Merge pull request 'Feat/sales management' (#23) from feat/sales-management into Dev

Reviewed-on: #23

Backend/ERPCore/Controllers/CustomersController.cs

@@ -0,0 +1,69 @@
+using ERPCore.Domain.Enums;
+using ERPCore.Dtos.Common;
+using ERPCore.Dtos.Customers;
+using ERPCore.Services.Interfaces;
+using Microsoft.AspNetCore.Mvc;
+
+namespace ERPCore.Controllers;
+
+/// <summary>Customer master endpoints for Phase 1 sales.</summary>
+[Route("api/v1/customers")]
+public sealed class CustomersController : ApiControllerBase
+{
+    private readonly ICustomerService _customers;
+
+    public CustomersController(ICustomerService customers) => _customers = customers;
+
+    [HttpGet]
+    [ProducesResponseType(typeof(PagedResponse<CustomerDto>), StatusCodes.Status200OK)]
+    public async Task<ActionResult<PagedResponse<CustomerDto>>> List(
+        [FromQuery] PageQuery query,
+        [FromQuery] EntityStatus? status,
+        [FromQuery] CustomerType? customerType,
+        CancellationToken ct)
+        => Ok(await _customers.ListAsync(query, status, customerType, ct));
+
+    [HttpGet("{customerId:int}")]
+    [ProducesResponseType(typeof(CustomerDto), StatusCodes.Status200OK)]
+    [ProducesResponseType(StatusCodes.Status404NotFound)]
+    public async Task<ActionResult<CustomerDto>> GetById(int customerId, CancellationToken ct)
+    {
+        var result = await _customers.GetAsync(customerId, ct);
+        if (result is null) return NotFound();
+
+        SetETag(result.RowVersion);
+        return Ok(result.Value);
+    }
+
+    [HttpPost]
+    [ProducesResponseType(typeof(CustomerDto), StatusCodes.Status201Created)]
+    [ProducesResponseType(StatusCodes.Status409Conflict)]
+    public async Task<ActionResult<CustomerDto>> Create([FromBody] CreateCustomerRequest request, CancellationToken ct)
+    {
+        var result = await _customers.CreateAsync(request, ct);
+        SetETag(result.RowVersion);
+        return Created($"/api/v1/customers/{result.Value.CustomerId}", result.Value);
+    }
+
+    [HttpPut("{customerId:int}")]
+    [ProducesResponseType(typeof(CustomerDto), StatusCodes.Status200OK)]
+    [ProducesResponseType(StatusCodes.Status404NotFound)]
+    [ProducesResponseType(StatusCodes.Status409Conflict)]
+    [ProducesResponseType(StatusCodes.Status412PreconditionFailed)]
+    public async Task<ActionResult<CustomerDto>> Update(int customerId, [FromBody] UpdateCustomerRequest request, CancellationToken ct)
+    {
+        var expected = RequireIfMatch();
+        var result = await _customers.UpdateAsync(customerId, request, expected, ct);
+        SetETag(result.RowVersion);
+        return Ok(result.Value);
+    }
+
+    [HttpPatch("{customerId:int}/status")]
+    [ProducesResponseType(StatusCodes.Status204NoContent)]
+    [ProducesResponseType(StatusCodes.Status404NotFound)]
+    public async Task<IActionResult> SetStatus(int customerId, [FromBody] UpdateCustomerStatusRequest request, CancellationToken ct)
+    {
+        await _customers.SetStatusAsync(customerId, request.Status, ct);
+        return NoContent();
+    }
+}

Backend/ERPCore/Controllers/SalesInvoicesController.cs

@@ -0,0 +1,67 @@
+using ERPCore.Domain.Enums;
+using ERPCore.Dtos.Common;
+using ERPCore.Dtos.Sales;
+using ERPCore.Services.Interfaces;
+using Microsoft.AspNetCore.Mvc;
+
+namespace ERPCore.Controllers;
+
+[Route("api/v1/sales-invoices")]
+public sealed class SalesInvoicesController : ApiControllerBase
+{
+    private readonly ISalesInvoiceService _invoices;
+
+    public SalesInvoicesController(ISalesInvoiceService invoices) => _invoices = invoices;
+
+    [HttpGet]
+    [ProducesResponseType(typeof(PagedResponse<SalesInvoiceSummaryDto>), StatusCodes.Status200OK)]
+    public async Task<ActionResult<PagedResponse<SalesInvoiceSummaryDto>>> List(
+        [FromQuery] PageQuery query,
+        [FromQuery] SalesInvoiceStatus? status,
+        [FromQuery] int? customerId,
+        [FromQuery] int? warehouseId,
+        CancellationToken ct)
+        => Ok(await _invoices.ListAsync(query, status, customerId, warehouseId, ct));
+
+    [HttpGet("{salesInvoiceId:int}")]
+    [ProducesResponseType(typeof(SalesInvoiceDto), StatusCodes.Status200OK)]
+    [ProducesResponseType(StatusCodes.Status404NotFound)]
+    public async Task<ActionResult<SalesInvoiceDto>> GetById(int salesInvoiceId, CancellationToken ct)
+    {
+        var result = await _invoices.GetAsync(salesInvoiceId, ct);
+        if (result is null) return NotFound();
+        SetETag(result.RowVersion);
+        return Ok(result.Value);
+    }
+
+    [HttpPost]
+    [ProducesResponseType(typeof(SalesInvoiceDto), StatusCodes.Status201Created)]
+    public async Task<ActionResult<SalesInvoiceDto>> Create([FromBody] CreateSalesInvoiceRequest request, CancellationToken ct)
+    {
+        var result = await _invoices.CreateAsync(request, ct);
+        SetETag(result.RowVersion);
+        return Created($"/api/v1/sales-invoices/{result.Value.SalesInvoiceId}", result.Value);
+    }
+
+    [HttpPut("{salesInvoiceId:int}")]
+    [ProducesResponseType(typeof(SalesInvoiceDto), StatusCodes.Status200OK)]
+    [ProducesResponseType(StatusCodes.Status404NotFound)]
+    [ProducesResponseType(StatusCodes.Status412PreconditionFailed)]
+    public async Task<ActionResult<SalesInvoiceDto>> Update(int salesInvoiceId, [FromBody] UpdateSalesInvoiceRequest request, CancellationToken ct)
+    {
+        var expected = RequireIfMatch();
+        var result = await _invoices.UpdateAsync(salesInvoiceId, request, expected, ct);
+        SetETag(result.RowVersion);
+        return Ok(result.Value);
+    }
+
+    [HttpPost("{salesInvoiceId:int}/post")]
+    [ProducesResponseType(typeof(SalesInvoiceDto), StatusCodes.Status200OK)]
+    public async Task<ActionResult<SalesInvoiceDto>> Post(int salesInvoiceId, CancellationToken ct)
+        => Ok(await _invoices.PostAsync(salesInvoiceId, ct));
+
+    [HttpPost("{salesInvoiceId:int}/cancel")]
+    [ProducesResponseType(typeof(SalesInvoiceDto), StatusCodes.Status200OK)]
+    public async Task<ActionResult<SalesInvoiceDto>> Cancel(int salesInvoiceId, CancellationToken ct)
+        => Ok(await _invoices.CancelAsync(salesInvoiceId, ct));
+}

Backend/ERPCore/Controllers/SalesReportsController.cs

@@ -0,0 +1,49 @@
+using ERPCore.Dtos.Sales;
+using ERPCore.Services.Interfaces;
+using Microsoft.AspNetCore.Mvc;
+
+namespace ERPCore.Controllers;
+
+[Route("api/v1/reports/sales")]
+public sealed class SalesReportsController : ApiControllerBase
+{
+    private readonly ISalesReportService _reports;
+
+    public SalesReportsController(ISalesReportService reports) => _reports = reports;
+
+    [HttpGet("daily-summary")]
+    [ProducesResponseType(typeof(IReadOnlyList<SalesDailySummaryRowDto>), StatusCodes.Status200OK)]
+    public async Task<ActionResult<IReadOnlyList<SalesDailySummaryRowDto>>> DailySummary(
+        [FromQuery] DateOnly from, [FromQuery] DateOnly to, CancellationToken ct)
+        => Ok(await _reports.DailySummaryAsync(from, to, ct));
+
+    [HttpGet("item-wise")]
+    [ProducesResponseType(typeof(IReadOnlyList<SalesItemSummaryRowDto>), StatusCodes.Status200OK)]
+    public async Task<ActionResult<IReadOnlyList<SalesItemSummaryRowDto>>> ItemWise(
+        [FromQuery] DateOnly from, [FromQuery] DateOnly to, [FromQuery] int? itemId, [FromQuery] int? warehouseId, CancellationToken ct)
+        => Ok(await _reports.ItemSummaryAsync(from, to, itemId, warehouseId, ct));
+
+    [HttpGet("customer-wise")]
+    [ProducesResponseType(typeof(IReadOnlyList<SalesCustomerSummaryRowDto>), StatusCodes.Status200OK)]
+    public async Task<ActionResult<IReadOnlyList<SalesCustomerSummaryRowDto>>> CustomerWise(
+        [FromQuery] DateOnly from, [FromQuery] DateOnly to, [FromQuery] int? customerId, CancellationToken ct)
+        => Ok(await _reports.CustomerSummaryAsync(from, to, customerId, ct));
+
+    [HttpGet("warehouse-wise")]
+    [ProducesResponseType(typeof(IReadOnlyList<SalesWarehouseSummaryRowDto>), StatusCodes.Status200OK)]
+    public async Task<ActionResult<IReadOnlyList<SalesWarehouseSummaryRowDto>>> WarehouseWise(
+        [FromQuery] DateOnly from, [FromQuery] DateOnly to, [FromQuery] int? warehouseId, CancellationToken ct)
+        => Ok(await _reports.WarehouseSummaryAsync(from, to, warehouseId, ct));
+
+    [HttpGet("discount-summary")]
+    [ProducesResponseType(typeof(IReadOnlyList<SalesDiscountSummaryRowDto>), StatusCodes.Status200OK)]
+    public async Task<ActionResult<IReadOnlyList<SalesDiscountSummaryRowDto>>> DiscountSummary(
+        [FromQuery] DateOnly from, [FromQuery] DateOnly to, CancellationToken ct)
+        => Ok(await _reports.DiscountSummaryAsync(from, to, ct));
+
+    [HttpGet("free-issue-summary")]
+    [ProducesResponseType(typeof(IReadOnlyList<SalesFreeIssueSummaryRowDto>), StatusCodes.Status200OK)]
+    public async Task<ActionResult<IReadOnlyList<SalesFreeIssueSummaryRowDto>>> FreeIssueSummary(
+        [FromQuery] DateOnly from, [FromQuery] DateOnly to, CancellationToken ct)
+        => Ok(await _reports.FreeIssueSummaryAsync(from, to, ct));
+}

Backend/ERPCore/Controllers/SalesSlipsController.cs

@@ -0,0 +1,67 @@
+using ERPCore.Domain.Enums;
+using ERPCore.Dtos.Common;
+using ERPCore.Dtos.Sales;
+using ERPCore.Services.Interfaces;
+using Microsoft.AspNetCore.Mvc;
+
+namespace ERPCore.Controllers;
+
+[Route("api/v1/sales-slips")]
+public sealed class SalesSlipsController : ApiControllerBase
+{
+    private readonly ISalesSlipService _slips;
+
+    public SalesSlipsController(ISalesSlipService slips) => _slips = slips;
+
+    [HttpGet]
+    [ProducesResponseType(typeof(PagedResponse<SalesSlipSummaryDto>), StatusCodes.Status200OK)]
+    public async Task<ActionResult<PagedResponse<SalesSlipSummaryDto>>> List(
+        [FromQuery] PageQuery query,
+        [FromQuery] SalesSlipStatus? status,
+        [FromQuery] int? customerId,
+        [FromQuery] int? warehouseId,
+        CancellationToken ct)
+        => Ok(await _slips.ListAsync(query, status, customerId, warehouseId, ct));
+
+    [HttpGet("{salesSlipId:int}")]
+    [ProducesResponseType(typeof(SalesSlipDto), StatusCodes.Status200OK)]
+    [ProducesResponseType(StatusCodes.Status404NotFound)]
+    public async Task<ActionResult<SalesSlipDto>> GetById(int salesSlipId, CancellationToken ct)
+    {
+        var result = await _slips.GetAsync(salesSlipId, ct);
+        if (result is null) return NotFound();
+        SetETag(result.RowVersion);
+        return Ok(result.Value);
+    }
+
+    [HttpPost]
+    [ProducesResponseType(typeof(SalesSlipDto), StatusCodes.Status201Created)]
+    public async Task<ActionResult<SalesSlipDto>> Create([FromBody] CreateSalesSlipRequest request, CancellationToken ct)
+    {
+        var result = await _slips.CreateAsync(request, ct);
+        SetETag(result.RowVersion);
+        return Created($"/api/v1/sales-slips/{result.Value.SalesSlipId}", result.Value);
+    }
+
+    [HttpPut("{salesSlipId:int}")]
+    [ProducesResponseType(typeof(SalesSlipDto), StatusCodes.Status200OK)]
+    [ProducesResponseType(StatusCodes.Status404NotFound)]
+    [ProducesResponseType(StatusCodes.Status412PreconditionFailed)]
+    public async Task<ActionResult<SalesSlipDto>> Update(int salesSlipId, [FromBody] UpdateSalesSlipRequest request, CancellationToken ct)
+    {
+        var expected = RequireIfMatch();
+        var result = await _slips.UpdateAsync(salesSlipId, request, expected, ct);
+        SetETag(result.RowVersion);
+        return Ok(result.Value);
+    }
+
+    [HttpPost("{salesSlipId:int}/post")]
+    [ProducesResponseType(typeof(SalesSlipDto), StatusCodes.Status200OK)]
+    public async Task<ActionResult<SalesSlipDto>> Post(int salesSlipId, CancellationToken ct)
+        => Ok(await _slips.PostAsync(salesSlipId, ct));
+
+    [HttpPost("{salesSlipId:int}/cancel")]
+    [ProducesResponseType(typeof(SalesSlipDto), StatusCodes.Status200OK)]
+    public async Task<ActionResult<SalesSlipDto>> Cancel(int salesSlipId, CancellationToken ct)
+        => Ok(await _slips.CancelAsync(salesSlipId, ct));
+}

Backend/ERPCore/Domain/DocumentTypes.cs

@@ -17,4 +17,6 @@ public static class DocumentTypes
 
     /// <summary>Production run (docs/30 FR-MFG-08) — <c>PRD-2026-00001</c>.</summary>
     public const string Production = "PRD";
+    public const string SalesInvoice = "SI";
+    public const string SalesSlip = "SSL";
 }

Backend/ERPCore/Domain/Entities/Customer.cs

@@ -0,0 +1,38 @@
+using ERPCore.Domain.Enums;
+
+namespace ERPCore.Domain.Entities;
+
+/// <summary>
+/// Customer master for both B2B and B2C sales.
+/// Phase 1 keeps this lean: identity, contact, tax, credit, and default warehouse.
+/// </summary>
+public class Customer
+{
+    public int CustomerId { get; set; }
+    public string CustomerCode { get; set; } = string.Empty;
+    public CustomerType CustomerType { get; set; } = CustomerType.B2C;
+
+    public string Name { get; set; } = string.Empty;
+    public string? DisplayName { get; set; }
+    public string? Phone { get; set; }
+    public string? Email { get; set; }
+
+    public string? AddressLine1 { get; set; }
+    public string? AddressLine2 { get; set; }
+    public string? City { get; set; }
+    public string? Country { get; set; }
+
+    public string? TaxRegistrationNo { get; set; }
+    public decimal CreditLimit { get; set; }
+    public int CreditDays { get; set; }
+
+    public int? DefaultWarehouseId { get; set; }
+    public Warehouse? DefaultWarehouse { get; set; }
+
+    public EntityStatus Status { get; set; } = EntityStatus.Active;
+    public DateTime CreatedAt { get; set; }
+    public DateTime? UpdatedAt { get; set; }
+
+    /// <summary>PostgreSQL xmin-backed optimistic concurrency token (ETag source).</summary>
+    public uint RowVersion { get; set; }
+}

Backend/ERPCore/Domain/Entities/SalesInvoice.cs

@@ -0,0 +1,41 @@
+using ERPCore.Domain.Enums;
+
+namespace ERPCore.Domain.Entities;
+
+public class SalesInvoice
+{
+    public int SalesInvoiceId { get; set; }
+    public string InvoiceNo { get; set; } = string.Empty;
+    public DateTime InvoiceDate { get; set; }
+
+    public int CustomerId { get; set; }
+    public Customer? Customer { get; set; }
+
+    public string CustomerSnapshotName { get; set; } = string.Empty;
+    public string? CustomerSnapshotTaxNo { get; set; }
+
+    public int WarehouseId { get; set; }
+    public Warehouse? Warehouse { get; set; }
+
+    public SalesInvoiceType InvoiceType { get; set; } = SalesInvoiceType.B2C;
+    public SalesInvoiceStatus Status { get; set; } = SalesInvoiceStatus.Draft;
+
+    public decimal Subtotal { get; set; }
+    public decimal DiscountTotal { get; set; }
+    public decimal TaxTotal { get; set; }
+    public decimal GrandTotal { get; set; }
+    public decimal RoundOff { get; set; }
+    public decimal NetPayable { get; set; }
+    public decimal PaidAmount { get; set; }
+    public decimal BalanceAmount { get; set; }
+
+    public int CreatedBy { get; set; }
+    public User? Creator { get; set; }
+
+    public DateTime CreatedAt { get; set; }
+    public DateTime? UpdatedAt { get; set; }
+
+    public uint RowVersion { get; set; }
+
+    public ICollection<SalesInvoiceLine> Lines { get; set; } = new List<SalesInvoiceLine>();
+}

Backend/ERPCore/Domain/Entities/SalesInvoiceLine.cs

@@ -0,0 +1,38 @@
+using ERPCore.Domain.Enums;
+
+namespace ERPCore.Domain.Entities;
+
+public class SalesInvoiceLine
+{
+    public int SalesInvoiceLineId { get; set; }
+
+    public int SalesInvoiceId { get; set; }
+    public SalesInvoice? SalesInvoice { get; set; }
+
+    public int ItemId { get; set; }
+    public Item? Item { get; set; }
+
+    public string Description { get; set; } = string.Empty;
+
+    public decimal Qty { get; set; }
+    public decimal FreeQty { get; set; }
+    public int UomId { get; set; }
+    public Uom? Uom { get; set; }
+    public int WarehouseId { get; set; }
+    public Warehouse? Warehouse { get; set; }
+
+    public decimal UnitPrice { get; set; }
+    public decimal BaseCost { get; set; }
+    public string PriceSource { get; set; } = string.Empty;
+    public SalesDiscountMode DiscountMode { get; set; } = SalesDiscountMode.Percentage;
+    public decimal DiscountPct { get; set; }
+    public decimal DiscountAmount { get; set; }
+    public decimal NetUnitPrice { get; set; }
+    public decimal LineTotal { get; set; }
+    public decimal TaxPct { get; set; }
+    public decimal TaxAmount { get; set; }
+    public bool IsFreeIssue { get; set; }
+    public int? ParentLineId { get; set; }
+
+    public uint RowVersion { get; set; }
+}

Backend/ERPCore/Domain/Entities/SalesSlip.cs

@@ -0,0 +1,36 @@
+using ERPCore.Domain.Enums;
+
+namespace ERPCore.Domain.Entities;
+
+public class SalesSlip
+{
+    public int SalesSlipId { get; set; }
+    public string SlipNo { get; set; } = string.Empty;
+    public DateTime SlipDate { get; set; }
+
+    public int CustomerId { get; set; }
+    public Customer? Customer { get; set; }
+
+    public string CustomerSnapshotName { get; set; } = string.Empty;
+    public int WarehouseId { get; set; }
+    public Warehouse? Warehouse { get; set; }
+
+    public int CashierUserId { get; set; }
+    public User? CashierUser { get; set; }
+
+    public SalesSlipStatus Status { get; set; } = SalesSlipStatus.Draft;
+
+    public decimal Subtotal { get; set; }
+    public decimal DiscountTotal { get; set; }
+    public decimal TaxTotal { get; set; }
+    public decimal GrandTotal { get; set; }
+    public decimal PaidAmount { get; set; }
+    public decimal BalanceAmount { get; set; }
+
+    public DateTime CreatedAt { get; set; }
+    public DateTime? UpdatedAt { get; set; }
+
+    public uint RowVersion { get; set; }
+
+    public ICollection<SalesSlipLine> Lines { get; set; } = new List<SalesSlipLine>();
+}

Backend/ERPCore/Domain/Entities/SalesSlipLine.cs

@@ -0,0 +1,38 @@
+using ERPCore.Domain.Enums;
+
+namespace ERPCore.Domain.Entities;
+
+public class SalesSlipLine
+{
+    public int SalesSlipLineId { get; set; }
+
+    public int SalesSlipId { get; set; }
+    public SalesSlip? SalesSlip { get; set; }
+
+    public int ItemId { get; set; }
+    public Item? Item { get; set; }
+
+    public string Description { get; set; } = string.Empty;
+
+    public decimal Qty { get; set; }
+    public decimal FreeQty { get; set; }
+    public int UomId { get; set; }
+    public Uom? Uom { get; set; }
+    public int WarehouseId { get; set; }
+    public Warehouse? Warehouse { get; set; }
+
+    public decimal UnitPrice { get; set; }
+    public decimal BaseCost { get; set; }
+    public string PriceSource { get; set; } = string.Empty;
+    public SalesDiscountMode DiscountMode { get; set; } = SalesDiscountMode.Percentage;
+    public decimal DiscountPct { get; set; }
+    public decimal DiscountAmount { get; set; }
+    public decimal NetUnitPrice { get; set; }
+    public decimal LineTotal { get; set; }
+    public decimal TaxPct { get; set; }
+    public decimal TaxAmount { get; set; }
+    public bool IsFreeIssue { get; set; }
+    public int? ParentLineId { get; set; }
+
+    public uint RowVersion { get; set; }
+}

Backend/ERPCore/Domain/Enums/CustomerType.cs

@@ -0,0 +1,8 @@
+namespace ERPCore.Domain.Enums;
+
+public enum CustomerType
+{
+    B2B = 1,
+    B2C = 2,
+    WalkIn = 3
+}

Backend/ERPCore/Domain/Enums/SalesDiscountMode.cs

@@ -0,0 +1,7 @@
+namespace ERPCore.Domain.Enums;
+
+public enum SalesDiscountMode
+{
+    Percentage = 1,
+    FixedAmount = 2
+}

Backend/ERPCore/Domain/Enums/SalesInvoiceStatus.cs

@@ -0,0 +1,8 @@
+namespace ERPCore.Domain.Enums;
+
+public enum SalesInvoiceStatus
+{
+    Draft = 1,
+    Posted = 2,
+    Cancelled = 3
+}

Backend/ERPCore/Domain/Enums/SalesInvoiceType.cs

@@ -0,0 +1,9 @@
+namespace ERPCore.Domain.Enums;
+
+public enum SalesInvoiceType
+{
+    B2B = 1,
+    B2C = 2,
+    Cash = 3,
+    Credit = 4
+}

Backend/ERPCore/Domain/Enums/SalesSlipStatus.cs

@@ -0,0 +1,8 @@
+namespace ERPCore.Domain.Enums;
+
+public enum SalesSlipStatus
+{
+    Draft = 1,
+    Posted = 2,
+    Cancelled = 3
+}

Backend/ERPCore/Dtos/Customers/CustomerDtos.cs

@@ -0,0 +1,66 @@
+using System.ComponentModel.DataAnnotations;
+using ERPCore.Domain.Enums;
+
+namespace ERPCore.Dtos.Customers;
+
+/// <summary>Customer resource used by sales documents.</summary>
+public sealed record CustomerDto(
+    int CustomerId,
+    string CustomerCode,
+    CustomerType CustomerType,
+    string Name,
+    string? DisplayName,
+    string? Phone,
+    string? Email,
+    string? AddressLine1,
+    string? AddressLine2,
+    string? City,
+    string? Country,
+    string? TaxRegistrationNo,
+    decimal CreditLimit,
+    int CreditDays,
+    int? DefaultWarehouseId,
+    EntityStatus Status,
+    DateTime CreatedAt,
+    DateTime? UpdatedAt);
+
+public sealed class CreateCustomerRequest
+{
+    [Required, StringLength(50)] public string CustomerCode { get; set; } = string.Empty;
+    [Required, EnumDataType(typeof(CustomerType))] public CustomerType CustomerType { get; set; } = CustomerType.B2C;
+    [Required, StringLength(200)] public string Name { get; set; } = string.Empty;
+    [StringLength(200)] public string? DisplayName { get; set; }
+    [StringLength(30)] public string? Phone { get; set; }
+    [StringLength(100)] public string? Email { get; set; }
+    [StringLength(250)] public string? AddressLine1 { get; set; }
+    [StringLength(250)] public string? AddressLine2 { get; set; }
+    [StringLength(100)] public string? City { get; set; }
+    [StringLength(100)] public string? Country { get; set; }
+    [StringLength(50)] public string? TaxRegistrationNo { get; set; }
+    [Range(0, double.MaxValue)] public decimal CreditLimit { get; set; }
+    [Range(0, int.MaxValue)] public int CreditDays { get; set; }
+    public int? DefaultWarehouseId { get; set; }
+}
+
+public sealed class UpdateCustomerRequest
+{
+    [Required, StringLength(50)] public string CustomerCode { get; set; } = string.Empty;
+    [Required, EnumDataType(typeof(CustomerType))] public CustomerType CustomerType { get; set; } = CustomerType.B2C;
+    [Required, StringLength(200)] public string Name { get; set; } = string.Empty;
+    [StringLength(200)] public string? DisplayName { get; set; }
+    [StringLength(30)] public string? Phone { get; set; }
+    [StringLength(100)] public string? Email { get; set; }
+    [StringLength(250)] public string? AddressLine1 { get; set; }
+    [StringLength(250)] public string? AddressLine2 { get; set; }
+    [StringLength(100)] public string? City { get; set; }
+    [StringLength(100)] public string? Country { get; set; }
+    [StringLength(50)] public string? TaxRegistrationNo { get; set; }
+    [Range(0, double.MaxValue)] public decimal CreditLimit { get; set; }
+    [Range(0, int.MaxValue)] public int CreditDays { get; set; }
+    public int? DefaultWarehouseId { get; set; }
+}
+
+public sealed class UpdateCustomerStatusRequest
+{
+    [Required, EnumDataType(typeof(EntityStatus))] public EntityStatus Status { get; set; }
+}

Backend/ERPCore/Dtos/Sales/SalesInvoiceDtos.cs

@@ -0,0 +1,59 @@
+using System.ComponentModel.DataAnnotations;
+using ERPCore.Domain.Enums;
+
+namespace ERPCore.Dtos.Sales;
+
+public sealed record SalesInvoiceLineDto(
+    int SalesInvoiceLineId, int ItemId, string Description, decimal Qty, decimal FreeQty, int UomId,
+    int WarehouseId, decimal UnitPrice, decimal BaseCost, string PriceSource, decimal DiscountPct,
+    decimal DiscountAmount, SalesDiscountMode DiscountMode, decimal NetUnitPrice, decimal LineTotal,
+    decimal TaxPct, decimal TaxAmount, bool IsFreeIssue, int? ParentLineId);
+
+public sealed record SalesInvoiceTotalsDto(
+    decimal Subtotal, decimal DiscountTotal, decimal FreeQtyTotal, decimal TaxTotal, decimal GrandTotal,
+    decimal RoundOff, decimal NetPayable, decimal PaidAmount, decimal BalanceAmount);
+
+public sealed record SalesInvoiceDto(
+    int SalesInvoiceId, string InvoiceNo, DateTime InvoiceDate, int CustomerId,
+    string CustomerSnapshotName, string? CustomerSnapshotTaxNo, int WarehouseId,
+    SalesInvoiceType InvoiceType, SalesInvoiceStatus Status, int CreatedBy, DateTime CreatedAt,
+    DateTime? UpdatedAt, SalesInvoiceTotalsDto Totals, IReadOnlyList<SalesInvoiceLineDto> Lines);
+
+public sealed record SalesInvoiceSummaryDto(
+    int SalesInvoiceId, string InvoiceNo, DateTime InvoiceDate, int CustomerId,
+    string CustomerSnapshotName, int WarehouseId, SalesInvoiceType InvoiceType,
+    SalesInvoiceStatus Status, SalesInvoiceTotalsDto Totals, DateTime CreatedAt);
+
+public sealed class CreateSalesInvoiceLineRequest
+{
+    [Required] public int ItemId { get; set; }
+    [Required] public int UomId { get; set; }
+    [Required] public int WarehouseId { get; set; }
+    [Range(0.0001, double.MaxValue)] public decimal Qty { get; set; }
+    [Range(0, double.MaxValue)] public decimal FreeQty { get; set; }
+    [Range(0, double.MaxValue)] public decimal? UnitPrice { get; set; }
+    public bool AllowManualPriceOverride { get; set; }
+    [Required, EnumDataType(typeof(SalesDiscountMode))] public SalesDiscountMode DiscountMode { get; set; } = SalesDiscountMode.Percentage;
+    [Range(0, 100)] public decimal DiscountPct { get; set; }
+    [Range(0, double.MaxValue)] public decimal DiscountAmount { get; set; }
+    [Range(0, double.MaxValue)] public decimal DiscountValue { get; set; }
+    [Range(0, 100)] public decimal TaxPct { get; set; }
+    public bool IsFreeIssue { get; set; }
+    public int? ParentLineId { get; set; }
+}
+
+public sealed class CreateSalesInvoiceRequest
+{
+    [Required] public int CustomerId { get; set; }
+    [Required] public int WarehouseId { get; set; }
+    [Required, EnumDataType(typeof(SalesInvoiceType))] public SalesInvoiceType InvoiceType { get; set; } = SalesInvoiceType.B2C;
+    [Required, MinLength(1)] public List<CreateSalesInvoiceLineRequest> Lines { get; set; } = new();
+}
+
+public sealed class UpdateSalesInvoiceRequest
+{
+    [Required] public int CustomerId { get; set; }
+    [Required] public int WarehouseId { get; set; }
+    [Required, EnumDataType(typeof(SalesInvoiceType))] public SalesInvoiceType InvoiceType { get; set; } = SalesInvoiceType.B2C;
+    [Required, MinLength(1)] public List<CreateSalesInvoiceLineRequest> Lines { get; set; } = new();
+}

Backend/ERPCore/Dtos/Sales/SalesReportDtos.cs

@@ -0,0 +1,68 @@
+namespace ERPCore.Dtos.Sales;
+
+public sealed record SalesDailySummaryRowDto(
+    DateOnly Date,
+    int InvoiceCount,
+    int SlipCount,
+    decimal InvoiceSubtotal,
+    decimal SlipSubtotal,
+    decimal DiscountTotal,
+    decimal FreeQtyTotal,
+    decimal TaxTotal,
+    decimal GrandTotal);
+
+public sealed record SalesItemSummaryRowDto(
+    int ItemId,
+    string ItemName,
+    decimal SoldQty,
+    decimal FreeQty,
+    decimal GrossAmount,
+    decimal DiscountTotal,
+    decimal TaxTotal,
+    decimal NetAmount);
+
+public sealed record SalesCustomerSummaryRowDto(
+    int CustomerId,
+    string CustomerName,
+    int InvoiceCount,
+    int SlipCount,
+    decimal SoldQty,
+    decimal FreeQty,
+    decimal GrossAmount,
+    decimal DiscountTotal,
+    decimal TaxTotal,
+    decimal NetAmount);
+
+public sealed record SalesWarehouseSummaryRowDto(
+    int WarehouseId,
+    string WarehouseName,
+    int InvoiceCount,
+    int SlipCount,
+    decimal SoldQty,
+    decimal FreeQty,
+    decimal GrossAmount,
+    decimal DiscountTotal,
+    decimal TaxTotal,
+    decimal NetAmount);
+
+public sealed record SalesDiscountSummaryRowDto(
+    string DocumentType,
+    string DocumentNo,
+    DateTime DocumentDate,
+    string CustomerName,
+    decimal Subtotal,
+    decimal DiscountTotal,
+    decimal TaxTotal,
+    decimal NetAmount);
+
+public sealed record SalesFreeIssueSummaryRowDto(
+    string DocumentType,
+    string DocumentNo,
+    DateTime DocumentDate,
+    string CustomerName,
+    int ItemId,
+    string ItemName,
+    decimal FreeQty,
+    decimal FreeValue,
+    int WarehouseId,
+    string WarehouseName);

Backend/ERPCore/Dtos/Sales/SalesSlipDtos.cs

@@ -0,0 +1,58 @@
+using System.ComponentModel.DataAnnotations;
+using ERPCore.Domain.Enums;
+
+namespace ERPCore.Dtos.Sales;
+
+public sealed record SalesSlipLineDto(
+    int SalesSlipLineId, int ItemId, string Description, decimal Qty, decimal FreeQty, int UomId,
+    int WarehouseId, decimal UnitPrice, decimal BaseCost, string PriceSource, decimal DiscountPct,
+    decimal DiscountAmount, SalesDiscountMode DiscountMode, decimal NetUnitPrice, decimal LineTotal,
+    decimal TaxPct, decimal TaxAmount, bool IsFreeIssue, int? ParentLineId);
+
+public sealed record SalesSlipTotalsDto(
+    decimal Subtotal, decimal DiscountTotal, decimal FreeQtyTotal, decimal TaxTotal, decimal GrandTotal,
+    decimal PaidAmount, decimal BalanceAmount);
+
+public sealed record SalesSlipDto(
+    int SalesSlipId, string SlipNo, DateTime SlipDate, int CustomerId,
+    string CustomerSnapshotName, int WarehouseId, int CashierUserId, SalesSlipStatus Status,
+    DateTime CreatedAt, DateTime? UpdatedAt, SalesSlipTotalsDto Totals, IReadOnlyList<SalesSlipLineDto> Lines);
+
+public sealed record SalesSlipSummaryDto(
+    int SalesSlipId, string SlipNo, DateTime SlipDate, int CustomerId,
+    string CustomerSnapshotName, int WarehouseId, SalesSlipStatus Status,
+    SalesSlipTotalsDto Totals, DateTime CreatedAt);
+
+public sealed class CreateSalesSlipLineRequest
+{
+    [Required] public int ItemId { get; set; }
+    [Required] public int UomId { get; set; }
+    [Required] public int WarehouseId { get; set; }
+    [Range(0.0001, double.MaxValue)] public decimal Qty { get; set; }
+    [Range(0, double.MaxValue)] public decimal FreeQty { get; set; }
+    [Range(0, double.MaxValue)] public decimal? UnitPrice { get; set; }
+    public bool AllowManualPriceOverride { get; set; }
+    [Required, EnumDataType(typeof(SalesDiscountMode))] public SalesDiscountMode DiscountMode { get; set; } = SalesDiscountMode.Percentage;
+    [Range(0, 100)] public decimal DiscountPct { get; set; }
+    [Range(0, double.MaxValue)] public decimal DiscountAmount { get; set; }
+    [Range(0, double.MaxValue)] public decimal DiscountValue { get; set; }
+    [Range(0, 100)] public decimal TaxPct { get; set; }
+    public bool IsFreeIssue { get; set; }
+    public int? ParentLineId { get; set; }
+}
+
+public sealed class CreateSalesSlipRequest
+{
+    [Required] public int CustomerId { get; set; }
+    [Required] public int WarehouseId { get; set; }
+    [Required] public int CashierUserId { get; set; }
+    [Required, MinLength(1)] public List<CreateSalesSlipLineRequest> Lines { get; set; } = new();
+}
+
+public sealed class UpdateSalesSlipRequest
+{
+    [Required] public int CustomerId { get; set; }
+    [Required] public int WarehouseId { get; set; }
+    [Required] public int CashierUserId { get; set; }
+    [Required, MinLength(1)] public List<CreateSalesSlipLineRequest> Lines { get; set; } = new();
+}

Backend/ERPCore/Infra/Persistence/Configurations/CustomerConfiguration.cs

@@ -0,0 +1,50 @@
+using ERPCore.Domain.Entities;
+using ERPCore.Domain.Enums;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+
+namespace ERPCore.Infra.Persistence.Configurations;
+
+public sealed class CustomerConfiguration : IEntityTypeConfiguration<Customer>
+{
+    public void Configure(EntityTypeBuilder<Customer> builder)
+    {
+        builder.ToTable("customers");
+        builder.HasKey(c => c.CustomerId);
+
+        builder.Property(c => c.CustomerCode).IsRequired().HasMaxLength(50);
+        builder.HasIndex(c => c.CustomerCode).IsUnique();
+
+        builder.Property(c => c.CustomerType)
+            .HasConversion<string>().HasMaxLength(20).IsRequired()
+            .HasDefaultValue(CustomerType.B2C);
+
+        builder.Property(c => c.Name).IsRequired().HasMaxLength(200);
+        builder.Property(c => c.DisplayName).HasMaxLength(200);
+        builder.Property(c => c.Phone).HasMaxLength(30);
+        builder.Property(c => c.Email).HasMaxLength(100);
+        builder.Property(c => c.AddressLine1).HasMaxLength(250);
+        builder.Property(c => c.AddressLine2).HasMaxLength(250);
+        builder.Property(c => c.City).HasMaxLength(100);
+        builder.Property(c => c.Country).HasMaxLength(100);
+        builder.Property(c => c.TaxRegistrationNo).HasMaxLength(50);
+
+        builder.Property(c => c.CreditLimit).HasPrecision(18, 4);
+        builder.Property(c => c.CreditDays).IsRequired();
+
+        builder.HasOne(c => c.DefaultWarehouse)
+            .WithMany()
+            .HasForeignKey(c => c.DefaultWarehouseId)
+            .OnDelete(DeleteBehavior.SetNull);
+
+        builder.Property(c => c.Status)
+            .HasConversion<string>().HasMaxLength(20).IsRequired()
+            .HasDefaultValue(EntityStatus.Active);
+
+        builder.Property(c => c.CreatedAt).IsRequired();
+        builder.Property(c => c.RowVersion).IsRowVersion();
+
+        builder.HasIndex(c => c.Status);
+        builder.HasIndex(c => c.CustomerType);
+    }
+}

Backend/ERPCore/Infra/Persistence/Configurations/SalesInvoiceConfiguration.cs

@@ -0,0 +1,95 @@
+using ERPCore.Domain.Entities;
+using ERPCore.Domain.Enums;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+
+namespace ERPCore.Infra.Persistence.Configurations;
+
+public sealed class SalesInvoiceConfiguration : IEntityTypeConfiguration<SalesInvoice>
+{
+    public void Configure(EntityTypeBuilder<SalesInvoice> builder)
+    {
+        builder.ToTable("sales_invoices");
+        builder.HasKey(x => x.SalesInvoiceId);
+
+        builder.Property(x => x.InvoiceNo).IsRequired().HasMaxLength(50);
+        builder.HasIndex(x => x.InvoiceNo).IsUnique();
+
+        builder.Property(x => x.InvoiceDate).IsRequired();
+
+        builder.HasOne(x => x.Customer)
+            .WithMany()
+            .HasForeignKey(x => x.CustomerId)
+            .OnDelete(DeleteBehavior.Restrict);
+
+        builder.Property(x => x.CustomerSnapshotName).IsRequired().HasMaxLength(200);
+        builder.Property(x => x.CustomerSnapshotTaxNo).HasMaxLength(50);
+
+        builder.HasOne(x => x.Warehouse)
+            .WithMany()
+            .HasForeignKey(x => x.WarehouseId)
+            .OnDelete(DeleteBehavior.Restrict);
+
+        builder.Property(x => x.InvoiceType)
+            .HasConversion<string>().HasMaxLength(20).IsRequired()
+            .HasDefaultValue(SalesInvoiceType.B2C);
+
+        builder.Property(x => x.Status)
+            .HasConversion<string>().HasMaxLength(20).IsRequired()
+            .HasDefaultValue(SalesInvoiceStatus.Draft);
+
+        foreach (var p in new[] { nameof(SalesInvoice.Subtotal), nameof(SalesInvoice.DiscountTotal), nameof(SalesInvoice.TaxTotal), nameof(SalesInvoice.GrandTotal), nameof(SalesInvoice.RoundOff), nameof(SalesInvoice.NetPayable), nameof(SalesInvoice.PaidAmount), nameof(SalesInvoice.BalanceAmount) })
+            builder.Property<decimal>(p).HasPrecision(18, 4);
+
+        builder.Property(x => x.CreatedAt).IsRequired();
+        builder.Property(x => x.RowVersion).IsRowVersion();
+
+        builder.HasIndex(x => x.Status);
+        builder.HasIndex(x => x.InvoiceDate);
+
+        builder.HasMany(x => x.Lines)
+            .WithOne(x => x.SalesInvoice)
+            .HasForeignKey(x => x.SalesInvoiceId)
+            .OnDelete(DeleteBehavior.Cascade);
+    }
+}
+
+public sealed class SalesInvoiceLineConfiguration : IEntityTypeConfiguration<SalesInvoiceLine>
+{
+    public void Configure(EntityTypeBuilder<SalesInvoiceLine> builder)
+    {
+        builder.ToTable("sales_invoice_lines");
+        builder.HasKey(x => x.SalesInvoiceLineId);
+
+        builder.HasOne(x => x.Item)
+            .WithMany()
+            .HasForeignKey(x => x.ItemId)
+            .OnDelete(DeleteBehavior.Restrict);
+
+        builder.Property(x => x.Description).IsRequired().HasMaxLength(200);
+
+        builder.Property(x => x.Qty).HasPrecision(18, 4);
+        builder.Property(x => x.FreeQty).HasPrecision(18, 4);
+        builder.Property(x => x.UnitPrice).HasPrecision(18, 4);
+        builder.Property(x => x.BaseCost).HasPrecision(18, 4);
+        builder.Property(x => x.DiscountPct).HasPrecision(9, 4);
+        builder.Property(x => x.DiscountAmount).HasPrecision(18, 4);
+        builder.Property(x => x.NetUnitPrice).HasPrecision(18, 4);
+        builder.Property(x => x.LineTotal).HasPrecision(18, 4);
+        builder.Property(x => x.TaxPct).HasPrecision(9, 4);
+        builder.Property(x => x.TaxAmount).HasPrecision(18, 4);
+
+        builder.HasOne(x => x.Uom)
+            .WithMany()
+            .HasForeignKey(x => x.UomId)
+            .OnDelete(DeleteBehavior.Restrict);
+
+        builder.HasOne(x => x.Warehouse)
+            .WithMany()
+            .HasForeignKey(x => x.WarehouseId)
+            .OnDelete(DeleteBehavior.Restrict);
+
+        builder.Property(x => x.PriceSource).HasMaxLength(50);
+        builder.Property(x => x.RowVersion).IsRowVersion();
+    }
+}

Backend/ERPCore/Infra/Persistence/Configurations/SalesSlipConfiguration.cs

@@ -0,0 +1,95 @@
+using ERPCore.Domain.Entities;
+using ERPCore.Domain.Enums;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+
+namespace ERPCore.Infra.Persistence.Configurations;
+
+public sealed class SalesSlipConfiguration : IEntityTypeConfiguration<SalesSlip>
+{
+    public void Configure(EntityTypeBuilder<SalesSlip> builder)
+    {
+        builder.ToTable("sales_slips");
+        builder.HasKey(x => x.SalesSlipId);
+
+        builder.Property(x => x.SlipNo).IsRequired().HasMaxLength(50);
+        builder.HasIndex(x => x.SlipNo).IsUnique();
+
+        builder.Property(x => x.SlipDate).IsRequired();
+
+        builder.HasOne(x => x.Customer)
+            .WithMany()
+            .HasForeignKey(x => x.CustomerId)
+            .OnDelete(DeleteBehavior.Restrict);
+
+        builder.Property(x => x.CustomerSnapshotName).IsRequired().HasMaxLength(200);
+
+        builder.HasOne(x => x.Warehouse)
+            .WithMany()
+            .HasForeignKey(x => x.WarehouseId)
+            .OnDelete(DeleteBehavior.Restrict);
+
+        builder.HasOne(x => x.CashierUser)
+            .WithMany()
+            .HasForeignKey(x => x.CashierUserId)
+            .OnDelete(DeleteBehavior.Restrict);
+
+        builder.Property(x => x.Status)
+            .HasConversion<string>().HasMaxLength(20).IsRequired()
+            .HasDefaultValue(SalesSlipStatus.Draft);
+
+        foreach (var p in new[] { nameof(SalesSlip.Subtotal), nameof(SalesSlip.DiscountTotal), nameof(SalesSlip.TaxTotal), nameof(SalesSlip.GrandTotal), nameof(SalesSlip.PaidAmount), nameof(SalesSlip.BalanceAmount) })
+            builder.Property<decimal>(p).HasPrecision(18, 4);
+
+        builder.Property(x => x.CreatedAt).IsRequired();
+        builder.Property(x => x.RowVersion).IsRowVersion();
+
+        builder.HasIndex(x => x.Status);
+        builder.HasIndex(x => x.SlipDate);
+
+        builder.HasMany(x => x.Lines)
+            .WithOne(x => x.SalesSlip)
+            .HasForeignKey(x => x.SalesSlipId)
+            .OnDelete(DeleteBehavior.Cascade);
+    }
+}
+
+public sealed class SalesSlipLineConfiguration : IEntityTypeConfiguration<SalesSlipLine>
+{
+    public void Configure(EntityTypeBuilder<SalesSlipLine> builder)
+    {
+        builder.ToTable("sales_slip_lines");
+        builder.HasKey(x => x.SalesSlipLineId);
+
+        builder.HasOne(x => x.Item)
+            .WithMany()
+            .HasForeignKey(x => x.ItemId)
+            .OnDelete(DeleteBehavior.Restrict);
+
+        builder.Property(x => x.Description).IsRequired().HasMaxLength(200);
+
+        builder.Property(x => x.Qty).HasPrecision(18, 4);
+        builder.Property(x => x.FreeQty).HasPrecision(18, 4);
+        builder.Property(x => x.UnitPrice).HasPrecision(18, 4);
+        builder.Property(x => x.BaseCost).HasPrecision(18, 4);
+        builder.Property(x => x.DiscountPct).HasPrecision(9, 4);
+        builder.Property(x => x.DiscountAmount).HasPrecision(18, 4);
+        builder.Property(x => x.NetUnitPrice).HasPrecision(18, 4);
+        builder.Property(x => x.LineTotal).HasPrecision(18, 4);
+        builder.Property(x => x.TaxPct).HasPrecision(9, 4);
+        builder.Property(x => x.TaxAmount).HasPrecision(18, 4);
+
+        builder.HasOne(x => x.Uom)
+            .WithMany()
+            .HasForeignKey(x => x.UomId)
+            .OnDelete(DeleteBehavior.Restrict);
+
+        builder.HasOne(x => x.Warehouse)
+            .WithMany()
+            .HasForeignKey(x => x.WarehouseId)
+            .OnDelete(DeleteBehavior.Restrict);
+
+        builder.Property(x => x.PriceSource).HasMaxLength(50);
+        builder.Property(x => x.RowVersion).IsRowVersion();
+    }
+}

Backend/ERPCore/Infra/Persistence/ErpDbContext.cs

@@ -22,6 +22,7 @@ public class ErpDbContext : DbContext
     }
 
     // --- Master Data (docs/10 Part C.1) ---
+    public DbSet<Customer> Customers => Set<Customer>();
     public DbSet<Category> Categories => Set<Category>();
     public DbSet<SubCategory> SubCategories => Set<SubCategory>();
     public DbSet<Brand> Brands => Set<Brand>();
@@ -82,6 +83,12 @@ public class ErpDbContext : DbContext
     public DbSet<PurchaseReturn> PurchaseReturns => Set<PurchaseReturn>();
     public DbSet<PurchaseReturnLine> PurchaseReturnLines => Set<PurchaseReturnLine>();
 
+    // --- Sales (Phase 1) ---
+    public DbSet<SalesInvoice> SalesInvoices => Set<SalesInvoice>();
+    public DbSet<SalesInvoiceLine> SalesInvoiceLines => Set<SalesInvoiceLine>();
+    public DbSet<SalesSlip> SalesSlips => Set<SalesSlip>();
+    public DbSet<SalesSlipLine> SalesSlipLines => Set<SalesSlipLine>();
+
     // --- Reference data (docs/10 Part C.7) ---
     public DbSet<ReasonCode> ReasonCodes => Set<ReasonCode>();
 

Backend/ERPCore/Infra/Persistence/Migrations/ErpDbContextModelSnapshot.cs

@@ -407,6 +407,106 @@ namespace ERPCore.Infra.Persistence.Migrations
                     b.ToTable("categories", (string)null);
                 });
 
+            modelBuilder.Entity("ERPCore.Domain.Entities.Customer", b =>
+                {
+                    b.Property<int>("CustomerId")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("integer");
+
+                    NpgsqlPropertyBuilderExtensions.UseIdentityByDefaultColumn(b.Property<int>("CustomerId"));
+
+                    b.Property<string>("AddressLine1")
+                        .HasMaxLength(250)
+                        .HasColumnType("character varying(250)");
+
+                    b.Property<string>("AddressLine2")
+                        .HasMaxLength(250)
+                        .HasColumnType("character varying(250)");
+
+                    b.Property<string>("City")
+                        .HasMaxLength(100)
+                        .HasColumnType("character varying(100)");
+
+                    b.Property<string>("Country")
+                        .HasMaxLength(100)
+                        .HasColumnType("character varying(100)");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<int>("CreditDays")
+                        .HasColumnType("integer");
+
+                    b.Property<decimal>("CreditLimit")
+                        .HasPrecision(18, 4)
+                        .HasColumnType("numeric(18,4)");
+
+                    b.Property<string>("CustomerCode")
+                        .IsRequired()
+                        .HasMaxLength(50)
+                        .HasColumnType("character varying(50)");
+
+                    b.Property<string>("CustomerType")
+                        .IsRequired()
+                        .ValueGeneratedOnAdd()
+                        .HasMaxLength(20)
+                        .HasColumnType("character varying(20)")
+                        .HasDefaultValue("B2C");
+
+                    b.Property<int?>("DefaultWarehouseId")
+                        .HasColumnType("integer");
+
+                    b.Property<string>("DisplayName")
+                        .HasMaxLength(200)
+                        .HasColumnType("character varying(200)");
+
+                    b.Property<string>("Email")
+                        .HasMaxLength(100)
+                        .HasColumnType("character varying(100)");
+
+                    b.Property<string>("Name")
+                        .IsRequired()
+                        .HasMaxLength(200)
+                        .HasColumnType("character varying(200)");
+
+                    b.Property<string>("Phone")
+                        .HasMaxLength(30)
+                        .HasColumnType("character varying(30)");
+
+                    b.Property<uint>("RowVersion")
+                        .IsConcurrencyToken()
+                        .ValueGeneratedOnAddOrUpdate()
+                        .HasColumnType("xid")
+                        .HasColumnName("xmin");
+
+                    b.Property<string>("Status")
+                        .IsRequired()
+                        .ValueGeneratedOnAdd()
+                        .HasMaxLength(20)
+                        .HasColumnType("character varying(20)")
+                        .HasDefaultValue("Active");
+
+                    b.Property<string>("TaxRegistrationNo")
+                        .HasMaxLength(50)
+                        .HasColumnType("character varying(50)");
+
+                    b.Property<DateTime?>("UpdatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.HasKey("CustomerId");
+
+                    b.HasIndex("CustomerCode")
+                        .IsUnique();
+
+                    b.HasIndex("CustomerType");
+
+                    b.HasIndex("DefaultWarehouseId");
+
+                    b.HasIndex("Status");
+
+                    b.ToTable("customers", (string)null);
+                });
+
             modelBuilder.Entity("ERPCore.Domain.Entities.Department", b =>
                 {
                     b.Property<int>("DepartmentId")
@@ -3302,6 +3402,406 @@ namespace ERPCore.Infra.Persistence.Migrations
                     b.ToTable("hr_salary_components", (string)null);
                 });
 
+            modelBuilder.Entity("ERPCore.Domain.Entities.SalesInvoice", b =>
+                {
+                    b.Property<int>("SalesInvoiceId")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("integer");
+
+                    NpgsqlPropertyBuilderExtensions.UseIdentityByDefaultColumn(b.Property<int>("SalesInvoiceId"));
+
+                    b.Property<decimal>("BalanceAmount")
+                        .HasPrecision(18, 4)
+                        .HasColumnType("numeric(18,4)");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<int>("CreatedBy")
+                        .HasColumnType("integer");
+
+                    b.Property<int?>("CreatorUserId")
+                        .HasColumnType("integer");
+
+                    b.Property<int>("CustomerId")
+                        .HasColumnType("integer");
+
+                    b.Property<string>("CustomerSnapshotName")
+                        .IsRequired()
+                        .HasMaxLength(200)
+                        .HasColumnType("character varying(200)");
+
+                    b.Property<string>("CustomerSnapshotTaxNo")
+                        .HasMaxLength(50)
+                        .HasColumnType("character varying(50)");
+
+                    b.Property<decimal>("DiscountTotal")
+                        .HasPrecision(18, 4)
+                        .HasColumnType("numeric(18,4)");
+
+                    b.Property<decimal>("GrandTotal")
+                        .HasPrecision(18, 4)
+                        .HasColumnType("numeric(18,4)");
+
+                    b.Property<DateTime>("InvoiceDate")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<string>("InvoiceNo")
+                        .IsRequired()
+                        .HasMaxLength(50)
+                        .HasColumnType("character varying(50)");
+
+                    b.Property<string>("InvoiceType")
+                        .IsRequired()
+                        .ValueGeneratedOnAdd()
+                        .HasMaxLength(20)
+                        .HasColumnType("character varying(20)")
+                        .HasDefaultValue("B2C");
+
+                    b.Property<decimal>("NetPayable")
+                        .HasPrecision(18, 4)
+                        .HasColumnType("numeric(18,4)");
+
+                    b.Property<decimal>("PaidAmount")
+                        .HasPrecision(18, 4)
+                        .HasColumnType("numeric(18,4)");
+
+                    b.Property<decimal>("RoundOff")
+                        .HasPrecision(18, 4)
+                        .HasColumnType("numeric(18,4)");
+
+                    b.Property<uint>("RowVersion")
+                        .IsConcurrencyToken()
+                        .ValueGeneratedOnAddOrUpdate()
+                        .HasColumnType("xid")
+                        .HasColumnName("xmin");
+
+                    b.Property<string>("Status")
+                        .IsRequired()
+                        .ValueGeneratedOnAdd()
+                        .HasMaxLength(20)
+                        .HasColumnType("character varying(20)")
+                        .HasDefaultValue("Draft");
+
+                    b.Property<decimal>("Subtotal")
+                        .HasPrecision(18, 4)
+                        .HasColumnType("numeric(18,4)");
+
+                    b.Property<decimal>("TaxTotal")
+                        .HasPrecision(18, 4)
+                        .HasColumnType("numeric(18,4)");
+
+                    b.Property<DateTime?>("UpdatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<int>("WarehouseId")
+                        .HasColumnType("integer");
+
+                    b.HasKey("SalesInvoiceId");
+
+                    b.HasIndex("CreatorUserId");
+
+                    b.HasIndex("CustomerId");
+
+                    b.HasIndex("InvoiceDate");
+
+                    b.HasIndex("InvoiceNo")
+                        .IsUnique();
+
+                    b.HasIndex("Status");
+
+                    b.HasIndex("WarehouseId");
+
+                    b.ToTable("sales_invoices", (string)null);
+                });
+
+            modelBuilder.Entity("ERPCore.Domain.Entities.SalesInvoiceLine", b =>
+                {
+                    b.Property<int>("SalesInvoiceLineId")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("integer");
+
+                    NpgsqlPropertyBuilderExtensions.UseIdentityByDefaultColumn(b.Property<int>("SalesInvoiceLineId"));
+
+                    b.Property<decimal>("BaseCost")
+                        .HasPrecision(18, 4)
+                        .HasColumnType("numeric(18,4)");
+
+                    b.Property<string>("Description")
+                        .IsRequired()
+                        .HasMaxLength(200)
+                        .HasColumnType("character varying(200)");
+
+                    b.Property<decimal>("DiscountAmount")
+                        .HasPrecision(18, 4)
+                        .HasColumnType("numeric(18,4)");
+
+                    b.Property<int>("DiscountMode")
+                        .HasColumnType("integer");
+
+                    b.Property<decimal>("DiscountPct")
+                        .HasPrecision(9, 4)
+                        .HasColumnType("numeric(9,4)");
+
+                    b.Property<decimal>("FreeQty")
+                        .HasPrecision(18, 4)
+                        .HasColumnType("numeric(18,4)");
+
+                    b.Property<bool>("IsFreeIssue")
+                        .HasColumnType("boolean");
+
+                    b.Property<int>("ItemId")
+                        .HasColumnType("integer");
+
+                    b.Property<decimal>("LineTotal")
+                        .HasPrecision(18, 4)
+                        .HasColumnType("numeric(18,4)");
+
+                    b.Property<decimal>("NetUnitPrice")
+                        .HasPrecision(18, 4)
+                        .HasColumnType("numeric(18,4)");
+
+                    b.Property<int?>("ParentLineId")
+                        .HasColumnType("integer");
+
+                    b.Property<string>("PriceSource")
+                        .IsRequired()
+                        .HasMaxLength(50)
+                        .HasColumnType("character varying(50)");
+
+                    b.Property<decimal>("Qty")
+                        .HasPrecision(18, 4)
+                        .HasColumnType("numeric(18,4)");
+
+                    b.Property<uint>("RowVersion")
+                        .IsConcurrencyToken()
+                        .ValueGeneratedOnAddOrUpdate()
+                        .HasColumnType("xid")
+                        .HasColumnName("xmin");
+
+                    b.Property<int>("SalesInvoiceId")
+                        .HasColumnType("integer");
+
+                    b.Property<decimal>("TaxAmount")
+                        .HasPrecision(18, 4)
+                        .HasColumnType("numeric(18,4)");
+
+                    b.Property<decimal>("TaxPct")
+                        .HasPrecision(9, 4)
+                        .HasColumnType("numeric(9,4)");
+
+                    b.Property<decimal>("UnitPrice")
+                        .HasPrecision(18, 4)
+                        .HasColumnType("numeric(18,4)");
+
+                    b.Property<int>("UomId")
+                        .HasColumnType("integer");
+
+                    b.Property<int>("WarehouseId")
+                        .HasColumnType("integer");
+
+                    b.HasKey("SalesInvoiceLineId");
+
+                    b.HasIndex("ItemId");
+
+                    b.HasIndex("SalesInvoiceId");
+
+                    b.HasIndex("UomId");
+
+                    b.HasIndex("WarehouseId");
+
+                    b.ToTable("sales_invoice_lines", (string)null);
+                });
+
+            modelBuilder.Entity("ERPCore.Domain.Entities.SalesSlip", b =>
+                {
+                    b.Property<int>("SalesSlipId")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("integer");
+
+                    NpgsqlPropertyBuilderExtensions.UseIdentityByDefaultColumn(b.Property<int>("SalesSlipId"));
+
+                    b.Property<decimal>("BalanceAmount")
+                        .HasPrecision(18, 4)
+                        .HasColumnType("numeric(18,4)");
+
+                    b.Property<int>("CashierUserId")
+                        .HasColumnType("integer");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<int>("CustomerId")
+                        .HasColumnType("integer");
+
+                    b.Property<string>("CustomerSnapshotName")
+                        .IsRequired()
+                        .HasMaxLength(200)
+                        .HasColumnType("character varying(200)");
+
+                    b.Property<decimal>("DiscountTotal")
+                        .HasPrecision(18, 4)
+                        .HasColumnType("numeric(18,4)");
+
+                    b.Property<decimal>("GrandTotal")
+                        .HasPrecision(18, 4)
+                        .HasColumnType("numeric(18,4)");
+
+                    b.Property<decimal>("PaidAmount")
+                        .HasPrecision(18, 4)
+                        .HasColumnType("numeric(18,4)");
+
+                    b.Property<uint>("RowVersion")
+                        .IsConcurrencyToken()
+                        .ValueGeneratedOnAddOrUpdate()
+                        .HasColumnType("xid")
+                        .HasColumnName("xmin");
+
+                    b.Property<DateTime>("SlipDate")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<string>("SlipNo")
+                        .IsRequired()
+                        .HasMaxLength(50)
+                        .HasColumnType("character varying(50)");
+
+                    b.Property<string>("Status")
+                        .IsRequired()
+                        .ValueGeneratedOnAdd()
+                        .HasMaxLength(20)
+                        .HasColumnType("character varying(20)")
+                        .HasDefaultValue("Draft");
+
+                    b.Property<decimal>("Subtotal")
+                        .HasPrecision(18, 4)
+                        .HasColumnType("numeric(18,4)");
+
+                    b.Property<decimal>("TaxTotal")
+                        .HasPrecision(18, 4)
+                        .HasColumnType("numeric(18,4)");
+
+                    b.Property<DateTime?>("UpdatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<int>("WarehouseId")
+                        .HasColumnType("integer");
+
+                    b.HasKey("SalesSlipId");
+
+                    b.HasIndex("CashierUserId");
+
+                    b.HasIndex("CustomerId");
+
+                    b.HasIndex("SlipDate");
+
+                    b.HasIndex("SlipNo")
+                        .IsUnique();
+
+                    b.HasIndex("Status");
+
+                    b.HasIndex("WarehouseId");
+
+                    b.ToTable("sales_slips", (string)null);
+                });
+
+            modelBuilder.Entity("ERPCore.Domain.Entities.SalesSlipLine", b =>
+                {
+                    b.Property<int>("SalesSlipLineId")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("integer");
+
+                    NpgsqlPropertyBuilderExtensions.UseIdentityByDefaultColumn(b.Property<int>("SalesSlipLineId"));
+
+                    b.Property<decimal>("BaseCost")
+                        .HasPrecision(18, 4)
+                        .HasColumnType("numeric(18,4)");
+
+                    b.Property<string>("Description")
+                        .IsRequired()
+                        .HasMaxLength(200)
+                        .HasColumnType("character varying(200)");
+
+                    b.Property<decimal>("DiscountAmount")
+                        .HasPrecision(18, 4)
+                        .HasColumnType("numeric(18,4)");
+
+                    b.Property<int>("DiscountMode")
+                        .HasColumnType("integer");
+
+                    b.Property<decimal>("DiscountPct")
+                        .HasPrecision(9, 4)
+                        .HasColumnType("numeric(9,4)");
+
+                    b.Property<decimal>("FreeQty")
+                        .HasPrecision(18, 4)
+                        .HasColumnType("numeric(18,4)");
+
+                    b.Property<bool>("IsFreeIssue")
+                        .HasColumnType("boolean");
+
+                    b.Property<int>("ItemId")
+                        .HasColumnType("integer");
+
+                    b.Property<decimal>("LineTotal")
+                        .HasPrecision(18, 4)
+                        .HasColumnType("numeric(18,4)");
+
+                    b.Property<decimal>("NetUnitPrice")
+                        .HasPrecision(18, 4)
+                        .HasColumnType("numeric(18,4)");
+
+                    b.Property<int?>("ParentLineId")
+                        .HasColumnType("integer");
+
+                    b.Property<string>("PriceSource")
+                        .IsRequired()
+                        .HasMaxLength(50)
+                        .HasColumnType("character varying(50)");
+
+                    b.Property<decimal>("Qty")
+                        .HasPrecision(18, 4)
+                        .HasColumnType("numeric(18,4)");
+
+                    b.Property<uint>("RowVersion")
+                        .IsConcurrencyToken()
+                        .ValueGeneratedOnAddOrUpdate()
+                        .HasColumnType("xid")
+                        .HasColumnName("xmin");
+
+                    b.Property<int>("SalesSlipId")
+                        .HasColumnType("integer");
+
+                    b.Property<decimal>("TaxAmount")
+                        .HasPrecision(18, 4)
+                        .HasColumnType("numeric(18,4)");
+
+                    b.Property<decimal>("TaxPct")
+                        .HasPrecision(9, 4)
+                        .HasColumnType("numeric(9,4)");
+
+                    b.Property<decimal>("UnitPrice")
+                        .HasPrecision(18, 4)
+                        .HasColumnType("numeric(18,4)");
+
+                    b.Property<int>("UomId")
+                        .HasColumnType("integer");
+
+                    b.Property<int>("WarehouseId")
+                        .HasColumnType("integer");
+
+                    b.HasKey("SalesSlipLineId");
+
+                    b.HasIndex("ItemId");
+
+                    b.HasIndex("SalesSlipId");
+
+                    b.HasIndex("UomId");
+
+                    b.HasIndex("WarehouseId");
+
+                    b.ToTable("sales_slip_lines", (string)null);
+                });
+
             modelBuilder.Entity("ERPCore.Domain.Entities.Serial", b =>
                 {
                     b.Property<int>("SerialId")
@@ -4649,6 +5149,16 @@ namespace ERPCore.Infra.Persistence.Migrations
                     b.Navigation("Warehouse");
                 });
 
+            modelBuilder.Entity("ERPCore.Domain.Entities.Customer", b =>
+                {
+                    b.HasOne("ERPCore.Domain.Entities.Warehouse", "DefaultWarehouse")
+                        .WithMany()
+                        .HasForeignKey("DefaultWarehouseId")
+                        .OnDelete(DeleteBehavior.SetNull);
+
+                    b.Navigation("DefaultWarehouse");
+                });
+
             modelBuilder.Entity("ERPCore.Domain.Entities.Department", b =>
                 {
                     b.HasOne("ERPCore.Domain.Entities.Branch", "Branch")
@@ -5472,6 +5982,128 @@ namespace ERPCore.Infra.Persistence.Migrations
                     b.Navigation("Uom");
                 });
 
+            modelBuilder.Entity("ERPCore.Domain.Entities.SalesInvoice", b =>
+                {
+                    b.HasOne("ERPCore.Domain.Entities.User", "Creator")
+                        .WithMany()
+                        .HasForeignKey("CreatorUserId");
+
+                    b.HasOne("ERPCore.Domain.Entities.Customer", "Customer")
+                        .WithMany()
+                        .HasForeignKey("CustomerId")
+                        .OnDelete(DeleteBehavior.Restrict)
+                        .IsRequired();
+
+                    b.HasOne("ERPCore.Domain.Entities.Warehouse", "Warehouse")
+                        .WithMany()
+                        .HasForeignKey("WarehouseId")
+                        .OnDelete(DeleteBehavior.Restrict)
+                        .IsRequired();
+
+                    b.Navigation("Creator");
+
+                    b.Navigation("Customer");
+
+                    b.Navigation("Warehouse");
+                });
+
+            modelBuilder.Entity("ERPCore.Domain.Entities.SalesInvoiceLine", b =>
+                {
+                    b.HasOne("ERPCore.Domain.Entities.Item", "Item")
+                        .WithMany()
+                        .HasForeignKey("ItemId")
+                        .OnDelete(DeleteBehavior.Restrict)
+                        .IsRequired();
+
+                    b.HasOne("ERPCore.Domain.Entities.SalesInvoice", "SalesInvoice")
+                        .WithMany("Lines")
+                        .HasForeignKey("SalesInvoiceId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.HasOne("ERPCore.Domain.Entities.Uom", "Uom")
+                        .WithMany()
+                        .HasForeignKey("UomId")
+                        .OnDelete(DeleteBehavior.Restrict)
+                        .IsRequired();
+
+                    b.HasOne("ERPCore.Domain.Entities.Warehouse", "Warehouse")
+                        .WithMany()
+                        .HasForeignKey("WarehouseId")
+                        .OnDelete(DeleteBehavior.Restrict)
+                        .IsRequired();
+
+                    b.Navigation("Item");
+
+                    b.Navigation("SalesInvoice");
+
+                    b.Navigation("Uom");
+
+                    b.Navigation("Warehouse");
+                });
+
+            modelBuilder.Entity("ERPCore.Domain.Entities.SalesSlip", b =>
+                {
+                    b.HasOne("ERPCore.Domain.Entities.User", "CashierUser")
+                        .WithMany()
+                        .HasForeignKey("CashierUserId")
+                        .OnDelete(DeleteBehavior.Restrict)
+                        .IsRequired();
+
+                    b.HasOne("ERPCore.Domain.Entities.Customer", "Customer")
+                        .WithMany()
+                        .HasForeignKey("CustomerId")
+                        .OnDelete(DeleteBehavior.Restrict)
+                        .IsRequired();
+
+                    b.HasOne("ERPCore.Domain.Entities.Warehouse", "Warehouse")
+                        .WithMany()
+                        .HasForeignKey("WarehouseId")
+                        .OnDelete(DeleteBehavior.Restrict)
+                        .IsRequired();
+
+                    b.Navigation("CashierUser");
+
+                    b.Navigation("Customer");
+
+                    b.Navigation("Warehouse");
+                });
+
+            modelBuilder.Entity("ERPCore.Domain.Entities.SalesSlipLine", b =>
+                {
+                    b.HasOne("ERPCore.Domain.Entities.Item", "Item")
+                        .WithMany()
+                        .HasForeignKey("ItemId")
+                        .OnDelete(DeleteBehavior.Restrict)
+                        .IsRequired();
+
+                    b.HasOne("ERPCore.Domain.Entities.SalesSlip", "SalesSlip")
+                        .WithMany("Lines")
+                        .HasForeignKey("SalesSlipId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.HasOne("ERPCore.Domain.Entities.Uom", "Uom")
+                        .WithMany()
+                        .HasForeignKey("UomId")
+                        .OnDelete(DeleteBehavior.Restrict)
+                        .IsRequired();
+
+                    b.HasOne("ERPCore.Domain.Entities.Warehouse", "Warehouse")
+                        .WithMany()
+                        .HasForeignKey("WarehouseId")
+                        .OnDelete(DeleteBehavior.Restrict)
+                        .IsRequired();
+
+                    b.Navigation("Item");
+
+                    b.Navigation("SalesSlip");
+
+                    b.Navigation("Uom");
+
+                    b.Navigation("Warehouse");
+                });
+
             modelBuilder.Entity("ERPCore.Domain.Entities.Serial", b =>
                 {
                     b.HasOne("ERPCore.Domain.Entities.Item", "Item")
@@ -6014,6 +6646,16 @@ namespace ERPCore.Infra.Persistence.Migrations
                     b.Navigation("Outputs");
                 });
 
+            modelBuilder.Entity("ERPCore.Domain.Entities.SalesInvoice", b =>
+                {
+                    b.Navigation("Lines");
+                });
+
+            modelBuilder.Entity("ERPCore.Domain.Entities.SalesSlip", b =>
+                {
+                    b.Navigation("Lines");
+                });
+
             modelBuilder.Entity("ERPCore.Domain.Entities.StockAdjustment", b =>
                 {
                     b.Navigation("Lines");

Backend/ERPCore/Program.cs

@@ -8,6 +8,7 @@ using ERPCore.Infra.UoW;
 using ERPCore.Repositories;
 using ERPCore.Repositories.Interfaces;
 using ERPCore.Services;
+using ERPCore.Services.Interfaces;
 using ERPCore.Services.Auth;
 using ERPCore.Services.Hrm;
 using ERPCore.Services.Interfaces;
@@ -72,6 +73,7 @@ builder.Services.AddScoped<IUnitOfWork, UnitOfWork>();
 builder.Services.AddScoped(typeof(IRepository<>), typeof(Repository<>));
 
 // Master-data services (docs/11 §2)
+builder.Services.AddScoped<ICustomerService, CustomerService>();
 builder.Services.AddScoped<IItemService, ItemService>();
 builder.Services.AddScoped<IUomService, UomService>();
 builder.Services.AddScoped<ICategoryService, CategoryService>();
@@ -97,6 +99,12 @@ builder.Services.AddScoped<IFifoCostingService, FifoCostingService>();
 builder.Services.AddScoped<IStockService, StockService>();
 builder.Services.AddScoped<IGrnService, GrnService>();
 
+// Sales (Phase 1)
+builder.Services.AddScoped<ISalesPricingService, SalesPricingService>();
+builder.Services.AddScoped<ISalesInvoiceService, SalesInvoiceService>();
+builder.Services.AddScoped<ISalesSlipService, SalesSlipService>();
+builder.Services.AddScoped<ISalesReportService, SalesReportService>();
+
 // Stock transactions + reference data (docs/11 §5–6)
 builder.Services.AddScoped<IStockMutator, StockMutator>();
 builder.Services.AddScoped<IReasonCodeService, ReasonCodeService>();

Backend/ERPCore/Services/CustomerService.cs

@@ -0,0 +1,168 @@
+using ERPCore.Common.Http;
+using ERPCore.Domain.Entities;
+using ERPCore.Domain.Enums;
+using ERPCore.Dtos.Common;
+using ERPCore.Dtos.Customers;
+using ERPCore.Infra.UoW;
+using ERPCore.Repositories.Interfaces;
+using ERPCore.Services.Interfaces;
+using ERPCore.System.Errors;
+using Microsoft.EntityFrameworkCore;
+
+namespace ERPCore.Services;
+
+public sealed class CustomerService : ICustomerService
+{
+    private readonly IRepository<Customer> _customers;
+    private readonly IRepository<Warehouse> _warehouses;
+    private readonly IUnitOfWork _uow;
+
+    public CustomerService(IRepository<Customer> customers, IRepository<Warehouse> warehouses, IUnitOfWork uow)
+    {
+        _customers = customers;
+        _warehouses = warehouses;
+        _uow = uow;
+    }
+
+    public async Task<PagedResponse<CustomerDto>> ListAsync(PageQuery query, EntityStatus? status, CustomerType? customerType, CancellationToken ct = default)
+    {
+        var q = _customers.Query().AsNoTracking();
+        if (!string.IsNullOrWhiteSpace(query.Q))
+        {
+            var term = query.Q.Trim();
+            q = q.Where(c => EF.Functions.ILike(c.Name, $"%{term}%")
+                             || EF.Functions.ILike(c.CustomerCode, $"%{term}%")
+                             || (c.DisplayName != null && EF.Functions.ILike(c.DisplayName, $"%{term}%")));
+        }
+        if (status is not null) q = q.Where(c => c.Status == status);
+        if (customerType is not null) q = q.Where(c => c.CustomerType == customerType);
+
+        var total = await q.CountAsync(ct);
+        var rows = await q.OrderBy(c => c.Name)
+            .Skip(query.Skip).Take(query.PageSize)
+            .Select(c => new CustomerDto(
+                c.CustomerId, c.CustomerCode, c.CustomerType, c.Name, c.DisplayName, c.Phone, c.Email,
+                c.AddressLine1, c.AddressLine2, c.City, c.Country, c.TaxRegistrationNo,
+                c.CreditLimit, c.CreditDays, c.DefaultWarehouseId, c.Status, c.CreatedAt, c.UpdatedAt))
+            .ToListAsync(ct);
+
+        return PagedResponse<CustomerDto>.Create(rows, query.Page, query.PageSize, total);
+    }
+
+    public async Task<ETagged<CustomerDto>?> GetAsync(int customerId, CancellationToken ct = default)
+    {
+        var customer = await _customers.Query().AsNoTracking()
+            .FirstOrDefaultAsync(c => c.CustomerId == customerId, ct);
+        return customer is null ? null : new ETagged<CustomerDto>(Map(customer), customer.RowVersion);
+    }
+
+    public async Task<ETagged<CustomerDto>> CreateAsync(CreateCustomerRequest request, CancellationToken ct = default)
+    {
+        var code = request.CustomerCode.Trim();
+        var name = request.Name.Trim();
+
+        if (await _customers.Query().AnyAsync(c => c.CustomerCode.ToLower() == code.ToLower(), ct))
+            throw new ConflictException($"A customer code '{code}' already exists.");
+
+        if (!string.IsNullOrWhiteSpace(request.Email))
+        {
+            var email = request.Email.Trim();
+            if (await _customers.Query().AnyAsync(c => c.Email != null && c.Email.ToLower() == email.ToLower(), ct))
+                throw new ConflictException($"A customer with email '{email}' already exists.");
+        }
+
+        if (request.DefaultWarehouseId is not null)
+        {
+            var exists = await _warehouses.Query().AnyAsync(w => w.WarehouseId == request.DefaultWarehouseId, ct);
+            if (!exists) throw new NotFoundException($"Warehouse {request.DefaultWarehouseId} was not found.");
+        }
+
+        var customer = new Customer
+        {
+            CustomerCode = code,
+            CustomerType = request.CustomerType,
+            Name = name,
+            DisplayName = Normalize(request.DisplayName),
+            Phone = Normalize(request.Phone),
+            Email = Normalize(request.Email),
+            AddressLine1 = Normalize(request.AddressLine1),
+            AddressLine2 = Normalize(request.AddressLine2),
+            City = Normalize(request.City),
+            Country = Normalize(request.Country),
+            TaxRegistrationNo = Normalize(request.TaxRegistrationNo),
+            CreditLimit = request.CreditLimit,
+            CreditDays = request.CreditDays,
+            DefaultWarehouseId = request.DefaultWarehouseId,
+            Status = EntityStatus.Active,
+            CreatedAt = DateTime.UtcNow
+        };
+
+        await _customers.AddAsync(customer, ct);
+        await _uow.SaveChangesAsync(ct);
+
+        return new ETagged<CustomerDto>(Map(customer), customer.RowVersion);
+    }
+
+    public async Task<ETagged<CustomerDto>> UpdateAsync(int customerId, UpdateCustomerRequest request, uint expectedRowVersion, CancellationToken ct = default)
+    {
+        var customer = await _customers.GetByIdAsync(customerId, ct)
+            ?? throw new NotFoundException($"Customer {customerId} was not found.");
+
+        if (customer.RowVersion != expectedRowVersion)
+            throw new DomainException(ErrorCodes.ConcurrencyConflict, "The customer was modified by another request.", 412);
+
+        var code = request.CustomerCode.Trim();
+        var name = request.Name.Trim();
+
+        if (!string.Equals(customer.CustomerCode, code, StringComparison.Ordinal)
+            && await _customers.Query().AnyAsync(c => c.CustomerCode.ToLower() == code.ToLower() && c.CustomerId != customerId, ct))
+            throw new ConflictException($"A customer code '{code}' already exists.");
+
+        if (!string.Equals(customer.Email, request.Email?.Trim(), StringComparison.OrdinalIgnoreCase)
+            && !string.IsNullOrWhiteSpace(request.Email)
+            && await _customers.Query().AnyAsync(c => c.Email != null && c.Email.ToLower() == request.Email!.Trim().ToLower() && c.CustomerId != customerId, ct))
+            throw new ConflictException($"A customer with email '{request.Email.Trim()}' already exists.");
+
+        if (request.DefaultWarehouseId is not null)
+        {
+            var exists = await _warehouses.Query().AnyAsync(w => w.WarehouseId == request.DefaultWarehouseId, ct);
+            if (!exists) throw new NotFoundException($"Warehouse {request.DefaultWarehouseId} was not found.");
+        }
+
+        customer.CustomerCode = code;
+        customer.CustomerType = request.CustomerType;
+        customer.Name = name;
+        customer.DisplayName = Normalize(request.DisplayName);
+        customer.Phone = Normalize(request.Phone);
+        customer.Email = Normalize(request.Email);
+        customer.AddressLine1 = Normalize(request.AddressLine1);
+        customer.AddressLine2 = Normalize(request.AddressLine2);
+        customer.City = Normalize(request.City);
+        customer.Country = Normalize(request.Country);
+        customer.TaxRegistrationNo = Normalize(request.TaxRegistrationNo);
+        customer.CreditLimit = request.CreditLimit;
+        customer.CreditDays = request.CreditDays;
+        customer.DefaultWarehouseId = request.DefaultWarehouseId;
+        customer.UpdatedAt = DateTime.UtcNow;
+
+        await _uow.SaveChangesAsync(ct);
+        return new ETagged<CustomerDto>(Map(customer), customer.RowVersion);
+    }
+
+    public async Task SetStatusAsync(int customerId, EntityStatus status, CancellationToken ct = default)
+    {
+        var customer = await _customers.GetByIdAsync(customerId, ct)
+            ?? throw new NotFoundException($"Customer {customerId} was not found.");
+
+        customer.Status = status;
+        customer.UpdatedAt = DateTime.UtcNow;
+        await _uow.SaveChangesAsync(ct);
+    }
+
+    private static CustomerDto Map(Customer c) => new(
+        c.CustomerId, c.CustomerCode, c.CustomerType, c.Name, c.DisplayName, c.Phone, c.Email,
+        c.AddressLine1, c.AddressLine2, c.City, c.Country, c.TaxRegistrationNo,
+        c.CreditLimit, c.CreditDays, c.DefaultWarehouseId, c.Status, c.CreatedAt, c.UpdatedAt);
+
+    private static string? Normalize(string? value) => string.IsNullOrWhiteSpace(value) ? null : value.Trim();
+}

Backend/ERPCore/Services/Interfaces/ICustomerService.cs

@@ -0,0 +1,15 @@
+using ERPCore.Common.Http;
+using ERPCore.Dtos.Common;
+using ERPCore.Dtos.Customers;
+using ERPCore.Domain.Enums;
+
+namespace ERPCore.Services.Interfaces;
+
+public interface ICustomerService
+{
+    Task<PagedResponse<CustomerDto>> ListAsync(PageQuery query, EntityStatus? status, CustomerType? customerType, CancellationToken ct = default);
+    Task<ETagged<CustomerDto>?> GetAsync(int customerId, CancellationToken ct = default);
+    Task<ETagged<CustomerDto>> CreateAsync(CreateCustomerRequest request, CancellationToken ct = default);
+    Task<ETagged<CustomerDto>> UpdateAsync(int customerId, UpdateCustomerRequest request, uint expectedRowVersion, CancellationToken ct = default);
+    Task SetStatusAsync(int customerId, EntityStatus status, CancellationToken ct = default);
+}

Backend/ERPCore/Services/Interfaces/ISalesInvoiceService.cs

@@ -0,0 +1,16 @@
+using ERPCore.Common.Http;
+using ERPCore.Dtos.Common;
+using ERPCore.Dtos.Sales;
+using ERPCore.Domain.Enums;
+
+namespace ERPCore.Services.Interfaces;
+
+public interface ISalesInvoiceService
+{
+    Task<PagedResponse<SalesInvoiceSummaryDto>> ListAsync(PageQuery query, SalesInvoiceStatus? status, int? customerId, int? warehouseId, CancellationToken ct = default);
+    Task<ETagged<SalesInvoiceDto>?> GetAsync(int salesInvoiceId, CancellationToken ct = default);
+    Task<ETagged<SalesInvoiceDto>> CreateAsync(CreateSalesInvoiceRequest request, CancellationToken ct = default);
+    Task<ETagged<SalesInvoiceDto>> UpdateAsync(int salesInvoiceId, UpdateSalesInvoiceRequest request, uint expectedRowVersion, CancellationToken ct = default);
+    Task<SalesInvoiceDto> PostAsync(int salesInvoiceId, CancellationToken ct = default);
+    Task<SalesInvoiceDto> CancelAsync(int salesInvoiceId, CancellationToken ct = default);
+}

Backend/ERPCore/Services/Interfaces/ISalesPricingService.cs

@@ -0,0 +1,16 @@
+namespace ERPCore.Services.Interfaces;
+
+public interface ISalesPricingService
+{
+    Task<SalesPriceResolution> ResolveAsync(
+        int itemId,
+        int warehouseId,
+        decimal? requestedUnitPrice,
+        bool allowManualOverride,
+        CancellationToken ct = default);
+}
+
+public sealed record SalesPriceResolution(
+    decimal UnitPrice,
+    string PriceSource,
+    decimal BaseCost);

Backend/ERPCore/Services/Interfaces/ISalesReportService.cs

@@ -0,0 +1,13 @@
+using ERPCore.Dtos.Sales;
+
+namespace ERPCore.Services.Interfaces;
+
+public interface ISalesReportService
+{
+    Task<IReadOnlyList<SalesDailySummaryRowDto>> DailySummaryAsync(DateOnly from, DateOnly to, CancellationToken ct = default);
+    Task<IReadOnlyList<SalesItemSummaryRowDto>> ItemSummaryAsync(DateOnly from, DateOnly to, int? itemId, int? warehouseId, CancellationToken ct = default);
+    Task<IReadOnlyList<SalesCustomerSummaryRowDto>> CustomerSummaryAsync(DateOnly from, DateOnly to, int? customerId, CancellationToken ct = default);
+    Task<IReadOnlyList<SalesWarehouseSummaryRowDto>> WarehouseSummaryAsync(DateOnly from, DateOnly to, int? warehouseId, CancellationToken ct = default);
+    Task<IReadOnlyList<SalesDiscountSummaryRowDto>> DiscountSummaryAsync(DateOnly from, DateOnly to, CancellationToken ct = default);
+    Task<IReadOnlyList<SalesFreeIssueSummaryRowDto>> FreeIssueSummaryAsync(DateOnly from, DateOnly to, CancellationToken ct = default);
+}

Backend/ERPCore/Services/Interfaces/ISalesSlipService.cs

@@ -0,0 +1,16 @@
+using ERPCore.Common.Http;
+using ERPCore.Dtos.Common;
+using ERPCore.Dtos.Sales;
+using ERPCore.Domain.Enums;
+
+namespace ERPCore.Services.Interfaces;
+
+public interface ISalesSlipService
+{
+    Task<PagedResponse<SalesSlipSummaryDto>> ListAsync(PageQuery query, SalesSlipStatus? status, int? customerId, int? warehouseId, CancellationToken ct = default);
+    Task<ETagged<SalesSlipDto>?> GetAsync(int salesSlipId, CancellationToken ct = default);
+    Task<ETagged<SalesSlipDto>> CreateAsync(CreateSalesSlipRequest request, CancellationToken ct = default);
+    Task<ETagged<SalesSlipDto>> UpdateAsync(int salesSlipId, UpdateSalesSlipRequest request, uint expectedRowVersion, CancellationToken ct = default);
+    Task<SalesSlipDto> PostAsync(int salesSlipId, CancellationToken ct = default);
+    Task<SalesSlipDto> CancelAsync(int salesSlipId, CancellationToken ct = default);
+}

Backend/ERPCore/Services/SalesInvoiceService.cs

@@ -0,0 +1,251 @@
+using ERPCore.Common.Http;
+using ERPCore.Domain;
+using ERPCore.Domain.Entities;
+using ERPCore.Domain.Enums;
+using ERPCore.Dtos.Common;
+using ERPCore.Dtos.Sales;
+using ERPCore.Infra.Auth;
+using ERPCore.Infra.UoW;
+using ERPCore.Repositories.Interfaces;
+using ERPCore.Services.Interfaces;
+using ERPCore.Services.Stock;
+using ERPCore.System.Errors;
+using Microsoft.EntityFrameworkCore;
+
+namespace ERPCore.Services;
+
+public sealed class SalesInvoiceService : ISalesInvoiceService
+{
+    private readonly IRepository<SalesInvoice> _invoices;
+    private readonly IRepository<Customer> _customers;
+    private readonly IRepository<Item> _items;
+    private readonly IRepository<Uom> _uoms;
+    private readonly IRepository<Warehouse> _warehouses;
+    private readonly ISalesPricingService _pricing;
+    private readonly IFifoCostingService _fifo;
+    private readonly ICurrentUser _currentUser;
+    private readonly INumberSequenceService _numbers;
+    private readonly IUnitOfWork _uow;
+
+    public SalesInvoiceService(
+        IRepository<SalesInvoice> invoices, IRepository<Customer> customers, IRepository<Item> items,
+        IRepository<Uom> uoms, IRepository<Warehouse> warehouses, ISalesPricingService pricing, IFifoCostingService fifo,
+        ICurrentUser currentUser, INumberSequenceService numbers, IUnitOfWork uow)
+    {
+        _invoices = invoices;
+        _customers = customers;
+        _items = items;
+        _uoms = uoms;
+        _warehouses = warehouses;
+        _pricing = pricing;
+        _fifo = fifo;
+        _currentUser = currentUser;
+        _numbers = numbers;
+        _uow = uow;
+    }
+
+    public async Task<PagedResponse<SalesInvoiceSummaryDto>> ListAsync(PageQuery query, SalesInvoiceStatus? status, int? customerId, int? warehouseId, CancellationToken ct = default)
+    {
+        IQueryable<SalesInvoice> q = _invoices.Query().AsNoTracking().Include(x => x.Lines);
+        if (!string.IsNullOrWhiteSpace(query.Q))
+        {
+            var term = query.Q.Trim();
+            q = q.Where(x => EF.Functions.ILike(x.InvoiceNo, $"%{term}%") || EF.Functions.ILike(x.CustomerSnapshotName, $"%{term}%"));
+        }
+        if (status is not null) q = q.Where(x => x.Status == status);
+        if (customerId is not null) q = q.Where(x => x.CustomerId == customerId);
+        if (warehouseId is not null) q = q.Where(x => x.WarehouseId == warehouseId);
+
+        var total = await q.CountAsync(ct);
+        var rows = await q.OrderByDescending(x => x.SalesInvoiceId).Skip(query.Skip).Take(query.PageSize).ToListAsync(ct);
+
+        return PagedResponse<SalesInvoiceSummaryDto>.Create(rows.Select(MapSummary).ToList(), query.Page, query.PageSize, total);
+    }
+
+    public async Task<ETagged<SalesInvoiceDto>?> GetAsync(int salesInvoiceId, CancellationToken ct = default)
+    {
+        var invoice = await _invoices.Query().AsNoTracking().Include(x => x.Lines)
+            .FirstOrDefaultAsync(x => x.SalesInvoiceId == salesInvoiceId, ct);
+        return invoice is null ? null : new ETagged<SalesInvoiceDto>(Map(invoice), invoice.RowVersion);
+    }
+
+    public async Task<ETagged<SalesInvoiceDto>> CreateAsync(CreateSalesInvoiceRequest request, CancellationToken ct = default)
+    {
+        await ValidateReferencesAsync(request.CustomerId, request.WarehouseId, request.Lines, ct);
+        var invoice = new SalesInvoice
+        {
+            InvoiceNo = await _numbers.NextAsync(DocumentTypes.SalesInvoice, ct),
+            InvoiceDate = DateTime.UtcNow,
+            CustomerId = request.CustomerId,
+            WarehouseId = request.WarehouseId,
+            InvoiceType = request.InvoiceType,
+            Status = SalesInvoiceStatus.Draft,
+            CreatedBy = _currentUser.AuditUserId,
+            CreatedAt = DateTime.UtcNow
+        };
+        invoice.CustomerSnapshotName = await _customers.Query().Where(x => x.CustomerId == request.CustomerId).Select(x => x.DisplayName ?? x.Name).FirstAsync(ct);
+        invoice.CustomerSnapshotTaxNo = await _customers.Query().Where(x => x.CustomerId == request.CustomerId).Select(x => x.TaxRegistrationNo).FirstAsync(ct);
+        invoice.Lines = await BuildLinesAsync(request.Lines, ct);
+        Recalculate(invoice);
+
+        await _invoices.AddAsync(invoice, ct);
+        await _uow.SaveChangesAsync(ct);
+        return new ETagged<SalesInvoiceDto>(Map(invoice), invoice.RowVersion);
+    }
+
+    public async Task<ETagged<SalesInvoiceDto>> UpdateAsync(int salesInvoiceId, UpdateSalesInvoiceRequest request, uint expectedRowVersion, CancellationToken ct = default)
+    {
+        var invoice = await _invoices.Query().Include(x => x.Lines).FirstOrDefaultAsync(x => x.SalesInvoiceId == salesInvoiceId, ct)
+            ?? throw new NotFoundException($"Sales invoice {salesInvoiceId} was not found.");
+        if (invoice.RowVersion != expectedRowVersion)
+            throw new DomainException(ErrorCodes.ConcurrencyConflict, "The sales invoice was modified by another request.", 412);
+        if (invoice.Status != SalesInvoiceStatus.Draft)
+            throw new ConflictException($"Sales invoice {salesInvoiceId} is {invoice.Status} and cannot be edited.");
+
+        await ValidateReferencesAsync(request.CustomerId, request.WarehouseId, request.Lines, ct);
+        invoice.CustomerId = request.CustomerId;
+        invoice.WarehouseId = request.WarehouseId;
+        invoice.InvoiceType = request.InvoiceType;
+        invoice.CustomerSnapshotName = await _customers.Query().Where(x => x.CustomerId == request.CustomerId).Select(x => x.DisplayName ?? x.Name).FirstAsync(ct);
+        invoice.CustomerSnapshotTaxNo = await _customers.Query().Where(x => x.CustomerId == request.CustomerId).Select(x => x.TaxRegistrationNo).FirstAsync(ct);
+        invoice.Lines.Clear();
+        foreach (var line in await BuildLinesAsync(request.Lines, ct)) invoice.Lines.Add(line);
+        Recalculate(invoice);
+        invoice.UpdatedAt = DateTime.UtcNow;
+        await _uow.SaveChangesAsync(ct);
+        return new ETagged<SalesInvoiceDto>(Map(invoice), invoice.RowVersion);
+    }
+
+    public async Task<SalesInvoiceDto> PostAsync(int salesInvoiceId, CancellationToken ct = default)
+    {
+        var invoice = await _invoices.Query().Include(x => x.Lines).FirstOrDefaultAsync(x => x.SalesInvoiceId == salesInvoiceId, ct)
+            ?? throw new NotFoundException($"Sales invoice {salesInvoiceId} was not found.");
+        if (invoice.Status != SalesInvoiceStatus.Draft)
+            throw new ConflictException($"Sales invoice {salesInvoiceId} is {invoice.Status} and cannot be posted.");
+
+        var posted = await _uow.ExecuteInTransactionAsync(async token =>
+        {
+            foreach (var line in invoice.Lines)
+            {
+                if (line.Qty <= 0) continue;
+                var consumed = await _fifo.ConsumeAsync(line.ItemId, line.WarehouseId, null, line.Qty + line.FreeQty, token);
+                var cost = consumed.Count == 0 ? 0m : consumed.Sum(x => x.Qty * x.UnitCost) / consumed.Sum(x => x.Qty);
+                await _fifo.PostLedgerAsync(line.ItemId, line.WarehouseId, null, null, null, _currentUser.AuditUserId,
+                    Direction.Out, line.Qty + line.FreeQty, cost, 0m, nameof(SalesInvoice), invoice.SalesInvoiceId, DateTime.UtcNow, token);
+            }
+
+            invoice.Status = SalesInvoiceStatus.Posted;
+            invoice.UpdatedAt = DateTime.UtcNow;
+            return invoice;
+        }, ct);
+
+        return Map(posted);
+    }
+
+    public async Task<SalesInvoiceDto> CancelAsync(int salesInvoiceId, CancellationToken ct = default)
+    {
+        var invoice = await _invoices.Query().Include(x => x.Lines).FirstOrDefaultAsync(x => x.SalesInvoiceId == salesInvoiceId, ct)
+            ?? throw new NotFoundException($"Sales invoice {salesInvoiceId} was not found.");
+        if (invoice.Status != SalesInvoiceStatus.Draft)
+            throw new ConflictException($"Sales invoice {salesInvoiceId} is {invoice.Status} and cannot be cancelled.");
+        invoice.Status = SalesInvoiceStatus.Cancelled;
+        invoice.UpdatedAt = DateTime.UtcNow;
+        await _uow.SaveChangesAsync(ct);
+        return Map(invoice);
+    }
+
+    private async Task ValidateReferencesAsync(int customerId, int warehouseId, List<CreateSalesInvoiceLineRequest> lines, CancellationToken ct)
+    {
+        if (!await _customers.Query().AnyAsync(x => x.CustomerId == customerId, ct))
+            throw new NotFoundException($"Customer {customerId} was not found.");
+        if (!await _warehouses.Query().AnyAsync(x => x.WarehouseId == warehouseId, ct))
+            throw new NotFoundException($"Warehouse {warehouseId} was not found.");
+        foreach (var line in lines)
+        {
+            if (!await _items.Query().AnyAsync(x => x.ItemId == line.ItemId, ct))
+                throw new NotFoundException($"Item {line.ItemId} was not found.");
+            if (!await _uoms.Query().AnyAsync(x => x.UomId == line.UomId, ct))
+                throw new NotFoundException($"UOM {line.UomId} was not found.");
+            if (!await _warehouses.Query().AnyAsync(x => x.WarehouseId == line.WarehouseId, ct))
+                throw new NotFoundException($"Warehouse {line.WarehouseId} was not found.");
+        }
+    }
+
+    private async Task<List<SalesInvoiceLine>> BuildLinesAsync(List<CreateSalesInvoiceLineRequest> requests, CancellationToken ct)
+    {
+        var lines = new List<SalesInvoiceLine>();
+        foreach (var r in requests)
+        {
+            var item = await _items.Query().AsNoTracking().FirstAsync(x => x.ItemId == r.ItemId, ct);
+            var resolved = await _pricing.ResolveAsync(r.ItemId, r.WarehouseId, r.UnitPrice, r.AllowManualPriceOverride, ct);
+            var unitPrice = resolved.UnitPrice;
+            var priceSource = resolved.PriceSource;
+
+            var gross = r.Qty * unitPrice;
+            var discountTotal = r.IsFreeIssue
+                ? 0m
+                : CalculateDiscount(gross, r.DiscountMode, r.DiscountPct, r.DiscountValue, r.DiscountAmount);
+            var netUnit = r.Qty > 0 ? (gross - discountTotal) / r.Qty : 0m;
+            var lineTotal = gross - discountTotal;
+            var taxAmount = lineTotal * (r.TaxPct / 100m);
+
+            lines.Add(new SalesInvoiceLine
+            {
+                ItemId = r.ItemId,
+                Description = item.Name,
+                Qty = r.Qty,
+                FreeQty = r.FreeQty,
+                UomId = r.UomId,
+                WarehouseId = r.WarehouseId,
+                UnitPrice = unitPrice,
+                BaseCost = unitPrice,
+                PriceSource = priceSource,
+                DiscountPct = r.DiscountPct,
+                DiscountAmount = discountTotal,
+                DiscountMode = r.DiscountMode,
+                NetUnitPrice = netUnit,
+                LineTotal = lineTotal,
+                TaxPct = r.TaxPct,
+                TaxAmount = taxAmount,
+                IsFreeIssue = r.IsFreeIssue,
+                ParentLineId = r.ParentLineId
+            });
+        }
+        return lines;
+    }
+
+    private static void Recalculate(SalesInvoice invoice)
+    {
+        invoice.Subtotal = invoice.Lines.Sum(x => x.Qty * x.UnitPrice);
+        invoice.DiscountTotal = invoice.Lines.Sum(x => x.DiscountAmount);
+        invoice.TaxTotal = invoice.Lines.Sum(x => x.TaxAmount);
+        invoice.GrandTotal = invoice.Lines.Sum(x => x.LineTotal) + invoice.TaxTotal;
+        invoice.RoundOff = 0m;
+        invoice.NetPayable = invoice.GrandTotal + invoice.RoundOff;
+        invoice.PaidAmount = 0m;
+        invoice.BalanceAmount = invoice.NetPayable;
+    }
+
+    private static decimal CalculateDiscount(decimal gross, SalesDiscountMode mode, decimal discountPct, decimal discountValue, decimal legacyDiscountAmount)
+    {
+        var computed = mode == SalesDiscountMode.FixedAmount
+            ? discountValue
+            : gross * (discountPct / 100m);
+
+        if (computed <= 0m && legacyDiscountAmount > 0m)
+            computed = legacyDiscountAmount;
+
+        return Math.Min(gross, Math.Max(0m, computed));
+    }
+
+    private static SalesInvoiceSummaryDto MapSummary(SalesInvoice x) => new(
+        x.SalesInvoiceId, x.InvoiceNo, x.InvoiceDate, x.CustomerId, x.CustomerSnapshotName,
+        x.WarehouseId, x.InvoiceType, x.Status, new SalesInvoiceTotalsDto(
+            x.Subtotal, x.DiscountTotal, x.Lines.Sum(l => l.FreeQty), x.TaxTotal, x.GrandTotal, x.RoundOff, x.NetPayable, x.PaidAmount, x.BalanceAmount), x.CreatedAt);
+
+    private static SalesInvoiceDto Map(SalesInvoice x) => new(
+        x.SalesInvoiceId, x.InvoiceNo, x.InvoiceDate, x.CustomerId, x.CustomerSnapshotName, x.CustomerSnapshotTaxNo,
+        x.WarehouseId, x.InvoiceType, x.Status, x.CreatedBy, x.CreatedAt, x.UpdatedAt,
+        new SalesInvoiceTotalsDto(x.Subtotal, x.DiscountTotal, x.Lines.Sum(l => l.FreeQty), x.TaxTotal, x.GrandTotal, x.RoundOff, x.NetPayable, x.PaidAmount, x.BalanceAmount),
+        x.Lines.Select(l => new SalesInvoiceLineDto(l.SalesInvoiceLineId, l.ItemId, l.Description, l.Qty, l.FreeQty, l.UomId, l.WarehouseId, l.UnitPrice, l.BaseCost, l.PriceSource, l.DiscountPct, l.DiscountAmount, l.DiscountMode, l.NetUnitPrice, l.LineTotal, l.TaxPct, l.TaxAmount, l.IsFreeIssue, l.ParentLineId)).ToList());
+}

Backend/ERPCore/Services/SalesPricingService.cs

@@ -0,0 +1,79 @@
+using ERPCore.Domain;
+using ERPCore.Domain.Entities;
+using ERPCore.Domain.Enums;
+using ERPCore.Repositories.Interfaces;
+using ERPCore.Services.Interfaces;
+using ERPCore.Services.Stock;
+using Microsoft.EntityFrameworkCore;
+
+namespace ERPCore.Services;
+
+public sealed class SalesPricingService : ISalesPricingService
+{
+    private readonly IRepository<Item> _items;
+    private readonly IRepository<GrnLine> _grnLines;
+    private readonly IFifoCostingService _fifo;
+
+    public SalesPricingService(IRepository<Item> items, IRepository<GrnLine> grnLines, IFifoCostingService fifo)
+    {
+        _items = items;
+        _grnLines = grnLines;
+        _fifo = fifo;
+    }
+
+    public async Task<SalesPriceResolution> ResolveAsync(
+        int itemId, int warehouseId, decimal? requestedUnitPrice, bool allowManualOverride, CancellationToken ct = default)
+    {
+        var item = await _items.Query().AsNoTracking().FirstOrDefaultAsync(x => x.ItemId == itemId, ct)
+            ?? throw new InvalidOperationException($"Item {itemId} was not found.");
+
+        if (requestedUnitPrice is not null)
+        {
+            if (!allowManualOverride)
+            {
+                if (item.SalePrice.HasValue)
+                    return new SalesPriceResolution(item.SalePrice.Value, "SALE_PRICE", item.SalePrice.Value);
+
+                var grnPrice = await GetWeightedGrnPriceAsync(itemId, warehouseId, ct);
+                if (grnPrice is not null)
+                    return new SalesPriceResolution(grnPrice.Value, "GRN_WEIGHTED_AVG", grnPrice.Value);
+
+                return new SalesPriceResolution(await GetFifoFallbackPriceAsync(itemId, warehouseId, ct), "FIFO_AVG", 0m);
+            }
+
+            return new SalesPriceResolution(requestedUnitPrice.Value, "MANUAL", requestedUnitPrice.Value);
+        }
+
+        if (item.SalePrice.HasValue)
+            return new SalesPriceResolution(item.SalePrice.Value, "SALE_PRICE", item.SalePrice.Value);
+
+        var weighted = await GetWeightedGrnPriceAsync(itemId, warehouseId, ct);
+        if (weighted is not null)
+            return new SalesPriceResolution(weighted.Value, "GRN_WEIGHTED_AVG", weighted.Value);
+
+        return new SalesPriceResolution(await GetFifoFallbackPriceAsync(itemId, warehouseId, ct), "FIFO_AVG", 0m);
+    }
+
+    private async Task<decimal?> GetWeightedGrnPriceAsync(int itemId, int warehouseId, CancellationToken ct)
+    {
+        var rows = await _grnLines.Query().AsNoTracking()
+            .Where(l => l.ItemId == itemId
+                        && l.Grn != null
+                        && l.Grn.WarehouseId == warehouseId
+                        && l.Grn.Status == GrnStatus.Confirmed)
+            .Select(l => new { l.Qty, l.ReceivedValue })
+            .ToListAsync(ct);
+
+        var totalQty = rows.Sum(x => x.Qty);
+        if (totalQty <= 0) return null;
+
+        var totalValue = rows.Sum(x => x.ReceivedValue);
+        return totalValue / totalQty;
+    }
+
+    private async Task<decimal> GetFifoFallbackPriceAsync(int itemId, int warehouseId, CancellationToken ct)
+    {
+        var valuation = await _fifo.GetValuationAsync(itemId, warehouseId, ct);
+        return valuation.TotalQty > 0 ? valuation.TotalValue / valuation.TotalQty : 0m;
+    }
+}

Backend/ERPCore/Services/SalesReportService.cs

@@ -0,0 +1,297 @@
+using ERPCore.Domain.Entities;
+using ERPCore.Domain.Enums;
+using ERPCore.Dtos.Sales;
+using ERPCore.Repositories.Interfaces;
+using ERPCore.Services.Interfaces;
+using Microsoft.EntityFrameworkCore;
+
+namespace ERPCore.Services;
+
+public sealed class SalesReportService : ISalesReportService
+{
+    private readonly IRepository<SalesInvoice> _invoices;
+    private readonly IRepository<SalesSlip> _slips;
+
+    public SalesReportService(IRepository<SalesInvoice> invoices, IRepository<SalesSlip> slips)
+    {
+        _invoices = invoices;
+        _slips = slips;
+    }
+
+    public async Task<IReadOnlyList<SalesDailySummaryRowDto>> DailySummaryAsync(DateOnly from, DateOnly to, CancellationToken ct = default)
+    {
+        var invoiceRows = await _invoices.Query().AsNoTracking()
+            .Where(x => x.Status == SalesInvoiceStatus.Posted && x.InvoiceDate >= from.ToDateTime(TimeOnly.MinValue) && x.InvoiceDate < to.AddDays(1).ToDateTime(TimeOnly.MinValue))
+            .GroupBy(x => DateOnly.FromDateTime(x.InvoiceDate))
+            .Select(g => new
+            {
+                Date = g.Key,
+                InvoiceCount = g.Count(),
+                SlipCount = 0,
+                InvoiceSubtotal = g.Sum(x => x.Subtotal),
+                SlipSubtotal = 0m,
+                DiscountTotal = g.Sum(x => x.DiscountTotal),
+                FreeQtyTotal = g.Sum(x => x.Lines.Sum(l => l.FreeQty)),
+                TaxTotal = g.Sum(x => x.TaxTotal),
+                GrandTotal = g.Sum(x => x.GrandTotal)
+            })
+            .ToListAsync(ct);
+
+        var slipRows = await _slips.Query().AsNoTracking()
+            .Where(x => x.Status == SalesSlipStatus.Posted && x.SlipDate >= from.ToDateTime(TimeOnly.MinValue) && x.SlipDate < to.AddDays(1).ToDateTime(TimeOnly.MinValue))
+            .GroupBy(x => DateOnly.FromDateTime(x.SlipDate))
+            .Select(g => new
+            {
+                Date = g.Key,
+                InvoiceCount = 0,
+                SlipCount = g.Count(),
+                InvoiceSubtotal = 0m,
+                SlipSubtotal = g.Sum(x => x.Subtotal),
+                DiscountTotal = g.Sum(x => x.DiscountTotal),
+                FreeQtyTotal = g.Sum(x => x.Lines.Sum(l => l.FreeQty)),
+                TaxTotal = g.Sum(x => x.TaxTotal),
+                GrandTotal = g.Sum(x => x.GrandTotal)
+            })
+            .ToListAsync(ct);
+
+        return invoiceRows.Concat(slipRows)
+            .GroupBy(x => x.Date)
+            .OrderBy(x => x.Key)
+            .Select(g => new SalesDailySummaryRowDto(
+                g.Key,
+                g.Sum(x => x.InvoiceCount),
+                g.Sum(x => x.SlipCount),
+                g.Sum(x => x.InvoiceSubtotal),
+                g.Sum(x => x.SlipSubtotal),
+                g.Sum(x => x.DiscountTotal),
+                g.Sum(x => x.FreeQtyTotal),
+                g.Sum(x => x.TaxTotal),
+                g.Sum(x => x.GrandTotal)))
+            .ToList();
+    }
+
+    public async Task<IReadOnlyList<SalesItemSummaryRowDto>> ItemSummaryAsync(DateOnly from, DateOnly to, int? itemId, int? warehouseId, CancellationToken ct = default)
+    {
+        var invoiceLines = _invoices.Query().AsNoTracking()
+            .Where(x => x.Status == SalesInvoiceStatus.Posted && x.InvoiceDate >= from.ToDateTime(TimeOnly.MinValue) && x.InvoiceDate < to.AddDays(1).ToDateTime(TimeOnly.MinValue));
+        if (warehouseId is not null) invoiceLines = invoiceLines.Where(x => x.WarehouseId == warehouseId);
+        var invoiceQuery = invoiceLines.SelectMany(x => x.Lines.Select(l => new
+        {
+            l.ItemId,
+            l.Description,
+            l.Qty,
+            l.FreeQty,
+            Gross = l.Qty * l.UnitPrice,
+            l.DiscountAmount,
+            l.TaxAmount,
+            l.LineTotal,
+            l.WarehouseId
+        }));
+        if (itemId is not null) invoiceQuery = invoiceQuery.Where(x => x.ItemId == itemId);
+
+        var slipLines = _slips.Query().AsNoTracking()
+            .Where(x => x.Status == SalesSlipStatus.Posted && x.SlipDate >= from.ToDateTime(TimeOnly.MinValue) && x.SlipDate < to.AddDays(1).ToDateTime(TimeOnly.MinValue));
+        if (warehouseId is not null) slipLines = slipLines.Where(x => x.WarehouseId == warehouseId);
+        var slipQuery = slipLines.SelectMany(x => x.Lines.Select(l => new
+        {
+            l.ItemId,
+            l.Description,
+            l.Qty,
+            l.FreeQty,
+            Gross = l.Qty * l.UnitPrice,
+            l.DiscountAmount,
+            l.TaxAmount,
+            l.LineTotal,
+            l.WarehouseId
+        }));
+        if (itemId is not null) slipQuery = slipQuery.Where(x => x.ItemId == itemId);
+
+        var rows = await invoiceQuery.Concat(slipQuery)
+            .GroupBy(x => new { x.ItemId, x.Description })
+            .Select(g => new SalesItemSummaryRowDto(
+                g.Key.ItemId,
+                g.Key.Description,
+                g.Sum(x => x.Qty),
+                g.Sum(x => x.FreeQty),
+                g.Sum(x => x.Gross),
+                g.Sum(x => x.DiscountAmount),
+                g.Sum(x => x.TaxAmount),
+                g.Sum(x => x.LineTotal + x.TaxAmount)))
+            .OrderByDescending(x => x.NetAmount)
+            .ToListAsync(ct);
+
+        return rows;
+    }
+
+    public async Task<IReadOnlyList<SalesCustomerSummaryRowDto>> CustomerSummaryAsync(DateOnly from, DateOnly to, int? customerId, CancellationToken ct = default)
+    {
+        var invoiceQuery = _invoices.Query().AsNoTracking()
+            .Where(x => x.Status == SalesInvoiceStatus.Posted && x.InvoiceDate >= from.ToDateTime(TimeOnly.MinValue) && x.InvoiceDate < to.AddDays(1).ToDateTime(TimeOnly.MinValue));
+        if (customerId is not null) invoiceQuery = invoiceQuery.Where(x => x.CustomerId == customerId);
+
+        var slipQuery = _slips.Query().AsNoTracking()
+            .Where(x => x.Status == SalesSlipStatus.Posted && x.SlipDate >= from.ToDateTime(TimeOnly.MinValue) && x.SlipDate < to.AddDays(1).ToDateTime(TimeOnly.MinValue));
+        if (customerId is not null) slipQuery = slipQuery.Where(x => x.CustomerId == customerId);
+
+        var invoiceRows = await invoiceQuery
+            .GroupBy(x => new { x.CustomerId, x.CustomerSnapshotName })
+            .Select(g => new
+            {
+                g.Key.CustomerId,
+                CustomerName = g.Key.CustomerSnapshotName,
+                InvoiceCount = g.Count(),
+                SlipCount = 0,
+                SoldQty = g.Sum(x => x.Lines.Sum(l => l.Qty)),
+                FreeQty = g.Sum(x => x.Lines.Sum(l => l.FreeQty)),
+                GrossAmount = g.Sum(x => x.Subtotal),
+                DiscountTotal = g.Sum(x => x.DiscountTotal),
+                TaxTotal = g.Sum(x => x.TaxTotal),
+                NetAmount = g.Sum(x => x.GrandTotal)
+            })
+            .ToListAsync(ct);
+
+        var slipRows = await slipQuery
+            .GroupBy(x => new { x.CustomerId, x.CustomerSnapshotName })
+            .Select(g => new
+            {
+                g.Key.CustomerId,
+                CustomerName = g.Key.CustomerSnapshotName,
+                InvoiceCount = 0,
+                SlipCount = g.Count(),
+                SoldQty = g.Sum(x => x.Lines.Sum(l => l.Qty)),
+                FreeQty = g.Sum(x => x.Lines.Sum(l => l.FreeQty)),
+                GrossAmount = g.Sum(x => x.Subtotal),
+                DiscountTotal = g.Sum(x => x.DiscountTotal),
+                TaxTotal = g.Sum(x => x.TaxTotal),
+                NetAmount = g.Sum(x => x.GrandTotal)
+            })
+            .ToListAsync(ct);
+
+        return invoiceRows.Concat(slipRows)
+            .GroupBy(x => new { x.CustomerId, x.CustomerName })
+            .OrderByDescending(g => g.Sum(x => x.NetAmount))
+            .Select(g => new SalesCustomerSummaryRowDto(
+                g.Key.CustomerId,
+                g.Key.CustomerName,
+                g.Sum(x => x.InvoiceCount),
+                g.Sum(x => x.SlipCount),
+                g.Sum(x => x.SoldQty),
+                g.Sum(x => x.FreeQty),
+                g.Sum(x => x.GrossAmount),
+                g.Sum(x => x.DiscountTotal),
+                g.Sum(x => x.TaxTotal),
+                g.Sum(x => x.NetAmount)))
+            .ToList();
+    }
+
+    public async Task<IReadOnlyList<SalesWarehouseSummaryRowDto>> WarehouseSummaryAsync(DateOnly from, DateOnly to, int? warehouseId, CancellationToken ct = default)
+    {
+        var invoiceQuery = _invoices.Query().AsNoTracking()
+            .Where(x => x.Status == SalesInvoiceStatus.Posted && x.InvoiceDate >= from.ToDateTime(TimeOnly.MinValue) && x.InvoiceDate < to.AddDays(1).ToDateTime(TimeOnly.MinValue));
+        if (warehouseId is not null) invoiceQuery = invoiceQuery.Where(x => x.WarehouseId == warehouseId);
+
+        var slipQuery = _slips.Query().AsNoTracking()
+            .Where(x => x.Status == SalesSlipStatus.Posted && x.SlipDate >= from.ToDateTime(TimeOnly.MinValue) && x.SlipDate < to.AddDays(1).ToDateTime(TimeOnly.MinValue));
+        if (warehouseId is not null) slipQuery = slipQuery.Where(x => x.WarehouseId == warehouseId);
+
+        var invoiceRows = await invoiceQuery
+            .GroupBy(x => new { x.WarehouseId, x.Warehouse!.Name })
+            .Select(g => new
+            {
+                g.Key.WarehouseId,
+                WarehouseName = g.Key.Name,
+                InvoiceCount = g.Count(),
+                SlipCount = 0,
+                SoldQty = g.Sum(x => x.Lines.Sum(l => l.Qty)),
+                FreeQty = g.Sum(x => x.Lines.Sum(l => l.FreeQty)),
+                GrossAmount = g.Sum(x => x.Subtotal),
+                DiscountTotal = g.Sum(x => x.DiscountTotal),
+                TaxTotal = g.Sum(x => x.TaxTotal),
+                NetAmount = g.Sum(x => x.GrandTotal)
+            })
+            .ToListAsync(ct);
+
+        var slipRows = await slipQuery
+            .GroupBy(x => new { x.WarehouseId, x.Warehouse!.Name })
+            .Select(g => new
+            {
+                g.Key.WarehouseId,
+                WarehouseName = g.Key.Name,
+                InvoiceCount = 0,
+                SlipCount = g.Count(),
+                SoldQty = g.Sum(x => x.Lines.Sum(l => l.Qty)),
+                FreeQty = g.Sum(x => x.Lines.Sum(l => l.FreeQty)),
+                GrossAmount = g.Sum(x => x.Subtotal),
+                DiscountTotal = g.Sum(x => x.DiscountTotal),
+                TaxTotal = g.Sum(x => x.TaxTotal),
+                NetAmount = g.Sum(x => x.GrandTotal)
+            })
+            .ToListAsync(ct);
+
+        return invoiceRows.Concat(slipRows)
+            .GroupBy(x => new { x.WarehouseId, x.WarehouseName })
+            .OrderByDescending(g => g.Sum(x => x.NetAmount))
+            .Select(g => new SalesWarehouseSummaryRowDto(
+                g.Key.WarehouseId,
+                g.Key.WarehouseName,
+                g.Sum(x => x.InvoiceCount),
+                g.Sum(x => x.SlipCount),
+                g.Sum(x => x.SoldQty),
+                g.Sum(x => x.FreeQty),
+                g.Sum(x => x.GrossAmount),
+                g.Sum(x => x.DiscountTotal),
+                g.Sum(x => x.TaxTotal),
+                g.Sum(x => x.NetAmount)))
+            .ToList();
+    }
+
+    public async Task<IReadOnlyList<SalesDiscountSummaryRowDto>> DiscountSummaryAsync(DateOnly from, DateOnly to, CancellationToken ct = default)
+    {
+        var invoices = await _invoices.Query().AsNoTracking()
+            .Where(x => x.Status == SalesInvoiceStatus.Posted && x.InvoiceDate >= from.ToDateTime(TimeOnly.MinValue) && x.InvoiceDate < to.AddDays(1).ToDateTime(TimeOnly.MinValue) && x.DiscountTotal > 0m)
+            .Select(x => new SalesDiscountSummaryRowDto("Invoice", x.InvoiceNo, x.InvoiceDate, x.CustomerSnapshotName, x.Subtotal, x.DiscountTotal, x.TaxTotal, x.GrandTotal))
+            .ToListAsync(ct);
+
+        var slips = await _slips.Query().AsNoTracking()
+            .Where(x => x.Status == SalesSlipStatus.Posted && x.SlipDate >= from.ToDateTime(TimeOnly.MinValue) && x.SlipDate < to.AddDays(1).ToDateTime(TimeOnly.MinValue) && x.DiscountTotal > 0m)
+            .Select(x => new SalesDiscountSummaryRowDto("Slip", x.SlipNo, x.SlipDate, x.CustomerSnapshotName, x.Subtotal, x.DiscountTotal, x.TaxTotal, x.GrandTotal))
+            .ToListAsync(ct);
+
+        return invoices.Concat(slips).OrderByDescending(x => x.DiscountTotal).ToList();
+    }
+
+    public async Task<IReadOnlyList<SalesFreeIssueSummaryRowDto>> FreeIssueSummaryAsync(DateOnly from, DateOnly to, CancellationToken ct = default)
+    {
+        var invoiceRows = await _invoices.Query().AsNoTracking()
+            .Where(x => x.Status == SalesInvoiceStatus.Posted && x.InvoiceDate >= from.ToDateTime(TimeOnly.MinValue) && x.InvoiceDate < to.AddDays(1).ToDateTime(TimeOnly.MinValue))
+            .SelectMany(x => x.Lines.Where(l => l.FreeQty > 0m).Select(l => new SalesFreeIssueSummaryRowDto(
+                "Invoice",
+                x.InvoiceNo,
+                x.InvoiceDate,
+                x.CustomerSnapshotName,
+                l.ItemId,
+                l.Description,
+                l.FreeQty,
+                l.FreeQty * l.UnitPrice,
+                l.WarehouseId,
+                x.Warehouse!.Name)))
+            .ToListAsync(ct);
+
+        var slipRows = await _slips.Query().AsNoTracking()
+            .Where(x => x.Status == SalesSlipStatus.Posted && x.SlipDate >= from.ToDateTime(TimeOnly.MinValue) && x.SlipDate < to.AddDays(1).ToDateTime(TimeOnly.MinValue))
+            .SelectMany(x => x.Lines.Where(l => l.FreeQty > 0m).Select(l => new SalesFreeIssueSummaryRowDto(
+                "Slip",
+                x.SlipNo,
+                x.SlipDate,
+                x.CustomerSnapshotName,
+                l.ItemId,
+                l.Description,
+                l.FreeQty,
+                l.FreeQty * l.UnitPrice,
+                l.WarehouseId,
+                x.Warehouse!.Name)))
+            .ToListAsync(ct);
+
+        return invoiceRows.Concat(slipRows).OrderByDescending(x => x.FreeQty).ToList();
+    }
+}

Backend/ERPCore/Services/SalesSlipService.cs

@@ -0,0 +1,248 @@
+using ERPCore.Common.Http;
+using ERPCore.Domain;
+using ERPCore.Domain.Entities;
+using ERPCore.Domain.Enums;
+using ERPCore.Dtos.Common;
+using ERPCore.Dtos.Sales;
+using ERPCore.Infra.Auth;
+using ERPCore.Infra.UoW;
+using ERPCore.Repositories.Interfaces;
+using ERPCore.Services.Interfaces;
+using ERPCore.Services.Stock;
+using ERPCore.System.Errors;
+using Microsoft.EntityFrameworkCore;
+
+namespace ERPCore.Services;
+
+public sealed class SalesSlipService : ISalesSlipService
+{
+    private readonly IRepository<SalesSlip> _slips;
+    private readonly IRepository<Customer> _customers;
+    private readonly IRepository<Item> _items;
+    private readonly IRepository<Uom> _uoms;
+    private readonly IRepository<Warehouse> _warehouses;
+    private readonly IRepository<User> _users;
+    private readonly ISalesPricingService _pricing;
+    private readonly IFifoCostingService _fifo;
+    private readonly ICurrentUser _currentUser;
+    private readonly INumberSequenceService _numbers;
+    private readonly IUnitOfWork _uow;
+
+    public SalesSlipService(
+        IRepository<SalesSlip> slips, IRepository<Customer> customers, IRepository<Item> items,
+        IRepository<Uom> uoms, IRepository<Warehouse> warehouses, IRepository<User> users, ISalesPricingService pricing, IFifoCostingService fifo,
+        ICurrentUser currentUser, INumberSequenceService numbers, IUnitOfWork uow)
+    {
+        _slips = slips;
+        _customers = customers;
+        _items = items;
+        _uoms = uoms;
+        _warehouses = warehouses;
+        _users = users;
+        _pricing = pricing;
+        _fifo = fifo;
+        _currentUser = currentUser;
+        _numbers = numbers;
+        _uow = uow;
+    }
+
+    public async Task<PagedResponse<SalesSlipSummaryDto>> ListAsync(PageQuery query, SalesSlipStatus? status, int? customerId, int? warehouseId, CancellationToken ct = default)
+    {
+        IQueryable<SalesSlip> q = _slips.Query().AsNoTracking().Include(x => x.Lines);
+        if (!string.IsNullOrWhiteSpace(query.Q))
+        {
+            var term = query.Q.Trim();
+            q = q.Where(x => EF.Functions.ILike(x.SlipNo, $"%{term}%") || EF.Functions.ILike(x.CustomerSnapshotName, $"%{term}%"));
+        }
+        if (status is not null) q = q.Where(x => x.Status == status);
+        if (customerId is not null) q = q.Where(x => x.CustomerId == customerId);
+        if (warehouseId is not null) q = q.Where(x => x.WarehouseId == warehouseId);
+
+        var total = await q.CountAsync(ct);
+        var rows = await q.OrderByDescending(x => x.SalesSlipId).Skip(query.Skip).Take(query.PageSize).ToListAsync(ct);
+        return PagedResponse<SalesSlipSummaryDto>.Create(rows.Select(MapSummary).ToList(), query.Page, query.PageSize, total);
+    }
+
+    public async Task<ETagged<SalesSlipDto>?> GetAsync(int salesSlipId, CancellationToken ct = default)
+    {
+        var slip = await _slips.Query().AsNoTracking().Include(x => x.Lines)
+            .FirstOrDefaultAsync(x => x.SalesSlipId == salesSlipId, ct);
+        return slip is null ? null : new ETagged<SalesSlipDto>(Map(slip), slip.RowVersion);
+    }
+
+    public async Task<ETagged<SalesSlipDto>> CreateAsync(CreateSalesSlipRequest request, CancellationToken ct = default)
+    {
+        await ValidateReferencesAsync(request.CustomerId, request.WarehouseId, request.CashierUserId, request.Lines, ct);
+
+        var slip = new SalesSlip
+        {
+            SlipNo = await _numbers.NextAsync(DocumentTypes.SalesSlip, ct),
+            SlipDate = DateTime.UtcNow,
+            CustomerId = request.CustomerId,
+            WarehouseId = request.WarehouseId,
+            CashierUserId = request.CashierUserId,
+            Status = SalesSlipStatus.Draft,
+            CreatedAt = DateTime.UtcNow
+        };
+        slip.CustomerSnapshotName = await _customers.Query().Where(x => x.CustomerId == request.CustomerId).Select(x => x.DisplayName ?? x.Name).FirstAsync(ct);
+        slip.Lines = await BuildLinesAsync(request.Lines, ct);
+        Recalculate(slip);
+
+        await _slips.AddAsync(slip, ct);
+        await _uow.SaveChangesAsync(ct);
+        return new ETagged<SalesSlipDto>(Map(slip), slip.RowVersion);
+    }
+
+    public async Task<ETagged<SalesSlipDto>> UpdateAsync(int salesSlipId, UpdateSalesSlipRequest request, uint expectedRowVersion, CancellationToken ct = default)
+    {
+        var slip = await _slips.Query().Include(x => x.Lines).FirstOrDefaultAsync(x => x.SalesSlipId == salesSlipId, ct)
+            ?? throw new NotFoundException($"Sales slip {salesSlipId} was not found.");
+        if (slip.RowVersion != expectedRowVersion)
+            throw new DomainException(ErrorCodes.ConcurrencyConflict, "The sales slip was modified by another request.", 412);
+        if (slip.Status != SalesSlipStatus.Draft)
+            throw new ConflictException($"Sales slip {salesSlipId} is {slip.Status} and cannot be edited.");
+
+        await ValidateReferencesAsync(request.CustomerId, request.WarehouseId, request.CashierUserId, request.Lines, ct);
+        slip.CustomerId = request.CustomerId;
+        slip.WarehouseId = request.WarehouseId;
+        slip.CashierUserId = request.CashierUserId;
+        slip.CustomerSnapshotName = await _customers.Query().Where(x => x.CustomerId == request.CustomerId).Select(x => x.DisplayName ?? x.Name).FirstAsync(ct);
+        slip.Lines.Clear();
+        foreach (var line in await BuildLinesAsync(request.Lines, ct)) slip.Lines.Add(line);
+        Recalculate(slip);
+        slip.UpdatedAt = DateTime.UtcNow;
+        await _uow.SaveChangesAsync(ct);
+        return new ETagged<SalesSlipDto>(Map(slip), slip.RowVersion);
+    }
+
+    public async Task<SalesSlipDto> PostAsync(int salesSlipId, CancellationToken ct = default)
+    {
+        var slip = await _slips.Query().Include(x => x.Lines).FirstOrDefaultAsync(x => x.SalesSlipId == salesSlipId, ct)
+            ?? throw new NotFoundException($"Sales slip {salesSlipId} was not found.");
+        if (slip.Status != SalesSlipStatus.Draft)
+            throw new ConflictException($"Sales slip {salesSlipId} is {slip.Status} and cannot be posted.");
+
+        var posted = await _uow.ExecuteInTransactionAsync(async token =>
+        {
+            foreach (var line in slip.Lines)
+            {
+                if (line.Qty <= 0 && line.FreeQty <= 0) continue;
+                var consumed = await _fifo.ConsumeAsync(line.ItemId, line.WarehouseId, null, line.Qty + line.FreeQty, token);
+                var cost = consumed.Count == 0 ? 0m : consumed.Sum(x => x.Qty * x.UnitCost) / consumed.Sum(x => x.Qty);
+                await _fifo.PostLedgerAsync(line.ItemId, line.WarehouseId, null, null, null, _currentUser.AuditUserId,
+                    Direction.Out, line.Qty + line.FreeQty, cost, 0m, nameof(SalesSlip), slip.SalesSlipId, DateTime.UtcNow, token);
+            }
+
+            slip.Status = SalesSlipStatus.Posted;
+            slip.UpdatedAt = DateTime.UtcNow;
+            return slip;
+        }, ct);
+
+        return Map(posted);
+    }
+
+    public async Task<SalesSlipDto> CancelAsync(int salesSlipId, CancellationToken ct = default)
+    {
+        var slip = await _slips.Query().Include(x => x.Lines).FirstOrDefaultAsync(x => x.SalesSlipId == salesSlipId, ct)
+            ?? throw new NotFoundException($"Sales slip {salesSlipId} was not found.");
+        if (slip.Status != SalesSlipStatus.Draft)
+            throw new ConflictException($"Sales slip {salesSlipId} is {slip.Status} and cannot be cancelled.");
+        slip.Status = SalesSlipStatus.Cancelled;
+        slip.UpdatedAt = DateTime.UtcNow;
+        await _uow.SaveChangesAsync(ct);
+        return Map(slip);
+    }
+
+    private async Task ValidateReferencesAsync(int customerId, int warehouseId, int cashierUserId, List<CreateSalesSlipLineRequest> lines, CancellationToken ct)
+    {
+        if (!await _customers.Query().AnyAsync(x => x.CustomerId == customerId, ct))
+            throw new NotFoundException($"Customer {customerId} was not found.");
+        if (!await _warehouses.Query().AnyAsync(x => x.WarehouseId == warehouseId, ct))
+            throw new NotFoundException($"Warehouse {warehouseId} was not found.");
+        if (!await _users.Query().AnyAsync(x => x.UserId == cashierUserId, ct))
+            throw new NotFoundException($"User {cashierUserId} was not found.");
+        foreach (var line in lines)
+        {
+            if (!await _items.Query().AnyAsync(x => x.ItemId == line.ItemId, ct))
+                throw new NotFoundException($"Item {line.ItemId} was not found.");
+            if (!await _uoms.Query().AnyAsync(x => x.UomId == line.UomId, ct))
+                throw new NotFoundException($"UOM {line.UomId} was not found.");
+            if (!await _warehouses.Query().AnyAsync(x => x.WarehouseId == line.WarehouseId, ct))
+                throw new NotFoundException($"Warehouse {line.WarehouseId} was not found.");
+        }
+    }
+
+    private async Task<List<SalesSlipLine>> BuildLinesAsync(List<CreateSalesSlipLineRequest> requests, CancellationToken ct)
+    {
+        var lines = new List<SalesSlipLine>();
+        foreach (var r in requests)
+        {
+            var item = await _items.Query().AsNoTracking().FirstAsync(x => x.ItemId == r.ItemId, ct);
+            var resolved = await _pricing.ResolveAsync(r.ItemId, r.WarehouseId, r.UnitPrice, r.AllowManualPriceOverride, ct);
+            var unitPrice = resolved.UnitPrice;
+            var priceSource = resolved.PriceSource;
+
+            var gross = r.Qty * unitPrice;
+            var discountTotal = r.IsFreeIssue
+                ? 0m
+                : CalculateDiscount(gross, r.DiscountMode, r.DiscountPct, r.DiscountValue, r.DiscountAmount);
+            var netUnit = r.Qty > 0 ? (gross - discountTotal) / r.Qty : 0m;
+            var lineTotal = gross - discountTotal;
+            var taxAmount = lineTotal * (r.TaxPct / 100m);
+
+            lines.Add(new SalesSlipLine
+            {
+                ItemId = r.ItemId,
+                Description = item.Name,
+                Qty = r.Qty,
+                FreeQty = r.FreeQty,
+                UomId = r.UomId,
+                WarehouseId = r.WarehouseId,
+                UnitPrice = unitPrice,
+                BaseCost = unitPrice,
+                PriceSource = priceSource,
+                DiscountMode = r.DiscountMode,
+                DiscountPct = r.DiscountPct,
+                DiscountAmount = discountTotal,
+                NetUnitPrice = netUnit,
+                LineTotal = lineTotal,
+                TaxPct = r.TaxPct,
+                TaxAmount = taxAmount,
+                IsFreeIssue = r.IsFreeIssue,
+                ParentLineId = r.ParentLineId
+            });
+        }
+        return lines;
+    }
+
+    private static void Recalculate(SalesSlip slip)
+    {
+        slip.Subtotal = slip.Lines.Sum(x => x.Qty * x.UnitPrice);
+        slip.DiscountTotal = slip.Lines.Sum(x => x.DiscountAmount);
+        slip.TaxTotal = slip.Lines.Sum(x => x.TaxAmount);
+        slip.GrandTotal = slip.Lines.Sum(x => x.LineTotal) + slip.TaxTotal;
+        slip.PaidAmount = 0m;
+        slip.BalanceAmount = slip.GrandTotal - slip.PaidAmount;
+    }
+
+    private static decimal CalculateDiscount(decimal gross, SalesDiscountMode mode, decimal discountPct, decimal discountValue, decimal legacyDiscountAmount)
+    {
+        var computed = mode == SalesDiscountMode.FixedAmount
+            ? discountValue
+            : gross * (discountPct / 100m);
+
+        if (computed <= 0m && legacyDiscountAmount > 0m)
+            computed = legacyDiscountAmount;
+
+        return Math.Min(gross, Math.Max(0m, computed));
+    }
+
+    private static SalesSlipSummaryDto MapSummary(SalesSlip x) => new(
+        x.SalesSlipId, x.SlipNo, x.SlipDate, x.CustomerId, x.CustomerSnapshotName, x.WarehouseId, x.Status,
+        new SalesSlipTotalsDto(x.Subtotal, x.DiscountTotal, x.Lines.Sum(l => l.FreeQty), x.TaxTotal, x.GrandTotal, x.PaidAmount, x.BalanceAmount), x.CreatedAt);
+
+    private static SalesSlipDto Map(SalesSlip x) => new(
+        x.SalesSlipId, x.SlipNo, x.SlipDate, x.CustomerId, x.CustomerSnapshotName, x.WarehouseId, x.CashierUserId, x.Status, x.CreatedAt, x.UpdatedAt,
+        new SalesSlipTotalsDto(x.Subtotal, x.DiscountTotal, x.Lines.Sum(l => l.FreeQty), x.TaxTotal, x.GrandTotal, x.PaidAmount, x.BalanceAmount),
+        x.Lines.Select(l => new SalesSlipLineDto(l.SalesSlipLineId, l.ItemId, l.Description, l.Qty, l.FreeQty, l.UomId, l.WarehouseId, l.UnitPrice, l.BaseCost, l.PriceSource, l.DiscountPct, l.DiscountAmount, l.DiscountMode, l.NetUnitPrice, l.LineTotal, l.TaxPct, l.TaxAmount, l.IsFreeIssue, l.ParentLineId)).ToList());
+}

docs/SALES_MODULE_PLAN.md

@@ -0,0 +1,383 @@
+# Sales Module Plan
+
+## Summary
+This sales module is split into two phases:
+- **Phase 1**: basic, standard sales features that fit the current ERP architecture
+- **Phase 2**: enterprise extensions that can be added after the core flow is stable
+
+The design stays aligned with the existing backend patterns:
+- controller thinness
+- service-based business rules
+- repository + unit of work
+- ETag concurrency
+- audit logging
+- stock FIFO and ledger posting
+
+Returns, credit notes, and sales returns are **out of scope for Phase 1**.
+
+---
+
+## Phase 1 - Basic Standard Sales Module
+
+### Goal
+Implement the minimum sales flow needed for both B2B and B2C:
+- maintain customers
+- create sales invoices
+- create sales slips
+- support fixed sale price fallback and GRN-based cost fallback
+- support discounts by percentage and value
+- support free issue lines
+- post stock movement and ledger entries
+- generate basic sales reports
+
+### In Scope
+- Customer master
+- Sales invoice
+- Sales invoice lines
+- Sales slip
+- Sales slip lines
+- Pricing resolver
+- Discount calculation
+- Free issue handling
+- Stock posting
+- Basic sales reports
+
+### Not in Scope for Phase 1
+- customer groups
+- price lists
+- promotions
+- reservations
+- sales payments allocation
+- approval workflow
+- returns and credit notes
+- advanced customer segmentation
+
+### Phase 1 Entity Design
+
+#### `Customer`
+Basic customer master used for both B2B and B2C.
+
+Fields:
+- `CustomerId`
+- `CustomerCode`
+- `CustomerType` (`B2B`, `B2C`, `WalkIn`)
+- `Name`
+- `DisplayName`
+- `Phone`
+- `Email`
+- `AddressLine1`
+- `AddressLine2`
+- `City`
+- `Country`
+- `TaxRegistrationNo`
+- `CreditLimit`
+- `CreditDays`
+- `DefaultWarehouseId`
+- `Status`
+- `CreatedAt`
+- `UpdatedAt`
+- `RowVersion`
+
+#### `SalesInvoice`
+Primary posted sales document.
+
+Fields:
+- `SalesInvoiceId`
+- `InvoiceNo`
+- `InvoiceDate`
+- `CustomerId`
+- `CustomerSnapshotName`
+- `CustomerSnapshotTaxNo`
+- `WarehouseId`
+- `InvoiceType` (`B2B`, `B2C`, `Cash`, `Credit`)
+- `Status` (`Draft`, `Posted`, `Cancelled`)
+- `Subtotal`
+- `DiscountTotal`
+- `TaxTotal`
+- `GrandTotal`
+- `RoundOff`
+- `NetPayable`
+- `PaidAmount`
+- `BalanceAmount`
+- `CreatedBy`
+- `CreatedAt`
+- `UpdatedAt`
+- `RowVersion`
+
+#### `SalesInvoiceLine`
+Invoice line with pricing, discount, and free issue support.
+
+Fields:
+- `SalesInvoiceLineId`
+- `SalesInvoiceId`
+- `ItemId`
+- `Description`
+- `Qty`
+- `FreeQty`
+- `UomId`
+- `WarehouseId`
+- `UnitPrice`
+- `BaseCost`
+- `PriceSource`
+- `DiscountPct`
+- `DiscountAmount`
+- `NetUnitPrice`
+- `LineTotal`
+- `TaxPct`
+- `TaxAmount`
+- `IsFreeIssue`
+- `ParentLineId`
+- `RowVersion`
+
+#### `SalesSlip`
+Fast retail or counter-sale document.
+
+Fields:
+- `SalesSlipId`
+- `SlipNo`
+- `SlipDate`
+- `CustomerId`
+- `CustomerSnapshotName`
+- `WarehouseId`
+- `CashierUserId`
+- `Status`
+- `Subtotal`
+- `DiscountTotal`
+- `TaxTotal`
+- `GrandTotal`
+- `PaidAmount`
+- `BalanceAmount`
+- `CreatedAt`
+- `UpdatedAt`
+- `RowVersion`
+
+#### `SalesSlipLine`
+Slip line with the same sales calculation rules as invoices.
+
+Fields:
+- `SalesSlipLineId`
+- `SalesSlipId`
+- `ItemId`
+- `Description`
+- `Qty`
+- `FreeQty`
+- `UomId`
+- `WarehouseId`
+- `UnitPrice`
+- `BaseCost`
+- `PriceSource`
+- `DiscountPct`
+- `DiscountAmount`
+- `NetUnitPrice`
+- `LineTotal`
+- `TaxPct`
+- `TaxAmount`
+- `IsFreeIssue`
+- `ParentLineId`
+- `RowVersion`
+
+### Phase 1 Pricing Rule
+Use the following order:
+1. fixed `Item.SalePrice`
+2. GRN-derived stock cost fallback
+3. FIFO valuation fallback
+
+Important:
+- use a weighted average when deriving from multiple GRNs
+- keep the resolved source in `PriceSource`
+- allow manual override only if permitted by business rule
+
+### Phase 1 Discount Rule
+Support:
+- percentage discount
+- fixed value discount
+
+Discount must be computed server-side and stored in line and document totals.
+
+### Phase 1 Free Issue Rule
+Support free issue lines in the same invoice/slip document.
+
+Rules:
+- free quantity must be separate from paid quantity
+- free issue still reduces stock
+- free issue must be visible in reports
+- free issue should not be merged into discount
+
+### Phase 1 Stock Posting Rule
+When an invoice or slip is posted:
+- reduce stock from the selected warehouse
+- consume FIFO layers
+- write `StockLedger` rows
+- maintain source document traceability
+- update totals in the same transaction
+
+### Phase 1 API Route List
+- `GET /api/v1/customers`
+- `GET /api/v1/customers/{id}`
+- `POST /api/v1/customers`
+- `PUT /api/v1/customers/{id}`
+- `PATCH /api/v1/customers/{id}/status`
+- `GET /api/v1/sales-invoices`
+- `GET /api/v1/sales-invoices/{id}`
+- `POST /api/v1/sales-invoices`
+- `PUT /api/v1/sales-invoices/{id}`
+- `POST /api/v1/sales-invoices/{id}/post`
+- `POST /api/v1/sales-invoices/{id}/cancel`
+- `GET /api/v1/sales-invoices/{id}/print-preview`
+- `GET /api/v1/sales-slips`
+- `GET /api/v1/sales-slips/{id}`
+- `POST /api/v1/sales-slips`
+- `POST /api/v1/sales-slips/{id}/post`
+- `POST /api/v1/sales-slips/{id}/cancel`
+- `GET /api/v1/sales-reports/daily-summary`
+- `GET /api/v1/sales-reports/item-wise`
+- `GET /api/v1/sales-reports/customer-wise`
+- `GET /api/v1/sales-reports/warehouse-wise`
+- `GET /api/v1/sales-reports/discount-summary`
+- `GET /api/v1/sales-reports/free-issue-summary`
+- `GET /api/v1/sales-reports/margin-summary`
+
+### Phase 1 Folder / Module Plan
+- `Domain/Entities`
+  - add `Customer`, `SalesInvoice`, `SalesInvoiceLine`, `SalesSlip`, `SalesSlipLine`
+- `Domain/Enums`
+  - add sales status enums and invoice/slip type enums
+- `Dtos/Sales`
+  - add request and response DTOs for customer, invoice, slip, and reports
+- `Services/Interfaces`
+  - add `ICustomerService`, `ISalesInvoiceService`, `ISalesSlipService`, `ISalesPricingService`, `ISalesReportService`
+- `Services`
+  - implement the sales services with transaction-safe logic
+- `Controllers`
+  - add `CustomersController`, `SalesInvoicesController`, `SalesSlipsController`, `SalesReportsController`
+- `Infra/Persistence/Configurations`
+  - add EF Core mappings for all sales entities
+- `Infra/Persistence/ErpDbContext.cs`
+  - register sales `DbSet`s
+- `Infra/Persistence/Migrations`
+  - add the sales schema migration after the model is defined
+
+### Phase 1 Implementation Order
+1. Customer master
+2. Sales invoice entity and DTOs
+3. Sales slip entity and DTOs
+4. Pricing resolver
+5. Discount computation
+6. Free issue handling
+7. Stock posting and ledger integration
+8. Basic sales reports
+9. Controllers and swagger wiring
+
+---
+
+## Phase 2 - Enterprise Extensions
+
+### Goal
+Add richer commercial features after Phase 1 is stable and tested.
+
+### In Scope
+- customer groups
+- price lists
+- promotions
+- free issue schemes
+- reservations
+- payment allocation
+- approval flow
+- advanced reporting dimensions
+
+### Phase 2 Entity Additions
+
+#### `CustomerGroup`
+Used only if group-level pricing or segmentation is needed.
+
+#### `PriceList`
+Customer, group, warehouse, or global price policies.
+
+#### `PriceListItem`
+Per-item pricing rows inside a price list.
+
+#### `Promotion`
+Promotional header.
+
+#### `PromotionRule`
+Buy-X-get-Y, discount, or reward rules.
+
+#### `FreeIssueScheme`
+Separate free issue header.
+
+#### `FreeIssueSchemeLine`
+Rule lines for free issue behavior.
+
+#### `SalesReservation`
+Stock reservation header for B2B order fulfillment.
+
+#### `SalesReservationLine`
+Reserved item quantities.
+
+#### `SalesPayment`
+Payment header for cash or credit settlement.
+
+#### `SalesPaymentAllocation`
+Allocation of a payment across invoices.
+
+### Phase 2 API Routes
+- `GET /api/v1/customer-groups`
+- `POST /api/v1/customer-groups`
+- `PUT /api/v1/customer-groups/{id}`
+- `PATCH /api/v1/customer-groups/{id}/status`
+- `GET /api/v1/price-lists`
+- `POST /api/v1/price-lists`
+- `PUT /api/v1/price-lists/{id}`
+- `PATCH /api/v1/price-lists/{id}/status`
+- `GET /api/v1/price-lists/{id}/items`
+- `PUT /api/v1/price-lists/{id}/items`
+- `GET /api/v1/pricing/resolve`
+- `GET /api/v1/promotions`
+- `POST /api/v1/promotions`
+- `PUT /api/v1/promotions/{id}`
+- `PATCH /api/v1/promotions/{id}/status`
+- `GET /api/v1/free-issue-schemes`
+- `POST /api/v1/free-issue-schemes`
+- `PUT /api/v1/free-issue-schemes/{id}`
+- `PATCH /api/v1/free-issue-schemes/{id}/status`
+- `POST /api/v1/sales-orders`
+- `POST /api/v1/sales-orders/{id}/reserve`
+- `POST /api/v1/sales-orders/{id}/confirm`
+- `POST /api/v1/sales-payments`
+- `POST /api/v1/sales-payments/{id}/allocate`
+- extended reporting routes for channel, cashier, tax, and credit views
+
+### Phase 2 Folder / Module Plan
+- extend the same sales folders rather than creating a separate module
+- add new entities and DTOs under the same sales namespace
+- add new service interfaces and service implementations next to Phase 1 sales services
+- add new controllers only for the advanced routes
+- add migrations incrementally so Phase 1 tables remain stable
+
+### Phase 2 Implementation Order
+1. customer groups
+2. price lists
+3. promotions and free issue schemes
+4. sales orders and reservations
+5. payments and allocations
+6. advanced reports
+7. permissions and approval workflow
+
+---
+
+## Test Plan
+- Verify customer CRUD with ETag concurrency and status changes.
+- Verify invoice and slip create/update/post flows.
+- Verify fixed sale price fallback works.
+- Verify GRN-derived fallback uses weighted average.
+- Verify discounts calculate correctly by percentage and fixed value.
+- Verify free issue lines post stock and appear in reports.
+- Verify stock ledger entries are created once per posted document.
+- Verify Phase 1 routes remain stable before Phase 2 is added.
+
+## Assumptions
+- Phase 1 is intentionally minimal and should not include customer groups or price lists.
+- `SalesInvoice` is the primary posted sales document.
+- `SalesSlip` is a simplified retail document.
+- Returns are deferred to a later step.
+- Existing ERP patterns must be preserved: repository, unit of work, audit, ETag, and FIFO stock posting.