# Copyright (c) 2011 X.commerce, a business unit of eBay Inc.
# Copyright 2010 United States Government as represented by the
# Administrator of the National Aeronautics and Space Administration.
# Copyright 2011 Piston Cloud Computing, Inc.
# Copyright 2012 Cloudscaling Group, Inc.
# All Rights Reserved.
#
#    Licensed under the Apache License, Version 2.0 (the "License"); you may
#    not use this file except in compliance with the License. You may obtain
#    a copy of the License at
#
#         http://www.apache.org/licenses/LICENSE-2.0
#
#    Unless required by applicable law or agreed to in writing, software
#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
#    License for the specific language governing permissions and limitations
#    under the License.
"""
SQLAlchemy models.
"""

import six

from oslo_utils import timeutils
from sqlalchemy import Column
from sqlalchemy import DateTime
from sqlalchemy.orm import object_mapper

from oslo_db.sqlalchemy import types


class ModelBase(six.Iterator):
    """Base class for models."""
    __table_initialized__ = False

    def save(self, session):
        """Save this object."""

        # NOTE(boris-42): This part of code should be look like:
        #                       session.add(self)
        #                       session.flush()
        #                 But there is a bug in sqlalchemy and eventlet that
        #                 raises NoneType exception if there is no running
        #                 transaction and rollback is called. As long as
        #                 sqlalchemy has this bug we have to create transaction
        #                 explicitly.
        with session.begin(subtransactions=True):
            session.add(self)
            session.flush()

    def __setitem__(self, key, value):
        setattr(self, key, value)

    def __getitem__(self, key):
        return getattr(self, key)

    def __contains__(self, key):
        # Don't use hasattr() because hasattr() catches any exception, not only
        # AttributeError. We want to passthrough SQLAlchemy exceptions
        # (ex: sqlalchemy.orm.exc.DetachedInstanceError).
        try:
            getattr(self, key)
        except AttributeError:
            return False
        else:
            return True

    def get(self, key, default=None):
        return getattr(self, key, default)

    @property
    def _extra_keys(self):
        """Specifies custom fields

        Subclasses can override this property to return a list
        of custom fields that should be included in their dict
        representation.

        For reference check tests/db/sqlalchemy/test_models.py
        """
        return []

    def __iter__(self):
        columns = list(dict(object_mapper(self).columns).keys())
        # NOTE(russellb): Allow models to specify other keys that can be looked
        # up, beyond the actual db columns.  An example would be the 'name'
        # property for an Instance.
        columns.extend(self._extra_keys)

        return ModelIterator(self, iter(columns))

    def update(self, values):
        """Make the model object behave like a dict."""
        for k, v in values.items():
            setattr(self, k, v)

    def _as_dict(self):
        """Make the model object behave like a dict.

        Includes attributes from joins.
        """
        local = dict((key, value) for key, value in self)
        joined = dict([(k, v) for k, v in self.__dict__.items()
                      if not k[0] == '_'])
        local.update(joined)
        return local

    def iteritems(self):
        """Make the model object behave like a dict."""
        return self._as_dict().items()

    def items(self):
        """Make the model object behave like a dict."""
        return self._as_dict().items()

    def keys(self):
        """Make the model object behave like a dict."""
        return [key for key, value in self.iteritems()]


class ModelIterator(six.Iterator):

    def __init__(self, model, columns):
        self.model = model
        self.i = columns

    def __iter__(self):
        return self

    # In Python 3, __next__() has replaced next().
    def __next__(self):
        n = six.advance_iterator(self.i)
        return n, getattr(self.model, n)


class TimestampMixin(object):
    created_at = Column(DateTime, default=lambda: timeutils.utcnow())
    updated_at = Column(DateTime, onupdate=lambda: timeutils.utcnow())


class SoftDeleteMixin(object):
    deleted_at = Column(DateTime)
    deleted = Column(types.SoftDeleteInteger, default=0)

    def soft_delete(self, session):
        """Mark this object as deleted."""
        self.deleted = self.id
        self.deleted_at = timeutils.utcnow()
        self.save(session=session)