class Eth::Client

def transact(contract, function_name, *args, **kwargs)
  gas_limit = Tx.estimate_intrinsic_gas(contract.bin) + Tx::CREATE_GAS
  fun = contract.functions.select { |func| func.name == function_name }[0]
  params = {
    value: 0,
    gas_limit: gas_limit,
    chain_id: chain_id,
    to: kwargs[:address] || contract.address,
    data: call_payload(fun, args),
  }
  if kwargs[:legacy]
    params.merge!({
      gas_price: max_fee_per_gas,
    })
  else
    params.merge!({
      priority_fee: max_priority_fee_per_gas,
      max_gas_fee: max_fee_per_gas,
    })
  end
  unless kwargs[:sender_key].nil?
    # use the provided key as sender and signer
    params.merge!({
      from: kwargs[:sender_key].address,
      nonce: get_nonce(kwargs[:sender_key].address),
    })
    tx = Eth::Tx.new(params)
    tx.sign kwargs[:sender_key]
    return eth_send_raw_transaction(tx.hex)["result"]
  else
    # use the default account as sender and external signer
    params.merge!({
      from: default_account,
      nonce: get_nonce(default_account),
    })
    return eth_send_transaction(params)["result"]
  end
end