from alembic import context
from sqlalchemy import engine_from_config, pool, text

from app.config import settings
from app.models import Base

config = context.config
config.set_main_option("sqlalchemy.url", settings.database_url.replace("%", "%%"))
target_metadata = Base.metadata
MIGRATION_LOCK = 703000  # advisory-lock: одна реплика мигрирует, остальные ждут и видят актуальную схему


def run():
    engine = engine_from_config(config.get_section(config.config_ini_section), prefix="sqlalchemy.", poolclass=pool.NullPool)
    with engine.connect() as lock_conn:  # отдельное соединение держит блокировку до конца миграций
        lock_conn.execute(text("SELECT pg_advisory_lock(:k)"), {"k": MIGRATION_LOCK})
        with engine.connect() as conn:
            context.configure(connection=conn, target_metadata=target_metadata)
            with context.begin_transaction():
                context.run_migrations()
        lock_conn.execute(text("SELECT pg_advisory_unlock(:k)"), {"k": MIGRATION_LOCK})
        lock_conn.commit()


run()