From c084a0de7e92bbc500234e66dcec690475ac9121 Mon Sep 17 00:00:00 2001
From: Craig Raw <craigraw@gmail.com>
Date: Thu, 4 Mar 2021 12:59:49 +0200
Subject: [PATCH] dont allow negative values to enter tx when send max true

---
 src/main/java/com/sparrowwallet/drongo/wallet/Wallet.java | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/main/java/com/sparrowwallet/drongo/wallet/Wallet.java b/src/main/java/com/sparrowwallet/drongo/wallet/Wallet.java
index e17f7c7..d772166 100644
--- a/src/main/java/com/sparrowwallet/drongo/wallet/Wallet.java
+++ b/src/main/java/com/sparrowwallet/drongo/wallet/Wallet.java
@@ -497,11 +497,15 @@ public class Wallet {
 
             //If sending all selected utxos, set the recipient amount to equal to total of those utxos less the no change fee
             long maxSendAmt = totalSelectedAmt - noChangeFeeRequiredAmt;
+            if(maxSendAmt < 0) {
+                throw new InsufficientFundsException("Not enough combined value in selected UTXOs for fee of " + noChangeFeeRequiredAmt);
+            }
+
             Optional<Payment> optMaxPayment = payments.stream().filter(payment -> payment.isSendMax()).findFirst();
             if(optMaxPayment.isPresent()) {
                 Payment maxPayment = optMaxPayment.get();
                 maxSendAmt = maxSendAmt - payments.stream().filter(payment -> !maxPayment.equals(payment)).map(Payment::getAmount).mapToLong(v -> v).sum();
-                if(maxPayment.getAmount() != maxSendAmt) {
+                if(maxSendAmt > 0 && maxPayment.getAmount() != maxSendAmt) {
                     maxPayment.setAmount(maxSendAmt);
                     totalPaymentAmount = payments.stream().map(Payment::getAmount).mapToLong(v -> v).sum();
                     continue;