lnwallet/errors: create concrete errors for settle/fail

lnwallet/errors.go

@@ -125,3 +125,49 @@ func ErrChanTooSmall(chanSize, minChanSize btcutil.Amount) ReservationError {
 			chanSize, minChanSize),
 	}
 }
+
+// ErrHtlcIndexAlreadyFailed is returned when the HTLC index has already been
+// failed, but has not been committed by our commitment state.
+type ErrHtlcIndexAlreadyFailed uint64
+
+// Error returns a message indicating the index that had already been failed.
+func (e ErrHtlcIndexAlreadyFailed) Error() string {
+	return fmt.Sprintf("HTLC with ID %d has already been failed", e)
+}
+
+// ErrHtlcIndexAlreadySettled is returned when the HTLC index has already been
+// settled, but has not been committed by our commitment state.
+type ErrHtlcIndexAlreadySettled uint64
+
+// Error returns a message indicating the index that had already been settled.
+func (e ErrHtlcIndexAlreadySettled) Error() string {
+	return fmt.Sprintf("HTLC with ID %d has already been settled", e)
+}
+
+// ErrInvalidSettlePreimage is returned when trying to settle an HTLC, but the
+// preimage does not correspond to the payment hash.
+type ErrInvalidSettlePreimage struct {
+	preimage []byte
+	rhash    []byte
+}
+
+// Error returns an error message with the offending preimage and intended
+// payment hash.
+func (e ErrInvalidSettlePreimage) Error() string {
+	return fmt.Sprintf("Invalid payment preimage %x for hash %x",
+		e.preimage, e.rhash)
+}
+
+// ErrUnknownHtlcIndex is returned when locally settling or failing an HTLC, but
+// the HTLC index is not known to the channel. This typically indicates that the
+// HTLC was already settled in a prior commitment.
+type ErrUnknownHtlcIndex struct {
+	chanID lnwire.ShortChannelID
+	index  uint64
+}
+
+// Error returns an error logging the channel and HTLC index that was unknown.
+func (e ErrUnknownHtlcIndex) Error() string {
+	return fmt.Sprintf("No HTLC with ID %d in channel %v",
+		e.index, e.chanID)
+}