from six import PY3, binary_type, text_type

from cryptography.hazmat.bindings.openssl.binding import Binding
binding = Binding()
ffi = binding.ffi
lib = binding.lib



def text(charp):
    """
    Get a native string type representing of the given CFFI ``char*`` object.

    :param charp: A C-style string represented using CFFI.

    :return: :class:`str`
    """
    return native(ffi.string(charp))



def exception_from_error_queue(exception_type):
    """
    Convert an OpenSSL library failure into a Python exception.

    When a call to the native OpenSSL library fails, this is usually signalled
    by the return value, and an error code is stored in an error queue
    associated with the current thread. The err library provides functions to
    obtain these error codes and textual error messages.
    """

    errors = []

    while True:
        error = lib.ERR_get_error()
        if error == 0:
            break
        errors.append((
                text(lib.ERR_lib_error_string(error)),
                text(lib.ERR_func_error_string(error)),
                text(lib.ERR_reason_error_string(error))))

    raise exception_type(errors)



def native(s):
    """
    Convert :py:class:`bytes` or :py:class:`unicode` to the native
    :py:class:`str` type, using UTF-8 encoding if conversion is necessary.

    :raise UnicodeError: The input string is not UTF-8 decodeable.

    :raise TypeError: The input is neither :py:class:`bytes` nor
        :py:class:`unicode`.
    """
    if not isinstance(s, (binary_type, text_type)):
        raise TypeError("%r is neither bytes nor unicode" % s)
    if PY3:
        if isinstance(s, binary_type):
            return s.decode("utf-8")
    else:
        if isinstance(s, text_type):
            return s.encode("utf-8")
    return s



if PY3:
    def byte_string(s):
        return s.encode("charmap")
else:
    def byte_string(s):
        return s