"""Alembic environment.

Reads VELODROME_DATABASE_URL directly from the environment rather than importing
velodrome.config.Settings — keeps a migration-only invocation from needing every other runtime
env var the app requires, even though today they'd resolve to the same value. There's no more
separate migration/owner role to reason about here (docs/DECISIONS.md D15): SQLite has no roles,
so migrations run against the exact same file and connection the app itself uses.
"""

import asyncio
import os

from sqlalchemy.engine import Connection
from sqlalchemy.ext.asyncio import async_engine_from_config

from alembic import context
from velodrome.models import Base

config = context.config
target_metadata = Base.metadata


def _database_url() -> str:
    url = os.environ.get("VELODROME_DATABASE_URL")
    if not url:
        # Local-dev convenience only — CI and deploy/ both set this explicitly.
        url = "sqlite+aiosqlite:///./velodrome.db"
    return url


def run_migrations_offline() -> None:
    context.configure(
        url=_database_url(),
        target_metadata=target_metadata,
        literal_binds=True,
        dialect_opts={"paramstyle": "named"},
    )
    with context.begin_transaction():
        context.run_migrations()


def _do_run_migrations(connection: Connection) -> None:
    context.configure(connection=connection, target_metadata=target_metadata)
    with context.begin_transaction():
        context.run_migrations()


async def run_migrations_online() -> None:
    configuration = config.get_section(config.config_ini_section) or {}
    configuration["sqlalchemy.url"] = _database_url()
    connectable = async_engine_from_config(configuration, prefix="sqlalchemy.")

    async with connectable.connect() as connection:
        await connection.run_sync(_do_run_migrations)

    await connectable.dispose()


if context.is_offline_mode():
    run_migrations_offline()
else:
    asyncio.run(run_migrations_online())