# -*- coding: utf-8 -*-
"""비동기 DB 세션 + Base + 공통 타임스탬프 믹스인.

castad 는 공통 base 가 없어 컬럼을 매번 반복하지만, 여기선 TimestampMixin 으로 정리.
"""
from collections.abc import AsyncGenerator
from datetime import datetime

from sqlalchemy import DateTime, func
from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine
from sqlalchemy.orm import DeclarativeBase, Mapped, mapped_column

from .config import settings

engine = create_async_engine(settings.DATABASE_URL, echo=False, future=True)
SessionLocal = async_sessionmaker(bind=engine, class_=AsyncSession, expire_on_commit=False, autoflush=False)


class Base(DeclarativeBase):
    pass


class TimestampMixin:
    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), server_default=func.now())


async def get_session() -> AsyncGenerator[AsyncSession, None]:
    async with SessionLocal() as session:
        try:
            yield session
        except Exception:
            await session.rollback()
            raise


async def create_tables() -> None:
    from . import models  # noqa: F401  (테이블 메타데이터 등록)
    async with engine.begin() as conn:
        await conn.run_sync(Base.metadata.create_all)
        await _lightweight_migrate(conn)


# create_all 은 기존 테이블에 새 컬럼을 추가하지 않는다. 개발용 SQLite 를 위한 최소 마이그레이션.
# (운영 MySQL 은 Alembic 등 정식 마이그레이션 사용 권장)
_ADD_COLUMNS = {
    "user": [
        ("profile_image_url", "TEXT"),
        ("bio", "VARCHAR(200)"),
    ],
}


async def _lightweight_migrate(conn) -> None:
    from sqlalchemy import text
    dialect = conn.dialect.name
    if dialect != "sqlite":
        return  # 운영 DB 는 정식 마이그레이션으로 처리
    for table, cols in _ADD_COLUMNS.items():
        rows = (await conn.exec_driver_sql(f"PRAGMA table_info({table})")).fetchall()
        existing = {r[1] for r in rows}
        for name, ddl in cols:
            if name not in existing:
                await conn.exec_driver_sql(f"ALTER TABLE {table} ADD COLUMN {name} {ddl}")