six

def add_metaclass(metaclass):
    """Class decorator for creating a class with a metaclass."""

    def wrapper(cls):
        orig_vars = cls.__dict__.copy()
        slots = orig_vars.get("__slots__")
        if slots is not None:
            if isinstance(slots, str):
                slots = [slots]
            for slots_var in slots:
                orig_vars.pop(slots_var)
        orig_vars.pop("__dict__", None)
        orig_vars.pop("__weakref__", None)
        if hasattr(cls, "__qualname__"):
            orig_vars["__qualname__"] = cls.__qualname__
        return metaclass(cls.__name__, cls.__bases__, orig_vars)

    return wrapper

def add_move(move):
    """Add an item to six.moves."""
    setattr(_MovedItems, move.name, move)

def ensure_binary(s, encoding="utf-8", errors="strict"):
    """Coerce **s** to six.binary_type.

    For Python 2:
      - `unicode` -> encoded to `str`
      - `str` -> `str`

    For Python 3:
      - `str` -> encoded to `bytes`
      - `bytes` -> `bytes`
    """
    if isinstance(s, binary_type):
        return s
    if isinstance(s, text_type):
        return s.encode(encoding, errors)
    raise TypeError("not expecting type '%s'" % type(s))

def ensure_str(s, encoding="utf-8", errors="strict"):
    """Coerce *s* to `str`.

    For Python 2:
      - `unicode` -> encoded to `str`
      - `str` -> `str`

    For Python 3:
      - `str` -> `str`
      - `bytes` -> decoded to `str`
    """
    # Optimization: Fast return for the common case.
    if type(s) is str:
        return s
    if PY2 and isinstance(s, text_type):
        return s.encode(encoding, errors)
    elif PY3 and isinstance(s, binary_type):
        return s.decode(encoding, errors)
    elif not isinstance(s, (text_type, binary_type)):
        raise TypeError("not expecting type '%s'" % type(s))
    return s

def ensure_text(s, encoding="utf-8", errors="strict"):
    """Coerce *s* to six.text_type.

    For Python 2:
      - `unicode` -> `unicode`
      - `str` -> `unicode`

    For Python 3:
      - `str` -> `str`
      - `bytes` -> decoded to `str`
    """
    if isinstance(s, binary_type):
        return s.decode(encoding, errors)
    elif isinstance(s, text_type):
        return s
    else:
        raise TypeError("not expecting type '%s'" % type(s))

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_""")

def python_2_unicode_compatible(klass):
    """
    A class decorator that defines __unicode__ and __str__ methods under Python 2.
    Under Python 3 it does nothing.

    To support Python 2 and 3 with a single code base, define a __str__ method
    returning text and apply this decorator to the class.
    """
    if PY2:
        if "__str__" not in klass.__dict__:
            raise ValueError(
                "@python_2_unicode_compatible cannot be applied "
                "to %s because it doesn't define __str__()." % klass.__name__
            )
        klass.__unicode__ = klass.__str__
        klass.__str__ = lambda self: self.__unicode__().encode("utf-8")
    return klass

def remove_move(name):
    """Remove item from six.moves."""
    try:
        delattr(_MovedItems, name)
    except AttributeError:
        try:
            del moves.__dict__[name]
        except KeyError:
            raise AttributeError("no such move, %r" % (name,))

def with_metaclass(meta, *bases):
    """Create a base class with a metaclass."""
    # This requires a bit of explanation: the basic idea is to make a dummy
    # metaclass for one level of class instantiation that replaces itself with
    # the actual metaclass.
    class metaclass(type):
        def __new__(cls, name, this_bases, d):
            if sys.version_info[:2] >= (3, 7):
                # This version introduced PEP 560 that requires a bit
                # of extra care (we mimic what is done by __build_class__).
                resolved_bases = types.resolve_bases(bases)
                if resolved_bases is not bases:
                    d["__orig_bases__"] = bases
            else:
                resolved_bases = bases
            return meta(name, resolved_bases, d)

        @classmethod
        def __prepare__(cls, name, this_bases):
            return meta.__prepare__(name, bases)

    return type.__new__(metaclass, "temporary_class", (), {})