From 1e2cc1c65983e379d72518b3db29b0bbd604244c Mon Sep 17 00:00:00 2001
From: Nico Vergauwen <vergauwennico@gmail.com>
Date: Tue, 5 Jan 2021 16:56:58 +0100
Subject: [PATCH] WIP

---
 eth/backend.go      | 18 +++++++++++++++++-
 eth/backend_test.go |  2 +-
 eth/client.go       |  2 +-
 3 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/eth/backend.go b/eth/backend.go
index 5a6ab6b6ca..d88bebd97c 100644
--- a/eth/backend.go
+++ b/eth/backend.go
@@ -47,9 +47,11 @@ type backend struct {
 	abiMap       map[string]*abi.ABI
 	nonceManager *NonceManager
 	signer       types.Signer
+
+	maxGasPrice *big.Int
 }
 
-func NewBackend(client *ethclient.Client, signer types.Signer) (Backend, error) {
+func NewBackend(client *ethclient.Client, signer types.Signer, maxGasPrice *big.Int) (Backend, error) {
 	abiMap, err := makeABIMap()
 	if err != nil {
 		return nil, err
@@ -60,6 +62,7 @@ func NewBackend(client *ethclient.Client, signer types.Signer) (Backend, error)
 		abiMap,
 		NewNonceManager(client),
 		signer,
+		maxGasPrice,
 	}, nil
 }
 
@@ -99,6 +102,19 @@ func (b *backend) SendTransaction(ctx context.Context, tx *types.Transaction) er
 	return nil
 }
 
+func (b *backend) SuggestGasPrice(ctx context.Context) (*big.Int, error) {
+	gp, err := b.Client.SuggestGasPrice(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	if b.maxGasPrice != nil && gp.Cmp(b.maxGasPrice) >= 0 {
+		return nil, fmt.Errorf("current gas price exceeds maximum gas price")
+	}
+
+	return gp, nil
+}
+
 type txLog struct {
 	method string
 	inputs string
diff --git a/eth/backend_test.go b/eth/backend_test.go
index 99adbaf82e..e947b6837f 100644
--- a/eth/backend_test.go
+++ b/eth/backend_test.go
@@ -80,7 +80,7 @@ func TestSendTransaction_SendErr_DontUpdateNonce(t *testing.T) {
 	signedTx, err := types.SignTx(tx, signer, privateKey)
 	require.Nil(t, err)
 
-	bi, err := NewBackend(client, signer)
+	bi, err := NewBackend(client, signer, nil)
 	require.Nil(t, err)
 
 	nonceLockBefore := bi.(*backend).nonceManager.getNonceLock(fromAddress)
diff --git a/eth/client.go b/eth/client.go
index e72c4b3538..b32e10dba5 100644
--- a/eth/client.go
+++ b/eth/client.go
@@ -158,7 +158,7 @@ func NewClient(accountAddr ethcommon.Address, keystoreDir string, eth *ethclient
 
 	signer := types.NewEIP155Signer(chainID)
 
-	backend, err := NewBackend(eth, signer)
+	backend, err := NewBackend(eth, signer, nil)
 	if err != nil {
 		return nil, err
 	}