import re
import traceback
import DNS

from zerver.lib.str_utils import NonBinaryStr, force_str

def compute_mit_user_fullname(email: NonBinaryStr) -> NonBinaryStr:
    try:
        # Input is either e.g. username@mit.edu or user|CROSSREALM.INVALID@mit.edu
        match_user = re.match(r'^([a-zA-Z0-9_.-]+)(\|.+)?@mit\.edu$', email.lower())
        if match_user and match_user.group(2) is None:
            answer = DNS.dnslookup(
                "%s.passwd.ns.athena.mit.edu" % (match_user.group(1),),
                DNS.Type.TXT)
            hesiod_name = force_str(answer[0][0]).split(':')[4].split(',')[0].strip()
            if hesiod_name != "":
                return hesiod_name
        elif match_user:
            return match_user.group(1).lower() + "@" + match_user.group(2).upper()[1:]
    except DNS.Base.ServerError:
        pass
    except Exception:
        print("Error getting fullname for %s:" % (email,))
        traceback.print_exc()
    return email.lower()