def _estimate_gas(self, token_amount: TokenAmount, account: Account,
transaction_params: dict, **kw):
latest_block = self.w3.eth.getBlock("latest")
deadline = latest_block.timestamp + WEB3_TIMEOUT
return estimate_gas(
self.w3,
account,
self.router_proxy.functions.swapETHForExactTokens,
token_amount.as_wei,
[self.weth_address, token_amount.address],
account.address,
deadline,
**transaction_params,
)
def _estimate_gas(self, token_amount: TokenAmount, account: Account,
transaction_params: dict, **kw):
exchange_rate = kw.get("exchange_rate")
if exchange_rate is None:
raise ExchangeError(
f"An exchange rate is needed to estimate gas for a swap on {self.name}"
)
eth_address = self.get_token_network_address(TokenTicker("ETH"))
return estimate_gas(
self.w3,
account,
self.network_contract_proxy.functions.trade,
eth_address,
transaction_params["value"],
self.get_token_network_address(token_amount.ticker),
account.address,
token_amount.as_wei,
exchange_rate.as_wei,
account.address,
**transaction_params,
)
def _calculate_transaction_costs(self, token_amount: TokenAmount,
account: Account) -> dict:
exchange_rate = self.get_current_rate(token_amount)
eth_sold = EthereumAmount(token_amount.value * exchange_rate.value)
gas_price = EthereumAmount(Wei(self.w3.eth.generateGasPrice()))
exchange_proxy = self._get_exchange_proxy(token_amount.ticker)
latest_block = self.w3.eth.getBlock("latest")
deadline = latest_block.timestamp + self.EXCHANGE_TIMEOUT
transaction_params = {
"from": account.address,
"value": eth_sold.as_wei,
"gasPrice": gas_price.as_wei,
}
gas = estimate_gas(
self.w3,
account,
exchange_proxy.functions.ethToTokenSwapOutput,
token_amount.as_wei,
deadline,
**transaction_params,
)
max_gas_limit = Wei(int(latest_block["gasLimit"] * 0.9))
gas_with_margin = Wei(int(gas * GAS_LIMIT_MARGIN))
gas = min(gas_with_margin, max_gas_limit)
gas_cost = EthereumAmount(Wei(gas * gas_price.as_wei))
total = EthereumAmount(gas_cost.value + eth_sold.value)
log.debug("transaction cost",
gas_price=gas_price,
gas=gas,
eth=eth_sold)
return {
"gas_price": gas_price,
"gas": gas,
"eth_sold": eth_sold,
"total": total,
"exchange_rate": exchange_rate,
}