import os
import base64
import json

import logging

from google.cloud.bigtable import Client
from slack_client import SlackClient
from config import Config

MIN_NODES = 1


def scale(data: dict) -> int:
    slack_client = SlackClient(slack_token=Config.slack_token)
    meta_info = Config.get_config_str() + '\n' + str(data)
    logging.info(meta_info)
    try:
        if Config.cluster_baseline < 1:
            raise Exception('Invalid cluster baseline')

        client = Client(project=Config.project_id, admin=True)
        instance = client.instance(Config.instance_id)
        cluster = instance.cluster(Config.cluster_id)
        cluster.reload()
        logging.info(cluster.__dict__)

        if 'scale' in data:
            serve_nodes = Config.cluster_baseline + int(data['scale'])
            if serve_nodes < MIN_NODES:
                raise Exception(
                    'Unable to change size of cluster to less than MIN_NODES')
            if serve_nodes <= Config.cluster_max_size:
                cluster.serve_nodes = serve_nodes
                cluster.update()
            else:
                raise Exception('Failed to scaled - exceeded max nodes amount')
        elif 'to_baseline' in data:
            if cluster.serve_nodes != Config.cluster_baseline:
                cluster.serve_nodes = Config.cluster_baseline
                cluster.update()
        else:
            raise Exception('Unknown operation')

        operation_status = "Operation has been performed successfully"
        logging.info(operation_status)
        slack_client.post_success_message(channel=Config.slack_channel_id,
                                          blocks=[meta_info, operation_status])
        return 0
    except Exception as e:
        slack_client.post_error_message(
            channel=Config.slack_channel_id,
            blocks=[meta_info, f"Exception msg:\n{str(e)}"])
        logging.error(str(e))
        raise RuntimeError from e


def main(event, context):
    """Background Cloud Function to be triggered by Pub/Sub.
    Args:
         event (dict):  The dictionary with data specific to this type of
         event. The `data` field contains the PubsubMessage message. The
         `attributes` field will contain custom attributes if there are any.
         context (google.cloud.functions.Context): The Cloud Functions event
         metadata. The `event_id` field contains the Pub/Sub message ID. The
         `timestamp` field contains the publish time.
    """
    print("""This Function was triggered by messageId {} published at {}
        """.format(context.event_id, context.timestamp))

    logging.basicConfig(encoding='utf-8', level=logging.INFO)
    if 'data' in event:
        data = json.loads(base64.b64decode(event['data']).decode('utf-8'))
        return scale(data)
    else:
        raise Exception('data is missing')