# -*- coding: utf-8 -*-
"""
    rhodecode.model.__init__
    ~~~~~~~~~~~~~~~~~~~~~~~~

    The application's model objects

    :created_on: Nov 25, 2010
    :author: marcink
    :copyright: (C) 2010-2012 Marcin Kuzminski <marcin@python-works.com>
    :license: GPLv3, see COPYING for more details.


    :example:

        .. code-block:: python

           from paste.deploy import appconfig
           from pylons import config
           from sqlalchemy import engine_from_config
           from rhodecode.config.environment import load_environment

           conf = appconfig('config:development.ini', relative_to = './../../')
           load_environment(conf.global_conf, conf.local_conf)

           engine = engine_from_config(config, 'sqlalchemy.')
           init_model(engine)
           # RUN YOUR CODE HERE

"""
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

import logging

from rhodecode.model import meta

log = logging.getLogger(__name__)


def init_model(engine):
    """
    Initializes db session, bind the engine with the metadata,
    Call this before using any of the tables or classes in the model,
    preferably once in application start

    :param engine: engine to bind to
    """
    log.info("initializing db for %s" % engine)
    meta.Base.metadata.bind = engine


class BaseModel(object):
    """
    Base Model for all RhodeCode models, it adds sql alchemy session
    into instance of model

    :param sa: If passed it reuses this session instead of creating a new one
    """

    def __init__(self, sa=None):
        if sa is not None:
            self.sa = sa
        else:
            self.sa = meta.Session

    def _get_instance(self, cls, instance, callback=None):
        """
        Get's instance of given cls using some simple lookup mechanism.

        :param cls: class to fetch
        :param instance: int or Instance
        :param callback: callback to call if all lookups failed
        """

        if isinstance(instance, cls):
            return instance
        elif isinstance(instance, (int, long)) or str(instance).isdigit():
            return cls.get(instance)
        else:
            if instance:
                if callback is None:
                    raise Exception(
                        'given object must be int, long or Instance of %s '
                        'got %s, no callback provided' % (cls, type(instance))
                    )
                else:
                    return callback(instance)