from logging.config import fileConfig

from sqlalchemy import engine_from_config
from sqlalchemy import pool

from alembic import context

# this is the Alembic Config object, which provides
# access to values within the .ini file in use.
config = context.config

# 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 Base
# target_metadata = Base.metadata
from flask import current_app
from app.extensions import db

config.set_main_option('sqlalchemy.url',
                       current_app.config.get('SQLALCHEMY_DATABASE_URI'))
target_metadata = db.metadata 

# Function to filter objects for autogenerate
def include_object(object, name, type_, reflected, compare_to):
    """
    Control which objects are included in the autogenerate process.
    Only include objects that are part of the Flask app's declared models.
    """
    if type_ == "table" and reflected and name not in target_metadata.tables:
        return False # Exclude tables that are in DB but not in models
    return True # Include everything else (e.g., our modeled tables, columns, etc.)

def run_migrations_offline():
    """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 database to begin with.

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

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

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


def run_migrations_online():
    """Run migrations in 'online' mode.

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

    """
    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,
            include_object=include_object
        )

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


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