from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine
from sqlalchemy.orm import sessionmaker, declarative_base
from config import settings

DATABASE_URL = settings.database_url

if not DATABASE_URL:
    raise ValueError(
        "DATABASE_URL not found in environment variables. "
        "Please set it in .env file. Example: "
        "postgresql+asyncpg://user:password@localhost:5432/kairo_db"
    )

# Create async engine
engine = create_async_engine(
    DATABASE_URL,
    echo=False,  # Set to True for SQL logging
    future=True,
    pool_pre_ping=True,  # Verify connections before using
    pool_size=10,
    max_overflow=20,
)

# Create async session factory
async_session = sessionmaker(
    engine, class_=AsyncSession, expire_on_commit=False, autoflush=False
)

# Base class for all models
Base = declarative_base()


async def get_db() -> AsyncSession:
    """Dependency for getting async database session"""
    async with async_session() as session:
        try:
            yield session
        finally:
            await session.close()


async def init_db():
    """Initialize database by creating all tables"""
    async with engine.begin() as conn:
        await conn.run_sync(Base.metadata.create_all)


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