"""Alembic async env — reads ``IX_POSTGRES_URL`` from the environment.

Mirrors mammon's ``alembic/env.py`` pattern (async engine + ``run_sync`` bridge)
so anyone familiar with that repo can read this one without context switch.
The only deviations:

* We source the URL from ``IX_POSTGRES_URL`` via ``os.environ`` rather than via
  the alembic.ini ``sqlalchemy.url`` setting. Config parsing happens at import
  time and depending on pydantic-settings here would introduce a cycle with
  ``src/ix/config.py`` (which lands in Task 3.2).
* We use ``NullPool`` — migrations open/close their connection once, pooling
  would hold an unused async connection open after ``alembic upgrade head``
  returned, which breaks the container's CMD chain.

Run offline by setting ``-x url=...`` or the env var + ``--sql``.
"""

from __future__ import annotations

import asyncio
import os
from logging.config import fileConfig

from alembic import context
from sqlalchemy.ext.asyncio import create_async_engine
from sqlalchemy.pool import NullPool

from ix.store.models import Base

config = context.config
if config.config_file_name is not None:
    fileConfig(config.config_file_name)

target_metadata = Base.metadata


def _database_url() -> str:
    """Resolve the connection URL from env, falling back to alembic.ini.

    The env var is the primary source (container CMD sets it). The ini value
    remains available so ``alembic -x url=...`` or a manual ``alembic.ini``
    edit still work for one-off scripts.
    """

    env_url = os.environ.get("IX_POSTGRES_URL")
    if env_url:
        return env_url
    ini_url = config.get_main_option("sqlalchemy.url")
    if ini_url and ini_url != "driver://user:pass@localhost/dbname":
        return ini_url
    raise RuntimeError(
        "IX_POSTGRES_URL not set and alembic.ini sqlalchemy.url not configured"
    )


def run_migrations_offline() -> None:
    """Emit migrations as SQL without a live connection."""

    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) -> None:  # type: ignore[no-untyped-def]
    context.configure(connection=connection, target_metadata=target_metadata)
    with context.begin_transaction():
        context.run_migrations()


async def run_async_migrations() -> None:
    engine = create_async_engine(_database_url(), poolclass=NullPool)
    async with engine.connect() as connection:
        await connection.run_sync(do_run_migrations)
    await engine.dispose()


def run_migrations_online() -> None:
    asyncio.run(run_async_migrations())


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