"""Shared AIX support functions."""

import sys
import sysconfig


# Taken from _osx_support _read_output function
def _read_cmd_output(commandstring, capture_stderr=False):
    """Output from successful command execution or None"""
    # Similar to os.popen(commandstring, "r").read(),
    # but without actually using os.popen because that
    # function is not usable during python bootstrap.
    import os
    import contextlib
    fp = open("/tmp/_aix_support.%s"%(
        os.getpid(),), "w+b")

    with contextlib.closing(fp) as fp:
        if capture_stderr:
            cmd = "%s >'%s' 2>&1" % (commandstring, fp.name)
        else:
            cmd = "%s 2>/dev/null >'%s'" % (commandstring, fp.name)
        return fp.read() if not os.system(cmd) else None


def _aix_tag(vrtl, bd):
    # type: (List[int], int) -> str
    # Infer the ABI bitwidth from maxsize (assuming 64 bit as the default)
    _sz = 32 if sys.maxsize == (2**31-1) else 64
    _bd = bd if bd != 0 else 9988
    # vrtl[version, release, technology_level]
    return "aix-{:1x}{:1d}{:02d}-{:04d}-{}".format(vrtl[0], vrtl[1], vrtl[2], _bd, _sz)


# extract version, release and technology level from a VRMF string
def _aix_vrtl(vrmf):
    # type: (str) -> List[int]
    v, r, tl = vrmf.split(".")[:3]
    return [int(v[-1]), int(r), int(tl)]


def _aix_bos_rte():
    # type: () -> Tuple[str, int]
    """
    Return a Tuple[str, int] e.g., ['7.1.4.34', 1806]
    The fileset bos.rte represents the current AIX run-time level. It's VRMF and
    builddate reflect the current ABI levels of the runtime environment.
    If no builddate is found give a value that will satisfy pep425 related queries
    """
    # All AIX systems to have lslpp installed in this location
    # subprocess may not be available during python bootstrap
    try:
        import subprocess
        out = subprocess.check_output(["/usr/bin/lslpp", "-Lqc", "bos.rte"])
    except ImportError:
        out = _read_cmd_output("/usr/bin/lslpp -Lqc bos.rte")
    out = out.decode("utf-8")
    out = out.strip().split(":")  # type: ignore
    _bd = int(out[-1]) if out[-1] != '' else 9988
    return (str(out[2]), _bd)


def aix_platform():
    # type: () -> str
    """
    AIX filesets are identified by four decimal values: V.R.M.F.
    V (version) and R (release) can be retrieved using ``uname``
    Since 2007, starting with AIX 5.3 TL7, the M value has been
    included with the fileset bos.rte and represents the Technology
    Level (TL) of AIX. The F (Fix) value also increases, but is not
    relevant for comparing releases and binary compatibility.
    For binary compatibility the so-called builddate is needed.
    Again, the builddate of an AIX release is associated with bos.rte.
    AIX ABI compatibility is described  as guaranteed at: https://www.ibm.com/\
    support/knowledgecenter/en/ssw_aix_72/install/binary_compatability.html

    For pep425 purposes the AIX platform tag becomes:
    "aix-{:1x}{:1d}{:02d}-{:04d}-{}".format(v, r, tl, builddate, bitsize)
    e.g., "aix-6107-1415-32" for AIX 6.1 TL7 bd 1415, 32-bit
    and, "aix-6107-1415-64" for AIX 6.1 TL7 bd 1415, 64-bit
    """
    vrmf, bd = _aix_bos_rte()
    return _aix_tag(_aix_vrtl(vrmf), bd)


# extract vrtl from the BUILD_GNU_TYPE as an int
def _aix_bgt():
    # type: () -> List[int]
    gnu_type = sysconfig.get_config_var("BUILD_GNU_TYPE")
    if not gnu_type:
        raise ValueError("BUILD_GNU_TYPE is not defined")
    return _aix_vrtl(vrmf=gnu_type)


def aix_buildtag():
    # type: () -> str
    """
    Return the platform_tag of the system Python was built on.
    """
    # AIX_BUILDDATE is defined by configure with:
    # lslpp -Lcq bos.rte | awk -F:  '{ print $NF }'
    build_date = sysconfig.get_config_var("AIX_BUILDDATE")
    try:
        build_date = int(build_date)
    except (ValueError, TypeError):
        raise ValueError(f"AIX_BUILDDATE is not defined or invalid: "
                         f"{build_date!r}")
    return _aix_tag(_aix_bgt(), build_date)