src/database/database.py

"""
database.py

This module sets up the SQLAlchemy database connection for the Expressive TTS Arena project.
It initializes the PostgreSQL engine, creates a session factory for handling database transactions,
and defines a declarative base class for ORM models.

If no DATABASE_URL environment variable is set, then create a dummy database to fail gracefully
"""

# Standard Library Imports
import os

# Third-Party Library Imports
from sqlalchemy import create_engine
from sqlalchemy.orm import declarative_base, sessionmaker

# Local Application Imports
from src.config import APP_ENV

DATABASE_URL = os.getenv("DATABASE_URL")

if APP_ENV == "prod":
    # In production, a valid DATABASE_URL is required.
    if not DATABASE_URL:
        raise ValueError("DATABASE_URL must be set in production!")

    engine = create_engine(DATABASE_URL)
    SessionLocal = sessionmaker(bind=engine)
# In development, if a DATABASE_URL is provided, use it.
elif DATABASE_URL:
    engine = create_engine(DATABASE_URL)
    SessionLocal = sessionmaker(bind=engine)
else:
    # No DATABASE_URL is provided; use a DummySession that does nothing.
    engine = None

    class DummySession:
        is_dummy = True  # Flag to indicate this is a dummy session.

        def __enter__(self):
            return self

        def __exit__(self, exc_type, exc_value, traceback):
            pass

        def add(self, _instance, _warn=True):
            # No-op: simply ignore adding the instance.
            pass

        def commit(self):
            # Raise an exception to simulate failure when attempting a write.
            raise RuntimeError("DummySession does not support commit operations.")

        def refresh(self, _instance):
            # Raise an exception to simulate failure when attempting to refresh.
            raise RuntimeError("DummySession does not support refresh operations.")

        def rollback(self):
            # No-op: there's nothing to roll back.
            pass

        def close(self):
            # No-op: nothing to close.
            pass

    def dummy_session_factory():
        return DummySession()

    SessionLocal = dummy_session_factory

# Declarative base class for ORM models.
Base = declarative_base()