models.py

# flake8: noqa: DJ01

from __future__ import annotations

from datetime import date, datetime, time, timedelta
from typing import Dict, Optional, Tuple, Union

from django.core.exceptions import ValidationError
from django.db import models
from django.db.models import Max, Min, Q
from django.db.models.functions import Coalesce
from django.forms import Media
from django.urls import reverse
from django.utils import timezone
from django.utils.decorators import classproperty
from django.utils.formats import date_format
from django.utils.translation import gettext_lazy as _

from calendarweek.django import CalendarWeek, i18n_day_abbrs_lazy, i18n_day_names_lazy
from colorfield.fields import ColorField
from django_global_request.middleware import get_request

from aleksis.apps.chronos.managers import (
    AbsenceQuerySet,
    CurrentSiteManager,
    EventQuerySet,
    ExtraLessonQuerySet,
    GroupPropertiesMixin,
    HolidayQuerySet,
    LessonPeriodManager,
    LessonPeriodQuerySet,
    LessonSubstitutionManager,
    LessonSubstitutionQuerySet,
    SupervisionQuerySet,
    TeacherPropertiesMixin,
    ValidityRangeQuerySet,
)
from aleksis.apps.chronos.mixins import ValidityRangeRelatedExtensibleModel
from aleksis.apps.chronos.util.format import format_m2m
from aleksis.core.managers import CurrentSiteManagerWithoutMigrations
from aleksis.core.mixins import ExtensibleModel, SchoolTermRelatedExtensibleModel
from aleksis.core.models import DashboardWidget, SchoolTerm
from aleksis.core.util.core_helpers import has_person


class ValidityRange(ExtensibleModel):
    """Validity range model.

    This is used to link data to a validity range.
    """

    objects = CurrentSiteManagerWithoutMigrations.from_queryset(ValidityRangeQuerySet)()

    school_term = models.ForeignKey(
        SchoolTerm,
        on_delete=models.CASCADE,
        verbose_name=_("School term"),
        related_name="validity_ranges",
    )
    name = models.CharField(verbose_name=_("Name"), max_length=255, blank=True)

    date_start = models.DateField(verbose_name=_("Start date"))
    date_end = models.DateField(verbose_name=_("End date"))

    @classmethod
    def get_current(cls, day: Optional[date] = None):
        if not day:
            day = timezone.now().date()
        try:
            return cls.objects.on_day(day).first()
        except ValidityRange.DoesNotExist:
            return None

    @classproperty
    def current(cls):
        return cls.get_current()

    def clean(self):
        """Ensure there is only one validity range at each point of time."""
        if self.date_end < self.date_start:
            raise ValidationError(
                _("The start date must be earlier than the end date.")
            )

        if self.school_term:
            if (
                self.date_end > self.school_term.date_end
                or self.date_start < self.school_term.date_start
            ):
                raise ValidationError(
                    _("The validity range must be within the school term.")
                )

        qs = ValidityRange.objects.within_dates(self.date_start, self.date_end)
        if self.pk:
            qs.exclude(pk=self.pk)
        if qs.exists():
            raise ValidationError(
                _(
                    "There is already a validity range for this time or a part of this time."
                )
            )

    def __str__(self):
        return (
            self.name or f"{date_format(self.date_start)}–{date_format(self.date_end)}"
        )

    class Meta:
        verbose_name = _("Validity range")
        verbose_name_plural = _("Validity ranges")
        unique_together = ["date_start", "date_end"]


class TimePeriod(ValidityRangeRelatedExtensibleModel):
    WEEKDAY_CHOICES = list(enumerate(i18n_day_names_lazy()))
    WEEKDAY_CHOICES_SHORT = list(enumerate(i18n_day_abbrs_lazy()))

    weekday = models.PositiveSmallIntegerField(
        verbose_name=_("Week day"), choices=WEEKDAY_CHOICES
    )
    period = models.PositiveSmallIntegerField(verbose_name=_("Number of period"))

    time_start = models.TimeField(verbose_name=_("Start time"))
    time_end = models.TimeField(verbose_name=_("End time"))

    def __str__(self) -> str:
        return f"{self.get_weekday_display()}, {self.period}."

    @classmethod
    def get_times_dict(cls) -> Dict[int, Tuple[datetime, datetime]]:
        periods = {}
        for period in cls.objects.for_current_or_all().all():
            periods[period.period] = (period.time_start, period.time_end)

        return periods

    def get_date(self, week: Optional[Union[CalendarWeek, int]] = None) -> date:
        if isinstance(week, CalendarWeek):
            wanted_week = week
        else:
            year = date.today().year
            week_number = week or getattr(self, "_week", None) or CalendarWeek().week

            if week_number < SchoolTerm.current.date_start.isocalendar()[1]:
                year += 1

            wanted_week = CalendarWeek(year=year, week=week_number)

        return wanted_week[self.weekday]

    def get_datetime_start(
        self, week: Optional[Union[CalendarWeek, int]] = None
    ) -> datetime:
        """Get datetime of lesson start in a specific week."""
        day = self.get_date(week)
        return datetime.combine(day, self.time_start)

    def get_datetime_end(
        self, week: Optional[Union[CalendarWeek, int]] = None
    ) -> datetime:
        """Get datetime of lesson end in a specific week."""
        day = self.get_date(week)
        return datetime.combine(day, self.time_end)

    @classmethod
    def get_next_relevant_day(
        cls, day: Optional[date] = None, time: Optional[time] = None, prev: bool = False
    ) -> date:
        """Return next (previous) day with lessons depending on date and time."""
        if day is None:
            day = timezone.now().date()

        if time is not None and cls.time_max and not prev:
            if time > cls.time_max:
                day += timedelta(days=1)

        cw = CalendarWeek.from_date(day)

        if day.weekday() > cls.weekday_max:
            if prev:
                day = cw[cls.weekday_max]
            else:
                cw += 1
                day = cw[cls.weekday_min]
        elif day.weekday() < TimePeriod.weekday_min:
            if prev:
                cw -= 1
                day = cw[cls.weekday_max]
            else:
                day = cw[cls.weekday_min]

        return day

    @classmethod
    def get_prev_next_by_day(cls, day: date, url: str) -> Tuple[str, str]:
        """Build URLs for previous/next day."""
        day_prev = cls.get_next_relevant_day(day - timedelta(days=1), prev=True)
        day_next = cls.get_next_relevant_day(day + timedelta(days=1))

        url_prev = reverse(url, args=[day_prev.year, day_prev.month, day_prev.day])
        url_next = reverse(url, args=[day_next.year, day_next.month, day_next.day])

        return url_prev, url_next

    @classproperty
    def period_min(cls) -> int:

        return (
            cls.objects.for_current_or_all()
            .aggregate(period__min=Coalesce(Min("period"), 1))
            .get("period__min")
        )

    @classproperty
    def period_max(cls) -> int:
        return (
            cls.objects.for_current_or_all()
            .aggregate(period__max=Coalesce(Max("period"), 7))
            .get("period__max")
        )

    @classproperty
    def time_min(cls) -> Optional[time]:
        return (
            cls.objects.for_current_or_all()
            .aggregate(Min("time_start"))
            .get("time_start__min")
        )

    @classproperty
    def time_max(cls) -> Optional[time]:
        return (
            cls.objects.for_current_or_all()
            .aggregate(Max("time_end"))
            .get("time_end__max")
        )

    @classproperty
    def weekday_min(cls) -> int:
        return (
            cls.objects.for_current_or_all()
            .aggregate(weekday__min=Coalesce(Min("weekday"), 0))
            .get("weekday__min")
        )

    @classproperty
    def weekday_max(cls) -> int:
        return (
            cls.objects.for_current_or_all()
            .aggregate(weekday__max=Coalesce(Max("weekday"), 6))
            .get("weekday__max")
        )

    class Meta:
        unique_together = [["weekday", "period", "validity"]]
        ordering = ["weekday", "period"]
        indexes = [models.Index(fields=["time_start", "time_end"])]
        verbose_name = _("Time period")
        verbose_name_plural = _("Time periods")


class Subject(ExtensibleModel):
    short_name = models.CharField(
        verbose_name=_("Short name"), max_length=255, unique=True
    )
    name = models.CharField(verbose_name=_("Long name"), max_length=255, unique=True)

    colour_fg = ColorField(verbose_name=_("Foreground colour"), blank=True)
    colour_bg = ColorField(verbose_name=_("Background colour"), blank=True)

    def __str__(self) -> str:
        return f"{self.short_name} ({self.name})"

    class Meta:
        ordering = ["name", "short_name"]
        verbose_name = _("Subject")
        verbose_name_plural = _("Subjects")


class Room(ExtensibleModel):
    short_name = models.CharField(
        verbose_name=_("Short name"), max_length=255, unique=True
    )
    name = models.CharField(verbose_name=_("Long name"), max_length=255)

    def __str__(self) -> str:
        return f"{self.name} ({self.short_name})"

    class Meta:
        ordering = ["name", "short_name"]
        verbose_name = _("Room")
        verbose_name_plural = _("Rooms")


class Lesson(
    ValidityRangeRelatedExtensibleModel, GroupPropertiesMixin, TeacherPropertiesMixin
):
    subject = models.ForeignKey(
        "Subject",
        on_delete=models.CASCADE,
        related_name="lessons",
        verbose_name=_("Subject"),
    )
    teachers = models.ManyToManyField(
        "core.Person", related_name="lessons_as_teacher", verbose_name=_("Teachers")
    )
    periods = models.ManyToManyField(
        "TimePeriod",
        related_name="lessons",
        through="LessonPeriod",
        verbose_name=_("Periods"),
    )
    groups = models.ManyToManyField(
        "core.Group", related_name="lessons", verbose_name=_("Groups")
    )

    def get_year(self, week: int) -> int:
        year = self.validity.date_start.year
        if week < int(self.validity.date_start.strftime("%V")):
            year += 1
        return year

    def get_calendar_week(self, week: int):
        year = self.get_year(week)

        return CalendarWeek(year=year, week=week)

    def __str__(self):
        return f"{format_m2m(self.groups)}, {self.subject.short_name}, {format_m2m(self.teachers)}"

    class Meta:
        ordering = ["validity__date_start", "subject"]
        verbose_name = _("Lesson")
        verbose_name_plural = _("Lessons")


class LessonSubstitution(ExtensibleModel):
    objects = LessonSubstitutionManager.from_queryset(LessonSubstitutionQuerySet)()

    week = models.IntegerField(
        verbose_name=_("Week"), default=CalendarWeek.current_week
    )

    lesson_period = models.ForeignKey(
        "LessonPeriod", models.CASCADE, "substitutions", verbose_name=_("Lesson period")
    )

    subject = models.ForeignKey(
        "Subject",
        on_delete=models.CASCADE,
        related_name="lesson_substitutions",
        null=True,
        blank=True,
        verbose_name=_("Subject"),
    )
    teachers = models.ManyToManyField(
        "core.Person",
        related_name="lesson_substitutions",
        blank=True,
        verbose_name=_("Teachers"),
    )
    room = models.ForeignKey(
        "Room", models.CASCADE, null=True, blank=True, verbose_name=_("Room")
    )

    cancelled = models.BooleanField(default=False, verbose_name=_("Cancelled?"))
    cancelled_for_teachers = models.BooleanField(
        default=False, verbose_name=_("Cancelled for teachers?")
    )

    comment = models.TextField(verbose_name=_("Comment"), blank=True, null=True)

    def clean(self) -> None:
        if self.subject and self.cancelled:
            raise ValidationError(
                _("Lessons can only be either substituted or cancelled.")
            )

    @property
    def date(self):
        week = CalendarWeek(week=self.week, year=self.lesson_period.lesson.get_year(self.week))
        return week[self.lesson_period.period.weekday]

    def __str__(self):
        return f"{self.lesson_period}, {date_format(self.date)}"

    class Meta:
        unique_together = [["lesson_period", "week"]]
        ordering = [
            "lesson_period__lesson__validity__date_start",
            "week",
            "lesson_period__period__weekday",
            "lesson_period__period__period",
        ]
        constraints = [
            models.CheckConstraint(
                check=~Q(cancelled=True, subject__isnull=False),
                name="either_substituted_or_cancelled",
            )
        ]
        verbose_name = _("Lesson substitution")
        verbose_name_plural = _("Lesson substitutions")


class LessonPeriod(ExtensibleModel):
    label_ = "lesson_period"

    objects = LessonPeriodManager.from_queryset(LessonPeriodQuerySet)()

    lesson = models.ForeignKey(
        "Lesson",
        models.CASCADE,
        related_name="lesson_periods",
        verbose_name=_("Lesson"),
    )
    period = models.ForeignKey(
        "TimePeriod",
        models.CASCADE,
        related_name="lesson_periods",
        verbose_name=_("Time period"),
    )

    room = models.ForeignKey(
        "Room",
        models.CASCADE,
        null=True,
        related_name="lesson_periods",
        verbose_name=_("Room"),
    )

    def get_substitution(self, week: Optional[int] = None) -> LessonSubstitution:
        wanted_week = week or getattr(self, "_week", None) or CalendarWeek().week

        # We iterate over all substitutions because this can make use of
        # prefetching when this model is loaded from outside, in contrast
        # to .filter()
        for substitution in self.substitutions.all():
            if substitution.week == wanted_week:
                return substitution
        return None

    def get_subject(self) -> Optional[Subject]:
        if self.get_substitution() and self.get_substitution().subject:
            return self.get_substitution().subject
        else:
            return self.lesson.subject

    def get_teachers(self) -> models.query.QuerySet:
        if self.get_substitution():
            return self.get_substitution().teachers
        else:
            return self.lesson.teachers

    def get_room(self) -> Optional[Room]:
        if self.get_substitution() and self.get_substitution().room:
            return self.get_substitution().room
        else:
            return self.room

    def get_teacher_names(self, sep: Optional[str] = ", ") -> str:
        return sep.join([teacher.full_name for teacher in self.get_teachers().all()])

    def get_groups(self) -> models.query.QuerySet:
        return self.lesson.groups

    def __str__(self) -> str:
        return f"{self.period}, {self.lesson}"

    @property
    def next(self) -> "LessonPeriod":
        """Get next lesson period of this lesson.

        .. warning::
            To use this property,  the provided lesson period must be annotated with a week.
        """
        return LessonPeriod.objects.filter(lesson=self.lesson).next_lesson(self)

    @property
    def prev(self) -> "LessonPeriod":
        """Get previous lesson period of this lesson.

        .. warning::
            To use this property,  the provided lesson period must be annotated with a week.
        """
        return LessonPeriod.objects.filter(lesson=self.lesson).next_lesson(self, -1)

    @property
    def week(self) -> Union[CalendarWeek, None]:
        """Get annotated week as `CalendarWeek`.

        Defaults to `None` if no week is annotated.
        """
        if hasattr(self, "_week"):
            return CalendarWeek(week=self._week, year=self._year)
        else:
            return None

    class Meta:
        ordering = [
            "lesson__validity__date_start",
            "period__weekday",
            "period__period",
            "lesson__subject",
        ]
        indexes = [models.Index(fields=["lesson", "period"])]
        verbose_name = _("Lesson period")
        verbose_name_plural = _("Lesson periods")


class TimetableWidget(DashboardWidget):
    template = "chronos/widget.html"

    def get_context(self):
        from aleksis.apps.chronos.util.build import build_timetable  # noqa

        request = get_request()
        context = {"has_plan": True}
        wanted_day = TimePeriod.get_next_relevant_day(
            timezone.now().date(), datetime.now().time()
        )

        if has_person(request.user):
            person = request.user.person
            type_ = person.timetable_type

            # Build timetable
            timetable = build_timetable("person", person, wanted_day)

            if type_ is None:
                # If no student or teacher, redirect to all timetables
                context["has_plan"] = False
            else:
                context["timetable"] = timetable
                context["holiday"] = Holiday.on_day(wanted_day)
                context["type"] = type_
                context["day"] = wanted_day
                context["periods"] = TimePeriod.get_times_dict()
                context["smart"] = True
        else:
            context["has_plan"] = False

        return context

    media = Media(css={"all": ("css/chronos/timetable.css",)})

    class Meta:
        proxy = True
        verbose_name = _("Timetable widget")
        verbose_name_plural = _("Timetable widgets")


class AbsenceReason(ExtensibleModel):
    short_name = models.CharField(verbose_name=_("Short name"), max_length=255)
    name = models.CharField(
        verbose_name=_("Name"), blank=True, null=True, max_length=255
    )

    def __str__(self):
        if self.name:
            return f"{self.short_name} ({self.name})"
        else:
            return self.short_name

    class Meta:
        verbose_name = _("Absence reason")
        verbose_name_plural = _("Absence reasons")


class Absence(SchoolTermRelatedExtensibleModel):
    objects = CurrentSiteManager.from_queryset(AbsenceQuerySet)()

    reason = models.ForeignKey(
        "AbsenceReason",
        on_delete=models.SET_NULL,
        related_name="absences",
        blank=True,
        null=True,
        verbose_name=_("Absence reason"),
    )

    teacher = models.ForeignKey(
        "core.Person",
        on_delete=models.CASCADE,
        related_name="absences",
        null=True,
        blank=True,
        verbose_name=_("Teacher"),
    )
    group = models.ForeignKey(
        "core.Group",
        on_delete=models.CASCADE,
        related_name="absences",
        null=True,
        blank=True,
        verbose_name=_("Group"),
    )
    room = models.ForeignKey(
        "Room",
        on_delete=models.CASCADE,
        related_name="absences",
        null=True,
        blank=True,
        verbose_name=_("Room"),
    )

    date_start = models.DateField(verbose_name=_("Start date"), null=True)
    date_end = models.DateField(verbose_name=_("End date"), null=True)
    period_from = models.ForeignKey(
        "TimePeriod",
        on_delete=models.CASCADE,
        verbose_name=_("Start period"),
        null=True,
        related_name="+",
    )
    period_to = models.ForeignKey(
        "TimePeriod",
        on_delete=models.CASCADE,
        verbose_name=_("End period"),
        null=True,
        related_name="+",
    )
    comment = models.TextField(verbose_name=_("Comment"), blank=True, null=True)

    def __str__(self):
        if self.teacher:
            return str(self.teacher)
        elif self.group:
            return str(self.group)
        elif self.room:
            return str(self.room)
        else:
            return _("Unknown absence")

    class Meta:
        ordering = ["date_start"]
        indexes = [models.Index(fields=["date_start", "date_end"])]
        verbose_name = _("Absence")
        verbose_name_plural = _("Absences")


class Exam(SchoolTermRelatedExtensibleModel):
    lesson = models.ForeignKey(
        "Lesson",
        on_delete=models.CASCADE,
        related_name="exams",
        verbose_name=_("Lesson"),
    )

    date = models.DateField(verbose_name=_("Date of exam"), null=True)
    period_from = models.ForeignKey(
        "TimePeriod",
        on_delete=models.CASCADE,
        verbose_name=_("Start period"),
        null=True,
        related_name="+",
    )
    period_to = models.ForeignKey(
        "TimePeriod",
        on_delete=models.CASCADE,
        verbose_name=_("End period"),
        null=True,
        related_name="+",
    )

    title = models.CharField(verbose_name=_("Title"), max_length=255)
    comment = models.TextField(verbose_name=_("Comment"), blank=True, null=True)

    class Meta:
        ordering = ["date"]
        indexes = [models.Index(fields=["date"])]
        verbose_name = _("Exam")
        verbose_name_plural = _("Exams")


class Holiday(ExtensibleModel):
    objects = CurrentSiteManager.from_queryset(HolidayQuerySet)()

    title = models.CharField(verbose_name=_("Title"), max_length=255)
    date_start = models.DateField(verbose_name=_("Start date"), null=True)
    date_end = models.DateField(verbose_name=_("End date"), null=True)
    comments = models.TextField(verbose_name=_("Comments"), blank=True, null=True)

    @classmethod
    def on_day(cls, day: date) -> Optional["Holiday"]:
        holidays = cls.objects.on_day(day)
        if holidays.exists():
            return holidays[0]
        else:
            return None

    @classmethod
    def in_week(cls, week: CalendarWeek) -> Dict[int, Optional["Holiday"]]:
        per_weekday = {}

        for weekday in range(TimePeriod.weekday_min, TimePeriod.weekday_max + 1):
            holiday_date = week[weekday]
            holidays = Holiday.objects.on_day(holiday_date)
            if holidays.exists():
                per_weekday[weekday] = holidays[0]

        return per_weekday

    def __str__(self):
        return self.title

    class Meta:
        ordering = ["date_start"]
        indexes = [models.Index(fields=["date_start", "date_end"])]
        verbose_name = _("Holiday")
        verbose_name_plural = _("Holidays")


class SupervisionArea(ExtensibleModel):
    short_name = models.CharField(verbose_name=_("Short name"), max_length=255)
    name = models.CharField(verbose_name=_("Long name"), max_length=255)
    colour_fg = ColorField(default="#000000")
    colour_bg = ColorField()

    def __str__(self):
        return f"{self.name} ({self.short_name})"

    class Meta:
        ordering = ["name"]
        verbose_name = _("Supervision area")
        verbose_name_plural = _("Supervision areas")


class Break(ValidityRangeRelatedExtensibleModel):
    short_name = models.CharField(verbose_name=_("Short name"), max_length=255)
    name = models.CharField(verbose_name=_("Long name"), max_length=255)

    after_period = models.ForeignKey(
        "TimePeriod",
        on_delete=models.CASCADE,
        verbose_name=_("Time period after break starts"),
        related_name="break_after",
        blank=True,
        null=True,
    )
    before_period = models.ForeignKey(
        "TimePeriod",
        on_delete=models.CASCADE,
        verbose_name=_("Time period before break ends"),
        related_name="break_before",
        blank=True,
        null=True,
    )

    @property
    def weekday(self):
        return (
            self.after_period.weekday
            if self.after_period
            else self.before_period.weekday
        )

    @property
    def after_period_number(self):
        return (
            self.after_period.period
            if self.after_period
            else self.before_period.period - 1
        )

    @property
    def before_period_number(self):
        return (
            self.before_period.period
            if self.before_period
            else self.after_period.period + 1
        )

    @property
    def time_start(self):
        return self.after_period.time_end if self.after_period else None

    @property
    def time_end(self):
        return self.before_period.time_start if self.before_period else None

    @classmethod
    def get_breaks_dict(cls) -> Dict[int, Tuple[datetime, datetime]]:
        breaks = {}
        for break_ in cls.objects.all():
            breaks[break_.before_period_number] = break_

        return breaks

    def __str__(self):
        return f"{self.name} ({self.short_name})"

    class Meta:
        ordering = ["after_period"]
        indexes = [models.Index(fields=["after_period", "before_period"])]
        verbose_name = _("Break")
        verbose_name_plural = _("Breaks")


class Supervision(ValidityRangeRelatedExtensibleModel):
    objects = CurrentSiteManager.from_queryset(SupervisionQuerySet)()

    area = models.ForeignKey(
        SupervisionArea,
        models.CASCADE,
        verbose_name=_("Supervision area"),
        related_name="supervisions",
    )
    break_item = models.ForeignKey(
        Break, models.CASCADE, verbose_name=_("Break"), related_name="supervisions"
    )
    teacher = models.ForeignKey(
        "core.Person",
        models.CASCADE,
        related_name="supervisions",
        verbose_name=_("Teacher"),
    )

    def get_substitution(
        self, week: Optional[int] = None
    ) -> Optional[SupervisionSubstitution]:
        wanted_week = week or getattr(self, "_week", None) or CalendarWeek().week
        wanted_week = CalendarWeek(week=wanted_week)
        # We iterate over all substitutions because this can make use of
        # prefetching when this model is loaded from outside, in contrast
        # to .filter()
        for substitution in self.substitutions.all():
            for weekday in range(0, 7):
                if substitution.date == wanted_week[weekday]:
                    return substitution
        return None

    @property
    def teachers(self):
        return [self.teacher]

    def __str__(self):
        return f"{self.break_item}, {self.area}, {self.teacher}"

    class Meta:
        ordering = ["area", "break_item"]
        verbose_name = _("Supervision")
        verbose_name_plural = _("Supervisions")


class SupervisionSubstitution(ExtensibleModel):
    date = models.DateField(verbose_name=_("Date"))
    supervision = models.ForeignKey(
        Supervision,
        models.CASCADE,
        verbose_name=_("Supervision"),
        related_name="substitutions",
    )
    teacher = models.ForeignKey(
        "core.Person",
        models.CASCADE,
        related_name="substituted_supervisions",
        verbose_name=_("Teacher"),
    )

    @property
    def teachers(self):
        return [self.teacher]

    def __str__(self):
        return f"{self.supervision}, {date_format(self.date)}"

    class Meta:
        ordering = ["date", "supervision"]
        verbose_name = _("Supervision substitution")
        verbose_name_plural = _("Supervision substitutions")


class Event(
    SchoolTermRelatedExtensibleModel, GroupPropertiesMixin, TeacherPropertiesMixin
):
    label_ = "event"

    objects = CurrentSiteManager.from_queryset(EventQuerySet)()

    title = models.CharField(
        verbose_name=_("Title"), max_length=255, blank=True, null=True
    )

    date_start = models.DateField(verbose_name=_("Start date"), null=True)
    date_end = models.DateField(verbose_name=_("End date"), null=True)

    period_from = models.ForeignKey(
        "TimePeriod",
        on_delete=models.CASCADE,
        verbose_name=_("Start time period"),
        related_name="+",
    )
    period_to = models.ForeignKey(
        "TimePeriod",
        on_delete=models.CASCADE,
        verbose_name=_("End time period"),
        related_name="+",
    )

    groups = models.ManyToManyField(
        "core.Group", related_name="events", verbose_name=_("Groups")
    )
    rooms = models.ManyToManyField(
        "Room", related_name="events", verbose_name=_("Rooms")
    )
    teachers = models.ManyToManyField(
        "core.Person", related_name="events", verbose_name=_("Teachers")
    )

    def __str__(self):
        if self.title:
            return self.title
        else:
            return _(f"Event {self.pk}")

    @property
    def period_from_on_day(self) -> int:
        day = getattr(self, "_date", timezone.now().date())
        if day != self.date_start:
            return TimePeriod.period_min
        else:
            return self.period_from.period

    @property
    def period_to_on_day(self) -> int:
        day = getattr(self, "_date", timezone.now().date())
        if day != self.date_end:
            return TimePeriod.period_max
        else:
            return self.period_to.period

    class Meta:
        ordering = ["date_start"]
        indexes = [
            models.Index(fields=["period_from", "period_to", "date_start", "date_end"])
        ]
        verbose_name = _("Event")
        verbose_name_plural = _("Events")


class ExtraLesson(SchoolTermRelatedExtensibleModel, GroupPropertiesMixin):
    label_ = "extra_lesson"

    objects = CurrentSiteManager.from_queryset(ExtraLessonQuerySet)()

    week = models.IntegerField(
        verbose_name=_("Week"), default=CalendarWeek.current_week
    )
    period = models.ForeignKey(
        "TimePeriod",
        models.CASCADE,
        related_name="extra_lessons",
        verbose_name=_("Time period"),
    )

    subject = models.ForeignKey(
        "Subject",
        on_delete=models.CASCADE,
        related_name="extra_lessons",
        verbose_name=_("Subject"),
    )
    groups = models.ManyToManyField(
        "core.Group", related_name="extra_lessons", verbose_name=_("Groups")
    )
    teachers = models.ManyToManyField(
        "core.Person",
        related_name="extra_lessons_as_teacher",
        verbose_name=_("Teachers"),
    )
    room = models.ForeignKey(
        "Room",
        models.CASCADE,
        null=True,
        related_name="extra_lessons",
        verbose_name=_("Room"),
    )

    comment = models.CharField(
        verbose_name=_("Comment"), blank=True, null=True, max_length=255
    )

    def __str__(self):
        return f"{self.week}, {self.period}, {self.subject}"

    class Meta:
        verbose_name = _("Extra lesson")
        verbose_name_plural = _("Extra lessons")


class ChronosGlobalPermissions(ExtensibleModel):
    class Meta:
        managed = False
        permissions = (
            ("view_all_timetables", _("Can view all timetables")),
            ("view_timetable_overview", _("Can view timetable overview")),
            ("view_lessons_day", _("Can view all lessons per day")),
        )