from collections import OrderedDict
from typing import Optional

from django.contrib.auth.decorators import login_required
from django.db.models import Exists, OuterRef, Q
from django.http import HttpRequest, HttpResponse, HttpResponseNotFound
from django.shortcuts import render
from django.views.decorators.cache import cache_page

from biscuit.apps.chronos.models import LessonPeriod, TimePeriod
from biscuit.apps.chronos.util import current_lesson_periods, current_week, week_days
from biscuit.core.models import Group, Person

from .forms import LessonDocumentationForm, PersonalNoteFormSet, SelectForm
from .models import LessonDocumentation, PersonalNote


@login_required
def lesson(request: HttpRequest, week: Optional[int] = None, period_id: Optional[int] = None) -> HttpResponse:
    context = {}

    if week and period_id:
        # Get a specific lesson period if provided in URL
        lesson_period = LessonPeriod.objects.get(pk=period_id)
        wanted_week = week
    else:
        # Determine current lesson by current date and time
        lesson_period = current_lesson_periods().filter(
            Q(substitutions__teachers=request.user.person) | Q(lesson__teachers=request.user.person)).first()
        wanted_week = current_week()

    context['lesson_period'] = lesson_period
    context['week'] = wanted_week
    context['day'] = week_days(wanted_week)[lesson_period.period.weekday]

    if not lesson_period:
        #XXX TODO: nice error page (“no lesson currently running for you?” or so)
        return HttpResponseNotFound("no current lesson found for you")

    # Create or get lesson documentation object; can be empty when first opening lesson
    lesson_documentation, created = LessonDocumentation.objects.get_or_create(
        lesson_period=lesson_period, week=wanted_week)
    lesson_documentation_form = LessonDocumentationForm(
        request.POST or None, instance=lesson_documentation, prefix='leson_documentation')

    # Create all missing personal notes about members of all groups in lesson
    missing_persons = Person.objects.annotate(
        no_personal_notes=~Exists(PersonalNote.objects.filter(
            week=wanted_week,
            lesson_period=lesson_period,
            person__pk=OuterRef('pk')
        ))
    ).filter(
        member_of__in=Group.objects.filter(pk__in=lesson_period.lesson.groups.all()),
        is_active=True,
        no_personal_notes=True
    )
    PersonalNote.objects.bulk_create([
        PersonalNote(person=person, lesson_period=lesson_period,
                     week=wanted_week) for person in missing_persons
    ])

    # Create a formset that holds all personal notes for all persons in this lesson
    persons_qs = PersonalNote.objects.select_related('person').filter(
        lesson_period=lesson_period, week=wanted_week)
    personal_note_formset = PersonalNoteFormSet(
        request.POST or None, queryset=persons_qs, prefix='personal_notes')

    if request.method == 'POST':
        if lesson_documentation_form.is_valid():
            lesson_documentation_form.save()
        if personal_note_formset.is_valid():
            personal_note_formset.save()

    context['lesson_documentation_form'] = lesson_documentation_form
    context['personal_note_formset'] = personal_note_formset

    return render(request, 'alsijil/lesson.html', context)


@login_required
@cache_page(60 * 60 * 4)
def group_week(request: HttpRequest, week: Optional[int] = None) -> HttpResponse:
    context = {}

    wanted_week = week or current_week()
    week_start = week_days(wanted_week)[0]
    week_end = week_days(wanted_week)[-1]

    if request.GET.get('group', None):
        # Use requested group
        group = Group.objects.get(pk=request.GET['group'])
    elif hasattr(request, 'user') and hasattr(request.user, 'person'):
        # Try to select group from owned groups of user
        group = request.user.person.owner_of.first()
    else:
        group = None

    periods_by_day_unsorted = {}
    if group:
        for act_group in [group] + list(group.child_groups.all()):
            for lesson in act_group.lessons.select_related(
                'lesson_period',
                'lesson_period__period',
                'lesson_period__period__lesson__teachers'
            ).filter(date_start__lte=week_start, date_end__gte=week_end):
                for lesson_period in lesson.lesson_periods.all():
                    periods_by_day_unsorted.setdefault(
                        lesson_period.period.weekday, []).append(lesson_period)

    periods_by_day = OrderedDict()
    for weekday, periods in sorted(periods_by_day_unsorted.items()):
        periods_by_day[dict(TimePeriod.WEEKDAY_CHOICES)[weekday]] = sorted(
            periods, key=lambda p: p.period.period)

    # Add a form to filter the view
    select_form = SelectForm(request.GET or None)

    context['week'] = wanted_week
    context['group'] = group
    context['periods_by_day'] = periods_by_day
    context['select_form'] = select_form

    return render(request, 'alsijil/group_week.html', context)