"""
Socket handling driver using the selectors module. epoll, kqueue, and devpoll
are used internally when available.
"""

import selectors
import threading

from pylinkirc import world
from pylinkirc.log import log

__all__ = ['register', 'unregister', 'start']


SELECT_TIMEOUT = 0.5

selector = selectors.DefaultSelector()

def _process_conns():
    """Main loop which processes connected sockets."""

    while not world.shutting_down.is_set():
        for socketkey, mask in selector.select(timeout=SELECT_TIMEOUT):
            irc = socketkey.data
            try:
                if mask & selectors.EVENT_READ and not irc._aborted.is_set():
                    irc._run_irc()
            except:
                log.exception('Error in select driver loop:')
                continue

def register(irc):
    """
    Registers a network to the global selectors instance.
    """
    log.debug('selectdriver: registering %s for network %s', irc._socket, irc.name)
    selector.register(irc._socket, selectors.EVENT_READ, data=irc)

def unregister(irc):
    """
    Removes a network from the global selectors instance.
    """
    if irc._socket.fileno() != -1:
        log.debug('selectdriver: de-registering %s for network %s', irc._socket, irc.name)
        selector.unregister(irc._socket)
    else:
        log.debug('selectdriver: skipping de-registering %s for network %s', irc._socket, irc.name)

def start():
    """
    Starts a thread to process connections.
    """
    t = threading.Thread(target=_process_conns, name="Selector driver loop")
    t.start()