from typing import Optional, Union

from aleksis.core.models import Person, Group

from .models import Lesson, LessonPeriod


@Person.property
def is_teacher(self):
    """ Check if the user has lessons as a teacher """

    return self.lesson_periods_as_teacher.exists()


@Person.property
def timetable_type(self) -> Optional[str]:
    """ Return which type of timetable this user has """

    if self.is_teacher:
        return "teacher"
    elif self.primary_group:
        return "group"
    else:
        return None


@Person.property
def timetable_object(self) -> Optional[Union[Group, Person]]:
    """ Return the object which has the user's timetable """

    type_ = self.timetable_type

    if type_ == "teacher":
        return self
    elif type_ == "group":
        return self.primary_group
    else:
        return None


@Person.property
def lessons_as_participant(self):
    """ Return a `QuerySet` containing all `Lesson`s this person
    participates in (as student).

    .. note:: Only available when AlekSIS-App-Chronos is installed.

    :Date: 2019-11-07
    :Authors:
        - Dominik George <dominik.george@teckids.org>
    """

    return Lesson.objects.filter(groups__members=self)


@Person.property
def lesson_periods_as_participant(self):
    """ Return a `QuerySet` containing all `LessonPeriod`s this person
    participates in (as student).

    .. note:: Only available when AlekSIS-App-Chronos is installed.

    :Date: 2019-11-07
    :Authors:
        - Dominik George <dominik.george@teckids.org>
    """

    return LessonPeriod.objects.filter(lesson__groups__members=self)


@Person.property
def lesson_periods_as_teacher(self):
    """ Return a `QuerySet` containing all `Lesson`s this person
    gives (as teacher).

    .. note:: Only available when AlekSIS-App-Chronos is installed.

    :Date: 2019-11-07
    :Authors:
        - Dominik George <dominik.george@teckids.org>
    """

    return LessonPeriod.objects.filter(lesson__teachers=self)