internal/contract/analytics_contract.go

@@ -140,7 +140,7 @@ type PurchasingIngredientData struct {
 }
 
 type PurchasingVendorData struct {
-	VendorID           *uuid.UUID `json:"vendor_id"`
+	VendorID           uuid.UUID `json:"vendor_id"`
 	VendorName         string    `json:"vendor_name"`
 	TotalCost          float64   `json:"total_cost"`
 	PurchaseOrderCount int64     `json:"purchase_order_count"`

internal/contract/purchase_order_contract.go

@@ -7,7 +7,7 @@ import (
 )
 
 type CreatePurchaseOrderRequest struct {
-	VendorID          *uuid.UUID                       `json:"vendor_id,omitempty" validate:"omitempty"`
+	VendorID          uuid.UUID                        `json:"vendor_id" validate:"required"`
 	PONumber          string                           `json:"po_number" validate:"required,min=1,max=50"`
 	TransactionDate   string                           `json:"transaction_date" validate:"required"`    // Format: YYYY-MM-DD
 	DueDate           *string                          `json:"due_date,omitempty" validate:"omitempty"` // Format: YYYY-MM-DD
@@ -52,7 +52,7 @@ type UpdatePurchaseOrderItemRequest struct {
 type PurchaseOrderResponse struct {
 	ID              uuid.UUID                         `json:"id"`
 	OrganizationID  uuid.UUID                         `json:"organization_id"`
-	VendorID        *uuid.UUID                        `json:"vendor_id"`
+	VendorID        uuid.UUID                         `json:"vendor_id"`
 	PONumber        string                            `json:"po_number"`
 	TransactionDate time.Time                         `json:"transaction_date"`
 	DueDate         *time.Time                        `json:"due_date"`

internal/entities/analytics.go

@@ -72,7 +72,7 @@ type PurchasingIngredientData struct {
 }
 
 type PurchasingVendorData struct {
-	VendorID           *uuid.UUID `json:"vendor_id"`
+	VendorID           uuid.UUID `json:"vendor_id"`
 	VendorName         string    `json:"vendor_name"`
 	TotalCost          float64   `json:"total_cost"`
 	PurchaseOrderCount int64     `json:"purchase_order_count"`

internal/entities/purchase_order.go

@@ -11,7 +11,7 @@ import (
 type PurchaseOrder struct {
 	ID              uuid.UUID  `gorm:"type:uuid;primary_key;default:gen_random_uuid()" json:"id"`
 	OrganizationID  uuid.UUID  `gorm:"type:uuid;not null" json:"organization_id" validate:"required"`
-	VendorID        *uuid.UUID `gorm:"type:uuid" json:"vendor_id" validate:"omitempty"`
+	VendorID        uuid.UUID  `gorm:"type:uuid;not null" json:"vendor_id" validate:"required"`
 	PONumber        string     `gorm:"not null;size:50" json:"po_number" validate:"required,min=1,max=50"`
 	TransactionDate time.Time  `gorm:"type:date;not null" json:"transaction_date" validate:"required"`
 	DueDate         *time.Time `gorm:"type:date" json:"due_date" validate:"omitempty"`

internal/models/analytics.go

@@ -150,7 +150,7 @@ type PurchasingIngredientData struct {
 
 // PurchasingVendorData represents purchasing analytics for a vendor
 type PurchasingVendorData struct {
-	VendorID           *uuid.UUID `json:"vendor_id"`
+	VendorID           uuid.UUID `json:"vendor_id"`
 	VendorName         string    `json:"vendor_name"`
 	TotalCost          float64   `json:"total_cost"`
 	PurchaseOrderCount int64     `json:"purchase_order_count"`

internal/models/purchase_order.go

@@ -9,7 +9,7 @@ import (
 type PurchaseOrder struct {
 	ID              uuid.UUID  `json:"id"`
 	OrganizationID  uuid.UUID  `json:"organization_id"`
-	VendorID        *uuid.UUID `json:"vendor_id"`
+	VendorID        uuid.UUID  `json:"vendor_id"`
 	PONumber        string     `json:"po_number"`
 	TransactionDate time.Time  `json:"transaction_date"`
 	DueDate         *time.Time `json:"due_date"`
@@ -44,7 +44,7 @@ type PurchaseOrderAttachment struct {
 type PurchaseOrderResponse struct {
 	ID              uuid.UUID                         `json:"id"`
 	OrganizationID  uuid.UUID                         `json:"organization_id"`
-	VendorID        *uuid.UUID                        `json:"vendor_id"`
+	VendorID        uuid.UUID                         `json:"vendor_id"`
 	PONumber        string                            `json:"po_number"`
 	TransactionDate time.Time                         `json:"transaction_date"`
 	DueDate         *time.Time                        `json:"due_date"`
@@ -84,7 +84,7 @@ type PurchaseOrderAttachmentResponse struct {
 }
 
 type CreatePurchaseOrderRequest struct {
-	VendorID          *uuid.UUID                       `json:"vendor_id,omitempty"`
+	VendorID          uuid.UUID                        `json:"vendor_id"`
 	PONumber          string                           `json:"po_number"`
 	TransactionDate   time.Time                        `json:"transaction_date"`
 	DueDate           *time.Time                       `json:"due_date,omitempty"`

internal/processor/purchase_order_processor.go

@@ -55,13 +55,11 @@ func NewPurchaseOrderProcessorImpl(
 }
 
 func (p *PurchaseOrderProcessorImpl) CreatePurchaseOrder(ctx context.Context, organizationID uuid.UUID, req *models.CreatePurchaseOrderRequest) (*models.PurchaseOrderResponse, error) {
-	// Check if vendor exists and belongs to organization when provided.
+	// Check if vendor exists and belongs to organization
-	if req.VendorID != nil {
+	_, err := p.vendorRepo.GetByIDAndOrganizationID(ctx, req.VendorID, organizationID)
-		_, err := p.vendorRepo.GetByIDAndOrganizationID(ctx, *req.VendorID, organizationID)
 	if err != nil {
 		return nil, fmt.Errorf("vendor not found: %w", err)
 	}
-	}
 
 	// Check if PO number already exists in organization
 	existingPO, err := p.purchaseOrderRepo.GetByPONumber(ctx, req.PONumber, organizationID)
@@ -188,7 +186,7 @@ func (p *PurchaseOrderProcessorImpl) UpdatePurchaseOrder(ctx context.Context, id
 		if err != nil {
 			return nil, fmt.Errorf("vendor not found: %w", err)
 		}
-		poEntity.VendorID = req.VendorID
+		poEntity.VendorID = *req.VendorID
 	}
 
 	// Check if PO number already exists (if PO number is being updated)

internal/repository/analytics_repository.go

@@ -162,7 +162,7 @@ func (r *AnalyticsRepositoryImpl) getPurchaseOrderPurchasingAnalytics(ctx contex
 				ELSE 0
 			END as average_purchase_order_value,
 			COUNT(DISTINCT i.id) as total_ingredients,
-			COUNT(DISTINCT COALESCE(po.vendor_id::text, 'no-vendor')) as total_vendors
+			COUNT(DISTINCT po.vendor_id) as total_vendors
 		`).
 		Joins("LEFT JOIN purchase_order_items poi ON poi.purchase_order_id = po.id").
 		Joins("LEFT JOIN ingredients i ON poi.ingredient_id = i.id").
@@ -197,7 +197,7 @@ func (r *AnalyticsRepositoryImpl) getPurchaseOrderPurchasingAnalytics(ctx contex
 			COUNT(DISTINCT po.id) as purchase_orders,
 			COALESCE(SUM(poi.quantity), 0) as quantity,
 			COUNT(DISTINCT i.id) as ingredients,
-			COUNT(DISTINCT COALESCE(po.vendor_id::text, 'no-vendor')) as vendors
+			COUNT(DISTINCT po.vendor_id) as vendors
 		`).
 		Joins("LEFT JOIN purchase_order_items poi ON poi.purchase_order_id = po.id").
 		Joins("LEFT JOIN ingredients i ON poi.ingredient_id = i.id").
@@ -247,20 +247,20 @@ func (r *AnalyticsRepositoryImpl) getPurchaseOrderPurchasingAnalytics(ctx contex
 		Table("purchase_orders po").
 		Select(`
 			v.id as vendor_id,
-			COALESCE(v.name, 'No Vendor') as vendor_name,
+			v.name as vendor_name,
 			COALESCE(SUM(poi.amount), 0) as total_cost,
 			COUNT(DISTINCT po.id) as purchase_order_count,
 			COUNT(DISTINCT i.id) as ingredient_count,
 			COALESCE(SUM(poi.quantity), 0) as quantity
 		`).
-		Joins("LEFT JOIN vendors v ON po.vendor_id = v.id").
+		Joins("JOIN vendors v ON po.vendor_id = v.id").
 		Joins("LEFT JOIN purchase_order_items poi ON poi.purchase_order_id = po.id").
 		Joins("LEFT JOIN ingredients i ON poi.ingredient_id = i.id").
 		Joins("LEFT JOIN units u ON poi.unit_id = u.id").
 		Where("po.organization_id = ?", organizationID).
 		Where("po.status != ?", "cancelled").
 		Where("po.transaction_date >= ? AND po.transaction_date <= ?", dateFrom, dateTo).
-		Group("v.id, COALESCE(v.name, 'No Vendor')").
+		Group("v.id, v.name").
 		Order("total_cost DESC")
 	vendorQuery = r.applyPurchaseOrderItemOutletFilter(vendorQuery, outletID)
 

internal/transformer/purchase_order_transformer_test.go

@@ -12,13 +12,12 @@ import (
 )
 
 func TestCreatePurchaseOrderRequestToModelAllowsMissingDueDate(t *testing.T) {
-	vendorID := uuid.New()
 	ingredientID := uuid.New()
 	quantity := 1.0
 	unitID := uuid.New()
 
 	result, err := CreatePurchaseOrderRequestToModel(&contract.CreatePurchaseOrderRequest{
-		VendorID:        &vendorID,
+		VendorID:        uuid.New(),
 		PONumber:        "PO-001",
 		TransactionDate: "2026-05-29",
 		Items: []contract.CreatePurchaseOrderItemRequest{
@@ -36,10 +35,9 @@ func TestCreatePurchaseOrderRequestToModelAllowsMissingDueDate(t *testing.T) {
 }
 
 func TestPurchaseOrderModelResponseToResponseIncludesNullDueDate(t *testing.T) {
-	vendorID := uuid.New()
 	result := PurchaseOrderModelResponseToResponse(&models.PurchaseOrderResponse{
 		ID:       uuid.New(),
-		VendorID: &vendorID,
+		VendorID: uuid.New(),
 		PONumber: "PO-001",
 	})
 
@@ -47,19 +45,3 @@ func TestPurchaseOrderModelResponseToResponseIncludesNullDueDate(t *testing.T) {
 	require.NoError(t, err)
 	require.Contains(t, string(payload), `"due_date":null`)
 }
-
-func TestCreatePurchaseOrderRequestToModelAllowsMissingVendor(t *testing.T) {
-	result, err := CreatePurchaseOrderRequestToModel(&contract.CreatePurchaseOrderRequest{
-		PONumber:        "PO-001",
-		TransactionDate: "2026-05-29",
-		Items: []contract.CreatePurchaseOrderItemRequest{
-			{
-				PurchaseCategoryID: uuid.New(),
-				Amount:             1000,
-			},
-		},
-	})
-
-	require.NoError(t, err)
-	require.Nil(t, result.VendorID)
-}

internal/validator/purchase_order_validator.go

@@ -29,8 +29,8 @@ func (v *PurchaseOrderValidatorImpl) ValidateCreatePurchaseOrderRequest(req *con
 		return errors.New("request body is required"), constants.MissingFieldErrorCode
 	}
 
-	if req.VendorID != nil && *req.VendorID == uuid.Nil {
+	if req.VendorID == uuid.Nil {
-		return errors.New("vendor_id cannot be empty"), constants.MalformedFieldErrorCode
+		return errors.New("vendor_id is required"), constants.MissingFieldErrorCode
 	}
 
 	if strings.TrimSpace(req.PONumber) == "" {

internal/validator/purchase_order_validator_test.go

@@ -11,13 +11,12 @@ import (
 )
 
 func validCreatePurchaseOrderRequest() *contract.CreatePurchaseOrderRequest {
-	vendorID := uuid.New()
 	ingredientID := uuid.New()
 	quantity := 1.0
 	unitID := uuid.New()
 
 	return &contract.CreatePurchaseOrderRequest{
-		VendorID:        &vendorID,
+		VendorID:        uuid.New(),
 		PONumber:        "PO-001",
 		TransactionDate: "2026-05-29",
 		Items: []contract.CreatePurchaseOrderItemRequest{
@@ -32,30 +31,6 @@ func validCreatePurchaseOrderRequest() *contract.CreatePurchaseOrderRequest {
 	}
 }
 
-func TestPurchaseOrderValidatorCreateAllowsMissingVendor(t *testing.T) {
-	validator := NewPurchaseOrderValidator()
-	req := validCreatePurchaseOrderRequest()
-	req.VendorID = nil
-
-	err, code := validator.ValidateCreatePurchaseOrderRequest(req)
-
-	require.NoError(t, err)
-	require.Empty(t, code)
-}
-
-func TestPurchaseOrderValidatorCreateRejectsEmptyVendor(t *testing.T) {
-	validator := NewPurchaseOrderValidator()
-	req := validCreatePurchaseOrderRequest()
-	vendorID := uuid.Nil
-	req.VendorID = &vendorID
-
-	err, code := validator.ValidateCreatePurchaseOrderRequest(req)
-
-	require.Error(t, err)
-	require.Equal(t, constants.MalformedFieldErrorCode, code)
-	require.Contains(t, err.Error(), "vendor_id cannot be empty")
-}
-
 func TestPurchaseOrderValidatorCreateAllowsMissingDueDate(t *testing.T) {
 	validator := NewPurchaseOrderValidator()
 

migrations/000081_make_purchase_order_vendor_nullable.down.sql

@@ -1,2 +0,0 @@
-ALTER TABLE purchase_orders
-    ALTER COLUMN vendor_id SET NOT NULL;

migrations/000081_make_purchase_order_vendor_nullable.up.sql

@@ -1,2 +0,0 @@
-ALTER TABLE purchase_orders
-    ALTER COLUMN vendor_id DROP NOT NULL;