import inspect
import collections

__all__ = ['signature', 'defop', 'overloaded', 'overload']

def make_signature(fn):
    return tuple(fn.__annotations__.get(arg, object) for arg in inspect.getfullargspec(fn)[0])

registry = {}

class MultiMethod(object):
    def __init__(self, name):
        self.name = name
        self.typemap = {}
    def __call__(self, *args):
        types = tuple(arg.__class__ for arg in args)
        function = self.typemap.get(types)
        if function is None:
            raise TypeError("no match")
        return function(*args)
    def register(self, types, function):
        if types in self.typemap:
            raise TypeError("duplicate registration")
        self.typemap[types] = function

def overload(fn):
    name = fn.__name__
    mm = registry.get(name)
    if mm is None:
        mm = registry[name] = MultiMethod(name)
    types = make_signature(fn)
    mm.register(types, fn)
    def _wrap(*args):
        return mm(*args)
    return _wrap

if __name__ == '__main__':
    @overload
    def foo(x:int, y:float):
        return 'int, float'
        
    @overload
    def foo(x:str, y:str):
        return 'str, str'
        
    print(foo(1, 2.0))
    print(foo('abc', 'def'))