# Generated by Django 2.2.11 on 2020-11-16 08:53

from django.db import connection, migrations
from django.db.models import Exists, OuterRef, Q

from baserow.contrib.database.fields.models import Field as FieldModel
from baserow.contrib.database.table.models import Table as TableModel


def forward(apps, schema_editor):
    """
    This migration fixes the not allowed situations where link row fields are primary
    fields or if a table doesn't have a primary field anymore (because it was
    deleted by the related link row field). In both cases a new primary text field is
    created because that is allowed.
    """

    Table = apps.get_model("database", "Table")
    Field = apps.get_model("database", "Field")
    LinkRowField = apps.get_model("database", "LinkRowField")
    TextField = apps.get_model("database", "TextField")
    ContentType = apps.get_model("contenttypes", "ContentType")
    text_field_content_type = ContentType.objects.get_for_model(TextField)

    # Check if there are tables without a primary field or where the primary field is
    # a link row field, which is not allowed.
    tables_without_primary = Table.objects.annotate(
        has_primary=Exists(Field.objects.filter(table=OuterRef("pk"), primary=True)),
        has_link_row_primary=Exists(
            LinkRowField.objects.filter(table=OuterRef("pk"), primary=True)
        ),
    ).filter(Q(has_primary=False) | Q(has_link_row_primary=True))
    for table in tables_without_primary:
        # If the table has a link row field as primary field it needs to be marked as
        # normal field because they are not allowed to be primary.
        if table.has_link_row_primary:
            link_row_primary = LinkRowField.objects.get(table=table, primary=True)
            link_row_primary.primary = False
            link_row_primary.save()

        # It might be possible in the future that the get_model or db_column methods
        # are going to disappear. If that is the case then the creation of the field
        # cannot be executed, so we can skip that.
        if not hasattr(TableModel, "get_model") or not hasattr(FieldModel, "db_column"):
            continue

        # We now know for sure there isn't a primary field in the table, so we can
        # create a new primary text field because the table expects one.
        new_primary = TextField.objects.create(
            table=table,
            name="Primary (auto created)",
            order=0,
            content_type=text_field_content_type,
            primary=True,
        )
        with connection.schema_editor() as tables_schema_editor:
            to_model = TableModel.get_model(table, field_ids=[new_primary.id])
            field_name = FieldModel.db_column.__get__(new_primary, FieldModel)
            model_field = to_model._meta.get_field(field_name)
            tables_schema_editor.add_field(to_model, model_field)


class Migration(migrations.Migration):
    dependencies = [
        ("database", "0019_filefield"),
    ]

    operations = [
        migrations.RunPython(forward, migrations.RunPython.noop),
    ]