using Fitness_core_BE.DTOs.Inventory;
using Fitness_core_BE.Exceptions;
using Fitness_core_BE.Helpers;
using Fitness_core_BE.Infra.UoW;
using Fitness_core_BE.Interfaces;
using Fitness_core_BE.Interfaces.Services;
using Fitness_core_BE.Models;
using System.Text.Json;

namespace Fitness_core_BE.Services
{
    public class InventoryService : IInventoryService
    {
        private static readonly string[] ValidReturnCategories =
            ["Expired", "Damaged", "Lost", "SupplierReturn", "CustomerReturn", "Other"];

        private readonly IInventoryRepository _inventoryRepository;
        private readonly ICustomerRepository _customerRepository;
        private readonly IUnitOfWork _uow;
        private readonly UserRoleHelper _userRoleHelper;

        public InventoryService(
            IInventoryRepository inventoryRepository,
            ICustomerRepository customerRepository,
            IUnitOfWork uow,
            UserRoleHelper userRoleHelper)
        {
            _inventoryRepository = inventoryRepository;
            _customerRepository = customerRepository;
            _uow = uow;
            _userRoleHelper = userRoleHelper;
        }

        // --- Products ---

        public async Task<object> GetProducts(object payload, HttpContext httpContext)
        {
            var data = DeserializePayload.Deserialize(payload);
            bool includeInactive = data.ContainsKey("includeInactive") && data["includeInactive"].GetBoolean();

            var clientId = await _userRoleHelper.GetClientId(DataExtractor.GetUserIdFromContext(httpContext));
            var products = await _inventoryRepository.GetProducts(clientId, includeInactive);

            return (await Task.WhenAll(products.Select(MapToDtoAsync))).ToList();
        }

        public async Task<object> GetProductById(object payload, HttpContext httpContext)
        {
            var data = DeserializePayload.Deserialize(payload);
            var productId = Guid.Parse(data["productId"].GetString()!);

            var clientId = await _userRoleHelper.GetClientId(DataExtractor.GetUserIdFromContext(httpContext));
            var product = await _inventoryRepository.GetProductById(productId);
            if (product == null || product.FKClientId != clientId)
                throw new KeyNotFoundException("Product not found");

            var grnItems = await _inventoryRepository.GetGrnItemsForProduct(productId);
            var saleItems = await _inventoryRepository.GetSaleItemsForProduct(productId);
            var returns = await _inventoryRepository.GetStockReturnsForProduct(productId);

            var movements = new List<ProductMovementDto>();
            movements.AddRange(grnItems.Select(i => new ProductMovementDto
            {
                Type = "GRN",
                Reference = i.Grn?.GrnNumber ?? string.Empty,
                QuantityChange = i.Quantity,
                Date = i.Grn?.ReceivedAt ?? DateTime.UtcNow
            }));
            movements.AddRange(saleItems.Select(i => new ProductMovementDto
            {
                Type = "Sale",
                Reference = i.Sale?.SaleNumber ?? string.Empty,
                QuantityChange = -i.Quantity,
                Date = i.Sale?.SoldAt ?? DateTime.UtcNow
            }));
            movements.AddRange(returns.Select(r => new ProductMovementDto
            {
                Type = "Return",
                Reference = r.Category,
                // CustomerReturn is the one category that adds back to stock -- see
                // StockReturn's doc comment.
                QuantityChange = r.Category == "CustomerReturn" ? r.Quantity : -r.Quantity,
                Date = r.ReturnedAt
            }));
            movements = movements.OrderByDescending(m => m.Date).ToList();

            var dto = await MapToDtoAsync(product);
            return new ProductDetailDto
            {
                ProductId = dto.ProductId,
                Name = dto.Name,
                Sku = dto.Sku,
                ImageUrl = dto.ImageUrl,
                UnitOfMeasure = dto.UnitOfMeasure,
                CostPrice = dto.CostPrice,
                SellingPrice = dto.SellingPrice,
                QuantityOnHand = dto.QuantityOnHand,
                IsActive = dto.IsActive,
                CreatedAt = dto.CreatedAt,
                Movements = movements
            };
        }

        public async Task<object> CreateProduct(object payload, HttpContext httpContext)
        {
            await _uow.BeginAsync();
            try
            {
                var data = DeserializePayload.Deserialize(payload);
                if (!data.ContainsKey("name")) throw new KeyNotFoundException("name is required");

                var sellingPrice = data.ContainsKey("sellingPrice") ? data["sellingPrice"].GetDecimal() : 0m;
                if (sellingPrice < 0) throw new ArgumentException("sellingPrice cannot be negative");

                var clientId = await _userRoleHelper.GetClientId(DataExtractor.GetUserIdFromContext(httpContext));

                var product = new Product
                {
                    FKClientId = clientId,
                    Name = data["name"].GetString() ?? "",
                    UnitOfMeasure = data.ContainsKey("unitOfMeasure") ? data["unitOfMeasure"].GetString() ?? "pcs" : "pcs",
                    SellingPrice = sellingPrice
                };

                var sequence = await _inventoryRepository.GetNextProductSequence(clientId);
                product.Sku = $"PRD-{sequence:D4}";

                var result = await _inventoryRepository.CreateProduct(product);
                await _uow.CommitAsync();

                return await MapToDtoAsync(result);
            }
            catch
            {
                await _uow.RollbackAsync();
                throw;
            }
        }

        public async Task<object> UpdateProduct(object payload, HttpContext httpContext)
        {
            await _uow.BeginAsync();
            try
            {
                var data = DeserializePayload.Deserialize(payload);
                var productId = Guid.Parse(data["productId"].GetString()!);

                var existing = await _inventoryRepository.GetProductById(productId)
                    ?? throw new KeyNotFoundException("Product not found");

                // Sku is system-generated at creation and never editable here.
                if (data.ContainsKey("name")) existing.Name = data["name"].GetString() ?? existing.Name;
                if (data.ContainsKey("unitOfMeasure")) existing.UnitOfMeasure = data["unitOfMeasure"].GetString() ?? existing.UnitOfMeasure;
                if (data.ContainsKey("sellingPrice"))
                {
                    var price = data["sellingPrice"].GetDecimal();
                    if (price < 0) throw new ArgumentException("sellingPrice cannot be negative");
                    existing.SellingPrice = price;
                }
                if (data.ContainsKey("isActive")) existing.IsActive = data["isActive"].GetBoolean();

                var result = await _inventoryRepository.UpdateProduct(existing);
                await _uow.CommitAsync();

                return await MapToDtoAsync(result);
            }
            catch
            {
                await _uow.RollbackAsync();
                throw;
            }
        }

        public async Task<object> UploadProductImage(Guid productId, IFormFile image, HttpContext httpContext)
        {
            var clientId = await _userRoleHelper.GetClientId(DataExtractor.GetUserIdFromContext(httpContext));
            var product = await _inventoryRepository.GetProductById(productId);
            if (product == null || product.FKClientId != clientId)
                throw new KeyNotFoundException("Product not found");

            if (image == null || image.Length == 0)
                throw new BadRequestException("No image file provided.");

            string extension = Path.GetExtension(image.FileName).ToLowerInvariant();
            string[] allowed = { ".jpg", ".jpeg", ".png", ".webp" };
            if (!allowed.Contains(extension))
                throw new BadRequestException("Image must be a jpg, png or webp file.");
            if (image.Length > 5 * 1024 * 1024)
                throw new BadRequestException("Image too large (max 5MB).");

            string uploadsRoot = Path.GetFullPath(Path.Combine(Directory.GetCurrentDirectory(), "..", "Uploads", "product-images", clientId.ToString()));
            if (!Directory.Exists(uploadsRoot))
                Directory.CreateDirectory(uploadsRoot);

            string filename = $"{productId}_{DateTime.UtcNow:yyyyMMdd_HHmmss}{extension}";
            string filePath = Path.Combine(uploadsRoot, filename);
            using (var stream = new FileStream(filePath, FileMode.Create))
            {
                await image.CopyToAsync(stream);
            }

            await _uow.BeginAsync();
            try
            {
                product.ImageId = $"/Uploads/product-images/{clientId}/{Uri.EscapeDataString(filename)}";
                await _uow.CommitAsync();
                return await MapToDtoAsync(product);
            }
            catch
            {
                await _uow.RollbackAsync();
                throw;
            }
        }

        // --- Suppliers ---

        public async Task<object> GetSuppliers(object payload, HttpContext httpContext)
        {
            var data = DeserializePayload.Deserialize(payload);
            bool includeInactive = data.ContainsKey("includeInactive") && data["includeInactive"].GetBoolean();

            var clientId = await _userRoleHelper.GetClientId(DataExtractor.GetUserIdFromContext(httpContext));
            var suppliers = await _inventoryRepository.GetSuppliers(clientId, includeInactive);

            return suppliers.Select(MapToDto).ToList();
        }

        public async Task<object> CreateSupplier(object payload, HttpContext httpContext)
        {
            await _uow.BeginAsync();
            try
            {
                var data = DeserializePayload.Deserialize(payload);
                if (!data.ContainsKey("name")) throw new KeyNotFoundException("name is required");

                var clientId = await _userRoleHelper.GetClientId(DataExtractor.GetUserIdFromContext(httpContext));

                var supplier = new Supplier
                {
                    FKClientId = clientId,
                    Name = data["name"].GetString() ?? "",
                    Phone = data.ContainsKey("phone") && data["phone"].ValueKind != JsonValueKind.Null ? data["phone"].GetString() : null,
                    Email = data.ContainsKey("email") && data["email"].ValueKind != JsonValueKind.Null ? data["email"].GetString() : null,
                    Address = data.ContainsKey("address") && data["address"].ValueKind != JsonValueKind.Null ? data["address"].GetString() : null
                };

                var result = await _inventoryRepository.CreateSupplier(supplier);
                await _uow.CommitAsync();

                return MapToDto(result);
            }
            catch
            {
                await _uow.RollbackAsync();
                throw;
            }
        }

        // --- GRN ---

        public async Task<object> CreateGrn(object payload, HttpContext httpContext)
        {
            await _uow.BeginAsync();
            try
            {
                var data = DeserializePayload.Deserialize(payload);
                var clientId = await _userRoleHelper.GetClientId(DataExtractor.GetUserIdFromContext(httpContext));

                // Optional -- some GRNs don't have a supplier on file.
                Supplier? supplier = null;
                Guid? supplierId = data.ContainsKey("supplierId") && data["supplierId"].ValueKind != JsonValueKind.Null
                    ? Guid.Parse(data["supplierId"].GetString()!)
                    : null;
                if (supplierId.HasValue)
                {
                    supplier = await _inventoryRepository.GetSupplierById(supplierId.Value);
                    if (supplier == null || supplier.FKClientId != clientId)
                        throw new KeyNotFoundException("Supplier not found");
                }

                if (!data.ContainsKey("items") || data["items"].ValueKind != JsonValueKind.Array)
                    throw new ArgumentException("At least one item is required");

                var receivedAt = data.ContainsKey("receivedAt") && data["receivedAt"].ValueKind != JsonValueKind.Null
                    ? DateTime.Parse(data["receivedAt"].GetString()!).ToUniversalTime()
                    : DateTime.UtcNow;

                var grn = new GoodsReceivedNote
                {
                    FKClientId = clientId,
                    FKSupplierId = supplierId,
                    ReceivedAt = receivedAt,
                    Notes = data.ContainsKey("notes") && data["notes"].ValueKind != JsonValueKind.Null ? data["notes"].GetString() : null
                };

                decimal total = 0m;
                var itemsArray = data["items"].EnumerateArray().ToList();
                if (itemsArray.Count == 0) throw new ArgumentException("At least one item is required");

                foreach (var itemEl in itemsArray)
                {
                    var productId = Guid.Parse(itemEl.GetProperty("productId").GetString()!);
                    var quantity = itemEl.GetProperty("quantity").GetDecimal();
                    var unitCost = itemEl.GetProperty("unitCost").GetDecimal();

                    if (quantity <= 0) throw new ArgumentException("Quantity must be greater than 0");
                    if (unitCost < 0) throw new ArgumentException("UnitCost cannot be negative");

                    var product = await _inventoryRepository.GetProductById(productId);
                    if (product == null || product.FKClientId != clientId)
                        throw new KeyNotFoundException("Product not found");

                    var lineTotal = quantity * unitCost;
                    grn.Items.Add(new GoodsReceivedNoteItem
                    {
                        FKProductId = productId,
                        Quantity = quantity,
                        UnitCost = unitCost,
                        LineTotal = lineTotal
                    });

                    product.QuantityOnHand += quantity;
                    product.CostPrice = unitCost;
                    total += lineTotal;
                }

                grn.TotalAmount = total;
                var sequence = await _inventoryRepository.GetNextGrnSequence(clientId);
                grn.GrnNumber = $"GRN-{sequence:D4}";

                var result = await _inventoryRepository.CreateGrn(grn);
                await _uow.CommitAsync();

                result.Supplier = supplier;
                return MapToDto(result);
            }
            catch
            {
                await _uow.RollbackAsync();
                throw;
            }
        }

        public async Task<object> GetGrns(object payload, HttpContext httpContext)
        {
            var clientId = await _userRoleHelper.GetClientId(DataExtractor.GetUserIdFromContext(httpContext));
            var grns = await _inventoryRepository.GetGrns(clientId);
            return grns.Select(MapToDto).ToList();
        }

        public async Task<object> GetGrnById(object payload, HttpContext httpContext)
        {
            var data = DeserializePayload.Deserialize(payload);
            var grnId = Guid.Parse(data["grnId"].GetString()!);

            var clientId = await _userRoleHelper.GetClientId(DataExtractor.GetUserIdFromContext(httpContext));
            var grn = await _inventoryRepository.GetGrnById(grnId);
            if (grn == null || grn.FKClientId != clientId)
                throw new KeyNotFoundException("GRN not found");

            return MapToDto(grn);
        }

        // --- Sales ---

        public async Task<object> CreateSale(object payload, HttpContext httpContext)
        {
            await _uow.BeginAsync();
            try
            {
                var data = DeserializePayload.Deserialize(payload);
                var clientId = await _userRoleHelper.GetClientId(DataExtractor.GetUserIdFromContext(httpContext));

                var paymentMethod = data.ContainsKey("paymentMethod") && data["paymentMethod"].ValueKind != JsonValueKind.Null
                    ? data["paymentMethod"].GetString() ?? "Cash" : "Cash";

                var customerId = await ResolveOptionalCustomerLinkAsync(data);

                if (!data.ContainsKey("items") || data["items"].ValueKind != JsonValueKind.Array)
                    throw new ArgumentException("At least one item is required");

                var soldAt = data.ContainsKey("soldAt") && data["soldAt"].ValueKind != JsonValueKind.Null
                    ? DateTime.Parse(data["soldAt"].GetString()!).ToUniversalTime()
                    : DateTime.UtcNow;

                var sale = new Sale
                {
                    FKClientId = clientId,
                    SoldAt = soldAt,
                    PaymentMethod = paymentMethod,
                    FKCustomerId = customerId,
                    CustomerName = data.ContainsKey("customerName") && data["customerName"].ValueKind != JsonValueKind.Null
                        ? data["customerName"].GetString() : null
                };

                decimal total = 0m;
                var itemsArray = data["items"].EnumerateArray().ToList();
                if (itemsArray.Count == 0) throw new ArgumentException("At least one item is required");

                // Load + validate every line before mutating stock, so a short line rejects the
                // whole sale rather than partially decrementing earlier lines.
                var lines = new List<(Product Product, decimal Quantity, decimal UnitPrice)>();
                foreach (var itemEl in itemsArray)
                {
                    var productId = Guid.Parse(itemEl.GetProperty("productId").GetString()!);
                    var quantity = itemEl.GetProperty("quantity").GetDecimal();
                    var unitPrice = itemEl.GetProperty("unitPrice").GetDecimal();

                    if (quantity <= 0) throw new ArgumentException("Quantity must be greater than 0");
                    if (unitPrice < 0) throw new ArgumentException("UnitPrice cannot be negative");

                    var product = await _inventoryRepository.GetProductById(productId);
                    if (product == null || product.FKClientId != clientId)
                        throw new KeyNotFoundException("Product not found");
                    if (product.QuantityOnHand < quantity)
                        throw new ArgumentException($"Not enough stock for \"{product.Name}\" (have {product.QuantityOnHand}, need {quantity})");

                    lines.Add((product, quantity, unitPrice));
                }

                foreach (var (product, quantity, unitPrice) in lines)
                {
                    var lineTotal = quantity * unitPrice;
                    sale.Items.Add(new SaleItem
                    {
                        FKProductId = product.ProductId,
                        Quantity = quantity,
                        UnitPrice = unitPrice,
                        LineTotal = lineTotal
                    });

                    product.QuantityOnHand -= quantity;
                    total += lineTotal;
                }

                sale.TotalAmount = total;
                var sequence = await _inventoryRepository.GetNextSaleSequence(clientId);
                sale.SaleNumber = $"SALE-{sequence:D4}";

                var result = await _inventoryRepository.CreateSale(sale);
                await _uow.CommitAsync();

                return MapToDto(result);
            }
            catch
            {
                await _uow.RollbackAsync();
                throw;
            }
        }

        public async Task<object> GetSales(object payload, HttpContext httpContext)
        {
            var clientId = await _userRoleHelper.GetClientId(DataExtractor.GetUserIdFromContext(httpContext));
            var sales = await _inventoryRepository.GetSales(clientId);
            return sales.Select(MapToDto).ToList();
        }

        public async Task<object> GetSaleById(object payload, HttpContext httpContext)
        {
            var data = DeserializePayload.Deserialize(payload);
            var saleId = Guid.Parse(data["saleId"].GetString()!);

            var clientId = await _userRoleHelper.GetClientId(DataExtractor.GetUserIdFromContext(httpContext));
            var sale = await _inventoryRepository.GetSaleById(saleId);
            if (sale == null || sale.FKClientId != clientId)
                throw new KeyNotFoundException("Sale not found");

            return MapToDto(sale);
        }

        // --- Returns ---

        public async Task<object> CreateStockReturn(object payload, HttpContext httpContext)
        {
            await _uow.BeginAsync();
            try
            {
                var data = DeserializePayload.Deserialize(payload);
                var clientId = await _userRoleHelper.GetClientId(DataExtractor.GetUserIdFromContext(httpContext));

                var productId = Guid.Parse(data["productId"].GetString()!);
                var quantity = data["quantity"].GetDecimal();
                if (quantity <= 0) throw new ArgumentException("Quantity must be greater than 0");

                var category = data["category"].GetString() ?? "Other";
                if (!ValidReturnCategories.Contains(category))
                    throw new ArgumentException($"category must be one of: {string.Join(", ", ValidReturnCategories)}");

                var product = await _inventoryRepository.GetProductById(productId);
                if (product == null || product.FKClientId != clientId)
                    throw new KeyNotFoundException("Product not found");

                // CustomerReturn is the one category that adds back to stock -- the item
                // physically comes back after an earlier sale already removed it, so there's no
                // "enough stock on hand" requirement (it may well be at 0). Every other category
                // removes from stock we currently hold, so it does require enough on hand.
                var addsBackToStock = category == "CustomerReturn";
                if (!addsBackToStock && product.QuantityOnHand < quantity)
                    throw new ArgumentException($"Not enough stock for \"{product.Name}\" (have {product.QuantityOnHand}, need {quantity})");

                // Optional traceability -- most returns have neither. Only validated for
                // existence/ownership, not cross-checked against the product/quantity.
                Guid? saleId = data.ContainsKey("saleId") && data["saleId"].ValueKind != JsonValueKind.Null
                    ? Guid.Parse(data["saleId"].GetString()!) : null;
                Sale? sale = null;
                if (saleId.HasValue)
                {
                    sale = await _inventoryRepository.GetSaleById(saleId.Value);
                    if (sale == null || sale.FKClientId != clientId)
                        throw new KeyNotFoundException("Sale not found");
                }

                Guid? grnId = data.ContainsKey("grnId") && data["grnId"].ValueKind != JsonValueKind.Null
                    ? Guid.Parse(data["grnId"].GetString()!) : null;
                GoodsReceivedNote? grn = null;
                if (grnId.HasValue)
                {
                    grn = await _inventoryRepository.GetGrnById(grnId.Value);
                    if (grn == null || grn.FKClientId != clientId)
                        throw new KeyNotFoundException("GRN not found");
                }

                var returnedAt = data.ContainsKey("returnedAt") && data["returnedAt"].ValueKind != JsonValueKind.Null
                    ? DateTime.Parse(data["returnedAt"].GetString()!).ToUniversalTime()
                    : DateTime.UtcNow;

                var stockReturn = new StockReturn
                {
                    FKClientId = clientId,
                    FKProductId = productId,
                    Quantity = quantity,
                    Category = category,
                    FKSaleId = saleId,
                    FKGrnId = grnId,
                    Notes = data.ContainsKey("notes") && data["notes"].ValueKind != JsonValueKind.Null ? data["notes"].GetString() : null,
                    ReturnedAt = returnedAt,
                    Amount = quantity * product.CostPrice
                };

                product.QuantityOnHand += addsBackToStock ? quantity : -quantity;

                var result = await _inventoryRepository.CreateStockReturn(stockReturn);
                await _uow.CommitAsync();

                result.Product = product;
                result.Sale = sale;
                result.Grn = grn;
                return MapToDto(result);
            }
            catch
            {
                await _uow.RollbackAsync();
                throw;
            }
        }

        public async Task<object> GetStockReturns(object payload, HttpContext httpContext)
        {
            var clientId = await _userRoleHelper.GetClientId(DataExtractor.GetUserIdFromContext(httpContext));
            var returns = await _inventoryRepository.GetStockReturns(clientId);
            return returns.Select(MapToDto).ToList();
        }

        public async Task<object> GetStockReturnById(object payload, HttpContext httpContext)
        {
            var data = DeserializePayload.Deserialize(payload);
            var stockReturnId = Guid.Parse(data["stockReturnId"].GetString()!);

            var clientId = await _userRoleHelper.GetClientId(DataExtractor.GetUserIdFromContext(httpContext));
            var stockReturn = await _inventoryRepository.GetStockReturnById(stockReturnId);
            if (stockReturn == null || stockReturn.FKClientId != clientId)
                throw new KeyNotFoundException("Return not found");

            return MapToDto(stockReturn);
        }

        /// <summary>Staff optionally picking an existing registered member to attach to a sale
        /// (search-and-pick, not free-typed) -- purely for identification, mirrors
        /// BookingService.ResolveOptionalCustomerLinkAsync exactly.</summary>
        private async Task<Guid?> ResolveOptionalCustomerLinkAsync(Dictionary<string, JsonElement> data)
        {
            if (!data.ContainsKey("customerId") || data["customerId"].ValueKind == JsonValueKind.Null)
                return null;

            var customerId = Guid.Parse(data["customerId"].GetString()!);
            _ = await _customerRepository.GetTenantCustomerLinkById(customerId)
                ?? throw new KeyNotFoundException("Customer not found");
            return customerId;
        }

        // ImageId is a relative /Uploads path (same convention as ClientBusiness.BusinessLogoId)
        // with no static-file serving configured for it, so it's inlined as a base64 data URL.
        private static async Task<ProductDto> MapToDtoAsync(Product p) => new()
        {
            ProductId = p.ProductId,
            Name = p.Name,
            Sku = p.Sku,
            ImageUrl = await BusinessLogoHelper.ReadAsDataUrlAsync(p.ImageId),
            UnitOfMeasure = p.UnitOfMeasure,
            CostPrice = p.CostPrice,
            SellingPrice = p.SellingPrice,
            QuantityOnHand = p.QuantityOnHand,
            IsActive = p.IsActive,
            CreatedAt = p.CreatedAt
        };

        private static SupplierDto MapToDto(Supplier s) => new()
        {
            SupplierId = s.SupplierId,
            Name = s.Name,
            Phone = s.Phone,
            Email = s.Email,
            Address = s.Address,
            IsActive = s.IsActive
        };

        private static GoodsReceivedNoteDto MapToDto(GoodsReceivedNote g) => new()
        {
            GrnId = g.GrnId,
            GrnNumber = g.GrnNumber,
            SupplierId = g.FKSupplierId,
            SupplierName = g.Supplier?.Name,
            ReceivedAt = g.ReceivedAt,
            Notes = g.Notes,
            TotalAmount = g.TotalAmount,
            Items = g.Items.Select(i => new GoodsReceivedNoteItemDto
            {
                ProductId = i.FKProductId,
                ProductName = i.Product?.Name ?? string.Empty,
                Quantity = i.Quantity,
                UnitCost = i.UnitCost,
                LineTotal = i.LineTotal
            }).ToList()
        };

        private static SaleDto MapToDto(Sale s) => new()
        {
            SaleId = s.SaleId,
            SaleNumber = s.SaleNumber,
            SoldAt = s.SoldAt,
            PaymentMethod = s.PaymentMethod,
            CustomerId = s.FKCustomerId,
            CustomerName = s.CustomerName,
            TotalAmount = s.TotalAmount,
            Items = s.Items.Select(i => new SaleItemDto
            {
                ProductId = i.FKProductId,
                ProductName = i.Product?.Name ?? string.Empty,
                Quantity = i.Quantity,
                UnitPrice = i.UnitPrice,
                LineTotal = i.LineTotal
            }).ToList()
        };

        private static StockReturnDto MapToDto(StockReturn r) => new()
        {
            StockReturnId = r.StockReturnId,
            ProductId = r.FKProductId,
            ProductName = r.Product?.Name ?? string.Empty,
            Quantity = r.Quantity,
            Category = r.Category,
            SaleId = r.FKSaleId,
            SaleNumber = r.Sale?.SaleNumber,
            GrnId = r.FKGrnId,
            GrnNumber = r.Grn?.GrnNumber,
            Notes = r.Notes,
            ReturnedAt = r.ReturnedAt,
            Amount = r.Amount
        };
    }
}