"""
Async MySQL Database Configuration
Uses SQLAlchemy 2.0+ with asyncmy driver
"""
from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine, async_sessionmaker
from sqlalchemy.orm import DeclarativeBase
from sqlalchemy.pool import QueuePool
from typing import AsyncGenerator

from app.config import settings


# Create async engine with connection pooling
connect_args = {}
if "sqlite" in settings.get_database_url:
    connect_args = {"check_same_thread": False}

engine = create_async_engine(
    settings.get_database_url,
    pool_size=settings.db_pool_size,
    max_overflow=settings.db_max_overflow,
    pool_timeout=settings.db_pool_timeout,
    pool_pre_ping=True,  # Enable connection health checks
    echo=settings.debug,  # Log SQL queries in debug mode
    pool_recycle=3600,  # Recycle connections after 1 hour
    connect_args=connect_args,
)

# Create async session factory
async_session_maker = async_sessionmaker(
    engine,
    class_=AsyncSession,
    expire_on_commit=False,
    autocommit=False,
    autoflush=False,
)


class Base(DeclarativeBase):
    """Base class for all SQLAlchemy models"""
    pass


async def get_db() -> AsyncGenerator[AsyncSession, None]:
    """
    Dependency to get database session.
    Automatically handles session lifecycle.
    
    Usage:
        @app.get("/example")
        async def example(db: AsyncSession = Depends(get_db)):
            ...
    """
    async with async_session_maker() as session:
        try:
            yield session
            await session.commit()
        except Exception:
            await session.rollback()
            raise
        finally:
            await session.close()


async def init_db():
    """Initialize database tables"""
    async with engine.begin() as conn:
        # Import all models to ensure they're registered
        from app.models import (
            user, driver, driver_account_settings, offer_profile,
            vehicle, ride, fare_bid, payment, rating, promo,
            notification, system_config
        )
        # Create tables (for development only; use Alembic in production)
        await conn.run_sync(Base.metadata.create_all)


async def close_db():
    """Close database connections"""
    await engine.dispose()