src/ctp_slack_bot/app.py

from asyncio import all_tasks, CancelledError, create_task, current_task, gather, get_running_loop, run
from loguru import logger
from signal import SIGINT, SIGTERM
from typing import Callable

from .containers import Container
from .core.logging import setup_logging


async def handle_shutdown_signal(*args) -> None:
    logger.info("Received shutdown signal.")
    for arg in args:
        await arg()
    logger.info("Executed shutdown tasks.")
    for task in all_tasks():
        if task is not current_task() and not task.done():
            task.cancel()
            logger.trace("Cancelled task {}.", task.get_name())
    logger.info("Cancelled all tasks.")


def create_shutdown_signal_handler(*args) -> Callable[[], None]:
    def shutdown_signal_handler() -> None:
        create_task(handle_shutdown_signal(*args))
    return shutdown_signal_handler


async def main() -> None:
    # Setup logging.
    setup_logging()
    logger.info("Starting application…")

    # Set up dependency injection container.
    container = Container()
    container.wire(packages=["ctp_slack_bot"])
    logger.debug("Created dependency injection container with providers: {}", '; '.join(container.providers))

    # Initialize/instantiate services which should be available from the start.
    await container.content_ingestion_service()
    await container.question_dispatch_service()
    http_server = await container.http_server()
    slack_service = await container.slack_service()
    task_service = await container.task_service()
    logger.debug("Initialized services.")

    # Install the shutdown signal handler.
    shutdown_signal_handler = create_shutdown_signal_handler(http_server.stop, slack_service.stop, task_service.stop)
    loop = get_running_loop()
    loop.add_signal_handler(SIGINT, shutdown_signal_handler)
    loop.add_signal_handler(SIGTERM, shutdown_signal_handler)

    # Start the HTTP server and Slack socket mode handler in the background; clean up resources when shut down.
    try:
        logger.info("Starting services…")
        await gather(http_server.start(), slack_service.start(), task_service.start())
    except CancelledError:
        logger.info("Shutting down application…")
    finally:
        await container.shutdown_resources()


if __name__ == "__main__":
    run(main())