backend/alembic/env.py

"""
Alembic Environment — Configures database migrations.
Reads DB URI from app.config to stay in sync with the application.
"""

import os
import sys
from logging.config import fileConfig

from sqlalchemy import engine_from_config, pool
from alembic import context

# Add backend to path so we can import app modules
sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))

# Alembic Config object
config = context.config

# Setup logging from alembic.ini
if config.config_file_name is not None:
    fileConfig(config.config_file_name)

# Override sqlalchemy.url from environment / app config
try:
    from dotenv import load_dotenv
    load_dotenv()
except ImportError:
    pass

db_url = os.environ.get("DB_URI")
if db_url:
    config.set_main_option("sqlalchemy.url", db_url)

# No metadata target — we use raw SQL migrations for maximum control
target_metadata = None


def run_migrations_offline() -> None:
    """Run migrations in 'offline' mode (generate SQL script)."""
    url = config.get_main_option("sqlalchemy.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 (execute against database)."""
    connectable = engine_from_config(
        config.get_section(config.config_ini_section, {}),
        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()