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#
#    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.

from oslo_utils import timeutils

SEND_ALL_TOPIC = 'D'
DB_SYNC_MINIMUM_INTERVAL = 180
UNIQUE_KEY_TABLE = 'unique_key'


class DbUpdate(object):
    """Encapsulates a DB update

    An instance of this object carries the information necessary to prioritize
    and process a request to update a DB entry.
    """
    def __init__(self, table, key, action, value, timestamp=None,
                 topic=SEND_ALL_TOPIC):
        if timestamp is None:
            timestamp = timeutils.utcnow()
        self.timestamp = timestamp
        self.key = key
        self.action = action
        self.table = table
        self.value = value
        self.topic = topic

    def to_dict(self):
        update = {
                'table': self.table,
                'key': self.key,
                'action': self.action,
                'value': self.value,
                'topic': self.topic
        }
        return update

    def __str__(self):
        return (
            "Action:%s, Table:%s, Key:%s Value:%s Topic:%s Timestamp: %s"
        ) % (
            self.action,
            self.table,
            self.key,
            self.value,
            self.topic,
            self.timestamp,
        )

    def __lt__(self, other):
        """Implements priority among updates

        Earlier timestamp always gets precedence. In the unlikely event that
        the timestamps are equal it falls back to a simple comparison of ids
        meaning the precedence is deteministic but meaningless.
        """
        if self.timestamp != other.timestamp:
            return self.timestamp < other.timestamp
        return self.key < other.key