import os
import pty
import termios
import threading

class VirtualSerialPort:
    def __init__(self, requestHandler):
        self._master, self._slave = pty.openpty()
        self._masterFile = os.fdopen(self._master, mode="r+b", closefd=False, buffering=0)
        self._portName = os.ttyname(self._slave)
        self._requestHandler = requestHandler

        self._mainThread = threading.Thread(target=self._mainLoop)
        self._mainThread.start()

    def stop(self) -> None:
        self._masterFile.close()
        os.close(self._master)
        os.close(self._slave)
        self._mainThread.join()

    def _mainLoop(self) -> None:
        while True:
            try:
                request = self._masterFile.readline().decode().strip()
                response = self._requestHandler(request)
                
                if response is not None:
                    self._masterFile.write(response.encode())
            except OSError as e:
                break

    def getPortName(self) -> str:
        return self._portName