"""Alembic env.py — async-aware, reads DATABASE_URL from environment."""

import asyncio
import os
from logging.config import fileConfig

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

from alembic import context

from meshbay_hub.db.models import Base

config = context.config

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

target_metadata = Base.metadata

# Three sources, in the order that keeps them from disagreeing.
#
# A caller that already resolved the URL wins: `meshbay-hub migrate` passes
# `cfg.db.url`, which is `load_config`'s answer — the very string the server
# will connect with. Reading the environment again here instead would be a
# second resolution of the same question, and the two would drift the day
# anything but the environment decides it.
#
# Then the environment, for `alembic` run by hand or from a deploy script,
# where `alembic.ini` carries only its placeholder. Then a local default, so
# a developer's checkout needs no setup.
_PLACEHOLDER = "driver://user:pass@localhost/dbname"

db_url = config.get_main_option("sqlalchemy.url", "")
if not db_url or db_url == _PLACEHOLDER:
    db_url = os.environ.get(
        "MESHBAY_DATABASE_URL",
        "postgresql+asyncpg://meshbay:meshbay@localhost/meshbay_hub",
    )
config.set_main_option("sqlalchemy.url", db_url)


def run_migrations_offline() -> None:
    context.configure(
        url=db_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_async_migrations() -> None:
    connectable = async_engine_from_config(
        config.get_section(config.config_ini_section, {}),
        prefix="sqlalchemy.",
        poolclass=pool.NullPool,
    )
    async with connectable.connect() as connection:
        await connection.run_sync(do_run_migrations)
    await connectable.dispose()


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


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