import ldap

from django.conf import settings

verbose_depts = {
    "bio": "Biologie",
    "chimie": "Chimie",
    "dec": "Études Cognitives",
    "geol": "Géosciences",
    "guests": "Invité·e",
    "info": "Informatique",
    "litt": "Lettres",
    "maths": "Mathématiques",
    "pei": "PEI",
    "phy": "Physique",
}


def parse_dept(home_dir):
    """Extrait le département d'entrée d'un·e élève à partir de son dossier.
    Le dossier a le format `/users/<promo>/<dept>/<login>`.
    """
    users, promo, dept, login = home_dir.split("/")[1:]

    if users != "users":
        raise ValueError("Invalid home directory")

    # Ça casse en 2100, mais le système de naming de sas aussi...
    promo = 2000 + int(promo)

    return promo, verbose_depts.get(dept, None)


def extract_ldap_info(entry, field):
    return entry[1].get(field, [b""])[0].decode("utf-8")


def get_ldap_infos(clipper_login):
    ldap_server = settings.LDAP["SPI"]
    ldap_obj = ldap.initialize("{PROTOCOL}://{URL}:{PORT}".format(**ldap_server))
    try:
        res = ldap_obj.search_s(
            "dc=spi,dc=ens,dc=fr",
            ldap.SCOPE_SUBTREE,
            "(uid={})".format(clipper_login),
            ["uid", "cn", "homeDirectory"],
        )
    except ldap.SERVER_DOWN:
        return None

    if not res:
        return None

    if len(res) != 1:
        raise RuntimeError("LDAP returned too many results: {}".format(res))
    (res,) = res
    promo, dept = parse_dept(extract_ldap_info(res, "homeDirectory"))

    return {"name": extract_ldap_info(res, "cn"), "promo": promo, "dept": dept}