import functools
import inspect
from abc import abstractproperty

try:
    from abc import abstractclassmethod, abstractstaticmethod
except ImportError:  # pragma: no cover
    abstractclassmethod = classmethod
    abstractstaticmethod = staticmethod

try:
    from inspect import signature
except ImportError:  # pragma: no cover
    from funcsigs import signature


# Abstract away differences between functions, methods and descriptors


def _get_member(member):
    if inspect.ismethod(member):
        return member.__func__
    if inspect.isdatadescriptor(member) and isinstance(
        member, (property, abstractproperty)
    ):
        return member.fget
    if inspect.ismethoddescriptor(member):
        if isinstance(member, (classmethod, abstractclassmethod)):
            return member.__get__(object, object).__func__
        if isinstance(member, (staticmethod, abstractstaticmethod)):
            return member.__get__(object, object)
    return member


def is_method(member):
    return inspect.isfunction(member) or inspect.ismethod(member)


def is_functional_member(member):
    """
    Check whether a class member from the __dict__ attribute is a method.

    This can be true in two ways:
        - It is literally a Python function
        - It is a method descriptor (wrapping a function)

    Args:
        member (object): An object in the class __dict__.

    Returns:
        bool: `True` if the member is a function (or acts like one).
    """
    return inspect.isfunction(member) or (
        inspect.ismethoddescriptor(member)
        and isinstance(member, (classmethod, staticmethod))
    )


def get_functional_signature(member):
    return signature(_get_member(member))


def functional_hasattr(member, attr):
    return hasattr(_get_member(member), attr)


def functional_getattr(member, attr, default=None):
    return getattr(_get_member(member), attr, default)


def functional_setattr(member, attr, value):
    setattr(_get_member(member), attr, value)


def functional_delattr(member, attr):
    delattr(_get_member(member), attr)


def get_functional_wrapper(member):
    """
    Return a new functional wrapper around the provided member.

    Since `interface_meta` rewrites documentation strings, if the affected
    method is from a parent class, then we need to create a new function wrapper
    so that mutating the documentation does not leak to higher classes. This
    function does just that.

    Args:
        member (functional): The functional object to be wrapped.

    Returns:
        functional: An object that is functionally equivalent to `member`,
            but which can have its own attributes.
    """
    class_method = isinstance(member, classmethod)
    property_method = isinstance(member, property)
    static_method = isinstance(member, staticmethod)

    function = _get_member(member)

    @functools.wraps(function)
    def wrapper(*args, **kwargs):  # pragma: no cover
        return function(*args, **kwargs)

    for attr in ["_quirks_method", "_quirks_mro", "__override__", "__override_force__"]:
        if hasattr(function, attr):
            setattr(wrapper, attr, getattr(function, attr))

    if class_method:
        return classmethod(wrapper)
    elif property_method:
        return property(fget=wrapper, fset=member.fset, fdel=member.fdel)
    elif static_method:
        return staticmethod(wrapper)
    return wrapper


# Override checking


def has_explicit_override(member):
    return functional_getattr(member, "__override__", False)


def set_explicit_override(member, override=True):
    return functional_setattr(member, "__override__", override)


def has_forced_override(member):
    return functional_getattr(member, "__override_force__", False)


def set_forced_override(member, force=True):
    return functional_setattr(member, "__override_force__", force)


# Skip interface conformance checks


def should_skip(member):
    return functional_getattr(member, "__interface_meta_skip__", False)


def set_skip(member, skip=True):
    return functional_setattr(member, "__interface_meta_skip__", skip)


# Documentation helpers


def has_updatable_docs(member):
    return (
        is_functional_member(member)
        or inspect.isdatadescriptor(member)
        and isinstance(member, (property, abstractproperty))
    )


def get_functional_docs(member, orig=True):
    if orig and functional_hasattr(member, "__doc_orig__"):
        return functional_getattr(member, "__doc_orig__")
    return functional_getattr(member, "__doc__")


def set_functional_docs(member, docs):
    if not functional_hasattr(member, "__doc_orig__"):
        functional_setattr(
            member, "__doc_orig__", functional_getattr(member, "__doc__")
        )
    functional_setattr(member, "__doc__", docs)


def has_class_attr_docs(cls):
    return hasattr(cls, "_{}__doc_attrs".format(cls.__name__))


def get_class_attr_docs(cls):
    return getattr(cls, "_{}__doc_attrs".format(cls.__name__))


# Quirk documentation helpers


def has_quirk_docs_method(member):
    return functional_hasattr(member, "_quirks_method")


def get_quirk_docs_method(member):
    return functional_getattr(member, "_quirks_method", None)


def set_quirk_docs_method(member, method):
    return functional_setattr(member, "_quirks_method", method)


def has_quirk_docs_mro(member):
    return functional_hasattr(member, "_quirks_mro")


def get_quirk_docs_mro(member):
    return functional_getattr(member, "_quirks_mro", True)


def set_quirk_docs_mro(member, mro):
    return functional_setattr(member, "_quirks_mro", mro)