"""

requests._internal_utils

~~~~~~~~~~~~~~

Provides utility functions that are consumed internally by Requests

which depend on extremely few external helpers (such as compat)

"""

import re

from .compat import builtin_str

_VALID_HEADER_NAME_RE_BYTE = re.compile(rb"^[^:\s][^:\r\n]*\Z")

_VALID_HEADER_NAME_RE_STR = re.compile(r"^[^:\s][^:\r\n]*\Z")

_VALID_HEADER_VALUE_RE_BYTE = re.compile(rb"^\S[^\r\n]*\Z|^\Z")

_VALID_HEADER_VALUE_RE_STR = re.compile(r"^\S[^\r\n]*\Z|^\Z")

_HEADER_VALIDATORS_STR = (_VALID_HEADER_NAME_RE_STR, _VALID_HEADER_VALUE_RE_STR)

_HEADER_VALIDATORS_BYTE = (_VALID_HEADER_NAME_RE_BYTE, _VALID_HEADER_VALUE_RE_BYTE)

HEADER_VALIDATORS = {

    bytes: _HEADER_VALIDATORS_BYTE,

    str: _HEADER_VALIDATORS_STR,

}

def to_native_string(string: str | bytes, encoding: str = "ascii") -> str:

    """Given a string object, regardless of type, returns a representation of

    that string in the native string type, encoding and decoding where

    necessary. This assumes ASCII unless told otherwise.

    """

    if isinstance(string, builtin_str):

        out = string

    else:

        out = string.decode(encoding)

    return out

def unicode_is_ascii(u_string: str) -> bool:

    """Determine if unicode string only contains ASCII characters.

    :param str u_string: unicode string to check. Must be unicode

        and not Python 2 `str`.

    :rtype: bool

    """

    assert isinstance(u_string, str)

    try:

        u_string.encode("ascii")

        return True

    except UnicodeEncodeError:

        return False