"""
Transcoding job slack notification lambda

Can be used with show or hide filters which can be specified
using environment variables MESSAGE_SHOW_FILTER or MESSAGE_HIDE_FILTER

Show filter specifies what kind of messages should be only sent to slack
Example:
     MESSAGE_SHOW_FILTER = {"status": "error"}
     In this case only messages which contain key "status"
     with value "error" will be sent to slack and other messages
     will never be sent

Hide filter specifies what kind of messages should not be sent to slack
Example:
    MESSAGE_HIDE_FILTER = {"status": "success"}
    In this case only messages which contain key "status"
    with value "success" will never be sent to slack, but
    others will be sent
"""

import json

from urllib import request
from urllib.error import URLError, HTTPError

import common_config # noqa
from common_config import logger  # noqa
from constants import errors # noqa
import config # noqa


def handler(event, context):
    try:
        message = json.loads(event['Records'][0]['Sns']['Message'])

        if config.MESSAGE_SHOW_FILTER:
            filters = json.loads(config.MESSAGE_SHOW_FILTER)
            logger.info("Filters: " + str(filters))
            for key, value in filters.items():
                if key not in message or message[key] != value:
                    logger.info(
                        "Message " + str(message) +
                        " does not satisfy show filter conditions")
                    return True
        elif config.MESSAGE_HIDE_FILTER:
            filters = json.loads(config.MESSAGE_HIDE_FILTER)
            logger.info('Filters: ' + str(filters))
            for key, value in filters.items():
                if key in message and message[key] == value:
                    logger.info(
                        "Message " + str(message) +
                        " satisfies hide filter conditions")
                    return True

        slack_message_data = {
            'channel': config.SLACK_CHANNEL,
            'username': 'ALERT',
            'text': event['Records'][0]['Sns']['TopicArn'],
            'icon_emoji': ':aws:',
            'attachments': [{
                'text': json.dumps(message),
                'color': config.SLACK_MESSAGE_COLOR
            }]
        }

        req = request.Request(
            config.SLACK_HOOK_URL,
            json.dumps(slack_message_data).encode('utf-8'))
        response = request.urlopen(req)
        response.read()
        logger.info("Message posted to %s", slack_message_data['channel'])
        return True
    except HTTPError as e:
        logger.error(errors.SLACK_HTTP_ERROR_MESSAGE.format(
            code=e.code, reason=e.reason))
        raise
    except URLError as e:
        logger.error(errors.SLACK_URL_ERROR_MESSAGE.format(
            reason=e.reason))
        raise
    except Exception as e:
        logger.exception(str(e))
        raise