String price, required String qty, required num discount}) {
+    int index = cartItemList.indexWhere((element) => element.productId == productId);
+    if (index != -1) {
+      cartItemList[index].unitPrice = num.tryParse(price);
+      cartItemList[index].quantity = num.tryParse(qty) ?? 0;
+      cartItemList[index].discountAmount = discount; // Store the product-wise discount
+      calculatePrice();
+    }
+  }
+
+  void calculatePrice({String? receivedAmount, String? shippingCharge, bool? stopRebuild}) {
+    totalAmount = 0;
+    totalPayableAmount = 0;
+    dueAmount = 0;
+
+    // Calculate Subtotal with Product-wise Discounts
+    for (var element in cartItemList) {
+      num unitPrice = element.unitPrice ?? 0;
+      num productDiscount = element.discountAmount ?? 0;
+      num quantity = element.quantity;
+
+      // Formula: (Unit Price - Discount) * Quantity
+      // Note: The validation in the form ensures Discount <= Unit Price
+      totalAmount += (unitPrice - productDiscount) * quantity;
+    }
+
+    totalPayableAmount = totalAmount;
+
+    // Apply Global Discount (on the already discounted subtotal)
+    if (discountAmount > totalAmount) {
+      calculateDiscount(
+        value: discountAmount.toString(),
+        rebuilding: false,
+      );
+    }
+    if (discountAmount >= 0) {
+      totalPayableAmount -= discountAmount;
+    }
+
+    // Apply VAT
+    if (selectedVat?.rate != null) {
+      vatAmount = (totalPayableAmount * selectedVat!.rate!) / 100;
+      vatAmountController.text = vatAmount.toStringAsFixed(2);
+    }
+    totalPayableAmount += vatAmount;
+
+    // Apply Shipping
+    if (shippingCharge != null) {
+      finalShippingCharge = num.tryParse(shippingCharge) ?? 0;
+    }
+    totalPayableAmount += finalShippingCharge;
+
+    // Rounding
+    actualTotalAmount = totalPayableAmount;
+    num tempTotalPayable = roundNumber(value: totalPayableAmount, roundingType: roundedOption);
+    roundingAmount = tempTotalPayable - totalPayableAmount;
+    totalPayableAmount = tempTotalPayable;
+
+    // Payment Calculation
+    if (receivedAmount != null) {
+      receiveAmount = num.tryParse(receivedAmount) ?? 0;
+    }
+
+    changeAmount = totalPayableAmount < receiveAmount ? receiveAmount - totalPayableAmount : 0;
+    dueAmount = totalPayableAmount < receiveAmount ? 0 : totalPayableAmount - receiveAmount;
+    if (dueAmount <= 0) isFullPaid = true;
+
+    if (stopRebuild ?? false) return;
+    notifyListeners();
+  }
+
+  void quantityIncrease(int index) {
+    final item = cartItemList[index];
+    final isCombo = item.productType?.toLowerCase().contains('combo') ?? false;
+    final stock = item.stock ?? 0;
+    final quantity = item.quantity;
+
+    // Allow increase if it's a Combo OR if stock is available
+    if (isCombo || stock > quantity) {
+      // If not a combo, perform strict stock check
+      if (!isCombo && stock < quantity + 1) {
+        cartItemList[index].quantity = stock;
+      } else {
+        cartItemList[index].quantity++;
+      }
+      calculatePrice();
+    } else {
+      EasyLoading.showError('Stock Overflow');
+    }
+  }
+
+  void quantityDecrease(int index) {
+    if (cartItemList[index].quantity > 1) {
+      cartItemList[index].quantity--;
+    }
+    calculatePrice();
+  }
+
+  void addToCartRiverPod({
+    required SaleCartModel cartItem,
+    bool? fromEditSales,
+    bool? isVariant,
+  }) {
+    final variantMode = isVariant ?? false;
+
+    final index = cartItemList.indexWhere((element) => variantMode ? element.stockId == cartItem.stockId : element.productId == cartItem.productId);
+
+    if (index != -1) {
+      variantMode ? cartItemList[index].quantity = cartItem.quantity : cartItemList[index].quantity++;
+    } else {
+      cartItemList.add(cartItem);
+    }
+
+    if (!(fromEditSales ?? false)) {
+      calculatePrice();
+    }
+  }
+
+  void deleteToCart(int index) {
+    cartItemList.removeAt(index);
+    calculatePrice();
+  }
+
+  void deleteAllVariant({required num productId}) {
+    cartItemList.removeWhere(
+      (element) => element.productId == productId,
+    );
+    calculatePrice();
+  }
+}