feat: billing subscription handler

openmeter/billing/README.md

@@ -149,3 +149,12 @@ The entity's `ChildrenWithIDReuse` call can be used to facilitate the line reuse
 Then the adapter layer will use those IDs to make decisions if they want to persist or recreate the records.
 
 We could do the same logic in the adapter layer, but this approach makes it more flexible on the calculation layer if we want to generate new lines or not. If this becomes a burden we can do the same matching logic as part of the upsert logic in adapter.
+
+## Subscription adapter
+
+The subscription adapter is responsible for feeding the billing with line items during the subscription's lifecycle. The generation of items is event-driven, new items are yielded when:
+- A subscription is created
+- A new invoice is created
+- A subscription is modified
+
+TODO: for new versions the previous line will be split and will not get the stuff from the other side -> this means that the unique id should encode the version of the item

openmeter/billing/adapter.go

@@ -45,6 +45,7 @@ type InvoiceLineAdapter interface {
 	ListInvoiceLines(ctx context.Context, input ListInvoiceLinesAdapterInput) ([]*Line, error)
 	AssociateLinesToInvoice(ctx context.Context, input AssociateLinesToInvoiceAdapterInput) ([]*Line, error)
 	GetInvoiceLine(ctx context.Context, input GetInvoiceLineAdapterInput) (*Line, error)
+	GetLinesForSubscription(ctx context.Context, input GetLinesForSubscriptionInput) ([]*Line, error)
 
 	GetInvoiceLineOwnership(ctx context.Context, input GetInvoiceLineOwnershipAdapterInput) (GetOwnershipAdapterResponse, error)
 }

openmeter/billing/adapter/invoice.go

@@ -43,7 +43,7 @@ func (a *adapter) GetInvoiceById(ctx context.Context, in billing.GetInvoiceByIdI
 			WithBillingWorkflowConfig()
 
 		if in.Expand.Lines {
-			query = tx.expandInvoiceLineItems(query, in.Expand.DeletedLines)
+			query = tx.expandInvoiceLineItems(query, in.Expand)
 		}
 
 		invoice, err := query.Only(ctx)
@@ -63,15 +63,20 @@ func (a *adapter) GetInvoiceById(ctx context.Context, in billing.GetInvoiceByIdI
 	})
 }
 
-func (a *adapter) expandInvoiceLineItems(query *db.BillingInvoiceQuery, includeDeleted bool) *db.BillingInvoiceQuery {
+func (a *adapter) expandInvoiceLineItems(query *db.BillingInvoiceQuery, expand billing.InvoiceExpand) *db.BillingInvoiceQuery {
 	return query.WithBillingInvoiceLines(func(q *db.BillingInvoiceLineQuery) {
-		if !includeDeleted {
+		if !expand.DeletedLines {
 			q = q.Where(billinginvoiceline.DeletedAtIsNil())
 		}
 
+		requestedStatuses := []billing.InvoiceLineStatus{billing.InvoiceLineStatusValid}
+		if expand.SplitLines {
+			requestedStatuses = append(requestedStatuses, billing.InvoiceLineStatusSplit)
+		}
+
 		q = q.Where(
 			// Detailed lines are sub-lines of a line and should not be included in the top-level invoice
-			billinginvoiceline.StatusIn(billing.InvoiceLineStatusValid),
+			billinginvoiceline.StatusIn(requestedStatuses...),
 		)
 
 		a.expandLineItems(q)
@@ -170,6 +175,10 @@ func (a *adapter) ListInvoices(ctx context.Context, input billing.ListInvoicesIn
 			query = query.Where(billinginvoice.StatusIn(input.ExtendedStatuses...))
 		}
 
+		if len(input.IDs) > 0 {
+			query = query.Where(billinginvoice.IDIn(input.IDs...))
+		}
+
 		if len(input.Statuses) > 0 {
 			query = query.Where(func(s *sql.Selector) {
 				s.Where(sql.Or(
@@ -190,7 +199,7 @@ func (a *adapter) ListInvoices(ctx context.Context, input billing.ListInvoicesIn
 		}
 
 		if input.Expand.Lines {
-			query = tx.expandInvoiceLineItems(query, input.Expand.DeletedLines)
+			query = tx.expandInvoiceLineItems(query, input.Expand)
 		}
 
 		switch input.OrderBy {

openmeter/billing/adapter/invoicelinemapper.go

@@ -52,6 +52,7 @@ func (a *adapter) mapInvoiceLineFromDB(ctx context.Context, invoiceLines []*db.B
 		if err != nil {
 			return nil, err
 		}
+
 		mappedEntities[dbLine.ID] = &entity
 	}
 

openmeter/billing/adapter/invoicelines.go

@@ -103,7 +103,7 @@ func (a *adapter) UpsertInvoiceLines(ctx context.Context, inputIn billing.Upsert
 					SetNillableInvoicingAppExternalID(lo.EmptyableToPtr(line.ExternalIDs.Invoicing))
 
 				if line.Subscription != nil {
-					create = create.SetSubscriptionID(line.Subscription.ItemID).
+					create = create.SetSubscriptionID(line.Subscription.SubscriptionID).
 						SetSubscriptionPhaseID(line.Subscription.PhaseID).
 						SetSubscriptionItemID(line.Subscription.ItemID)
 				}
@@ -492,3 +492,29 @@ func (a *adapter) GetInvoiceLineOwnership(ctx context.Context, in billing.GetInv
 		}, nil
 	})
 }
+
+func (a *adapter) GetLinesForSubscription(ctx context.Context, in billing.GetLinesForSubscriptionInput) ([]*billing.Line, error) {
+	if err := in.Validate(); err != nil {
+		return nil, billing.ValidationError{
+			Err: err,
+		}
+	}
+
+	return entutils.TransactingRepo(ctx, a, func(ctx context.Context, tx *adapter) ([]*billing.Line, error) {
+		query := tx.db.BillingInvoiceLine.Query().
+			Where(billinginvoiceline.Namespace(in.Namespace)).
+			Where(billinginvoiceline.SubscriptionID(in.SubscriptionID)).
+			// TODO: document issues with deleted lines
+			// Where(billinginvoiceline.DeletedAtIsNil()). TBD
+			Where(billinginvoiceline.ParentLineIDIsNil()) // This one is required so that we are not fetching split line's children directly, the mapper will handle that
+
+		query = tx.expandLineItems(query)
+
+		dbLines, err := query.All(ctx)
+		if err != nil {
+			return nil, fmt.Errorf("fetching lines: %w", err)
+		}
+
+		return tx.mapInvoiceLineFromDB(ctx, dbLines)
+	})
+}

openmeter/billing/defaults.go

@@ -4,4 +4,8 @@ import "time"
 
 const (
 	DefaultMeterResolution = time.Minute
+	// DefaultProratePercision is the default number of decimal places to round to when prorating, this should be
+	// at least one digit more than the smallest unit represented in the currency (e.g. 3 for USD)
+	// TODO[later]: This should come from the currency
+	DefaultProratePercision = 3
 )

openmeter/billing/invoice.go

@@ -137,13 +137,15 @@ type InvoiceExpand struct {
 	WorkflowApps bool
 	Lines        bool
 	DeletedLines bool
+	SplitLines   bool
 }
 
 var InvoiceExpandAll = InvoiceExpand{
 	Preceding:    true,
 	WorkflowApps: true,
 	Lines:        true,
 	DeletedLines: false,
+	SplitLines:   false,
 }
 
 func (e InvoiceExpand) Validate() error {
@@ -160,6 +162,11 @@ func (e InvoiceExpand) SetDeletedLines(v bool) InvoiceExpand {
 	return e
 }
 
+func (e InvoiceExpand) SetSplitLines(v bool) InvoiceExpand {
+	e.SplitLines = v
+	return e
+}
+
 type InvoiceBase struct {
 	Namespace string `json:"namespace"`
 	ID        string `json:"id"`
@@ -373,6 +380,7 @@ type ListInvoicesInput struct {
 	pagination.Page
 
 	Namespace string
+	IDs       []string
 	Customers []string
 	// Statuses searches by short InvoiceStatus (e.g. draft, issued)
 	Statuses []string
@@ -497,3 +505,21 @@ type GetOwnershipAdapterResponse struct {
 }
 
 type DeleteInvoiceInput = InvoiceID
+
+type UpdateInvoiceLinesInternalInput struct {
+	Namespace  string
+	CustomerID string
+	Lines      []*Line
+}
+
+func (i UpdateInvoiceLinesInternalInput) Validate() error {
+	if i.Namespace == "" {
+		return errors.New("namespace is required")
+	}
+
+	if i.CustomerID == "" {
+		return errors.New("customer ID is required")
+	}
+
+	return nil
+}

openmeter/billing/invoiceline.go

@@ -99,6 +99,10 @@ func (p Period) Contains(t time.Time) bool {
 	return t.After(p.Start) && t.Before(p.End)
 }
 
+func (p Period) Duration() time.Duration {
+	return p.End.Sub(p.Start)
+}
+
 // LineBase represents the common fields for an invoice item.
 type LineBase struct {
 	Namespace string `json:"namespace"`
@@ -409,6 +413,38 @@ func (i Line) ValidateUsageBased() error {
 	return nil
 }
 
+// DissacociateChildren removes the Children both from the DBState and the current line, so that the
+// line can be safely persisted/managed without the children.
+//
+// The childrens receive DBState objects, so that they can be safely persisted/managed without the parent.
+func (i *Line) DisassociateChildren() {
+	if i.Children.IsAbsent() {
+		return
+	}
+
+	// originalChildren := i.Children
+
+	i.Children = LineChildren{}
+	if i.DBState != nil {
+		i.DBState.Children = LineChildren{}
+	}
+	/*
+		 TODO
+			if i.DBState != nil {
+				dbChildrenByID := lo.GroupBy(i.DBState.Children.OrEmpty(), func(l *Line) string {
+					return l.ID
+				})
+				currentChildren := originalChildren.OrEmpty()
+
+				for _, child := range currentChildren {
+					if dbChild, ok := dbChildrenByID[child.ID]; ok {
+						child.DBState = dbChild[0]
+					}
+				}
+			}
+	*/
+}
+
 // TODO[OM-1016]: For events we need a json marshaler
 type LineChildren struct {
 	mo.Option[[]*Line]
@@ -471,7 +507,11 @@ func (c *LineChildren) ReplaceByID(id string, newLine *Line) bool {
 
 	for i, line := range lines {
 		if line.ID == id {
+			// Let's preserve the DB state of the original line (as we are only replacing the current state)
+			originalDBState := line.DBState
+
 			lines[i] = newLine
+			lines[i].DBState = originalDBState
 			return true
 		}
 	}
@@ -952,3 +992,20 @@ type GetInvoiceLineInput = LineID
 type GetInvoiceLineOwnershipAdapterInput = LineID
 
 type DeleteInvoiceLineInput = LineID
+
+type GetLinesForSubscriptionInput struct {
+	Namespace      string
+	SubscriptionID string
+}
+
+func (i GetLinesForSubscriptionInput) Validate() error {
+	if i.Namespace == "" {
+		return errors.New("namespace is required")
+	}
+
+	if i.SubscriptionID == "" {
+		return errors.New("subscription id is required")
+	}
+
+	return nil
+}

openmeter/billing/service.go

@@ -32,7 +32,9 @@ type CustomerOverrideService interface {
 type InvoiceLineService interface {
 	CreatePendingInvoiceLines(ctx context.Context, input CreateInvoiceLinesInput) ([]*Line, error)
 	GetInvoiceLine(ctx context.Context, input GetInvoiceLineInput) (*Line, error)
+	GetLinesForSubscription(ctx context.Context, input GetLinesForSubscriptionInput) ([]*Line, error)
 	UpdateInvoiceLine(ctx context.Context, input UpdateInvoiceLineInput) (*Line, error)
+
 	DeleteInvoiceLine(ctx context.Context, input DeleteInvoiceLineInput) error
 }
 
@@ -48,4 +50,11 @@ type InvoiceService interface {
 	ApproveInvoice(ctx context.Context, input ApproveInvoiceInput) (Invoice, error)
 	RetryInvoice(ctx context.Context, input RetryInvoiceInput) (Invoice, error)
 	DeleteInvoice(ctx context.Context, input DeleteInvoiceInput) error
+
+	// UpdateInvoiceLinesInternal updates the specified invoice lines and ensures that invoice states are properly syncronized
+	// This method is intended to be used by OpenMeter internal services only, as it allows for updating invoice line values,
+	// that are not allowed to be updated by external services.
+	//
+	// The call also ensures that the invoice's state is properly updated and invoice immutability is also considered.
+	UpdateInvoiceLinesInternal(ctx context.Context, input UpdateInvoiceLinesInternalInput) error
 }