"""Lambda function module."""

import json
from urllib import parse

from constants import common
import common_config
from constants import email
import ses
import sentry


def parse_dlq_message(event):
    """Parse SNS message sent by DLQ.

    Args:
        event (dict): SNS event

    Returns:
        dict: error details

    """
    records = event.get('Records')
    if not records:
        return {}

    sns = records[0].get('Sns')
    if sns:
        message = json.loads(records[0]['Sns']['Message'])
        s3_event = message.get('s3_event')['Records'][0]
    elif records[0].get('s3'):
        s3_event = records[0]
    else:
        return{}

    context = parse_s3_event(s3_event)
    context['error_detail'] = email.PROCESSING_ERROR
    return context


def parse_s3_event(event):
    """Parse the original S3 event.

    Args:
        event (dict): s3 event from message payload (['Records'][0])

    Returns:
        dict: error details

    """
    key = event['s3']['object']['key']
    full_file_name = key.split('/')[-1]
    upload_timestamp = event['eventTime']
    return {
        'full_file_name': parse.unquote_plus(full_file_name),
        'upload_timestamp': upload_timestamp,
    }


def prepare_message_body(template, message):
    """Prepare e-mail message body.

    Args:
        template (str): E-mail template
        message (dict): SNS message with error details.

    Returns:
        str: E-mail message body

    """
    s3_event = message.get('s3_event')
    error_detail = ''
    if s3_event:
        context = parse_s3_event(s3_event['Records'][0])
        verification_error = message.get('detailed', '')
        if verification_error:
            error_detail = '<p>{}</p>'.format(verification_error)
    else:
        context = parse_dlq_message(message)

    if not context:
        return ''
    if context.get('error_detail') is None:
        context['error_detail'] = error_detail
    context['workflow_link'] = email.WORKFLOW_LINK
    return template.format(**context)


@sentry.sentry_capture_exception
def handler(event, context):
    """Lambda entry point."""
    if common_config.IGNORE_ALL_EVENTS is not None:
        common_config.logger.warning(common.IGNORE_MESSAGE)
        return
    common_config.logger.info('Starting to process failure SNS message.')
    message = json.loads(event['Records'][0]['Sns']['Message'])
    body = prepare_message_body(email.ATTACHMENT_ERROR_BODY, message)
    if not body:
        common_config.logger.info(
            'Cannot parse DLQ event. Ignoring.')
        return
    common_config.logger.info('Sending an E-mail.')
    ses.send_email(
        recipient=common_config.ERROR_ATTACHMENT_EMAIL_RECIPIENT,
        sender=common_config.EMAIL_SENDER,
        subject=email.ATTACHMENT_ERROR_SUBJECT,
        message=body)
    common_config.logger.info('Done.')