app/database.py

from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker
from sqlalchemy.ext.declarative import declarative_base
from app.config import settings

# Use NEON_DATABASE_URL if available, otherwise fall back to DATABASE_URL or SQLite
SQLALCHEMY_DATABASE_URL = settings.NEON_DATABASE_URL or settings.DATABASE_URL

# If no database URL is provided or it's a placeholder, use SQLite as fallback
if (not SQLALCHEMY_DATABASE_URL or 
    SQLALCHEMY_DATABASE_URL.strip() == "" or 
    "your_" in SQLALCHEMY_DATABASE_URL or
    SQLALCHEMY_DATABASE_URL.startswith("postgresql://your") or
    SQLALCHEMY_DATABASE_URL.startswith("postgres://your")):
    SQLALCHEMY_DATABASE_URL = "sqlite:///./chat_database.db"
    print("⚠️  No database URL configured, using SQLite as fallback")

engine = create_engine(
    SQLALCHEMY_DATABASE_URL, 
    connect_args={"check_same_thread": False} if "sqlite" in SQLALCHEMY_DATABASE_URL else {}
)
SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
Base = declarative_base()

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