background/app/main.py

# 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 web app shows translations that have been previously requested, and
    provides a form to request a new translation.
"""

# [START getting_started_background_app_main]
import json
import os

from flask import Flask, redirect, render_template, request
from google.cloud import firestore
from google.cloud import pubsub


app = Flask(__name__)

# Get client objects to reuse over multiple invocations
db = firestore.Client()
publisher = pubsub.PublisherClient()

# Keep this list of supported languages up to date
ACCEPTABLE_LANGUAGES = ("de", "en", "es", "fr", "ja", "sw")
# [END getting_started_background_app_main]


# [START getting_started_background_app_list]
@app.route("/", methods=["GET"])
def index():
    """The home page has a list of prior translations and a form to
    ask for a new translation.
    """

    doc_list = []
    docs = db.collection("translations").stream()
    for doc in docs:
        doc_list.append(doc.to_dict())

    return render_template("index.html", translations=doc_list)


# [END getting_started_background_app_list]


# [START getting_started_background_app_request]
@app.route("/request-translation", methods=["POST"])
def translate():
    """Handle a request to translate a string (form field 'v') to a given
    language (form field 'lang'), by sending a PubSub message to a topic.
    """
    source_string = request.form.get("v", "")
    to_language = request.form.get("lang", "")

    if source_string == "":
        error_message = "Empty value"
        return error_message, 400

    if to_language not in ACCEPTABLE_LANGUAGES:
        error_message = "Unsupported language: {}".format(to_language)
        return error_message, 400

    message = {
        "Original": source_string,
        "Language": to_language,
        "Translated": "",
        "OriginalLanguage": "",
    }

    topic_name = "projects/{}/topics/{}".format(
        os.getenv("GOOGLE_CLOUD_PROJECT"), "translate"
    )
    publisher.publish(
        topic=topic_name, data=json.dumps(message).encode("utf8")
    )
    return redirect("/")


# [END getting_started_background_app_request]