# Copyright (C) 2012 Anaconda, Inc
# SPDX-License-Identifier: BSD-3-Clause
import sys
from functools import lru_cache
from logging import getLogger
from os import scandir

from genericpath import exists

log = getLogger(__name__)


@lru_cache(maxsize=None)
def linux_get_libc_version():
    """If on linux, returns (libc_family, version), otherwise (None, None)."""
    if not sys.platform.startswith("linux"):
        return None, None

    from os import confstr, confstr_names, readlink

    # Python 2.7 does not have either of these keys in confstr_names, so provide
    # hard-coded defaults and assert if the key is in confstr_names but differs.
    # These are defined by POSIX anyway so should never change.
    confstr_names_fallback = {
        "CS_GNU_LIBC_VERSION": 2,
        "CS_GNU_LIBPTHREAD_VERSION": 3,
    }

    val = None
    for k, v in confstr_names_fallback.items():
        assert (
            k not in confstr_names or confstr_names[k] == v
        ), "confstr_names_fallback for %s is %s yet in confstr_names it is %s" "" % (
            k,
            confstr_names_fallback[k],
            confstr_names[k],
        )
        try:
            val = str(confstr(v))
        except Exception:  # pragma: no cover
            pass
        else:
            if val:
                break

    if not val:  # pragma: no cover
        # Weird, play it safe and assume glibc 2.5
        family, version = "glibc", "2.5"
        log.warning(
            "Failed to detect libc family and version, assuming %s/%s", family, version
        )
        return family, version
    family, version = val.split(" ")

    # NPTL is just the name of the threading library, even though the
    # version refers to that of uClibc. readlink() can help to try to
    # figure out a better name instead.
    if family == "NPTL":  # pragma: no cover
        for clib in (
            entry.path for entry in scandir("/lib") if entry.name[:7] == "libc.so"
        ):
            clib = readlink(clib)
            if exists(clib):
                if clib.startswith("libuClibc"):
                    if version.startswith("0."):
                        family = "uClibc"
                    else:
                        family = "uClibc-ng"
                    return family, version
        # This could be some other C library; it is unlikely though.
        family = "uClibc"
        log.warning(
            "Failed to detect non-glibc family, assuming %s (%s)", family, version
        )
        return family, version
    return family, version