import ctypes
import multiprocessing
import os
import platform

import src.globalvars as gv


def collect_facts():
    # Populate src.globalvars.facts on import
    _uname = platform.uname()
    gv.facts["hostname"] = _uname.node
    gv.facts["system"] = _uname.system
    gv.facts["kernel"] = _uname.release
    gv.facts["arch"] = _uname.machine
    gv.facts["cpus"] = multiprocessing.cpu_count()
    gv.facts["LD_PRELOAD"] = os.environ.get("LD_PRELOAD", None)

    with open(os.path.join(gv.builddir, "ccinfo"), "r") as ccinfo:
        gv.facts["cc"] = ccinfo.readlines()[-1][:-1]


# Copied from pip.
# https://github.com/pypa/pip/blob/master/src/pip/_internal/utils/glibc.py
# Licensed under MIT.
def glibc_version_string(bin=None):
    "Returns glibc version string, or None if not using glibc."

    # ctypes.CDLL(None) internally calls dlopen(NULL), and as the dlopen
    # manpage says, "If filename is NULL, then the returned handle is for the
    # main program". This way we can let the linker do the work to figure out
    # which libc our process is actually using.
    try:
        process_namespace = ctypes.CDLL(bin)
    except OSError:
        return None

    try:
        gnu_get_libc_version = process_namespace.gnu_get_libc_version
    except AttributeError:
        # Symbol doesn't exist -> therefore, we are not linked to
        # glibc.
        return None

    # Call gnu_get_libc_version, which returns a string like "2.5"
    gnu_get_libc_version.restype = ctypes.c_char_p
    version_str = gnu_get_libc_version()
    # py2 / py3 compatibility:
    if not isinstance(version_str, str):
        version_str = version_str.decode("ascii")

    return version_str


# platform.libc_ver regularly returns completely nonsensical glibc
# versions. E.g. on my computer, platform says:
#
#   ~$ python2.7 -c 'import platform; print(platform.libc_ver())'
#   ('glibc', '2.7')
#   ~$ python3.5 -c 'import platform; print(platform.libc_ver())'
#   ('glibc', '2.9')
#
# But the truth is:
#
#   ~$ ldd --version
#   ldd (Debian GLIBC 2.22-11) 2.22
#
# This is unfortunate, because it means that the linehaul data on libc
# versions that was generated by pip 8.1.2 and earlier is useless and
# misleading. Solution: instead of using platform, use our code that actually
# works.
def libc_ver(bin=None):
    glibc_version = glibc_version_string(bin)
    if glibc_version is None:
        # For non-glibc platforms, fall back on platform.libc_ver
        return platform.libc_ver()
    else:
        return ("glibc", glibc_version)