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

"""
Tests for L{twisted.internet._sigchld}, an alternate, superior SIGCHLD
monitoring API.
"""

from __future__ import division, absolute_import

import os, signal, errno

from twisted.python.runtime import platformType
from twisted.python.log import msg
from twisted.trial.unittest import SynchronousTestCase
if platformType == "posix":
from twisted.internet.fdesc import setNonBlocking
from twisted.internet._signals import installHandler, isDefaultHandler
else:
skip = "These tests can only run on POSIX platforms."


class SetWakeupSIGCHLDTests(SynchronousTestCase):
"""
Tests for the L{signal.set_wakeup_fd} implementation of the
L{installHandler} and L{isDefaultHandler} APIs.
"""

def pipe(self):
"""
Create a non-blocking pipe which will be closed after the currently
running test.
"""
read, write = os.pipe()
self.addCleanup(os.close, read)
self.addCleanup(os.close, write)
setNonBlocking(read)
setNonBlocking(write)
return read, write


def setUp(self):
"""
Save the current SIGCHLD handler as reported by L{signal.signal} and
the current file descriptor registered with L{installHandler}.
"""
handler = signal.getsignal(signal.SIGCHLD)
if handler != signal.SIG_DFL:
self.signalModuleHandler = handler
signal.signal(signal.SIGCHLD, signal.SIG_DFL)
else:
self.signalModuleHandler = None

self.oldFD = installHandler(-1)

if self.signalModuleHandler is not None and self.oldFD != -1:
msg("Previous test didn't clean up after its SIGCHLD setup: %r %r"
% (self.signalModuleHandler, self.oldFD))


def tearDown(self):
"""
Restore whatever signal handler was present when setUp ran.
"""
# If tests set up any kind of handlers, clear them out.
installHandler(-1)
signal.signal(signal.SIGCHLD, signal.SIG_DFL)

# Now restore whatever the setup was before the test ran.
if self.signalModuleHandler is not None:
signal.signal(signal.SIGCHLD, self.signalModuleHandler)
elif self.oldFD != -1:
installHandler(self.oldFD)


def test_isDefaultHandler(self):
"""
L{isDefaultHandler} returns true if the SIGCHLD handler is SIG_DFL,
false otherwise.
"""
self.assertTrue(isDefaultHandler())
signal.signal(signal.SIGCHLD, signal.SIG_IGN)
self.assertFalse(isDefaultHandler())
signal.signal(signal.SIGCHLD, signal.SIG_DFL)
self.assertTrue(isDefaultHandler())
signal.signal(signal.SIGCHLD, lambda *args: None)
self.assertFalse(isDefaultHandler())


def test_returnOldFD(self):
"""
L{installHandler} returns the previously registered file descriptor.
"""
read, write = self.pipe()
oldFD = installHandler(write)
self.assertEqual(installHandler(oldFD), write)


def test_uninstallHandler(self):
"""
C{installHandler(-1)} removes the SIGCHLD handler completely.
"""
read, write = self.pipe()
self.assertTrue(isDefaultHandler())
installHandler(write)
self.assertFalse(isDefaultHandler())
installHandler(-1)
self.assertTrue(isDefaultHandler())


def test_installHandler(self):
"""
The file descriptor passed to L{installHandler} has a byte written to
it when SIGCHLD is delivered to the process.
"""
read, write = self.pipe()
installHandler(write)

exc = self.assertRaises(OSError, os.read, read, 1)
self.assertEqual(exc.errno, errno.EAGAIN)

os.kill(os.getpid(), signal.SIGCHLD)

self.assertEqual(len(os.read(read, 5)), 1)