from threading import Thread
from queue import Queue
from os import mkfifo, remove
from os.path import exists, join
from signal import signal, SIGTERM, SIGINT
from secrets import token_urlsafe


class PipeWriterThread(Thread):
    def __init__(self, to_write_queue, pipe_path):
        super().__init__()
        self._to_write_queue = to_write_queue
        self._pipe_path = pipe_path

    def run(self):
        while True:
            message = self._to_write_queue.get(block=True)
            if message is None:
                break
            with open(self._pipe_path, 'wb') as pipe:
                pipe.write(message)

    def stop(self):
        self._to_write_queue.put(None)
        self.join()


class PipeReaderThread(Thread):
    _stop_sequence = b'stop_reading'

    def __init__(self, results_queue, pipe_path):
        super().__init__()
        self._results_queue = results_queue
        self._pipe_path = pipe_path

    def run(self):
        while True:
            with open(self._pipe_path, 'rb') as pipe:
                message = pipe.read()
            if message == self._stop_sequence:
                break
            self._results_queue.put(message, block=True)

    def stop(self):
        with open(self._pipe_path, 'wb') as pipe:
            pipe.write(self._stop_sequence)
        self.join()


class PipeHandler:
    def __init__(self, pipe_path):
        self._pipe_path = pipe_path

    def recreate(self):
        self.remove()
        mkfifo(self._pipe_path)

    def remove(self):
        if exists(self._pipe_path):
            remove(self._pipe_path)


class PipeIOServer:
    def __init__(self, in_pipe=None, out_pipe=None):
        self.in_pipe, self.out_pipe = in_pipe, out_pipe
        self._create_pipes()

        self._message_queue = Queue()
        self._io_threads = {
            'reader': PipeReaderThread(self._message_queue, self.in_pipe),
            'writer': PipeWriterThread(self._message_queue, self.out_pipe)
        }

    def _create_pipes(self):
        if not self.in_pipe or not self.out_pipe:
            pipe_id = token_urlsafe(6)
            self.in_pipe = join('/tmp', f'in_pipe_{pipe_id}')
            self.out_pipe = join('/tmp', f'out_pipe_{pipe_id}')
        PipeHandler(self.in_pipe).recreate()
        PipeHandler(self.out_pipe).recreate()

    def run(self):
        for thread in self._io_threads.values():
            thread.start()

    def stop(self):
        for thread in self._io_threads.values():
            thread.stop()
        PipeHandler(self.in_pipe).remove()
        PipeHandler(self.out_pipe).remove()


if __name__ == "__main__":
    pipe_io = PipeIOServer()
    signal(SIGTERM, lambda a, b: pipe_io.stop())
    signal(SIGINT, lambda a, b: pipe_io.stop())
    pipe_io.run()
    print('Running pipe IO server with named pipes:')
    print(f'Input:  {pipe_io.in_pipe}')
    print(f'Output: {pipe_io.out_pipe}')