# Copyright 2015 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.

import base64
import json
import logging
import os

from flask import current_app, Flask, render_template, request
from google.cloud import pubsub_v1


app = Flask(__name__)

# Configure the following environment variables via app.yaml
# This is used in the push request handler to verify that the request came from
# pubsub and originated from a trusted source.
app.config["PUBSUB_VERIFICATION_TOKEN"] = os.environ["PUBSUB_VERIFICATION_TOKEN"]
app.config["PUBSUB_TOPIC"] = os.environ["PUBSUB_TOPIC"]
app.config["PROJECT"] = os.environ["GOOGLE_CLOUD_PROJECT"]


# Global list to storage messages received by this instance.
MESSAGES = []

# Initialize the publisher client once to avoid memory leak
# and reduce publish latency.
publisher = pubsub_v1.PublisherClient()


# [START gae_flex_pubsub_index]
@app.route("/", methods=["GET", "POST"])
def index():
    if request.method == "GET":
        return render_template("index.html", messages=MESSAGES)

    data = request.form.get("payload", "Example payload").encode("utf-8")

    # publisher = pubsub_v1.PublisherClient()
    topic_path = publisher.topic_path(
        current_app.config["PROJECT"], current_app.config["PUBSUB_TOPIC"]
    )

    publisher.publish(topic_path, data=data)

    return "OK", 200


# [END gae_flex_pubsub_index]


# [START gae_flex_pubsub_push]
@app.route("/pubsub/push", methods=["POST"])
def pubsub_push():
    if request.args.get("token", "") != current_app.config["PUBSUB_VERIFICATION_TOKEN"]:
        return "Invalid request", 400

    envelope = json.loads(request.data.decode("utf-8"))
    payload = base64.b64decode(envelope["message"]["data"])

    MESSAGES.append(payload)

    # Returning any 2xx status indicates successful receipt of the message.
    return "OK", 200


# [END gae_flex_pubsub_push]


@app.errorhandler(500)
def server_error(e):
    logging.exception("An error occurred during a request.")
    return (
        """
    An internal error occurred: <pre>{}</pre>
    See logs for full stacktrace.
    """.format(
            e
        ),
        500,
    )


if __name__ == "__main__":
    # This is used when running locally. Gunicorn is used to run the
    # application on Google App Engine. See entrypoint in app.yaml.
    app.run(host="127.0.0.1", port=8080, debug=True)