Add get transaction count method to eth client

ethereum/client.go

@@ -62,6 +62,7 @@ type Client interface {
 	BlockNumber(ctx context.Context) (*big.Int, error)
 	TransactionReceipt(ctx context.Context, txHash string) (*domain.TransactionReceipt, error)
 	ChainID(ctx context.Context) (*big.Int, error)
+	GetTransactionCount(ctx context.Context, address string, blockNumber *big.Int) (*big.Int, error)
 	TraceBlock(ctx context.Context, number *big.Int) ([]domain.Trace, error)
 	GetLogs(ctx context.Context, q ethereum.FilterQuery) ([]types.Log, error)
 	SubscribeToHead(ctx context.Context) (domain.HeaderCh, error)
@@ -76,6 +77,7 @@ const getLogs = "eth_getLogs"
 const transactionReceipt = "eth_getTransactionReceipt"
 const traceBlock = "trace_block"
 const chainId = "eth_chainId"
+const getTransactionCount = "eth_getTransactionCount"
 
 const defaultRetryInterval = time.Second * 15
 
@@ -343,6 +345,32 @@ func (e *streamEthClient) TransactionReceipt(ctx context.Context, txHash string)
 	return &result, err
 }
 
+// GetTransactionCount returns the transaction count for an address
+func (e *streamEthClient) GetTransactionCount(ctx context.Context, address string, blockNumber *big.Int) (*big.Int, error) {
+	name := fmt.Sprintf("%s(%s, %s)", getTransactionCount, address, blockNumber)
+	log.Debugf(name)
+	var result string
+	err := withBackoff(ctx, name, func(ctx context.Context) error {
+		err := e.rpcClient.CallContext(ctx, &result, getTransactionCount, address, blockNumber)
+		if err != nil {
+			return err
+		}
+		if result == "" {
+			return ErrNotFound
+		}
+		return nil
+	}, RetryOptions{
+		MinBackoff:     pointDur(e.retryInterval),
+		MaxElapsedTime: pointDur(12 * time.Hour),
+		MaxBackoff:     pointDur(e.retryInterval),
+	}, nil, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	return utils.HexToBigInt(result)
+}
+
 // SubscribeToHead subscribes to the blockchain head and returns a channel which provides
 // the latest block headers. The channel is closed when subscription encounters an error
 // or becomes inactive (e.g. due to a hanging connection).