feat(subs): normalize anchor time to closest iteration before activation

Author: GAlexIHU

openmeter/subscription/repo/mapping.go

@@ -60,7 +60,7 @@ func MapDBSubscription(sub *db.Subscription) (subscription.Subscription, error)
 		Currency:        sub.Currency,
 		BillingCadence:  billingCadence,
 		ProRatingConfig: sub.ProRatingConfig,
-		BillingAnchor:   sub.BillingAnchor,
+		BillingAnchor:   sub.BillingAnchor.UTC(),
 	}, nil
 }
 

openmeter/subscription/repo/subscriptionrepo.go

@@ -110,7 +110,7 @@ func (r *subscriptionRepo) Create(ctx context.Context, sub subscription.CreateSu
 			SetNillableDescription(sub.Description).
 			SetBillablesMustAlign(sub.BillablesMustAlign).
 			SetMetadata(sub.Metadata).
-			SetBillingAnchor(sub.BillingAnchor)
+			SetBillingAnchor(sub.BillingAnchor.UTC())
 
 		if sub.ActiveTo != nil {
 			command = command.SetActiveTo(*sub.ActiveTo)

openmeter/subscription/workflow/service/subscription.go

@@ -14,6 +14,7 @@ import (
 	"github.com/openmeterio/openmeter/pkg/clock"
 	"github.com/openmeterio/openmeter/pkg/framework/transaction"
 	"github.com/openmeterio/openmeter/pkg/models"
+	"github.com/openmeterio/openmeter/pkg/timeutil"
 )
 
 func (s *service) CreateFromPlan(ctx context.Context, inp subscriptionworkflow.CreateSubscriptionWorkflowInput, plan subscription.Plan) (subscription.SubscriptionView, error) {
@@ -43,6 +44,29 @@ func (s *service) CreateFromPlan(ctx context.Context, inp subscriptionworkflow.C
 		return def, fmt.Errorf("failed to resolve active from: %w", err)
 	}
 
+	// Let's normalize the billing anchor to the closest iteration based on the cadence
+	billingAnchor := lo.FromPtrOr(inp.BillingAnchor, activeFrom).UTC()
+
+	billingRecurrence, err := timeutil.RecurrenceFromISODuration(lo.ToPtr(plan.ToCreateSubscriptionPlanInput().BillingCadence), billingAnchor)
+	if err != nil {
+		return def, fmt.Errorf("failed to get billing recurrence: %w", err)
+	}
+
+	billingAnchor, err = billingRecurrence.PrevBefore(activeFrom)
+	if err != nil {
+		return def, fmt.Errorf("failed to get billing anchor: %w", err)
+	}
+
+	// When anchor = beforeTime (or falls on iteration boundary), PrevBefore will return an iteration early.
+	oneBefore, err := billingRecurrence.Prev(activeFrom)
+	if err != nil {
+		return def, fmt.Errorf("failed to get one iteration before billing anchor: %w", err)
+	}
+
+	if oneBefore.Equal(billingAnchor) {
+		billingAnchor = activeFrom
+	}
+
 	// Let's create the new Spec
 	spec, err := subscription.NewSpecFromPlan(plan, subscription.CreateSubscriptionCustomerInput{
 		CustomerId:    cust.ID,
@@ -51,7 +75,7 @@ func (s *service) CreateFromPlan(ctx context.Context, inp subscriptionworkflow.C
 		MetadataModel: inp.MetadataModel,
 		Name:          lo.CoalesceOrEmpty(inp.Name, plan.GetName()),
 		Description:   inp.Description,
-		BillingAnchor: lo.FromPtrOr(inp.BillingAnchor, activeFrom).UTC(),
+		BillingAnchor: billingAnchor,
 	})
 
 	if err := subscriptionworkflow.MapSubscriptionErrors(err); err != nil {

openmeter/subscription/workflow/service/subscription_test.go

@@ -27,6 +27,7 @@ import (
 	"github.com/openmeterio/openmeter/pkg/clock"
 	"github.com/openmeterio/openmeter/pkg/isodate"
 	"github.com/openmeterio/openmeter/pkg/models"
+	"github.com/openmeterio/openmeter/pkg/timeutil"
 )
 
 func TestCreateFromPlan(t *testing.T) {
@@ -89,6 +90,41 @@ func TestCreateFromPlan(t *testing.T) {
 				}
 			},
 		},
+		{
+			Name: "Should normalize billing anchor to the closest iteration",
+			Handler: func(t *testing.T, deps testCaseDeps) {
+				ctx, cancel := context.WithCancel(context.Background())
+				defer cancel()
+
+				cad := deps.Plan.ToCreateSubscriptionPlanInput().BillingCadence
+
+				activeFrom := deps.CurrentTime
+
+				billingAnchor := activeFrom.Add(time.Hour)
+
+				cadRec, err := timeutil.RecurrenceFromISODuration(lo.ToPtr(cad), billingAnchor)
+				require.Nil(t, err)
+
+				// Let's set an anchor one hour after the activeFrom, which will then be set to one iteration before
+
+				expectedBillingAnchor, err := cadRec.Prev(billingAnchor)
+				require.Nil(t, err)
+
+				subView, err := deps.WorkflowService.CreateFromPlan(ctx, subscriptionworkflow.CreateSubscriptionWorkflowInput{
+					ChangeSubscriptionWorkflowInput: subscriptionworkflow.ChangeSubscriptionWorkflowInput{
+						Timing: subscription.Timing{
+							Custom: &deps.CurrentTime,
+						},
+					},
+					CustomerID:    deps.Customer.ID,
+					Namespace:     subscriptiontestutils.ExampleNamespace,
+					BillingAnchor: &billingAnchor,
+				}, deps.Plan)
+				require.Nil(t, err)
+
+				require.Equal(t, expectedBillingAnchor, subView.Subscription.BillingAnchor)
+			},
+		},
 	}
 
 	for _, tc := range testCases {