# -*- coding: utf-8 -*-
"""
    celery.five
    ~~~~~~~~~~~

    Compatibility implementations of features
    only available in newer Python versions.


"""
from __future__ import absolute_import

# ############# py3k #########################################################
import sys
PY3 = sys.version_info[0] == 3

try:
    reload = reload                         # noqa
except NameError:                           # pragma: no cover
    try:
        from importlib import reload        # noqa
    except ImportError:                     # pragma: no cover
        from imp import reload              # noqa

try:
    from UserList import UserList           # noqa
except ImportError:                         # pragma: no cover
    from collections import UserList        # noqa

try:
    from UserDict import UserDict           # noqa
except ImportError:                         # pragma: no cover
    from collections import UserDict        # noqa

# ############# time.monotonic ###############################################

if sys.version_info < (3, 3):

    import platform
    SYSTEM = platform.system()

    try:
        import ctypes
    except ImportError:  # pragma: no cover
        ctypes = None  # noqa

    if SYSTEM == 'Darwin' and ctypes is not None:
        from ctypes.util import find_library
        libSystem = ctypes.CDLL(find_library('libSystem.dylib'))
        CoreServices = ctypes.CDLL(find_library('CoreServices'),
                                   use_errno=True)
        mach_absolute_time = libSystem.mach_absolute_time
        mach_absolute_time.restype = ctypes.c_uint64
        absolute_to_nanoseconds = CoreServices.AbsoluteToNanoseconds
        absolute_to_nanoseconds.restype = ctypes.c_uint64
        absolute_to_nanoseconds.argtypes = [ctypes.c_uint64]

        def _monotonic():
            return absolute_to_nanoseconds(mach_absolute_time()) * 1e-9

    elif SYSTEM == 'Linux' and ctypes is not None:
        # from stackoverflow:
        # questions/1205722/how-do-i-get-monotonic-time-durations-in-python
        import ctypes
        import os

        CLOCK_MONOTONIC = 1  # see <linux/time.h>

        class timespec(ctypes.Structure):
            _fields_ = [
                ('tv_sec', ctypes.c_long),
                ('tv_nsec', ctypes.c_long),
            ]

        librt = ctypes.CDLL('librt.so.1', use_errno=True)
        clock_gettime = librt.clock_gettime
        clock_gettime.argtypes = [
            ctypes.c_int, ctypes.POINTER(timespec),
        ]

        def _monotonic():  # noqa
            t = timespec()
            if clock_gettime(CLOCK_MONOTONIC, ctypes.pointer(t)) != 0:
                errno_ = ctypes.get_errno()
                raise OSError(errno_, os.strerror(errno_))
            return t.tv_sec + t.tv_nsec * 1e-9
    else:
        from time import time as _monotonic

try:
    from time import monotonic
except ImportError:
    monotonic = _monotonic  # noqa

if PY3:
    import builtins

    from queue import Queue, Empty, Full
    from itertools import zip_longest
    from io import StringIO, BytesIO

    map = map
    string = str
    string_t = str
    long_t = int
    text_t = str
    range = range
    int_types = (int, )

    def items(d):
        return d.items()

    def keys(d):
        return d.keys()

    def values(d):
        return d.values()

    def nextfun(it):
        return it.__next__

    exec_ = getattr(builtins, 'exec')

    def reraise(tp, value, tb=None):
        if value.__traceback__ is not tb:
            raise value.with_traceback(tb)
        raise value

    class WhateverIO(StringIO):

        def write(self, data):
            if isinstance(data, bytes):
                data = data.encode()
            StringIO.write(self, data)

else:
    import __builtin__ as builtins  # noqa
    from Queue import Queue, Empty, Full  # noqa
    from itertools import imap as map, izip_longest as zip_longest  # noqa
    from StringIO import StringIO   # noqa
    string = unicode                # noqa
    string_t = basestring           # noqa
    text_t = unicode
    long_t = long                   # noqa
    range = xrange
    int_types = (int, long)

    def items(d):                   # noqa
        return d.iteritems()

    def keys(d):                    # noqa
        return d.iterkeys()

    def values(d):                  # noqa
        return d.itervalues()

    def nextfun(it):                # noqa
        return it.next

    def exec_(code, globs=None, locs=None):
        """Execute code in a namespace."""
        if globs is None:
            frame = sys._getframe(1)
            globs = frame.f_globals
            if locs is None:
                locs = frame.f_locals
            del frame
        elif locs is None:
            locs = globs
        exec("""exec code in globs, locs""")

    exec_("""def reraise(tp, value, tb=None): raise tp, value, tb""")

    BytesIO = WhateverIO = StringIO         # noqa


def with_metaclass(Type, skip_attrs=set(['__dict__', '__weakref__'])):
    """Class decorator to set metaclass.

    Works with both Python 2 and Python 3 and it does not add
    an extra class in the lookup order like ``six.with_metaclass`` does
    (that is -- it copies the original class instead of using inheritance).

    """

    def _clone_with_metaclass(Class):
        attrs = dict((key, value) for key, value in items(vars(Class))
                     if key not in skip_attrs)
        return Type(Class.__name__, Class.__bases__, attrs)

    return _clone_with_metaclass
