database.py

from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker
import os

# Use PostgreSQL in production, SQLite locally
DATABASE_URL = os.getenv("DATABASE_URL", "sqlite:///./todos.db")

# Handle PostgreSQL URL format
if DATABASE_URL.startswith("postgres://"):
    DATABASE_URL = DATABASE_URL.replace("postgres://", "postgresql://", 1)

engine = create_engine(
    DATABASE_URL,
    connect_args={"check_same_thread": False} if DATABASE_URL.startswith("sqlite") else {}
)
SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)

Base = declarative_base()

def get_db():
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()