# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.

"""
A poll() based implementation of the twisted main loop.

To install the event loop (and you should do this before any connections,
listeners or connectors are added)::

from twisted.internet import pollreactor
pollreactor.install()
"""

from __future__ import division, absolute_import

# System imports
import errno
from select import error as SelectError, poll
from select import POLLIN, POLLOUT, POLLHUP, POLLERR, POLLNVAL

from zope.interface import implementer

# Twisted imports
from twisted.python import log
from twisted.internet import posixbase
from twisted.internet.interfaces import IReactorFDSet



@implementer(IReactorFDSet)
class PollReactor(posixbase.PosixReactorBase, posixbase._PollLikeMixin):
"""
A reactor that uses poll(2).

@ivar _poller: A L{poll} which will be used to check for I/O
readiness.

@ivar _selectables: A dictionary mapping integer file descriptors to
instances of L{FileDescriptor} which have been registered with the
reactor. All L{FileDescriptors} which are currently receiving read or
write readiness notifications will be present as values in this
dictionary.

@ivar _reads: A dictionary mapping integer file descriptors to arbitrary
values (this is essentially a set). Keys in this dictionary will be
registered with C{_poller} for read readiness notifications which will
be dispatched to the corresponding L{FileDescriptor} instances in
C{_selectables}.

@ivar _writes: A dictionary mapping integer file descriptors to arbitrary
values (this is essentially a set). Keys in this dictionary will be
registered with C{_poller} for write readiness notifications which will
be dispatched to the corresponding L{FileDescriptor} instances in
C{_selectables}.
"""

_POLL_DISCONNECTED = (POLLHUP | POLLERR | POLLNVAL)
_POLL_IN = POLLIN
_POLL_OUT = POLLOUT

def __init__(self):
"""
Initialize polling object, file descriptor tracking dictionaries, and
the base class.
"""
self._poller = poll()
self._selectables = {}
self._reads = {}
self._writes = {}
posixbase.PosixReactorBase.__init__(self)


def _updateRegistration(self, fd):
"""Register/unregister an fd with the poller."""
try:
self._poller.unregister(fd)
except KeyError:
pass

mask = 0
if fd in self._reads:
mask = mask | POLLIN
if fd in self._writes:
mask = mask | POLLOUT
if mask != 0:
self._poller.register(fd, mask)
else:
if fd in self._selectables:
del self._selectables[fd]

def _dictRemove(self, selectable, mdict):
try:
# the easy way
fd = selectable.fileno()
# make sure the fd is actually real. In some situations we can get
# -1 here.
mdict[fd]
except:
# the hard way: necessary because fileno() may disappear at any
# moment, thanks to python's underlying sockets impl
for fd, fdes in self._selectables.items():
if selectable is fdes:
break
else:
# Hmm, maybe not the right course of action? This method can't
# fail, because it happens inside error detection...
return
if fd in mdict:
del mdict[fd]
self._updateRegistration(fd)

def addReader(self, reader):
"""Add a FileDescriptor for notification of data available to read.
"""
fd = reader.fileno()
if fd not in self._reads:
self._selectables[fd] = reader
self._reads[fd] = 1
self._updateRegistration(fd)

def addWriter(self, writer):
"""Add a FileDescriptor for notification of data available to write.
"""
fd = writer.fileno()
if fd not in self._writes:
self._selectables[fd] = writer
self._writes[fd] = 1
self._updateRegistration(fd)

def removeReader(self, reader):
"""Remove a Selectable for notification of data available to read.
"""
return self._dictRemove(reader, self._reads)

def removeWriter(self, writer):
"""Remove a Selectable for notification of data available to write.
"""
return self._dictRemove(writer, self._writes)

def removeAll(self):
"""
Remove all selectables, and return a list of them.
"""
return self._removeAll(
[self._selectables[fd] for fd in self._reads],
[self._selectables[fd] for fd in self._writes])


def doPoll(self, timeout):
"""Poll the poller for new events."""
if timeout is not None:
timeout = int(timeout * 1000) # convert seconds to milliseconds

try:
l = self._poller.poll(timeout)
except SelectError as e:
if e.args[0] == errno.EINTR:
return
else:
raise
_drdw = self._doReadOrWrite
for fd, event in l:
try:
selectable = self._selectables[fd]
except KeyError:
# Handles the infrequent case where one selectable's
# handler disconnects another.
continue
log.callWithLogger(selectable, _drdw, selectable, fd, event)

doIteration = doPoll

def getReaders(self):
return [self._selectables[fd] for fd in self._reads]


def getWriters(self):
return [self._selectables[fd] for fd in self._writes]



def install():
"""Install the poll() reactor."""
p = PollReactor()
from twisted.internet.main import installReactor
installReactor(p)


__all__ = ["PollReactor", "install"]