# pylint: disable=invalid-name
"""Utility to invoke nvcc compiler in the system"""
from __future__ import absolute_import as _abs

import subprocess
import os
import warnings
from . import util
from .. import ndarray as nd
from ..api import register_func
from .._ffi.base import py_str

def compile_cuda(code,
                 target="ptx",
                 arch=None,
                 options=None,
                 path_target=None):
    """Compile cuda code with NVCC from env.

    Parameters
    ----------
    code : str
        The cuda code.

    target : str
        The target format

    arch : str
        The architecture

    options : str or list of str
        The additional options

    path_target : str, optional
        Output file.

    Return
    ------
    cubin : bytearray
        The bytearray of the cubin
    """
    temp = util.tempdir()
    if target not in ["cubin", "ptx", "fatbin"]:
        raise ValueError("target must be in cubin, ptx, fatbin")
    temp_code = temp.relpath("my_kernel.cu")
    temp_target = temp.relpath("my_kernel.%s" % target)

    with open(temp_code, "w") as out_file:
        out_file.write(code)

    if arch is None:
        if nd.gpu(0).exist:
            # auto detect the compute arch argument
            arch = "sm_" + "".join(nd.gpu(0).compute_version.split('.'))
        else:
            raise ValueError("arch(sm_xy) is not passed, and we cannot detect it from env")

    file_target = path_target if path_target else temp_target
    cmd = ["nvcc"]
    cmd += ["--%s" % target, "-O3"]
    cmd += ["-arch", arch]

    if options:
        if isinstance(options, str):
            cmd += [options]
        elif isinstance(options, list):
            cmd += options
        else:
            raise ValueError("options must be str or list of str")

    cmd += ["-o", file_target]
    cmd += [temp_code]

    proc = subprocess.Popen(
        cmd, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)

    (out, _) = proc.communicate()

    if proc.returncode != 0:
        msg = "Compilation error:\n"
        msg += py_str(out)
        raise RuntimeError(msg)

    data = bytearray(open(file_target, "rb").read())
    if not data:
        raise RuntimeError(
            "Compilation error: empty result is generated")
    return data

def find_cuda_path():
    """Utility function to find cuda path

    Returns
    -------
    path : str
        Path to cuda root.
    """
    if "CUDA_PATH" in os.environ:
        return os.environ["CUDA_PATH"]
    cmd = ["which", "nvcc"]
    proc = subprocess.Popen(
        cmd, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
    (out, _) = proc.communicate()
    out = py_str(out)
    if proc.returncode == 0:
        return os.path.realpath(os.path.join(str(out).strip(), "../.."))
    cuda_path = "/usr/local/cuda"
    if os.path.exists(os.path.join(cuda_path, "bin/nvcc")):
        return cuda_path
    raise RuntimeError("Cannot find cuda path")


def get_cuda_version(cuda_path):
    """Utility function to get cuda version

    Parameters
    ----------
    cuda_path : str
        Path to cuda root.

    Returns
    -------
    version : float
        The cuda version
    """
    version_file_path = os.path.join(cuda_path, "version.txt")
    try:
        with open(version_file_path) as f:
            version_str = f.readline().replace('\n', '').replace('\r', '')
            return float(version_str.split(" ")[2][:2])
    except:
        raise RuntimeError("Cannot read cuda version file")


@register_func("tvm_callback_libdevice_path")
def find_libdevice_path(arch):
    """Utility function to find libdevice

    Parameters
    ----------
    arch : int
        The compute architecture in int

    Returns
    -------
    path : str
        Path to libdevice.
    """
    cuda_path = find_cuda_path()
    lib_path = os.path.join(cuda_path, "nvvm/libdevice")
    selected_ver = 0
    selected_path = None
    cuda_ver = get_cuda_version(cuda_path)
    if cuda_ver in (9.0, 9.1, 10.0):
        path = os.path.join(lib_path, "libdevice.10.bc")
    else:
        for fn in os.listdir(lib_path):
            if not fn.startswith("libdevice"):
                continue
            ver = int(fn.split(".")[-3].split("_")[-1])
            if selected_ver < ver <= arch:
                selected_ver = ver
                selected_path = fn
        if selected_path is None:
            raise RuntimeError("Cannot find libdevice for arch {}".format(arch))
        path = os.path.join(lib_path, selected_path)
    return path


def callback_libdevice_path(arch):
    try:
        return find_libdevice_path(arch)
    except RuntimeError:
        warnings.warn("Cannot find libdevice path")
        return ""


def parse_compute_version(compute_version):
    """Parse compute capability string to divide major and minor version

    Parameters
    ----------
    compute_version : str
        compute capability of a GPU (e.g. "6.0")

    Returns
    -------
    major : int
        major version number
    minor : int
        minor version number
    """
    split_ver = compute_version.split('.')
    try:
        major = int(split_ver[0])
        minor = int(split_ver[1])
        return major, minor
    except (IndexError, ValueError) as err:
        raise RuntimeError("Compute version parsing error: " + str(err))


def have_fp16(compute_version):
    """Either fp16 support is provided in the compute capability or not

    Parameters
    ----------
    compute_version: str
        compute capability of a GPU (e.g. "6.0")
    """
    major, minor = parse_compute_version(compute_version)
    # fp 16 support in reference to:
    # https://docs.nvidia.com/cuda/cuda-c-programming-guide/#arithmetic-instructions
    if major == 5 and minor == 3:
        return True
    # NOTE: exclude compute capability 6.1 devices although it is actually available
    #       to compute fp16, because these devices only have low-rate fp16 performance.
    if major == 6 and minor != 1:
        return True
    if major == 7:
        return True

    return False

def have_int8(compute_version):
    """Either int8 support is provided in the compute capability or not

    Parameters
    ----------
    compute_version : str
        compute capability of a GPU (e.g. "6.1")
    """
    major, minor = parse_compute_version(compute_version)
    if major == 6 and minor == 1:
        return True

    return False

def have_tensorcore(compute_version):
    """Either TensorCore support is provided in the compute capability or not

    Parameters
    ----------
    compute_version : str
        compute capability of a GPU (e.g. "7.0")
    """
    major, _ = parse_compute_version(compute_version)
    if major == 7:
        return True

    return False
