allow access to underlying raw transaction signing method (#116)

* allow access to underlying raw transaction signing method

* change method signature to default chainId to 1

lib/src/core/client.dart

@@ -380,10 +380,10 @@ class Web3Client {
       client: this,
     );
 
-    return _signTransaction(
+    return signTransactionRaw(
       signingInput.transaction,
       signingInput.credentials,
-      signingInput.chainId,
+      chainId: signingInput.chainId,
     );
   }
 

lib/src/core/transaction_signer.dart

@@ -100,11 +100,11 @@ Uint8List prependTransactionType(int type, Uint8List transaction) {
     ..setAll(1, transaction);
 }
 
-Uint8List _signTransaction(
+Uint8List signTransactionRaw(
   Transaction transaction,
-  Credentials c,
-  int? chainId,
-) {
+  Credentials c, {
+  int? chainId = 1,
+  }) {
   if (transaction.isEIP1559 && chainId != null) {
     final encodedTx = LengthTrackingByteSink();
     encodedTx.addByte(0x02);

test/core/sign_transaction_test.dart

@@ -1,4 +1,5 @@
 import 'dart:convert';
+import 'dart:typed_data';
 
 import 'package:http/http.dart';
 import 'package:test/test.dart';
@@ -149,6 +150,44 @@ void main() {
     });
   });
 
+  test('sign eip 1559 transaction without client', ()  {
+    final data = jsonDecode(rawJson) as List<dynamic>;
+
+     Future.forEach(data, (element)  {
+      final tx = element as Map<String, dynamic>;
+      final credentials =
+      EthPrivateKey.fromHex(strip0x(tx['privateKey'] as String));
+      final transaction = Transaction(
+        from: credentials.address,
+        to: EthereumAddress.fromHex(tx['to'] as String),
+        nonce: tx['nonce'] as int,
+        maxGas: tx['gasLimit'] as int,
+        value: EtherAmount.inWei(BigInt.from(tx['value'] as int)),
+        maxFeePerGas: EtherAmount.fromBigInt(
+          EtherUnit.wei,
+          BigInt.from(tx['maxFeePerGas'] as int),
+        ),
+        maxPriorityFeePerGas: EtherAmount.fromBigInt(
+          EtherUnit.wei,
+          BigInt.from(tx['maxPriorityFeePerGas'] as int),
+        ),
+        data: tx['data'] ?? Uint8List(0),
+      );
+
+      final signature = signTransactionRaw(transaction, credentials, chainId: 4);
+
+      expect(
+        bytesToHex(
+          uint8ListFromList(
+            rlp.encode(prependTransactionType(0x02, signature)),
+          ),
+        ),
+        strip0x(tx['signedTransactionRLP'] as String),
+      );
+    });
+
+  });
+
   test('signs transactions', () async {
     final credentials = EthPrivateKey.fromHex(
       'a2fd51b96dc55aeb14b30d55a6b3121c7b9c599500c1beb92a389c3377adc86e',