from __future__ import with_statement

import os
import sys
from logging.config import fileConfig

from alembic import context
from sqlalchemy import engine_from_config

from snakeeyes.app import create_app
from snakeeyes.extensions import db

app = create_app()


# Include the project's folder on the system path.
sys.path.append(os.getcwd())

# Provides access to the values within the alembic.ini file.
config = context.config

# Configure logging.
fileConfig(config.config_file_name)

# Get the SQLAlchemy database URI.
config.set_main_option('sqlalchemy.url', app.config['SQLALCHEMY_DATABASE_URI'])

# Required for --autogenerate to work so that Alembic can attempt to find
# the difference between the current database and our models automatically.
target_metadata = db.metadata


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 DBAPI to be available.

    Calls to context.execute() here emit the given string to the script output.
    """
    context.configure(url=app.config['SQLALCHEMY_DATABASE_URI'],
                      target_metadata=target_metadata, literal_binds=True)

    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.
    """
    engine = engine_from_config(
        config.get_section(config.config_ini_section), prefix='sqlalchemy.')

    with engine.connect() as connection:
        context.configure(
            url=app.config['SQLALCHEMY_DATABASE_URI'],
            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()