channeldb: add new payment status StatusInitiated

This commit adds a new payment status, `StatusInitiated`, to properly
represent the state where a payment is newly created without attempting
any HTLCs. Since the `PaymentStatus` is a memory representation of a
given payment's status, the enum used for the statuses are directly
updated.

channeldb/payment_control.go

@@ -26,6 +26,10 @@ var (
 	// already "in flight" on the network.
 	ErrPaymentInFlight = errors.New("payment is in transition")
 
+	// ErrPaymentExists is returned when we try to initialize an already
+	// existing payment that is not failed.
+	ErrPaymentExists = errors.New("payment already exists")
+
 	// ErrPaymentNotInitiated is returned if the payment wasn't initiated.
 	ErrPaymentNotInitiated = errors.New("payment isn't initiated")
 
@@ -148,10 +152,15 @@ func (p *PaymentControl) InitPayment(paymentHash lntypes.Hash,
 		// retrying the payment or return a specific error.
 		case err == nil:
 			switch paymentStatus {
-
 			// We allow retrying failed payments.
 			case StatusFailed:
 
+			// We already have payment creation info for this
+			// payment so we won't allow creating a duplicate one.
+			case StatusInitiated:
+				updateErr = ErrPaymentExists
+				return nil
+
 			// We already have an InFlight payment on the network.
 			// We will disallow any new payments.
 			case StatusInFlight:
@@ -727,6 +736,9 @@ func ensureInFlight(payment *MPPayment) error {
 	paymentStatus := payment.Status
 
 	switch {
+	// Newly created payment is also inflight.
+	case paymentStatus == StatusInitiated:
+		return nil
 
 	// The payment was indeed InFlight.
 	case paymentStatus == StatusInFlight:

channeldb/payment_status.go

@@ -7,22 +7,29 @@ const (
 	// NOTE: PaymentStatus = 0 was previously used for status unknown and
 	// is now deprecated.
 
+	// StatusInitiated is the status where a payment has just been
+	// initiated.
+	StatusInitiated PaymentStatus = 1
+
 	// StatusInFlight is the status where a payment has been initiated, but
 	// a response has not been received.
-	StatusInFlight PaymentStatus = 1
+	StatusInFlight PaymentStatus = 2
 
 	// StatusSucceeded is the status where a payment has been initiated and
 	// the payment was completed successfully.
-	StatusSucceeded PaymentStatus = 2
+	StatusSucceeded PaymentStatus = 3
 
 	// StatusFailed is the status where a payment has been initiated and a
 	// failure result has come back.
-	StatusFailed PaymentStatus = 3
+	StatusFailed PaymentStatus = 4
 )
 
 // String returns readable representation of payment status.
 func (ps PaymentStatus) String() string {
 	switch ps {
+	case StatusInitiated:
+		return "Initiated"
+
 	case StatusInFlight:
 		return "In Flight"