"""Database configuration and session management."""

import os
from contextlib import contextmanager
from typing import Generator

from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker, Session

from models import Base


# Database configuration from environment variable
# Falls back to SQLite for local development if DATABASE_URL not set
DATABASE_URL = os.getenv("DATABASE_URL", "sqlite:///yottob.db")

# Create engine with appropriate configuration
engine_kwargs = {
    "echo": False,  # Set to True for SQL query logging
}

# SQLite-specific configuration
if DATABASE_URL.startswith("sqlite"):
    engine_kwargs["connect_args"] = {"check_same_thread": False}

engine = create_engine(DATABASE_URL, **engine_kwargs)

# Session factory
SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)


def init_db() -> None:
    """Initialize the database by creating all tables.

    This function should be called when the application starts.
    It creates all tables defined in the models if they don't exist.
    """
    Base.metadata.create_all(bind=engine)


@contextmanager
def get_db_session() -> Generator[Session, None, None]:
    """Context manager for database sessions.

    Usage:
        with get_db_session() as session:
            # Use session here
            session.query(...)

    The session is automatically committed on success and rolled back on error.
    """
    session = SessionLocal()
    try:
        yield session
        session.commit()
    except Exception:
        session.rollback()
        raise
    finally:
        session.close()


def get_db() -> Generator[Session, None, None]:
    """Dependency function for Flask routes to get a database session.

    Usage in Flask:
        session = next(get_db())
        try:
            # Use session
        finally:
            session.close()
    """
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()