from pathlib import Path

from alembic import command
from alembic.config import Config
from sqlalchemy import create_engine, text

from app.core.config import settings


def ensure_postgis_available() -> None:
    engine = create_engine(settings.DATABASE_URL_SYNC, echo=False)

    try:
        with engine.connect() as connection:
            result = connection.execute(
                text("select 1 from pg_available_extensions where name = 'postgis'")
            )
            if result.scalar() != 1:
                raise RuntimeError(
                    "PostGIS is not available on the PostgreSQL server. "
                    "Install/enable PostGIS before starting the backend."
                )
    finally:
        engine.dispose()

def run_startup_migrations() -> None:
    ensure_postgis_available()

    project_root = Path(__file__).resolve().parents[2]
    alembic_ini = project_root / "alembic.ini"
    alembic_dir = project_root / "alembic"

    config = Config(str(alembic_ini))
    config.set_main_option("script_location", str(alembic_dir))

    command.upgrade(config, "head")