ovdashboard/api/ovkiosk/dav_file.py

import asyncio
import functools
import logging
from io import BytesIO
from threading import Lock
from typing import Optional

from apscheduler.schedulers.asyncio import AsyncIOScheduler
from webdav3.client import Resource

_logger = logging.getLogger(__name__)


def run_in_executor(f):
    """
    Decorator to make blocking function call asyncio compatible
    https://stackoverflow.com/questions/41063331/how-to-use-asyncio-with-existing-blocking-library/
    """

    @functools.wraps(f)
    def inner(*args, **kwargs):
        loop = asyncio.get_running_loop()
        return loop.run_in_executor(
            None,
            functools.partial(f, *args, **kwargs),
        )

    return inner


class DavFile:
    __instances: Optional[list["DavFile"]] = None
    __scheduler = None

    def __init__(self, resource: Resource, refresh: bool = True) -> None:
        self.__resource: Resource = resource
        self.__buffer = BytesIO()
        self.__lock = Lock()

        # register
        if DavFile.__instances is None:
            DavFile.__instances = []

        if refresh:
            DavFile.__instances.append(self)

    async def download(self) -> None:

        @run_in_executor
        def download_inner() -> None:
            self.__resource.write_to(self.__buffer)

        _logger.info(f"updating {self.__resource}")
        with self.__lock:
            self.__buffer.seek(0)
            self.__buffer.truncate(0)
            await download_inner()

    @classmethod
    def refresh(cls, refresh_interval: int = 60) -> None:
        if cls.__scheduler is not None:
            cls.__scheduler.reschedule_job(
                job_id=cls.__name__,
                trigger="interval",
                seconds=refresh_interval,
            )
            return

        async def tick() -> None:
            for davfile in DavFile.__instances:
                await davfile.download()

        cls.__scheduler = AsyncIOScheduler()
        cls.__scheduler.start()

        cls.__scheduler.add_job(tick)
        cls.__scheduler.add_job(
            tick,
            id=cls.__name__,
            trigger="interval",
            seconds=refresh_interval,
        )

    @property
    def bytes(self) -> bytes:
        with self.__lock:
            self.__buffer.seek(0)
            return self.__buffer.read()

    def __str__(self) -> str:
        return self.bytes.decode(encoding="utf-8")