from typing import Union, List

import ldap3
from zope import component
from zope.interface import implementer

from .UWLDAPRecord import UWLDAPRecord
from ceo_common.interfaces import IUWLDAPService, IConfig


@implementer(IUWLDAPService)
class UWLDAPService:
    def __init__(self):
        cfg = component.getUtility(IConfig)
        self.uwldap_server_url = cfg.get('uwldap_server_url')
        self.uwldap_base = cfg.get('uwldap_base')

    def _get_conn(self) -> ldap3.Connection:
        return ldap3.Connection(
            self.uwldap_server_url, auto_bind=True, read_only=True,
            raise_exceptions=True)

    def get_user(self, username: str) -> Union[UWLDAPRecord, None]:
        conn = self._get_conn()
        conn.search(
            self.uwldap_base, f'(uid={username})',
            attributes=UWLDAPRecord.ldap_attributes, size_limit=1)
        if not conn.entries:
            return None
        return UWLDAPRecord.deserialize_from_ldap(conn.entries[0])

    def get_programs_for_users(self, usernames: List[str]) -> List[Union[str, None]]:
        filter_str = '(|' + ''.join([f'(uid={uid})' for uid in usernames]) + ')'
        programs = [None] * len(usernames)
        user_indices = {uid: i for i, uid in enumerate(usernames)}

        conn = self._get_conn()
        conn.search(
            self.uwldap_base, filter_str, attributes=['ou', 'uid'],
            size_limit=len(usernames))
        for entry in conn.entries:
            # some records in UWLDAP have two UIDs because UIDs
            # were historically limited to 8 characters
            uid = None
            for uw_uid in entry.uid.values:
                if uw_uid in user_indices:
                    uid = uw_uid
                    break
            # sanity check
            assert uid is not None
            idx = user_indices[uid]
            program = entry.ou.value
            if program:
                programs[idx] = program
        return programs