"""Lambda retry-sfn-execution."""

from lambdacommon.common_config import logger
import config


class RetryException(Exception):
    """RetryException class."""

    pass


def get_backoff_time(interval_secs, backoff_rate, retry_num):
    """Calculate exponential backoff time."""
    return interval_secs * sum(backoff_rate ** i for i in range(retry_num))


def handler(event, context):
    """Lambda entry point."""
    try:
        retries = int(event.get('retries', 0)) + 1
        backoff_s = get_backoff_time(config.BACKOFF_INTERVAL_S, config.BACKOFF_RATE, retries)

        if retries > config.MAX_RETRIES:
            raise RetryException(
                f'Exceeded max retries: {config.MAX_RETRIES} with {backoff_s}s backoff'
            )
        logger.info(f'Setting retry to {retries} with {backoff_s}s backoff')
        return {
            'status': 'OK',
            'retries': retries,
            'backoff_time_s': backoff_s
        }
    except Exception as e:
        logger.exception(str(e))
        raise e