import asyncio
from logging.config import fileConfig

from alembic import context
from sqlalchemy import pool
from sqlalchemy.ext.asyncio import async_engine_from_config

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

config = context.config
config.set_main_option("sqlalchemy.url", settings.database_url)
if config.config_file_name:
    fileConfig(config.config_file_name)
target_metadata = Base.metadata

# Arbitrary constant shared by every `alembic upgrade` (one per API replica's init container).
MIGRATION_LOCK_ID = 72150001


def run_migrations(connection):
    context.configure(connection=connection, target_metadata=target_metadata)
    with context.begin_transaction():
        # Held until this transaction commits; a concurrent run waits, then finds nothing to do.
        connection.exec_driver_sql(f"SELECT pg_advisory_xact_lock({MIGRATION_LOCK_ID})")
        context.run_migrations()


async def run_async():
    engine = async_engine_from_config(
        config.get_section(config.config_ini_section, {}), poolclass=pool.NullPool
    )
    async with engine.connect() as conn:
        await conn.run_sync(run_migrations)
    await engine.dispose()


def run_offline():
    """`alembic upgrade head --sql`: emit the SQL instead of running it."""
    context.configure(
        url=settings.database_url,
        target_metadata=target_metadata,
        literal_binds=True,
        dialect_opts={"paramstyle": "named"},
    )
    with context.begin_transaction():
        context.run_migrations()


if context.is_offline_mode():
    run_offline()
else:
    asyncio.run(run_async())