"""Module to apply event source mapping configurations after a dynamodb table is created."""

import logging
from typing import Any

logger = logging.getLogger(__name__)


class NoDynamodbStreamFailure(Exception):
    """Indicates the Dynamodb Table needs streams to be enabled."""

    pass


class NewEventSourceMappingFailure(Exception):
    """Indicates EventSourceMapping could not be created."""

    pass


def _get_dynamodb_stream_arn(dynamodb_client: Any, dynamodb_table: str) -> str:
    """Get the latest dynamodb stream arn."""
    logger.info('Fetching latest dynamodb stream arn')
    try:
        table_description = dynamodb_client.describe_table(TableName=dynamodb_table)
        dynamodb_stream_arn = table_description.get('Table', {}).get('LatestStreamArn')
        if not dynamodb_stream_arn:
            logger.warning(f'payload missing LatestStreamArn for {dynamodb_table}', extra={
                'describe_table': table_description,
            })
            raise NoDynamodbStreamFailure(f'missing stream arn for {dynamodb_table}')
    except Exception as e:
        logger.warning(f'missing stream arn for {dynamodb_table}', exc_info=e)
        raise NoDynamodbStreamFailure(f'missing stream arn for {dynamodb_table}') from e

    logger.info(f'Found latest dynamodb stream arn: {dynamodb_stream_arn}')
    return dynamodb_stream_arn


def _get_relevant_event_source_mapping_uuids(
    lambda_client: Any,
    lambda_arn: str,
    dynamodb_table: str,
) -> list[str]:
    """Find current event source mappings that need to be deleted."""
    logger.info('Fetching current event source mappings')
    relevant_mapping_uuids = []
    try:
        current_mappings = lambda_client.list_event_source_mappings(FunctionName=lambda_arn)
        # There could be multiple triggers. We only want the ones where
        # the stream arn is for dynamodb + our dynamodb_table
        relevant_mapping_uuids = [
            event_source_mapping['UUID']
            for event_source_mapping in current_mappings.get('EventSourceMappings', [])
            if 'arn:aws:dynamodb' in event_source_mapping[
                'EventSourceArn'] and dynamodb_table in event_source_mapping[
                    'EventSourceArn']
        ]
    except Exception as e:
        logger.warning(f'Could not obtain current event source mappings for {lambda_arn}')
        logger.warning(e)

    logger.info(f'Found relevant event source mappings {relevant_mapping_uuids}')
    return relevant_mapping_uuids


def _delete_event_source_mappings(
    lambda_client: Any,
    uuids: list[str],
) -> None:
    """Delete event source mappings."""
    logger.info(f'Deleting old event source mappings: {uuids}')
    for delete_uuid in uuids:
        try:
            lambda_client.delete_event_source_mapping(UUID=delete_uuid)
        except Exception as e:
            logger.warning(f'Failed to delete an event source mapping: {delete_uuid}')
            logger.warning(e)


def _create_event_source_mapping(
    lambda_client: Any,
    target_lambda_arn: str,
    dynamodb_stream_arn: str,
    **kwargs: Any,
) -> None:
    """Create new event source mapping."""
    logger.info(f'Creating new event source mapping for {dynamodb_stream_arn}')

    try:
        event_source_mapping = lambda_client.create_event_source_mapping(
            EventSourceArn=dynamodb_stream_arn,
            FunctionName=target_lambda_arn,
            Enabled=True,
            **kwargs,
        )
    except Exception as e:
        raise NewEventSourceMappingFailure(
            f'could not create event source mapping between {dynamodb_stream_arn} and {target_lambda_arn}') from e
    logger.info(f'Created event source mapping {event_source_mapping.get("UUID")}')


def set_lambda_event_source_mapping(
    dynamodb_client: Any,
    dynamodb_table: str,
    lambda_client: Any,
    target_lambda_arn: str,
    **kwargs: Any,
) -> None:
    """Upsert the lambda event source mapping.

    Any additional kwargs are passed as keyword arguments
        for creating the event source mapping

    * Determines the dynamodb table's stream
    * Fetches the current event source mappings on the target_lambda fn
    * Creates a new event source mapping on the target_lambda fn,
        triggered by the dynamodb table's stream
    * Deletes the existing event source mapping on the target lambda fn
    """
    logger.info('Setting lambda event source mapping')
    try:
        dynamodb_stream_arn = _get_dynamodb_stream_arn(dynamodb_client, dynamodb_table)
    except NoDynamodbStreamFailure:
        logger.error(f'Check stream enable configuration for {dynamodb_table} and start task again')
        return

    relevant_mapping_uuids = _get_relevant_event_source_mapping_uuids(lambda_client, target_lambda_arn, dynamodb_table)
    _create_event_source_mapping(lambda_client, target_lambda_arn, dynamodb_stream_arn, **kwargs)
    _delete_event_source_mappings(lambda_client, relevant_mapping_uuids)

    logger.info('Done setting lambda event source mapping')