# -*- coding: utf-8 -*-

"""

 (c) 2014-2018 - Copyright Red Hat Inc

 Authors:

   Pierre-Yves Chibon <pingou@pingoured.fr></pingou@pingoured.fr>

"""

from __future__ import unicode_literals, absolute_import

import sqlalchemy

from sqlalchemy.ext.declarative import declarative_base

from sqlalchemy.orm import sessionmaker

from sqlalchemy.orm import scoped_session

CONVENTION = {

    "ix": "ix_%(table_name)s_%(column_0_label)s",

    # Checks are currently buggy and prevent us from naming them correctly

    # "ck": "ck_%(table_name)s_%(constraint_name)s",

    "fk": "%(table_name)s_%(column_0_name)s_fkey",

    "pk": "%(table_name)s_pkey",

    "uq": "%(table_name)s_%(column_0_name)s_key",

}

BASE = declarative_base(

    metadata=sqlalchemy.MetaData(naming_convention=CONVENTION)

)

SESSIONMAKER = None

def create_session(db_url=None, debug=False, pool_recycle=3600):

    """ Create the Session object to use to query the database.

    :arg db_url: URL used to connect to the database. The URL contains

    information with regards to the database engine, the host to connect

    to, the user and password and the database name.

      ie: <engine>://<user>:<password>@<host>/<dbname></dbname></host></password></user></engine>

    :kwarg debug: a boolean specifying whether we should have the verbose

        output of sqlalchemy or not.

    :return a Session that can be used to query the database.

    """

    global SESSIONMAKER

    if SESSIONMAKER is None or (

        db_url and db_url != ("%s" % SESSIONMAKER.kw["bind"].engine.url)

    ):

        if db_url is None:

            raise ValueError("First call to create_session needs db_url")

        if db_url.startswith("postgres"):  # pragma: no cover

            engine = sqlalchemy.create_engine(

                db_url,

                echo=debug,

                pool_recycle=pool_recycle,

                client_encoding="utf8",

            )

        else:  # pragma: no cover

            engine = sqlalchemy.create_engine(

                db_url, echo=debug, pool_recycle=pool_recycle

            )

        if db_url.startswith("sqlite:"):

            # Ignore the warning about con_record

            # pylint: disable=unused-argument

            def _fk_pragma_on_connect(dbapi_con, _):  # pragma: no cover

                """ Tries to enforce referential constraints on sqlite. """

                dbapi_con.execute("pragma foreign_keys=ON")

            sqlalchemy.event.listen(engine, "connect", _fk_pragma_on_connect)

        SESSIONMAKER = sessionmaker(bind=engine)

    scopedsession = scoped_session(SESSIONMAKER)

    BASE.metadata.bind = scopedsession

    return scopedsession