From 91240b7ffe5eb35438103b91fa0fa7b4af709bdb Mon Sep 17 00:00:00 2001
From: Ferran Borreguero <ferranbt@protonmail.com>
Date: Sat, 16 Apr 2022 00:07:35 +0200
Subject: [PATCH] Add nonce when sending transaction in contract (#185)

* Add nonce when sending transaction in contract

* Add Changelog entry
---
 CHANGELOG.md              |  1 +
 contract/contract.go      |  9 +++++++++
 contract/contract_test.go | 21 ++++++++++++---------
 wallet/signer.go          | 14 ++++++++++++--
 wallet/signer_test.go     |  6 ++++++
 5 files changed, 40 insertions(+), 11 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 608f504b..bd96d2ac 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,7 @@
 
 # 0.1.1 (Not released)
 
+- Retrieve latest nonce when sending a transaction on `contract` [[GH-185](https://github.com/umbracle/ethgo/issues/185)]
 - Add `etherscan.GasPrice` function to return last block gas price [[GH-182](https://github.com/umbracle/ethgo/issues/182)]
 - Add `4byte` package and cli [[GH-178](https://github.com/umbracle/ethgo/issues/178)]
 - Install and use `ethers.js` spec tests for wallet private key decoding [[GH-177](https://github.com/umbracle/ethgo/issues/177)]
diff --git a/contract/contract.go b/contract/contract.go
index bad361cf..92a017c3 100644
--- a/contract/contract.go
+++ b/contract/contract.go
@@ -69,6 +69,13 @@ func (j *jsonRPCNodeProvider) Txn(addr ethgo.Address, key ethgo.Key, input []byt
 			return nil, err
 		}
 	}
+	// calculate the nonce
+	if opts.Nonce == 0 {
+		opts.Nonce, err = j.client.GetNonce(from, ethgo.Latest)
+		if err != nil {
+			return nil, fmt.Errorf("failed to calculate nonce: %v", err)
+		}
+	}
 
 	chainID, err := j.client.ChainID()
 	if err != nil {
@@ -82,6 +89,7 @@ func (j *jsonRPCNodeProvider) Txn(addr ethgo.Address, key ethgo.Key, input []byt
 		GasPrice: opts.GasPrice,
 		Gas:      opts.GasLimit,
 		Value:    opts.Value,
+		Nonce:    opts.Nonce,
 	}
 	if addr != ethgo.ZeroAddress {
 		rawTxn.To = &addr
@@ -244,6 +252,7 @@ type TxnOpts struct {
 	Value    *big.Int
 	GasPrice uint64
 	GasLimit uint64
+	Nonce    uint64
 }
 
 func (a *Contract) Txn(method string, args ...interface{}) (Txn, error) {
diff --git a/contract/contract_test.go b/contract/contract_test.go
index 6098857c..073d4b3e 100644
--- a/contract/contract_test.go
+++ b/contract/contract_test.go
@@ -149,15 +149,18 @@ func TestContract_Transaction(t *testing.T) {
 	abi, err := abi.NewABI(artifact.Abi)
 	assert.NoError(t, err)
 
-	// create a transaction
-	i := NewContract(addr, abi, WithJsonRPCEndpoint(s.HTTPAddr()), WithSender(key))
-	txn, err := i.Txn("setA")
-	assert.NoError(t, err)
+	// send multiple transactions
+	contract := NewContract(addr, abi, WithJsonRPCEndpoint(s.HTTPAddr()), WithSender(key))
 
-	err = txn.Do()
-	assert.NoError(t, err)
+	for i := 0; i < 10; i++ {
+		txn, err := contract.Txn("setA")
+		assert.NoError(t, err)
 
-	receipt, err := txn.Wait()
-	assert.NoError(t, err)
-	assert.Len(t, receipt.Logs, 1)
+		err = txn.Do()
+		assert.NoError(t, err)
+
+		receipt, err := txn.Wait()
+		assert.NoError(t, err)
+		assert.Len(t, receipt.Logs, 1)
+	}
 }
diff --git a/wallet/signer.go b/wallet/signer.go
index 323f21a7..135adcca 100644
--- a/wallet/signer.go
+++ b/wallet/signer.go
@@ -40,6 +40,16 @@ func (e *EIP1155Signer) RecoverSender(tx *ethgo.Transaction) (ethgo.Address, err
 	return addr, nil
 }
 
+func trimBytesZeros(b []byte) []byte {
+	var i int
+	for i = 0; i < len(b); i++ {
+		if b[i] != 0x0 {
+			break
+		}
+	}
+	return b[i:]
+}
+
 func (e *EIP1155Signer) SignTx(tx *ethgo.Transaction, key ethgo.Key) (*ethgo.Transaction, error) {
 	hash := signHash(tx, e.chainID)
 
@@ -50,8 +60,8 @@ func (e *EIP1155Signer) SignTx(tx *ethgo.Transaction, key ethgo.Key) (*ethgo.Tra
 
 	vv := uint64(sig[64]) + 35 + e.chainID*2
 
-	tx.R = sig[:32]
-	tx.S = sig[32:64]
+	tx.R = trimBytesZeros(sig[:32])
+	tx.S = trimBytesZeros(sig[32:64])
 	tx.V = new(big.Int).SetUint64(vv).Bytes()
 	return tx, nil
 }
diff --git a/wallet/signer_test.go b/wallet/signer_test.go
index c60502e1..3ac5a854 100644
--- a/wallet/signer_test.go
+++ b/wallet/signer_test.go
@@ -35,3 +35,9 @@ func TestSigner_EIP1155(t *testing.T) {
 		assert.NotEqual(t, from, from2)
 	*/
 }
+
+func TestTrimBytesZeros(t *testing.T) {
+	assert.Equal(t, trimBytesZeros([]byte{0x1, 0x2}), []byte{0x1, 0x2})
+	assert.Equal(t, trimBytesZeros([]byte{0x0, 0x1}), []byte{0x1})
+	assert.Equal(t, trimBytesZeros([]byte{0x0, 0x0}), []byte{})
+}