from django.db import migrations, models


def populate_code(apps, schema_editor):
    """为已有机构填充 code = 'INST-{pk}'。"""
    Institution = apps.get_model('user', 'Institution')
    for inst in Institution.objects.filter(code__isnull=True):
        inst.code = f'INST-{inst.pk}'
        inst.save(update_fields=['code'])


class Migration(migrations.Migration):

    dependencies = [
        ('user', '0003_institution_add_code_field'),
    ]

    operations = [
        migrations.RunPython(populate_code, migrations.RunPython.noop),
        migrations.AlterField(
            model_name='institution',
            name='code',
            field=models.CharField(max_length=100, unique=True, verbose_name='机构编码'),
        ),
    ]