from contextlib import suppress
from os import O_NONBLOCK, O_RDONLY, close
from os import open as osopen
from threading import Thread

from .terminate_process_on_failure import terminate_process_on_failure
from .deque import Deque


class PipeWriterThread(Thread):
    def __init__(self, pipe_path, stop_event):
        super().__init__(daemon=True)
        self._pipe_path = pipe_path
        self._stop_event = stop_event
        self._write_queue = Deque()

    def write(self, message):
        self._write_queue.push(message)

    @terminate_process_on_failure
    def run(self):
        with self._open() as pipe:
            while True:
                message = self._write_queue.pop()
                if message is None:
                    self._stop_event.set()
                    break
                try:
                    pipe.write(message + b'\n')
                    pipe.flush()
                except BrokenPipeError:
                    try:  # pipe was reopened, close() flushed the message
                        pipe.close()
                    except BrokenPipeError:  # close() discarded the message
                        self._write_queue.push_front(message)
                    pipe = self._open()

    def _open(self):
        return open(self._pipe_path, 'wb')

    def stop(self):
        while self.is_alive():
            self._unblock()
        self.join()

    def _unblock(self):
        with suppress(OSError):
            fd = osopen(self._pipe_path, O_RDONLY | O_NONBLOCK)
            self._write_queue.push_front(None)
            close(fd)