"""CodeEngine transform code."""

import copy
import json

import boto3

import awsconfig


ERROR_MESSAGE = 'Failed to send track event to CloudSearch'
SUCCESS_LAMBDA_STATUSES = [200, 202, 204]
# CloudSearch upload disabled now
CLOUDSEARCH_TABLES = ['track']
IGNORE_EVENT_TYPES = ['update-delete']


client = boto3.client(
    'lambda',
    aws_access_key_id=awsconfig.ACCESS_KEY,
    aws_secret_access_key=awsconfig.ACCESS_SECRET,
    region_name=awsconfig.AWS_REGION)


def send_to_cloudsearch(event):
    """Send event to CloudSearch by invoking lambda function.

    Args:
        event (dict): Alooma event

    Returns:
        int: HTTP status code for invocation request

    """
    converted_event = convert_event(event)
    res = client.invoke(
        FunctionName=awsconfig.LAMBDA_NAME,
        InvocationType='Event',
        Payload=json.dumps(converted_event))
    status_code = res.get('StatusCode')
    return status_code


def convert_event(event):
    """Converts an event to the required output format.

    - Cleanup unncecessary metadata
    - Change event type format

    Args:
        event (dict): Json event

    Returns:
        dict: converted event
    """
    converted_event = {}
    event_data = copy.deepcopy(event)
    del event_data['_metadata']
    converted_event['table'] = event['_metadata']['table']
    converted_event['data'] = event_data
    converted_event['type'] = convert_event_type(event['_metadata'])
    return converted_event


def convert_event_type(event_metadata):
    """Convert alooma event_metadata type to a more generic format.

    Args:
        event_metadata (dict): alooma event metadata

    Returns:
        str: event_type
    """
    source_event_type = event_metadata.get('type', 'insert')
    if source_event_type == 'insert':
        converted_event_type = 'insert'
    elif (source_event_type == 'deleted' and
            event_metadata.get('deleted')):
        converted_event_type = 'delete'
    elif source_event_type in ('update-insert', 'update'):
        converted_event_type = 'update'

    return converted_event_type


def transform(event):
    """Filter, transform, drop Alooma events.

    Args:
        event (dict): Event, reflecting a change in DB table.

    Returns:
        dict: transformed event (or None, for dropped events)

    """
    if (event['_metadata']['event_type'] in CLOUDSEARCH_TABLES and
            event['_metadata']['type'] not in IGNORE_EVENT_TYPES):
        status_code = send_to_cloudsearch(event)
        if status_code not in SUCCESS_LAMBDA_STATUSES:
            # In case of failure raise an exception to send the event
            # to restream queue.
            raise Exception(ERROR_MESSAGE)

    return None