"""Async engine / session factory."""

from __future__ import annotations

from collections.abc import AsyncIterator

from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine

from app.core.config import get_settings
from app.models import Base

_settings = get_settings()
engine = create_async_engine(
    _settings.database_url,
    echo=False,
    pool_pre_ping=True,
    connect_args={"timeout": 30} if _settings.database_url.startswith("sqlite") else {},
)
SessionLocal = async_sessionmaker(engine, expire_on_commit=False, class_=AsyncSession)


async def init_db() -> None:
    async with engine.begin() as conn:
        if _settings.database_url.startswith("sqlite"):
            await conn.exec_driver_sql("PRAGMA journal_mode=WAL")
            await conn.exec_driver_sql("PRAGMA foreign_keys=ON")
        await conn.run_sync(Base.metadata.create_all)
        await conn.run_sync(_add_missing_columns)


def _add_missing_columns(sync_conn) -> None:  # noqa: ANN001
    """Poor man's migration: ALTER TABLE ADD COLUMN for new nullable columns (SQLite/Postgres)."""
    from sqlalchemy import inspect, text

    insp = inspect(sync_conn)
    for table in Base.metadata.sorted_tables:
        if not insp.has_table(table.name):
            continue
        existing = {c["name"] for c in insp.get_columns(table.name)}
        for col in table.columns:
            if col.name in existing:
                continue
            ctype = col.type.compile(sync_conn.dialect)
            sync_conn.execute(text(f'ALTER TABLE {table.name} ADD COLUMN "{col.name}" {ctype}'))


async def get_session() -> AsyncIterator[AsyncSession]:
    async with SessionLocal() as session:
        yield session