"""
Implementation of `__new__` for arbitrary Cocoa classes

The __new__ method just translates invocations into the
corresponding invocation of the Cocoa pattern (
`cls.alloc().init()` or `cls.new()`), based on a mapping
maintaind in this file.

The mapping is updated in two ways:
    1. From framework bindings for native classes
    2. Based on `init` methods in Python subclasses

"""

import objc

__all__ = ()

# Mapping: class name -> { kwds: selector_name }
#
# That is, keys are names of Objective-C classes, values
# are mappings from keyword argument names to
# the name of a selector.
#
# The selector_name can be `None` to disable a
# mapping in a subclass.
#
# The complete mapping for a class is a chain map
# for the submaps of all classes on the MRO.
NEW_MAP = {
    "NSObject": {(): "init"},
}

# Sentinel value
UNSET = object()

# Added to the docstring for __new__
DOC_SUFFIX = "The order of keyword arguments is significant\n"


def calculate_new_doc(cls):
    """
    Calculate the docstring for the __new__
    for *cls*
    """
    result = {}
    for c in reversed(cls.__mro__):
        new_map = NEW_MAP.get(c.__name__, UNSET)
        if new_map is UNSET:
            continue

        for kwds, selector in new_map.items():
            if selector is None:
                result.pop(kwds, None)
                continue

            if not kwds:
                result[kwds] = f"{cls.__name__}():"
            else:
                result[kwds] = f"{cls.__name__}(*, " + ", ".join(kwds) + "):"
            if selector.startswith("init"):
                result[
                    kwds
                ] += f"\n   returns cls.alloc().{selector}({', '.join(kwds)})\n\n"
            else:
                result[kwds] += f"\n   returns cls.{selector}({', '.join(kwds)})\n\n"
    return "".join(sorted(result.values())) + DOC_SUFFIX


class function_wrapper:
    """
    Wrapper for the __new__ function to generate the
    docstring dynamically.
    """

    __slots__ = ("_function", "_cls")

    def __init__(self, function, cls):
        self._function = function
        self._cls = cls

    @property
    def __class__(self):
        return self._function.__class__

    @property
    def __doc__(self):
        return calculate_new_doc(self._cls)

    def __getattr__(self, name):
        return getattr(self._function, name)

    def __setattr__(self, name, value):
        if name in ("_function", "_cls"):
            object.__setattr__(self, name, value)
        return setattr(self._function, name, value)

    def __call__(self, *args, **kwds):
        return self._function(*args, **kwds)


def new_func(cls, *args, **kwds):
    """
    Generic implementation for Objective-C `__new__`.
    """
    key = tuple(kwds.keys())

    for c in cls.__mro__:
        new_map = NEW_MAP.get(c.__name__, UNSET)
        if new_map is UNSET:
            continue

        name = new_map.get(key, UNSET)
        if name is UNSET:
            continue

        if name is None:
            if key:
                raise TypeError(
                    f"{cls.__name__}() does not support keyword arguments {', '.join(repr(k) for k in key)}"
                )
            else:
                raise TypeError(f"{cls.__name__}() requires keyword arguments")

        if not isinstance(name, str):
            # Assume that 'name' is actually a callable.
            #
            # This is used to implement custom signatures for a number
            # of classes in the various ._convenience sibling modules.
            return name(cls, *args, **kwds)

        if args:
            raise TypeError(f"{cls.__name__}() does not accept positional arguments")

        args = [kwds[n] for n in key]
        if name.startswith("init") and len(name) == 4 or name[4].isupper():
            return getattr(cls.alloc(), name)(*args)

        else:
            return getattr(cls, name)(*args)

    if key in (("cobject",), ("c_void_p",)):
        # Support for creating instances from raw pointers in the default
        # __new__ implementation.
        return objc.objc_object.__new__(cls, **kwds)

    if key:  # pragma: no branch
        raise TypeError(
            f"{cls.__name__}() does not support keyword arguments {', '.join(repr(k) for k in key)}"
        )
    else:  # pragma: no cover
        # Should never be reached due to a similar test earlier
        # in this function.
        raise TypeError(f"{cls.__name__}() requires keyword arguments")


FunctionType = type(new_func)


def make_generic_new(cls, *, FunctionType=FunctionType, new_func=new_func):

    # XXX: Settings these helps, but does not yet result in the correct
    #      output from help()

    result = FunctionType(
        new_func.__code__,
        new_func.__globals__,
        cls.__name__ + ".__new__",
        new_func.__defaults__,
        new_func.__closure__,
    )
    result.__qualname__ = result.__name__
    result.__module__ = cls.__module__
    result = function_wrapper(result, cls)
    return result


objc.options._genericNewClass = function_wrapper