# 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.
import base64
import json
import logging
import os
import pandas
import matplotlib.pyplot as plt

from flask import Flask, request
from cloudevents.http import from_http
from google.cloud import bigquery
from google.cloud import storage

def read_config(var):
    value = os.environ.get(var)
    if value is None:
       raise Exception(f'{var} cannot be None')
    return value

bucket_name = read_config('BUCKET')

app = Flask(__name__)

@app.route('/', methods=['POST'])
def handle_post():
    app.logger.info(pretty_print_POST(request))

    # Read CloudEvent from the request
    cloud_event = from_http(request.headers, request.get_data())

    # Parse the event body
    country, tableId = read_event_data(cloud_event)

    query_covid_dataset(country, tableId)

    return 'OK', 200

def read_event_data(cloud_event):

    # Assume custom event by default
    event_data = cloud_event.data

    type = cloud_event['type']
    if type == 'google.cloud.pubsub.topic.v1.messagePublished':
        message = event_data['message']
        data = message['data']
        decoded = base64.b64decode(data)
        event_data = json.loads(decoded)

    return event_data['country'], event_data['tableId']

def query_covid_dataset(country, tableId):

    app.logger.info(f"query_covid_dataset with country '{country}' and tableId '{tableId}'")

    client = bigquery.Client()

    query = f"""
        SELECT
        date, num_reports
        FROM `covid19_jhu_csse.{tableId}`
        ORDER BY date ASC"""
    app.logger.info(f'Running query: {query}')

    query_job = client.query(query)

    results = query_job.result()
    # for row in results:
    #     print("{}: {} ".format(row.date, row.num_reports))

    df = (
        results
        .to_dataframe()
    )
    app.logger.info(df.tail())

    ax = df.plot(kind='line', x='date', y='num_reports')
    ax.set_title(f'Covid Cases in {country}')
    # ax.set_xlabel('Date')
    # ax.set_ylabel('Number of cases')
    #plt.show()

    file_name = f'chart-{tableId}.png'
    app.logger.info(f'Saving file locally: {file_name}')

    plt.savefig(file_name)

    upload_blob(file_name)

def upload_blob(file_name):
    storage_client = storage.Client()
    bucket = storage_client.bucket(bucket_name)
    blob = bucket.blob(file_name)
    blob.upload_from_filename(file_name)
    app.logger.info(f'File {file_name} uploaded to bucket {bucket_name}')

def pretty_print_POST(req):
    return '{}\r\n{}\r\n\r\n{}'.format(
        req.method + ' ' + req.url,
        '\r\n'.join('{}: {}'.format(k, v) for k, v in req.headers.items()),
        req.data,
    )

if __name__ != '__main__':
    # Redirect Flask logs to Gunicorn logs
    gunicorn_logger = logging.getLogger('gunicorn.error')
    app.logger.handlers = gunicorn_logger.handlers
    app.logger.setLevel(gunicorn_logger.level)
    plt.switch_backend('Agg') # to prevent background UI threads
    app.logger.info('Service started...')
else:
    plt.switch_backend('Agg') # to prevent background UI threads
    app.run(debug=True, host='0.0.0.0', port=int(os.environ.get('PORT', 8080)))