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# Copyright 2019 Google LLC 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.
""" This function handles messages posted to a pubsub topic by translating
the data in the message as requested. The message must be a JSON encoded
dictionary with fields:
Original - the string to translate
Language - the language to translate the string to
The dictionary may have other fields, which will be ignored.
"""
# [START getting_started_background_translate_setup]
import base64
import hashlib
import json
from google.cloud import firestore
from google.cloud import translate_v2 as translate
# [END getting_started_background_translate_setup]
# [START getting_started_background_translate_init]
# Get client objects once to reuse over multiple invocations.
xlate = translate.Client()
db = firestore.Client()
# [END getting_started_background_translate_init]
# [START getting_started_background_translate_string]
def translate_string(from_string, to_language):
""" Translates a string to a specified language.
from_string - the original string before translation
to_language - the language to translate to, as a two-letter code (e.g.,
'en' for english, 'de' for german)
Returns the translated string and the code for original language
"""
result = xlate.translate(from_string, target_language=to_language)
return result['translatedText'], result['detectedSourceLanguage']
# [END getting_started_background_translate_string]
# [START getting_started_background_translate]
def document_name(message):
""" Messages are saved in a Firestore database with document IDs generated
from the original string and destination language. If the exact same
translation is requested a second time, the result will overwrite the
prior result.
message - a dictionary with fields named Language and Original, and
optionally other fields with any names
Returns a unique name that is an allowed Firestore document ID
"""
key = '{}/{}'.format(message['Language'], message['Original'])
hashed = hashlib.sha512(key.encode()).digest()
# Note that document IDs should not contain the '/' character
name = base64.b64encode(hashed, altchars=b'+-').decode('utf-8')
return name
@firestore.transactional
def update_database(transaction, message):
name = document_name(message)
doc_ref = db.collection('translations').document(document_id=name)
try:
doc_ref.get(transaction=transaction)
except firestore.NotFound:
return # Don't replace an existing translation
transaction.set(doc_ref, message)
def translate_message(event, context):
""" Process a pubsub message requesting a translation
"""
message_data = base64.b64decode(event['data']).decode('utf-8')
message = json.loads(message_data)
from_string = message['Original']
to_language = message['Language']
to_string, from_language = translate_string(from_string, to_language)
message['Translated'] = to_string
message['OriginalLanguage'] = from_language
transaction = db.transaction()
update_database(transaction, message)
# [END getting_started_background_translate]