from __future__ import with_statement

from logging.config import fileConfig

from flask import current_app

from alembic import context

config = context.config

fileConfig(config.config_file_name)
logger = fileConfig


def get_engine():
    try:
        return current_app.extensions['migrate'].db.get_engine()
    except (TypeError, AttributeError):
        return current_app.extensions['migrate'].db.engine


def get_engine_url():
    try:
        return get_engine().url.render_as_string(hide_password=False).replace('%', '%%')
    except AttributeError:
        return str(get_engine().url).replace('%', '%%')


config.set_main_option('sqlalchemy.url', get_engine_url())
target_db = current_app.extensions['migrate'].db


def get_metadata():
    if hasattr(target_db, 'metadatas'):
        return target_db.metadatas[None]
    return target_db.metadata


def run_migrations_offline():
    url = config.get_main_option('sqlalchemy.url')
    conf_args = dict(current_app.extensions['migrate'].configure_args)
    conf_args.setdefault('compare_type', True)
    conf_args.setdefault('render_as_batch', True)

    context.configure(
        url=url,
        target_metadata=get_metadata(),
        literal_binds=True,
        **conf_args,
    )

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


def run_migrations_online():
    conf_args = dict(current_app.extensions['migrate'].configure_args)
    if conf_args.get('process_revision_directives') is None:
        def process_revision_directives(context_, revision, directives):
            if getattr(config.cmd_opts, 'autogenerate', False):
                script = directives[0]
                if script.upgrade_ops.is_empty():
                    directives[:] = []
                    print('No changes in schema detected.')
        conf_args['process_revision_directives'] = process_revision_directives

    connectable = get_engine()

    with connectable.connect() as connection:
        conf_args.setdefault('compare_type', True)
        conf_args.setdefault('render_as_batch', True)

        context.configure(
            connection=connection,
            target_metadata=get_metadata(),
            **conf_args,
        )

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


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