"""Lambda function module."""

from urllib import parse

from constants import common
import common_config
import s3  # noqa
import sentry  # noqa


def process_dynamodb_event(event):
    """Process a single DynamoDB event and extract bucket name and key.

    Args:
        event (dict): A single DynamoDB event

    Returns:
        tuple: (bucket_name, key) which are extracted from the event

    """
    data = event['dynamodb']['OldImage']
    bucket_name = data['bucket_name']['S']
    key = data['file_key']['S']
    key = parse.unquote_plus(key)
    return bucket_name, key


def process_dynamodb_events(records):
    """Process a list of DynamoDB events and extract remove records.

    Args:
        records (list): list of events

    Returns:
        list: list of keys to delete

    """
    keys = []
    for dynamodb_event in records:
        if dynamodb_event.get('eventName') != 'REMOVE':
            # ignore everything but REMOVE events
            continue

        bucket_name, key = process_dynamodb_event(dynamodb_event)
        unexpected_bucket = bucket_name != common_config.S3_BUCKET_NAME
        unexpected_dir = not key.startswith(
            common_config.S3_BUCKET_FOLDER)
        if unexpected_bucket or unexpected_dir:
            if unexpected_bucket:
                msg = 'Got unexpected bucket, expected: {}, got: {}'.format(
                    common_config.S3_BUCKET_NAME, bucket_name)
            else:
                msg = 'Got unexpected folder, expected: {}; got: {}'.format(
                    common_config.S3_BUCKET_FOLDER, key)
            common_config.logger.info(msg)
            continue
        keys.append(key)
    return keys


@sentry.sentry_capture_exception
def handler(event, context):
    """Process DynamoDB events from statement attachments error table."""
    if common_config.IGNORE_ALL_EVENTS is not None:
        common_config.logger.warning(common.IGNORE_MESSAGE)
        return
    records = event.get('Records')
    if records is None:
        return
    keys = process_dynamodb_events(records)
    if not keys:
        return
    common_config.logger.info('Deleting keys: {}'.format(keys))
    response = s3.delete_objects(
        bucket=common_config.S3_BUCKET_NAME, keys=keys, quiet=True)
    if response['ResponseMetadata']['HTTPStatusCode'] != 200:
        common_config.logger.error('Bad response: {}'.format(response))