# Posted to python-ideas on 2016 Feb 26 by Maxime S(chmeii) via gmane
# User Maxime S has not yet signed CLA, so this is not a 'contribution'.
# Use of self.app.createfilehandler limits this to unix-based systems.

class TkSelector(selectors._BaseSelectorImpl):
    """Selector based on the Tk event loop."""

    def __init__(self, app):       
        super().__init__()
        self.app = app
        self.ready = []
        self.is_timeout = False
        self.after_key = None
       
    def _file_cb(self, fileobj, mask):
        fd = self._fileobj_lookup(fileobj)
        self.ready.append((fd, mask))
   
    def _timeout_cb(self):
        self.is_timeout = True
       
    def _reset_state(self):
        del self.ready[:]
        self.is_timeout = False
        if self.after_key:
            self.app.after_cancel(self.after_key)
            self.after_key = None

    def register(self, fileobj, events, data=None):
        key = super().register(fileobj, events, data)
        flags = 0
        if events & EVENT_READ:
            flags |= tkinter.READABLE
        if events & EVENT_WRITE:
            flags |= tkinter.WRITABLE
        self.app.createfilehandler(fileobj, flags, self._file_cb)
        return key

    def unregister(self, fileobj):
        key = super().unregister(fileobj)
        self.app.deletefilehandler(fileobj)
        return key

    def select(self, timeout=None):
        if timeout is None:
            pass
        elif timeout <= 0:
            while self.app.dooneevent(_tkinter.DONT_WAIT):
                pass
            self.is_timeout = True
        else:
            self.after_key = self.app.after(
                math.ceil(timeout*1000), self._timeout_cb)
       
        while not (self.is_timeout or self.ready):
            self.app.dooneevent()                   
           
        ret = []
        for fd, mask in self.ready:
            events = 0
            if mask & tkinter.WRITABLE:
                events |= EVENT_WRITE
            if mask & tkinter.READABLE:
                events |= EVENT_READ

            key = self._key_from_fd(fd)
            if key:
                ret.append((key, events & key.events))
               
        self._reset_state()
       
        return ret

class TkEventLoop(asyncio.SelectorEventLoop):
    """Asyncio-compatible tkinter event loop."""
   
    def __init__(self, app):
        selector = TkSelector(app)
        super().__init__(selector=selector)