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

from .terminate_process_on_failure import terminate_process_on_failure


class PipeReaderThread(Thread):
    eof = b''
    stop_sequence = b'stop_reading'

    def __init__(self, pipe_path, stop_event, message_handler):
        super().__init__()
        self._message_handler = message_handler
        self._pipe_path = pipe_path
        self._stop_event = stop_event

    @terminate_process_on_failure
    def run(self):
        with open(self._pipe_path, 'rb') as pipe:
            while True:
                message = pipe.readline().rstrip()
                if message in (self.eof, self.stop_sequence):
                    self._stop_event.set()
                    break
                self._message_handler(message)

    def stop(self):
        self.unblock()
        self.join()

    def unblock(self):
        with suppress(OSError):
            fd = osopen(self._pipe_path, O_WRONLY | O_NONBLOCK)
            write(fd, self.stop_sequence + b'\n')
            close(fd)