from __future__ import unicode_literals

from django.db import migrations, models


def forwards(apps, schema_editor):
    db_alias = schema_editor.connection.alias

    ContentType = apps.get_model('contenttypes', 'ContentType')
    Permission = apps.get_model('auth', 'Permission')
    page_model = apps.get_model('cms', 'Page')
    page_opts = page_model._meta

    # Calling get_for_model directly causes Django to create
    # the Content Type for Page if it does not exist.
    # See django-cms#5589 & django#2342
    content_type_exists = (
        ContentType
        .objects
        .using(db_alias)
        .filter(app_label=page_opts.app_label, model=page_opts.model_name)
        .exists()
    )

    if content_type_exists:
        page_ctype = (
            ContentType
            .objects
            .db_manager(db_alias)
            .get_for_model(page_model)
        )
        Permission.objects.using(db_alias).filter(
            name='',
            codename='change_page',
            content_type_id=page_ctype.pk,
        ).update(name='Can change page')


def backwards(apps, schema_editor):
    # Do nothing, but allow backward migrations
    pass


class Migration(migrations.Migration):

    dependencies = [
        ('cms', '0013_urlconfrevision'),
        ('contenttypes', '0001_initial'),
    ]

    operations = [
        migrations.RunPython(forwards, backwards)
    ]