from datetime import date
from typing import Optional

from django.db.models import Exists, OuterRef

from biscuit.apps.chronos.models import Lesson, LessonPeriod
from biscuit.apps.chronos.util import CalendarWeek
from biscuit.core.models import Group, Person

from .models import PersonalNote


@Person.property
def lessons_as_participant(self):
    return Lesson.objects.filter(groups__members=self)


@Person.property
def lesson_periods_as_participant(self):
    return LessonPeriod.objects.filter(lesson__groups__members=self)


@Person.property
def lesson_periods_as_teacher(self):
    return LessonPeriod.objects.filter(lesson__teachers=self)


@Person.method
def mark_absent(self, day: date, starting_period: Optional[int] = 0, absent=True, excused=False):
    wanted_week = CalendarWeek.from_date(day)

    # Get all lessons of this person on the specified day
    lesson_periods = self.lesson_periods_as_participant.on_day(
        day
    ).filter(
        period__period__gte=starting_period
    )

    # Create and update all personal notes for the discovered lesson periods
    for lesson_period in lesson_periods:
        PersonalNote.objects.update_or_create(
            person=self,
            lesson_period=lesson_period,
            week=wanted_week.week,
            absent=absent,
            excused=excused
        )


@LessonPeriod.method
def get_personal_notes(self, wanted_week: CalendarWeek):
    # Find all persons in the associated groups that do not yet have a personal note for this lesson
    missing_persons = Person.objects.annotate(
        no_personal_notes=~Exists(PersonalNote.objects.filter(
            week=wanted_week.week,
            lesson_period=self,
            person__pk=OuterRef('pk')
        ))
    ).filter(
        member_of__in=Group.objects.filter(pk__in=self.lesson.groups.all()),
        is_active=True,
        no_personal_notes=True
    )

    # Create all missing personal notes
    PersonalNote.objects.bulk_create([
        PersonalNote(person=person, lesson_period=self,
                     week=wanted_week.week) for person in missing_persons
    ])

    return PersonalNote.objects.select_related('person').filter(
        lesson_period=self, week=wanted_week.week)