from .utils import typename

__all__ = ["VariadicSignatureType", "isvariadic", "VariadicSignatureMeta", "Variadic"]

class VariadicSignatureType(type):
    # checking if subclass is a subclass of self
    def __subclasscheck__(cls, subclass):
        other_type = (subclass.variadic_type if isvariadic(subclass)
                      else (subclass,))
        return subclass is cls or all(
            issubclass(other, cls.variadic_type) for other in other_type  # type: ignore[attr-defined]
        )

    def __eq__(cls, other):
        """
        Return True if other has the same variadic type
        Parameters
        ----------
        other : object (type)
            The object (type) to check
        Returns
        -------
        bool
            Whether or not `other` is equal to `self`
        """
        return (isvariadic(other) and
                set(cls.variadic_type) == set(other.variadic_type))  # type: ignore[attr-defined]

    def __hash__(cls):
        return hash((type(cls), frozenset(cls.variadic_type)))  # type: ignore[attr-defined]


def isvariadic(obj):
    """Check whether the type `obj` is variadic.
    Parameters
    ----------
    obj : type
        The type to check
    Returns
    -------
    bool
        Whether or not `obj` is variadic
    Examples
    --------
    >>> # xdoctest: +SKIP
    >>> isvariadic(int)
    False
    >>> isvariadic(Variadic[int])
    True
    """
    return isinstance(obj, VariadicSignatureType)


class VariadicSignatureMeta(type):
    """A metaclass that overrides ``__getitem__`` on the class. This is used to
    generate a new type for Variadic signatures. See the Variadic class for
    examples of how this behaves.
    """
    def __getitem__(cls, variadic_type):
        if not (isinstance(variadic_type, (type, tuple)) or type(variadic_type)):
            raise ValueError("Variadic types must be type or tuple of types"
                             " (Variadic[int] or Variadic[(int, float)]")

        if not isinstance(variadic_type, tuple):
            variadic_type = variadic_type,
        return VariadicSignatureType(
            'Variadic[%s]' % typename(variadic_type),
            (),
            dict(variadic_type=variadic_type, __slots__=())
        )


class Variadic(metaclass=VariadicSignatureMeta):
    """A class whose getitem method can be used to generate a new type
    representing a specific variadic signature.
    Examples
    --------
    >>> # xdoctest: +SKIP
    >>> Variadic[int]  # any number of int arguments
    <class 'multipledispatch.variadic.Variadic[int]'>
    >>> Variadic[(int, str)]  # any number of one of int or str arguments
    <class 'multipledispatch.variadic.Variadic[(int, str)]'>
    >>> issubclass(int, Variadic[int])
    True
    >>> issubclass(int, Variadic[(int, str)])
    True
    >>> issubclass(str, Variadic[(int, str)])
    True
    >>> issubclass(float, Variadic[(int, str)])
    False
    """
