# Copyright 2016 Google 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.

"""Contains classes used for the Django ORM storage."""

import base64
import pickle

from django.db import models
from django.utils import encoding
import jsonpickle

from google.oauth2.credentials import Credentials


class CredentialsField(models.Field):
    """Django ORM field for storing OAuth2 Credentials."""

    def __init__(self, *args, **kwargs):
        if "null" not in kwargs:
            kwargs["null"] = True
        super(CredentialsField, self).__init__(*args, **kwargs)

    def get_internal_type(self):
        return "BinaryField"

    def from_db_value(self, value, expression, connection, *args):
        """Overrides ``models.Field`` method. This converts the value
        returned from the database to an instance of this class.
        """
        return self.to_python(value)

    def to_python(self, value):
        """Overrides ``models.Field`` method. This is used to convert
        bytes (from serialization etc) to an instance of this class"""
        if value is None:
            return None
        elif isinstance(value, Credentials):
            return value
        else:
            try:
                return jsonpickle.decode(
                    base64.b64decode(encoding.smart_bytes(value)).decode()
                )
            except ValueError:
                return None

    def get_prep_value(self, value):
        """Overrides ``models.Field`` method. This is used to convert
        the value from an instances of this class to bytes that can be
        inserted into the database.
        """
        if value is None:
            return None
        else:
            return encoding.smart_str(
                base64.b64encode(jsonpickle.encode(value).encode())
            )

    def value_to_string(self, obj):
        """Convert the field value from the provided model to a string.
        Used during model serialization.
        Args:
            obj: db.Model, model object
        Returns:
            string, the serialized field value
        """
        value = self._get_val_from_obj(obj)
        return self.get_prep_value(value)
