from logging.config import fileConfig

from sqlalchemy import engine_from_config
from sqlalchemy import pool
import os
from dotenv import load_dotenv
from alembic import context
from backend.core.settings import SQLALCHEMY_DATABASE_URI
from backend.core.db import metadata
# Load .env manually (if not loaded by your settings.py or entry point)
load_dotenv()

# this is the Alembic Config object, which provides
# access to the values within the .ini file in use.
config = context.config
# Get environment (default to development if not set)
APP_ENV = os.getenv("APP_ENV")
config.set_main_option("sqlalchemy.url", SQLALCHEMY_DATABASE_URI)
# Interpret the config file for Python logging.
# This line sets up loggers basically.
if config.config_file_name is not None:
    fileConfig(config.config_file_name)

# add your model's MetaData object here
# for 'autogenerate' support
# from myapp import mymodel
# target_metadata = mymodel.Base.metadata
target_metadata = metadata

# other values from the config, defined by the needs of env.py,
# can be acquired:
# my_important_option = config.get_main_option("my_important_option")
# ... etc.
# Determine DB URL
if APP_ENV == "production":
    db_url = os.getenv("DATABASE_URL")
    if not db_url:
        raise RuntimeError("DATABASE_URL is required in production.")
else:
    # fallback to local SQLite db
    db_url = os.getenv("SQLALCHEMY_DATABASE_URI", "sqlite:///data/local.db")


def run_migrations_offline() -> None:
    """Run migrations in 'offline' mode.

    This configures the context with just a URL
    and not an Engine, though an Engine is acceptable
    here as well.  By skipping the Engine creation
    we don't even need a DBAPI to be available.

    Calls to context.execute() here emit the given string to the
    script output.

    """


    url = config.get_main_option("sqlalchemy.url", db_url)
    context.configure(
        url=url,
        target_metadata=target_metadata,
        literal_binds=True,
        dialect_opts={"paramstyle": "named"},
    )

    with context.begin_transaction():
        context.run_migrations()
print(f"→ Alembic using DB URL: {db_url}")

def run_migrations_online() -> None:
    """Run migrations in 'online' mode.

    In this scenario we need to create an Engine
    and associate a connection with the context.

    """
    connect_args = {"sslmode": "require"}
    connectable = engine_from_config(
        config.get_section(config.config_ini_section, {}),
        prefix="sqlalchemy.",
        connect_args=connect_args,
        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()