from django.contrib.auth.decorators import login_required
from django.shortcuts import render, get_object_or_404
from django.http import HttpResponse, Http404
from django.core.exceptions import PermissionDenied
from django.db import transaction
from django.db.models import Count, Sum, F, Func

from datetime import datetime
import json

from postgresqleu.util.db import exec_to_dict
from postgresqleu.util.request import get_int_or_error

from .models import ConferenceRegistration
from .models import VolunteerSlot, VolunteerAssignment
from .util import send_conference_notification_template, get_conference_or_404


def _check_admin(request, conference):
    if request.user.is_superuser:
        return True
    else:
        return conference.administrators.filter(pk=request.user.id).exists() or conference.series.administrators.filter(pk=request.user.id).exists()


def _get_conference_and_reg(request, urlname):
    conference = get_conference_or_404(urlname)
    is_admin = _check_admin(request, conference)
    if is_admin:
        reg = ConferenceRegistration.objects.get(conference=conference, attendee=request.user)
    else:
        try:
            reg = conference.volunteers.get(attendee=request.user)
        except ConferenceRegistration.DoesNotExist:
            raise Http404("Volunteer entry not found")

    return (conference, is_admin, reg)


def send_volunteer_notification(conference, assignment, subject, template):
    if not conference.notifyvolunteerstatus:
        return

    # No filter aggregates in our version of Django, so direct SQL it is
    pending = exec_to_dict("SELECT count(*) FILTER (WHERE NOT org_confirmed) AS admin, count(*) FILTER (WHERE NOT vol_confirmed) AS volunteer FROM  confreg_volunteerassignment a INNER JOIN confreg_volunteerslot s ON s.id=a.slot_id WHERE s.conference_id=%(confid)s", {
        'confid': conference.id,
    })[0]

    send_conference_notification_template(
        conference,
        subject,
        'confreg/mail/{}'.format(template), {
            'conference': conference,
            'assignment': assignment,
            'pending': pending,
        },
    )


def _get_volunteer_stats(conference):
    stats = ConferenceRegistration.objects.filter(conference=conference) \
                                          .filter(volunteers_set=conference) \
                                          .only('firstname', 'lastname') \
                                          .annotate(num_assignments=Count('volunteerassignment')) \
                                          .annotate(total_time=Sum(Func(
                                              Func(F('volunteerassignment__slot__timerange'), function='upper'),
                                              Func(F('volunteerassignment__slot__timerange'), function='lower'),
                                              function='age'))) \
                                          .order_by('lastname', 'firstname')

    return [{
        'name': r.fullname,
        'count': r.num_assignments,
        'time': str(r.total_time or '0:00:00'),
        'seconds': int(r.total_time.total_seconds()) if r.total_time else 0,
    } for r in stats]


def _slot_return_data(slot):
    return {
        'id': slot.id,
        'max_staff': slot.max_staff,
        'min_staff': slot.min_staff,
        'assignments': [{
            'id': a.id,
            'volid': a.reg.id,
            'volunteer': a.reg.fullname,
            'vol_confirmed': a.vol_confirmed,
            'org_confirmed': a.org_confirmed,
        } for a in slot.volunteerassignment_set.all()],
    }


@login_required
@transaction.atomic
def volunteerschedule_api(request, urlname, adm=False):
    try:
        (conference, can_admin, reg) = _get_conference_and_reg(request, urlname)
    except ConferenceRegistration.DoesNotExist:
        raise PermissionDenied()

    is_admin = can_admin and adm

    if request.method == 'GET':
        # GET just always returns the complete volunteer schedule
        slots = VolunteerSlot.objects.prefetch_related('volunteerassignment_set', 'volunteerassignment_set__reg').filter(conference=conference)
        return HttpResponse(json.dumps({
            'slots': [_slot_return_data(slot) for slot in slots],
            'volunteers': [{
                'id': vol.id,
                'name': vol.fullname,
            } for vol in conference.volunteers.all().order_by('firstname', 'lastname')],
            'meta': {
                'isadmin': is_admin,
                'isvolunteer': conference.volunteers.filter(pk=reg.pk).exists(),
                'regid': reg.id,
            },
            'stats': _get_volunteer_stats(conference),
        }), content_type='application/json')

    if request.method != 'POST':
        raise Http404()

    if 'op' not in request.POST:
        raise Http404()

    slotid = get_int_or_error(request.POST, 'slotid')
    volid = get_int_or_error(request.POST, 'volid')

    # We should always have a valid slot
    slot = get_object_or_404(VolunteerSlot, conference=conference, pk=slotid)

    code = None
    err = None

    if request.POST['op'] == 'signup':
        if volid != 0:
            raise PermissionDenied("Invalid post data")
        code, err = _signup(request, conference, reg, is_admin, slot)
    elif request.POST['op'] == 'remove':
        code, err = _remove(request, conference, reg, is_admin, slot, volid)
    elif request.POST['op'] == 'confirm':
        code, err = _confirm(request, conference, reg, is_admin, slot, volid)
    elif request.POST['op'] == 'add':
        code, err = _add(request, conference, reg, is_admin, slot, volid)
    else:
        raise Http404()

    if err:
        return HttpResponse(
            json.dumps({'err': err}),
            content_type='application/json',
            status=code,
        )

    # Re-query the database to pick up any changes, and return the complete object
    slot = VolunteerSlot.objects.prefetch_related('volunteerassignment_set', 'volunteerassignment_set__reg').filter(conference=conference, pk=slot.pk)[0]
    return HttpResponse(json.dumps({
        'err': None,
        'slot': _slot_return_data(slot),
        'stats': _get_volunteer_stats(conference),
    }), content_type='application/json')


@login_required
def volunteerschedule(request, urlname, adm=False):
    try:
        (conference, can_admin, reg) = _get_conference_and_reg(request, urlname)
    except ConferenceRegistration.DoesNotExist:
        return HttpResponse("Must be registered for conference to view volunteer schedule")

    is_admin = can_admin and adm

    slots = VolunteerSlot.objects.filter(conference=conference).order_by('timerange', 'title')

    return render(request, 'confreg/volunteer_schedule.html', {
        'basetemplate': is_admin and 'confreg/confadmin_base.html' or 'confreg/volunteer_base.html',
        'conference': conference,
        'admin': is_admin,
        'can_admin': can_admin,
        'reg': reg,
        'slots': slots,
        'helplink': 'volunteers',
    })


def _signup(request, conference, reg, adm, slot):
    if VolunteerAssignment.objects.filter(slot=slot, reg=reg).exists():
        return 409, "Already a volunteer for selected slot"
    elif slot.countvols >= slot.max_staff:
        return 409, "Volunteer slot is already full"
    elif VolunteerAssignment.objects.filter(reg=reg, slot__timerange__overlap=slot.timerange).exists():
        return 400, "Cannot sign up for an overlapping slot"
    elif not conference.volunteers.filter(pk=reg.pk).exists():
        return 400, "You are not a registered volunteer for this conference"
    else:
        a = VolunteerAssignment(slot=slot, reg=reg, vol_confirmed=True, org_confirmed=False)
        a.save()
        send_volunteer_notification(conference, a, 'Volunteer signed up', 'admin_notify_volunteer_signup.txt')
        return 200, None


def _add(request, conference, reg, adm, slot, volid):
    addreg = get_object_or_404(ConferenceRegistration, conference=conference, id=volid)
    if VolunteerAssignment.objects.filter(slot=slot, reg=addreg).exists():
        return 409, "Already a volunteer for selected slot"
    elif slot.countvols >= slot.max_staff:
        return 409, "Volunteer slot is already full"
    elif VolunteerAssignment.objects.filter(reg=addreg, slot__timerange__overlap=slot.timerange).exists():
        return 400, "Cannot add to an overlapping slot"
    else:
        VolunteerAssignment(slot=slot, reg=addreg, vol_confirmed=False, org_confirmed=True).save()
        return 200, None


def _remove(request, conference, reg, is_admin, slot, aid):
    if is_admin:
        a = get_object_or_404(VolunteerAssignment, slot=slot, id=aid)
    else:
        a = get_object_or_404(VolunteerAssignment, slot=slot, reg=reg, id=aid)

    if a.org_confirmed and not is_admin:
        return 403, "Cannot remove a confirmed assignment. Please contact the volunteer schedule coordinator for manual processing."
    else:
        a.delete()
        return 200, None


def _confirm(request, conference, reg, is_admin, slot, aid):
    if is_admin:
        # Admins can make organization confirms
        a = get_object_or_404(VolunteerAssignment, slot=slot, id=aid)
        if a.org_confirmed:
            return 209, "Assignment already confirmed"
        else:
            a.org_confirmed = True
            a.save()
            return 200, None
    else:
        # Regular users can confirm their own sessions only
        a = get_object_or_404(VolunteerAssignment, slot=slot, reg=reg, id=aid)
        if a.vol_confirmed:
            return 209, "Assignment already confirmed"
        else:
            a.vol_confirmed = True
            a.save()
            send_volunteer_notification(conference, a, 'Volunteer slot confirmed', 'admin_notify_volunteer_confirmed.txt')
            return 200, None


def ical(request, urlname, token):
    conference = get_conference_or_404(urlname)
    reg = get_object_or_404(ConferenceRegistration, regtoken=token)
    assignments = VolunteerAssignment.objects.filter(reg=reg).order_by('slot__timerange')
    resp = render(request, 'confreg/volunteer_schedule.ical', {
        'conference': conference,
        'assignments': assignments,
        'now': datetime.utcnow(),
    }, content_type='text/calendar')
    resp['Content-Disposition'] = 'attachment; filename="{}_volunteer.ical"'.format(conference.urlname)
    return resp