from django.db import migrations, models


def backfill_display_name(apps, schema_editor):
    User = apps.get_model("accounts", "User")
    for user in User.objects.all().iterator():
        if not (user.display_name or "").strip():
            User.objects.filter(pk=user.pk).update(display_name=user.user_name)


class Migration(migrations.Migration):

    dependencies = [
        ("accounts", "0004_sync_status_flags"),
    ]

    operations = [
        migrations.AddField(
            model_name="user",
            name="display_name",
            field=models.CharField(default="", max_length=100),
            preserve_default=False,
        ),
        migrations.RunPython(backfill_display_name, migrations.RunPython.noop),
    ]