import uri_template
from django.db import migrations
from django.db.backends.base.schema import BaseDatabaseSchemaEditor
from django.db.migrations.state import StateApps


def transform_to_url_template_syntax(
    apps: StateApps, schema_editor: BaseDatabaseSchemaEditor
) -> None:
    realm_playground_model = apps.get_model("zerver", "RealmPlayground")

    # Only the null entries are realm playgrounds that exist prior to the
    # addition of url_template
    realm_playgrounds = realm_playground_model.objects.filter(url_template__isnull=True)
    escape_table = str.maketrans(
        {
            "{": "%7B",
            "}": "%7D",
        }
    )
    for realm_playground in realm_playgrounds:
        # It is originally expected to have the code appended to the end of
        # url_prefix. Therefore, making a template having only one variable that
        # expands at the end of it should suffice to replicate the old behavior
        # for the legacy prefix strings. Note that we use simple expansion
        # instead of reserved expansion here (i.e.: {code} instead of {+code})
        # because the code segment is supposed to be URL encoded.
        converted_template = realm_playground.url_prefix.translate(escape_table) + "{code}"
        if not uri_template.validate(converted_template):
            raise RuntimeError(
                f'Failed to convert url prefix "{realm_playground.url_prefix}". The converted template "{converted_template}" is invalid.'
            )
        realm_playground.url_template = converted_template
    realm_playground_model.objects.bulk_update(realm_playgrounds, fields=["url_template"])


class Migration(migrations.Migration):
    dependencies = [
        ("zerver", "0462_realmplayground_url_template"),
    ]

    operations = [
        migrations.RunPython(
            transform_to_url_template_syntax,
            reverse_code=migrations.RunPython.noop,
            elidable=True,
        ),
    ]