public async Task <string> GetHubAddressAsync(string contractAddress)
{
var getHubAddr = new GetHubAddrFunction();
var getHubAddrHandler = _ethApiContractService.GetContractQueryHandler <GetHubAddrFunction>();
var address = await getHubAddrHandler
.QueryAsync <string>(contractAddress, getHubAddr)
.ConfigureAwait(false);
if (address == null)
{
throw new Exception($"Contract does not support Gas Station Network");
}
var code = await _ethApiContractService.GetCode
.SendRequestAsync(address)
.ConfigureAwait(false);
if (code.Length <= 2)
{
throw new Exception($"Relay hub is not deployed at address {address}");
}
var getHubVersion = new VersionFunction();
var getHubVersionHandler = _ethApiContractService.GetContractQueryHandler <VersionFunction>();
var hubVersion = await getHubVersionHandler
.QueryAsync <string>(address, getHubVersion)
.ConfigureAwait(false);
if (!hubVersion.StartsWith("1"))
{
throw new Exception($"Unsupported relay hub version {hubVersion}");
}
return(address);
}
public async Task Validate(
string hubAddress,
string recipient,
BigInteger gasLimit,
BigInteger gasPrice,
BigInteger relayFee)
{
var balanceOf = new BalanceOfFunction()
{
Target = recipient
};
var balanceOfHandler = _ethApiContractService.GetContractQueryHandler <BalanceOfFunction>();
var balance = await balanceOfHandler
.QueryAsync <BigInteger>(hubAddress, balanceOf)
.ConfigureAwait(false);
if (balance.IsZero)
{
throw new GSNLowBalanceException($"Recipient {recipient} has no funds for paying for relayed calls on the relay hub.");
}
var maxPossibleCharge = new MaxPossibleChargeFunction()
{
RelayedCallStipend = gasLimit,
GasPriceParam = gasPrice,
TransactionFee = relayFee
};
var maxPossibleChargeHandler = _ethApiContractService.GetContractQueryHandler <MaxPossibleChargeFunction>();
var maxCharge = await maxPossibleChargeHandler
.QueryAsync <BigInteger>(hubAddress, maxPossibleCharge)
.ConfigureAwait(false);
if (maxCharge.CompareTo(balance) == 1)
{
throw new GSNLowBalanceException($"Recipient {recipient} has not enough funds for paying for this relayed call (has {balance}, requires {maxCharge}).");
}
}