import time


def wait_for_transaction(blockchain_client, txn_hash, max_wait=60, sleep_time=5):
    start = time.time()
    while True:
        txn_receipt = blockchain_client.get_transaction_receipt(txn_hash)
        if txn_receipt is not None:
            break
        elif time.time() > start + max_wait:
            raise ValueError("Could not get transaction receipt")
        time.sleep(sleep_time)
    return txn_receipt


def wait_for_block(blockchain_client, block_number, max_wait=60, sleep_time=5):
    start = time.time()
    while time.time() < start + max_wait:
        latest_block_number = blockchain_client.get_block_number()
        if latest_block_number >= block_number:
            break
        time.sleep(sleep_time)
    else:
        raise ValueError("Did not reach block")
    return blockchain_client.get_block_by_number(block_number)


def get_max_gas(blockchain_client):
    latest_block = blockchain_client.get_block_by_number('latest')
    max_gas_hex = latest_block['gasLimit']
    max_gas = int(max_gas_hex, 16)
    return max_gas


def get_transaction_params(_from=None, to=None, gas=None, gas_price=None,
                           value=0, data=None):
    params = {}

    if _from is None:
        raise ValueError("No default from address specified")

    params['from'] = _from

    if to is None and data is None:
        raise ValueError("A `to` address is only optional for contract creation")
    elif to is not None:
        params['to'] = to

    if gas is not None:
        params['gas'] = hex(gas)

    if gas_price is not None:
        params['gasPrice'] = hex(gas_price)

    if value is not None:
        params['value'] = hex(value).rstrip('L')

    if data is not None:
        params['data'] = data

    return params


def 
(from_block=None, to_block=None, address=None,
                          topics=None):
    params = {}
    if from_block is not None:
        params["fromBlock"] = from_block
    if to_block is not None:
        params["toBlock"] = to_block
    if address is not None:
        params["address"] = address
    if topics is not None:
        params["topics"] = topics
    return(params)

construct_filter_args