"""
Copyright (C) 2025 283375

This file is part of "arcaea-apk-assets" (stated as "this program" below).

This program is free software: you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free Software
Foundation, either version 3 of the License, or (at your option) any later
version.

This program is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with
this program. If not, see <https://www.gnu.org/licenses/>.
"""

import re
from typing import Optional


def is_string_blank(string: str):
    """
    Check if a string equals to a blank string after stripped.

    >>> is_string_blank("abc")
    False

    >>> is_string_blank("")
    True

    >>> is_string_blank("   ")
    True

    >>> is_string_blank("   a   ")
    False
    """

    if not isinstance(string, str):
        msg = "A `str` object is expected"
        raise TypeError(msg)

    return string.strip() == ""


def blank_str_to_none(string: str):
    """
    Convert a blank string (see :func:`~is_string_blank`) to None, otherwise return the
    original string.

    >>> blank_str_to_none("") is None
    True

    >>> blank_str_to_none("abc") == "abc"
    True

    >>> blank_str_to_none("   ") is None
    True

    >>> blank_str_to_none("   abc   ") == "   abc   "
    True

    >>> blank_str_to_none(None) is None
    True
    """

    if string is None:
        return None

    if not isinstance(string, str):
        msg = "A `str` object is expected"
        raise TypeError(msg)

    return None if is_string_blank(string) else string


def replace_single_newline(text: Optional[str]):
    if text is None:
        return None

    return re.sub(r"\n+", lambda m: "\n" * (len(m.group()) - 1), text)