# Generated by Django 3.0.8 on 2020-08-03 22:04

import django.db.models.deletion
from django.db import migrations, models

def forwards_migrate_data(apps, schema_editor):
    EventRegistration = apps.get_model('events', 'EventRegistration')
    TimeSlot = apps.get_model('events', 'TimeSlot')
    Event = apps.get_model('events', 'Event')

    grouped = {}
    for event in Event.objects.all():
        if event.note in grouped:
            grouped[event.note].append(event)
        else:
            grouped[event.note] = [event]

    for note, events in grouped.items():
        event = events[0]
        new_event = Event(date=event.date, capacity=event.capacity, note=event.note,
                          responsible_person=event.responsible_person)
        new_event.save()

        # Create a corresponding timeslot for every event with the same description
        for event in events:
            new_timeslot = TimeSlot(time=event.time, event=new_event)
            new_timeslot.save()

            # Connect registrations to the timeslots instead of the events.
            for registration in EventRegistration.objects.filter(event_id=event.id).all():
                registration.time_slot = new_timeslot
                registration.save()

def forwards_remove_old_data(apps, schema_editor):
    # Remove old events here so the cascade doesnt remove the registrations.
    EventRegistration = apps.get_model('events', 'EventRegistration')
    TimeSlot = apps.get_model('events', 'TimeSlot')
    Event = apps.get_model('events', 'Event')

    # Remove all events without timeslot
    for event in Event.objects.exclude(id__in=TimeSlot.objects.values('event_id').all()):
        event.delete()



class Migration(migrations.Migration):
    dependencies = [
        ('events', '0001_initial'),
    ]

    operations = [
        migrations.CreateModel(
            name='TimeSlot',
            fields=[
                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
                ('time', models.IntegerField(choices=[(0, 'voormiddag'), (1, 'namiddag'), (2, 'avond')], default=0)),
                ('event', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, to='events.Event'))
            ],
        ),
        migrations.AddField(
            model_name='eventregistration',
            name='time_slot',
            field=models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, to='events.TimeSlot', null=True),
        ),
        migrations.AddConstraint(
            model_name='timeslot',
            constraint=models.UniqueConstraint(fields=('time', 'event'), name='no_duplicate_timeslots'),
        ),
        migrations.AddConstraint(
            model_name='eventregistration',
            constraint=models.UniqueConstraint(fields=('time_slot', 'user'), name='register_only_once_per_timeslot'),
        ),

        migrations.RunPython(forwards_migrate_data, hints={'target_db': 'default'}),

        migrations.RemoveField(
            model_name='event',
            name='time',
        ),

        # Django bugs out when removing constraints that are made on fk's. We manualy fix it here 2 'AlterField' calls
        # https://code.djangoproject.com/ticket/31335
        migrations.AlterField(
            model_name='eventregistration',
            name='event',
            field=models.ForeignKey(
                db_constraint=False,
                on_delete=django.db.models.deletion.CASCADE,
                related_name='eventregistrations',
                related_query_name='eventregistration',
                to='events.Event',
            ),
        ),
        migrations.RemoveConstraint(
            model_name='eventregistration',
            name='register_only_once',
        ),
        migrations.RemoveField(
            model_name='eventregistration',
            name='event',
        ),

        migrations.RunPython(forwards_remove_old_data, hints={'target_db': 'default'}),
    ]