from functools import wraps, reduce


def discard_empty_other(method):
    """Decorator for addition operator methods that returns the object itself if
    `other` is the empty string."""
    @wraps(method)
    def wrapper(obj, other):
        if other == '':
            return obj
        else:
            return method(obj, other)
    return wrapper


class String(str):
    @discard_empty_other
    def __radd__(self, other):
        return MixedString([other]).__add__(self)

    @discard_empty_other
    def __add__(self, other):
        return MixedString([self]).__add__(other)

    def __iadd__(self, other):
        return self.__add__(other)

    def replace(self, *args, **kwargs):
        return self.__class__(super(String, self).replace(*args, **kwargs))

    def rstrip(self, *args, **kwargs):
        return self.__class__(super(String, self).rstrip(*args, **kwargs))

    def lower(self):
        return self.__class__(super(String, self).lower())

    def upper(self):
        return self.__class__(super(String, self).upper())

    def soft_lower(self):
        return self.lower()

    def soft_upper(self):
        return self.upper()

    def capitalize_first(self):
        return self.__class__(self[0].upper() + self[1:])

    def words(self):
        for word in self.split():
            yield self.__class__(word)


class MixedString(list):
    @discard_empty_other
    def __add__(self, other):
        super_obj = super(MixedString, self)
        try:
            return self.__class__(super_obj.__add__(other))
        except TypeError:
            return self.__class__(super_obj.__add__(MixedString([other])))

    @discard_empty_other
    def __radd__(self, other):
        return self.__class__([other]).__add__(self)

    def __iadd__(self, other):
        return self.__add__(other)

    def __str__(self):
        return ''.join(map(str, self))

    def __getitem__(self, index):
        return str(self)[index]

    def replace(self, *args):
        return self.__class__([string.replace(*args) for string in self])

    def translate(self, table):
        return self.__class__([string.translate(table) for string in self])

    def lower(self):
        return self.__class__([string.lower() for string in self])

    def upper(self):
        return self.__class__([string.upper() for string in self])

    def title(self):
        return self.__class__([string.title() for string in self])

    def capitalize_first(self):
        self_iter = iter(self)
        output = [next(self_iter).capitalize_first()]
        output += [string for string in self_iter]
        return self.__class__(output)

    def isupper(self):
        return all(string.isupper() for string in self)

    def split(self, *args, **kwargs):
        return str(self).split(*args, **kwargs)

    def rstrip(self, *args, **kwargs):
        rev_iter = reversed(self)
        output = [next(rev_iter).rstrip(*args, **kwargs)]
        output += [string for string in rev_iter]
        return self.__class__(reversed(output))

    def words(self):
        for string in self:
            for word in string.words():
                yield word


class NoCase(String):
    def __repr__(self):
        return '{}({})'.format(self.__class__.__name__, str(self))

    def soft_lower(self):
        return self

    def soft_upper(self):
        return self

    def capitalize_first(self):
        return self


def join(items, delimiter=''):
    return reduce(lambda a, b: a + delimiter + b, items)