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message_transformer.py
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message_transformer.py
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# Copyright 2020 Google LLC
#
# 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 abc import ABC, abstractmethod
from typing import Callable
from google.pubsub_v1 import PubsubMessage
from overrides import overrides
from google.cloud.pubsublite_v1 import SequencedMessage
class MessageTransformer(ABC):
"""
A MessageTransformer turns Pub/Sub Lite message protos into Pub/Sub message protos.
"""
@abstractmethod
def transform(self, source: SequencedMessage) -> PubsubMessage:
"""Transform a SequencedMessage to a PubsubMessage.
Args:
source: The message to transform.
Raises:
GoogleAPICallError: To fail the client if raised inline.
"""
pass
@staticmethod
def of_callable(transformer: Callable[[SequencedMessage], PubsubMessage]):
class CallableTransformer(MessageTransformer):
@overrides
def transform(self, source: SequencedMessage) -> PubsubMessage:
return transformer(source)
return CallableTransformer()