Core_Be/Models/Sale.cs

using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;

namespace Fitness_core_BE.Models
{
    /// <summary>Stock going out to a customer. Creating one decrements each line's
    /// Product.QuantityOnHand -- the whole sale is rejected up front if any line would go
    /// negative (no backorders).</summary>
    public class Sale
    {
        [Key]
        public Guid SaleId { get; set; }

        public Guid FKClientId { get; set; }
        [ForeignKey(nameof(FKClientId))]
        public Client Client { get; set; }

        [MaxLength(32)]
        public string SaleNumber { get; set; } = string.Empty;

        public DateTime SoldAt { get; set; } = DateTime.UtcNow;

        /// <summary>"Cash" | "Bank" -- same convention as Booking.PaymentMethod.</summary>
        [MaxLength(20)]
        public string PaymentMethod { get; set; } = "Cash";

        /// <summary>Optional link to a registered member, purely for identification -- mirrors
        /// Booking.FKCustomerId (see BookingService.ResolveOptionalCustomerLinkAsync). A walk-in
        /// buyer leaves this null and uses CustomerName instead.</summary>
        public Guid? FKCustomerId { get; set; }

        [MaxLength(128)]
        public string? CustomerName { get; set; }

        public decimal TotalAmount { get; set; } = 0m;

        public DateTime CreatedAt { get; set; } = DateTime.UtcNow;

        public virtual ICollection<SaleItem> Items { get; set; } = new List<SaleItem>();
    }

    public class SaleItem
    {
        [Key]
        public Guid SaleItemId { get; set; }

        public Guid FKSaleId { get; set; }
        [ForeignKey(nameof(FKSaleId))]
        public Sale? Sale { get; set; }

        public Guid FKProductId { get; set; }
        [ForeignKey(nameof(FKProductId))]
        public Product? Product { get; set; }

        public decimal Quantity { get; set; }
        public decimal UnitPrice { get; set; }
        public decimal LineTotal { get; set; }
    }
}