#!/usr/bin/env python3

import distutils.file_util
import multiprocessing
import os
import platform
import shutil
import subprocess
import time

import common

parser = common.get_argparse(argparse_args={
    'description': '''\
Build our Linux kernel module without using Buildroot.

See also:https://github.com/cirosantilli/linux-kernel-module-cheat#host
'''
})
common.add_build_arguments(parser)
parser.add_argument(
    '--host',
    action='store_true',
    default=False,
    help='Build the Linux kernel modules for the host instead of guest',
)
parser.add_argument(
    'kernel_modules',
    default=[],
    help='Which kernel modules to build. Default: build all',
    metavar='kernel-modules',
    nargs='*',
)
args = common.setup(parser)
if args.host:
    build_dir = os.path.join(common.kernel_modules_build_host_dir)
else:
    build_dir = os.path.join(common.kernel_modules_build_dir)
if args.clean:
    common.rmrf(build_dir)
else:
    start_time = time.time()
    os.makedirs(build_dir, exist_ok=True)
    # I kid you not, out-of-tree build is not possible, O= does not work as for the kernel build:
    #
    # * https://stackoverflow.com/questions/5718899/building-an-out-of-tree-linux-kernel-module-in-a-separate-object-directory
    # * https://stackoverflow.com/questions/12244979/build-kernel-module-into-a-specific-directory
    # * https://stackoverflow.com/questions/18386182/out-of-tree-kernel-modules-multiple-module-single-makefile-same-source-file
    #
    # This copies only modified files as per:
    # https://stackoverflow.com/questions/5718899/building-an-out-of-tree-linux-kernel-module-in-a-separate-object-directory
    all_kernel_modules = []
    for basename in os.listdir(common.kernel_modules_src_dir):
        src = os.path.join(common.kernel_modules_src_dir, basename)
        if os.path.isfile(src):
            distutils.file_util.copy_file(
                src,
                os.path.join(build_dir, basename),
                update=1,
            )
            noext, ext = os.path.splitext(basename)
            if ext == common.c_ext:
                all_kernel_modules.append(noext)
    if args.kernel_modules == []:
        kernel_modules = all_kernel_modules
    else:
        kernel_modules = map(lambda x: os.path.splitext(os.path.split(x)[1])[0], args.kernel_modules)
    object_files = map(lambda x: x + common.obj_ext, kernel_modules)
    tool = 'gcc'
    if args.host:
        allowed_toolchains = ['host']
    else:
        allowed_toolchains = None
    gcc = common.get_toolchain_tool(tool, allowed_toolchains=allowed_toolchains)
    prefix = gcc[:-len(tool)]
    ccache = shutil.which('ccache')
    if ccache is not None:
        cc = '{} {}'.format(ccache, gcc)
    else:
        cc = gcc
    if args.verbose:
        verbose = ['V=1']
    else:
        verbose = []
    if args.host:
        linux_dir = os.path.join('/lib', 'modules', platform.uname().release, 'build')
    else:
        linux_dir = common.linux_build_dir
    assert common.run_cmd(
        (
            [
                'make',
                '-j', str(multiprocessing.cpu_count()),
                'ARCH={}'.format(common.linux_arch),
                'CC={}'.format(cc),
                'CROSS_COMPILE={}'.format(prefix),
                'LINUX_DIR={}'.format(linux_dir),
                'M={}'.format(build_dir),
                'OBJECT_FILES={}'.format(' '.join(object_files)),
            ] +
            verbose
        ),
        cwd=common.kernel_modules_src_dir,
    ) == 0
    end_time = time.time()
    common.print_time(end_time - start_time)