migrations/env.py

import os
from logging.config import fileConfig

from sqlalchemy import engine_from_config
from sqlalchemy import pool

from alembic import context

# Import your models here
from app.models.database import Base

# this is the Alembic Config object
config = context.config

# Interpret the config file for Python logging
if config.config_file_name is not None:
    fileConfig(config.config_file_name)

target_metadata = Base.metadata

def get_url():
    """Get database URL from environment variable."""
    return os.getenv(
        "DATABASE_URL",
        "sqlite:///app/storage/audiobooks.db"
    )

def run_migrations_offline() -> None:
    """Run migrations in 'offline' mode."""
    url = get_url()
    context.configure(
        url=url,
        target_metadata=target_metadata,
        literal_binds=True,
        dialect_opts={"paramstyle": "named"},
    )

    with context.begin_transaction():
        context.run_migrations()

def run_migrations_online() -> None:
    """Run migrations in 'online' mode."""
    configuration = config.get_section(config.config_ini_section)
    configuration["sqlalchemy.url"] = get_url()
    connectable = engine_from_config(
        configuration,
        prefix="sqlalchemy.",
        poolclass=pool.NullPool,
    )

    with connectable.connect() as connection:
        context.configure(
            connection=connection,
            target_metadata=target_metadata
        )

        with context.begin_transaction():
            context.run_migrations()

if context.is_offline_mode():
    run_migrations_offline()
else:
    run_migrations_online()