signBTCTransactionWithMPC method

Future<String> signBTCTransactionWithMPC({ required String accountId, required String publicKey, required String privateKey, required MpcTransactionInfo transactionInfo, required String mpcSenderPublicKey, String path = "flutterchain", String mpcContract = 'v2.multichain-mpc.testnet', })

Signs a Bitcoin transaction with the Near MPC.

Parameters:

• accountId: The account ID of the Near sender.
• publicKey: The public key of the Near sender.
• privateKey: The private key of the Near sender.
• transactionInfo: The transaction information obtained from the MPC.
• mpcSenderPublicKey: The public key of the sender provided by the MPC.
• path: The path used for the MPC signing.
• mpcContract: The contract address of the MPC.

Returns the signed transaction as a string.

Implementation

Future<String> signBTCTransactionWithMPC({
  required String accountId,
  required String publicKey,
  required String privateKey,
  required MpcTransactionInfo transactionInfo,
  required String mpcSenderPublicKey,
  String path = "flutterchain",
  String mpcContract = 'v2.multichain-mpc.testnet',
}) async {
  final unsignedTransaction = transactionInfo.transactionInfo;

  //Get payloads of all utxos
  final payloadsListEncoded = await jsVMService.callJS(
      "window.BitcoinUtils.getReversedPayloadsToSignForMPC('${unsignedTransaction['psbt']}', '${jsonEncode(unsignedTransaction['utxos'])}', '$mpcSenderPublicKey')");
  final payloadsList = jsonDecode(payloadsListEncoded) as List<dynamic>;

  final List<Map<String, dynamic>> signatures = [];

  //Get signatures for each payload
  for (var i = 0; i < payloadsList.length; i++) {
    final payload = Uint8List.fromList(List<int>.from(payloadsList[i]));

    final nearSignRequest = await callSmartContractFunction(
      NearTransferRequest(
        fromAddress: accountId,
        publicKey: publicKey,
        toAddress: mpcContract,
        privateKey: privateKey,
        gas: "300000000000000",
        arguments: NearBlockChainSmartContractArguments(
          method: "sign",
          args: {
            "payload": payload,
            "path": path,
            "key_version": 0,
          },
          transferAmount: '0',
        ),
      ),
    );

    if (nearSignRequest.data["error"] != null) {
      throw Exception(nearSignRequest.data["error"]);
    }

    final signatureValList =
        List<String>.from(jsonDecode(nearSignRequest.data["success"]));

    final signatureData = {
      "big_r": signatureValList[0],
      "big_s": signatureValList[1],
    };

    signatures.add(signatureData);
  }

  //Sign transaction
  final signedTransactionEncoded = await jsVMService.callJS(
      "window.BitcoinUtils.signTransactionWithMPCSignature('${unsignedTransaction['psbt']}', '${jsonEncode(signatures)}', '$mpcSenderPublicKey')");

  final signedTransaction = jsonDecode(signedTransactionEncoded) as String;

  return signedTransaction;
}