from django.db import migrations
import uuid


def generate_tokens(apps, schema_editor):
    Worker = apps.get_model('rota', 'Worker')
    db_alias = schema_editor.connection.alias
    for w in Worker.objects.using(db_alias).all():
        if not getattr(w, 'request_token', None):
            new_token = uuid.uuid4()
            # extremely unlikely collision, but guard anyway
            while Worker.objects.using(db_alias).filter(request_token=new_token).exists():
                new_token = uuid.uuid4()
            w.request_token = new_token
            w.save(update_fields=['request_token'])


class Migration(migrations.Migration):

    dependencies = [
        ('rota', '0005_add_request_token'),
    ]

    operations = [
        migrations.RunPython(generate_tokens, reverse_code=migrations.RunPython.noop),
    ]