import dns.resolver


def get_mx_domains(hostname) -> [str]:
    try:
        answers = dns.resolver.query(hostname, "MX")
    except dns.resolver.NoAnswer:
        return []

    ret = []

    for a in answers:
        record = a.to_text()  # for ex '20 alt2.aspmx.l.google.com.'
        r = record.split(" ")[1]  # alt2.aspmx.l.google.com.
        ret.append(r)

    return ret


_include_spf = "include:"


def get_spf_domain(hostname) -> [str]:
    """return all domains listed in *include:*"""
    try:
        answers = dns.resolver.query(hostname, "TXT")
    except dns.resolver.NoAnswer:
        return []

    ret = []

    for a in answers:  # type: dns.rdtypes.ANY.TXT.TXT
        for record in a.strings:
            record = record.decode()  # record is bytes

            if record.startswith("v=spf1"):
                parts = record.split(" ")
                for part in parts:
                    if part.startswith(_include_spf):
                        ret.append(part[part.find(_include_spf) + len(_include_spf) :])

    return ret