#    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.

import abc

import six


@six.add_metaclass(abc.ABCMeta)
class DbApi(object):

    @abc.abstractmethod
    def initialize(self, db_ip, db_port, **args):
        """Initialize the DB client

        :param db_ip:      DB server IP address
        :type db_ip:       string
        :param db_port:    DB server port number
        :type db_port:     int
        :param args:       Additional args that were read from configuration
                           file
        :type args:        dictionary of <string, object>
        :returns:          None
        """

    @abc.abstractmethod
    def create_table(self, table):
        """Create a table

        :param table:      table name
        :type table:       string
        :returns:          None
        """

    @abc.abstractmethod
    def delete_table(self, table):
        """Delete a table. Delete all items in the table.
        Reading any key from the table without re-creating it should
        raise an exception.

        :param table:      table name
        :type table:       string
        :returns:          None
        """

    @abc.abstractmethod
    def get_key(self, table, key, topic=None):
        """Get the value of a specific key in a table. If the key does not
        exist, raise a DBKeyNotFound error.

        topic is an optional value which may be used to optimise the search
        for the key.

        :param table:      table name
        :type table:       string
        :param key:        key name
        :type key:         string
        :param topic:      optional topic to aid in key lookup
        :type topic:       string
        :returns:          string - the key value
        :raises DragonflowException.DBKeyNotFound: if key not found
        """

    @abc.abstractmethod
    def set_key(self, table, key, value, topic=None):
        """Set a specific key in a table with value. If the key does not
        exist, the implementation may either:
        1. Raise a DBLeyNotFound error
        2. Create the key as if create_key was called.
        Exactly one of these two option must be implemented

        :param table:      table name
        :type table:       string
        :param key:        key name
        :type key:         string
        :param value:      value to set for the key
        :type value:       string
        :param topic:      optional topic to aid in key lookup
        :type topic:       string
        :returns:          None
        :raises DragonflowException.DBKeyNotFound: if key not found, and was
                not created
        """

    @abc.abstractmethod
    def create_key(self, table, key, value, topic=None):
        """Create a specific key in a table with value

        :param table:      table name
        :type table:       string
        :param key:        key name
        :type key:         string
        :param value:      value to set for the created key
        :type value:       string
        :param topic:      optional topic to aid in key lookup
        :type topic:       string
        :returns:          None
        """

    @abc.abstractmethod
    def delete_key(self, table, key, topic=None):
        """Delete a specific key from a table. If the key does not exist,
        raise a DBKeyNotFound error.

        :param table:      table name
        :type table:       string
        :param key:        key name
        :type key:         string
        :param topic:      optional topic to aid in key lookup
        :type topic:       string
        :returns:          None
        :raises DragonflowException.DBKeyNotFound: if key not found
        """

    @abc.abstractmethod
    def get_all_entries(self, table, topic=None):
        """Returns a list of all table entries values. If the table does
        not exist, or is empty, return an empty list.

        :param table:      table name
        :type table:       string
        :param topic:      get only entries matching this topic
        :type topic:       string
        :returns:          list of values
        """

    @abc.abstractmethod
    def get_all_keys(self, table, topic=None):
        """Returns a list of all table entries keys. If the table does not
        exist, or is empty, return an empty list.

        :param table:      table name
        :type table:       string
        :param topic:      get all keys matching this topic
        :type topic:       string
        :returns:          list of keys
        """

    @abc.abstractmethod
    def allocate_unique_key(self, table):
        """Allocate a unique id in the controller

        The allocation information should be managed in the 'unique_key'
        table and stored by table name, s.t. the state can be extracted and
        restored by get_key/set_key calls.

        :table:       The name of resource table
        :returns:     Unique id
        """

    @abc.abstractmethod
    def process_ha(self):
        """Process HA functions

        :returns:    None
        """