lnrpc: ability to spend unconfirmed coins

lnrpc/rpc_utils.go

@@ -2,6 +2,7 @@ package lnrpc
 
 import (
 	"encoding/hex"
+	"errors"
 	"sort"
 
 	"github.com/lightningnetwork/lnd/lnwallet"
@@ -52,3 +53,38 @@ func RPCTransactionDetails(txns []*lnwallet.TransactionDetail) *TransactionDetai
 
 	return txDetails
 }
+
+// ExtractMinConfs extracts the minimum number of confirmations that each
+// output used to fund a transaction should satisfy.
+func ExtractMinConfs(minConfs int32, spendUnconfirmed bool) (int32, error) {
+	switch {
+	// Ensure that the MinConfs parameter is non-negative.
+	case minConfs < 0:
+		return 0, errors.New("minimum number of confirmations must " +
+			"be a non-negative number")
+
+	// The transaction should not be funded with unconfirmed outputs
+	// unless explicitly specified by SpendUnconfirmed. We do this to
+	// provide sane defaults to the OpenChannel RPC, as otherwise, if the
+	// MinConfs field isn't explicitly set by the caller, we'll use
+	// unconfirmed outputs without the caller being aware.
+	case minConfs == 0 && !spendUnconfirmed:
+		return 1, nil
+
+	// In the event that the caller set MinConfs > 0 and SpendUnconfirmed to
+	// true, we'll return an error to indicate the conflict.
+	case minConfs > 0 && spendUnconfirmed:
+		return 0, errors.New("SpendUnconfirmed set to true with " +
+			"MinConfs > 0")
+
+	// The funding transaction of the new channel to be created can be
+	// funded with unconfirmed outputs.
+	case spendUnconfirmed:
+		return 0, nil
+
+	// If none of the above cases matched, we'll return the value set
+	// explicitly by the caller.
+	default:
+		return minConfs, nil
+	}
+}