import logging
from bootstrap import db
from werkzeug.exceptions import Forbidden, NotFound

logger = logging.getLogger(__name__)


class AbstractController(object):
    _db_cls = None  # reference to the database class
    _user_id_key = 'user_id'

    def __init__(self, user_id=None):
        """User id is a right management mechanism that should be used to
        filter objects in database on their denormalized "user_id" field
        (or "id" field for users).
        Should no user_id be provided, the Controller won't apply any filter
        allowing for a kind of "super user" mode.
        """
        self.user_id = user_id

    def _to_filters(self, **filters):
        """
        Will translate filters to sqlalchemy filter.
        This method will also apply user_id restriction if available.

        each parameters of the function is treated as an equality unless the
        name of the parameter ends with either "__gt", "__lt", "__ge", "__le",
        "__ne" or "__in".
        """
        if self.user_id is not None:
            filters[self._user_id_key] = self.user_id
        db_filters = set()
        for key, value in filters.items():
            if key.endswith('__gt'):
                db_filters.add(getattr(self._db_cls, key[:-4]) > value)
            elif key.endswith('__lt'):
                db_filters.add(getattr(self._db_cls, key[:-4]) < value)
            elif key.endswith('__ge'):
                db_filters.add(getattr(self._db_cls, key[:-4]) >= value)
            elif key.endswith('__le'):
                db_filters.add(getattr(self._db_cls, key[:-4]) <= value)
            elif key.endswith('__ne'):
                db_filters.add(getattr(self._db_cls, key[:-4]) != value)
            elif key.endswith('__in'):
                db_filters.add(getattr(self._db_cls, key[:-4]).in_(value))
            else:
                db_filters.add(getattr(self._db_cls, key) == value)
        return db_filters

    def _get(self, **filters):
        return self._db_cls.query.filter(*self._to_filters(**filters))

    def get(self, **filters):
        """Will return one single objects corresponding to filters"""
        obj = self._get(**filters).first()
        if not obj:
            raise NotFound({'message': 'No %r (%r)'
                                % (self._db_cls.__class__.__name__, filters)})

        if not self._has_right_on(obj):
            raise Forbidden({'message': 'No authorized to access %r (%r)'
                                % (self._db_cls.__class__.__name__, filters)})
        return obj

    def create(self, **attrs):
        assert self._user_id_key in attrs or self.user_id is not None, \
                "You must provide user_id one way or another"
        attrs[self._user_id_key] = self.user_id or attrs.get(self._user_id_key)
        obj = self._db_cls(**attrs)
        db.session.add(obj)
        db.session.commit()
        return obj

    def read(self, **filters):
        return self._get(**filters)

    def update(self, filters, attrs):
        result = self._get(**filters).update(attrs, synchronize_session=False)
        db.session.commit()
        return result

    def delete(self, obj_id):
        obj = self.get(id=obj_id)
        db.session.delete(obj)
        db.session.commit()
        return obj

    def _has_right_on(self, obj):
        # user_id == None is like being admin
        return self.user_id is None \
                or getattr(obj, self._user_id_key, None) == self.user_id