"""
Common utilities that have been ported to Python 3.

Ported to Python 3.
"""

from __future__ import unicode_literals
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function

from future.utils import PY2
if PY2:
    from builtins import filter, map, zip, ascii, chr, hex, input, next, oct, open, pow, round, super, bytes, dict, list, object, range, str, max, min  # noqa: F401
from past.builtins import unicode

import os
import time
import signal

from twisted.internet import defer, reactor
from twisted.application import service
from twisted.python import failure
from twisted.trial import unittest

from ..util.assertutil import precondition
from ..util.encodingutil import unicode_platform, get_filesystem_encoding
from ..util import log


class TimezoneMixin(object):

    def setTimezone(self, timezone):
        def tzset_if_possible():
            # Windows doesn't have time.tzset().
            if hasattr(time, 'tzset'):
                time.tzset()

        unset = object()
        originalTimezone = os.environ.get('TZ', unset)
        def restoreTimezone():
            if originalTimezone is unset:
                del os.environ['TZ']
            else:
                os.environ['TZ'] = originalTimezone
            tzset_if_possible()

        os.environ['TZ'] = timezone
        self.addCleanup(restoreTimezone)
        tzset_if_possible()

    def have_working_tzset(self):
        return hasattr(time, 'tzset')


class SignalMixin(object):
    # This class is necessary for any code which wants to use Processes
    # outside the usual reactor.run() environment. It is copied from
    # Twisted's twisted.test.test_process . Note that Twisted-8.2.0 uses
    # something rather different.
    sigchldHandler = None

    def setUp(self):
        # make sure SIGCHLD handler is installed, as it should be on
        # reactor.run(). problem is reactor may not have been run when this
        # test runs.
        if hasattr(reactor, "_handleSigchld") and hasattr(signal, "SIGCHLD"):
            self.sigchldHandler = signal.signal(signal.SIGCHLD,
                                                reactor._handleSigchld)
        return super(SignalMixin, self).setUp()

    def tearDown(self):
        if self.sigchldHandler:
            signal.signal(signal.SIGCHLD, self.sigchldHandler)
        return super(SignalMixin, self).tearDown()


class ShouldFailMixin(object):

    def shouldFail(self, expected_failure, which, substring,
                   callable, *args, **kwargs):
        assert substring is None or isinstance(substring, (bytes, unicode))
        d = defer.maybeDeferred(callable, *args, **kwargs)
        def done(res):
            if isinstance(res, failure.Failure):
                res.trap(expected_failure)
                if substring:
                    self.failUnless(substring in str(res),
                                    "%s: substring '%s' not in '%s'"
                                    % (which, substring, str(res)))
                # return the Failure for further analysis, but in a form that
                # doesn't make the Deferred chain think that we failed.
                return [res]
            else:
                self.fail("%s was supposed to raise %s, not get '%s'" %
                          (which, expected_failure, res))
        d.addBoth(done)
        return d


class ReallyEqualMixin(object):
    def failUnlessReallyEqual(self, a, b, msg=None):
        self.assertEqual(a, b, msg)
        self.assertEqual(type(a), type(b), "a :: %r, b :: %r, %r" % (a, b, msg))


def skip_if_cannot_represent_filename(u):
    precondition(isinstance(u, unicode))

    enc = get_filesystem_encoding()
    if not unicode_platform():
        try:
            u.encode(enc)
        except UnicodeEncodeError:
            raise unittest.SkipTest("A non-ASCII filename could not be encoded on this platform.")


class Marker(object):
    pass

class FakeCanary(object):
    """For use in storage tests.

    Can be moved back to test_storage.py once enough Python 3 porting has been
    done.
    """
    def __init__(self, ignore_disconnectors=False):
        self.ignore = ignore_disconnectors
        self.disconnectors = {}
    def notifyOnDisconnect(self, f, *args, **kwargs):
        if self.ignore:
            return
        m = Marker()
        self.disconnectors[m] = (f, args, kwargs)
        return m
    def dontNotifyOnDisconnect(self, marker):
        if self.ignore:
            return
        del self.disconnectors[marker]


class LoggingServiceParent(service.MultiService):
    def log(self, *args, **kwargs):
        return log.msg(*args, **kwargs)


class ShouldFailMixin(object):
    def shouldFail(self, expected_failure, which, substring,
                   callable, *args, **kwargs):
        """Assert that a function call raises some exception. This is a
        Deferred-friendly version of TestCase.assertRaises() .

        Suppose you want to verify the following function:

         def broken(a, b, c):
             if a < 0:
                 raise TypeError('a must not be negative')
             return defer.succeed(b+c)

        You can use:
            d = self.shouldFail(TypeError, 'test name',
                                'a must not be negative',
                                broken, -4, 5, c=12)
        in your test method. The 'test name' string will be included in the
        error message, if any, because Deferred chains frequently make it
        difficult to tell which assertion was tripped.

        The substring= argument, if not None, must appear in the 'repr'
        of the message wrapped by this Failure, or the test will fail.
        """

        assert substring is None or isinstance(substring, str)
        d = defer.maybeDeferred(callable, *args, **kwargs)
        def done(res):
            if isinstance(res, failure.Failure):
                res.trap(expected_failure)
                if substring:
                    message = repr(res.value.args[0])
                    self.failUnless(substring in message,
                                    "%s: substring '%s' not in '%s'"
                                    % (which, substring, message))
            else:
                self.fail("%s was supposed to raise %s, not get '%s'" %
                          (which, expected_failure, res))
        d.addBoth(done)
        return d