feat(statemachine): add promotional credit statemachine

Author: mark-vass-konghq

openmeter/billing/charges/creditpurchase/service/create.go

@@ -30,7 +30,23 @@ func (s *service) Create(ctx context.Context, input creditpurchase.CreateInput)
 		// Let's activate the state machine for the credit purchase charge
 		switch charge.Intent.Settlement.Type() {
 		case creditpurchase.SettlementTypePromotional:
-			charge, err = s.onPromotionalCreditPurchase(ctx, charge)
+			stateMachine, stateMachineErr := NewPromotionalCreditPurchaseStateMachine(StateMachineConfig{
+				Charge:  charge,
+				Adapter: s.adapter,
+				Service: s,
+			})
+			if stateMachineErr != nil {
+				return creditpurchase.ChargeWithGatheringLine{}, fmt.Errorf("new promotional state machine: %w", stateMachineErr)
+			}
+
+			advancedCharge, stateMachineErr := stateMachine.AdvanceUntilStateStable(ctx)
+			if stateMachineErr != nil {
+				return creditpurchase.ChargeWithGatheringLine{}, fmt.Errorf("advance promotional state machine: %w", stateMachineErr)
+			}
+
+			if advancedCharge != nil {
+				charge = *advancedCharge
+			}
 		case creditpurchase.SettlementTypeInvoice:
 			// noop, as we will transition to active state when the invoice is created, as
 			// - invocing based charges are driven by the invoice state machine

openmeter/billing/charges/creditpurchase/service/promotional.go

@@ -2,24 +2,15 @@ package service
 
 import (
 	"context"
-	"slices"
+	"fmt"
 
 	"github.com/openmeterio/openmeter/openmeter/billing/charges/creditpurchase"
 	"github.com/openmeterio/openmeter/openmeter/billing/charges/lineage"
+	"github.com/openmeterio/openmeter/openmeter/billing/charges/meta"
 	"github.com/openmeterio/openmeter/pkg/clock"
 )
 
-var activePromotionalCreditPurchaseStatuses = []creditpurchase.Status{
-	creditpurchase.StatusCreated,
-	creditpurchase.StatusActive,
-}
-
-func (s *service) onPromotionalCreditPurchase(ctx context.Context, charge creditpurchase.Charge) (creditpurchase.Charge, error) {
-	// Prevent re-processing of the charge
-	if !slices.Contains(activePromotionalCreditPurchaseStatuses, charge.Status) {
-		return creditpurchase.Charge{}, creditpurchase.ErrCreditPurchaseChargeNotActive.WithAttrs(charge.ErrorAttributes())
-	}
-
+func (s *service) grantPromotionalCredit(ctx context.Context, charge creditpurchase.Charge) (creditpurchase.Charge, error) {
 	ledgerTransactionGroupReference, err := s.handler.OnPromotionalCreditPurchase(ctx, charge)
 	if err != nil {
 		return creditpurchase.Charge{}, err
@@ -47,14 +38,54 @@ func (s *service) onPromotionalCreditPurchase(ctx context.Context, charge credit
 		}
 	}
 
-	charge.Status = creditpurchase.StatusFinal
+	return charge, nil
+}
+
+type PromotionalCreditpurchaseStateMachine struct {
+	*stateMachine
+}
+
+func NewPromotionalCreditPurchaseStateMachine(config StateMachineConfig) (*PromotionalCreditpurchaseStateMachine, error) {
+	if err := config.Validate(); err != nil {
+		return nil, fmt.Errorf("validate: %w", err)
+	}
+
+	if config.Charge.Intent.Settlement.Type() != creditpurchase.SettlementTypePromotional {
+		return nil, fmt.Errorf("charge %s is not promotional", config.Charge.ID)
+	}
 
-	updatedBase, err := s.adapter.UpdateCharge(ctx, charge.ChargeBase)
+	stateMachine, err := newStateMachineBase(config)
 	if err != nil {
-		return creditpurchase.Charge{}, err
+		return nil, fmt.Errorf("failed to create promotional credit purchase state machine: %w", err)
 	}
 
-	charge.ChargeBase = updatedBase
+	out := &PromotionalCreditpurchaseStateMachine{
+		stateMachine: stateMachine,
+	}
+	out.configureStates()
 
-	return charge, nil
+	return out, nil
+}
+
+func (s *PromotionalCreditpurchaseStateMachine) configureStates() {
+	s.Configure(creditpurchase.StatusCreated).
+		Permit(meta.TriggerNext, creditpurchase.StatusFinal)
+
+	s.Configure(creditpurchase.StatusActive).
+		Permit(meta.TriggerNext, creditpurchase.StatusFinal)
+
+	s.Configure(creditpurchase.StatusFinal).
+		OnEntry(func(ctx context.Context, _ ...any) error {
+			return s.GrantPromotionalCredit(ctx)
+		})
+}
+
+func (s *PromotionalCreditpurchaseStateMachine) GrantPromotionalCredit(ctx context.Context) error {
+	charge, err := s.Service.grantPromotionalCredit(ctx, s.Charge)
+	if err != nil {
+		return fmt.Errorf("grant promotional credit: %w", err)
+	}
+
+	s.Charge = charge
+	return nil
 }