#!/usr/bin/env python3
# SPDX-License-Identifier: LGPL-2.1-or-later
# -*- mode: python-mode -*-
#
# This file is part of systemd.
#
# systemd is free software; you can redistribute it and/or modify it
# under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation; either version 2.1 of the License, or
# (at your option) any later version.
#
# systemd is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public License
# along with systemd; If not, see <https://www.gnu.org/licenses/>.

# pylint: disable=missing-docstring,invalid-name,import-outside-toplevel
# pylint: disable=consider-using-with,unspecified-encoding,line-too-long
# pylint: disable=too-many-locals,too-many-statements,too-many-return-statements
# pylint: disable=too-many-branches,redefined-builtin,fixme

import argparse
import os
import runpy
import shlex
from pathlib import Path
from typing import Optional

__version__ = '{{PROJECT_VERSION}} ({{GIT_VERSION}})'

try:
    VERBOSE = int(os.environ['KERNEL_INSTALL_VERBOSE']) > 0
except (KeyError, ValueError):
    VERBOSE = False

# Override location of ukify and the boot stub for testing and debugging.
UKIFY = os.getenv('KERNEL_INSTALL_UKIFY', '/usr/lib/systemd/ukify')
BOOT_STUB = os.getenv('KERNEL_INSTALL_BOOT_STUB')


def shell_join(cmd):
    # TODO: drop in favour of shlex.join once shlex.join supports pathlib.Path.
    return ' '.join(shlex.quote(str(x)) for x in cmd)

def log(*args, **kwargs):
    if VERBOSE:
        print(*args, **kwargs)

def path_is_readable(p: Path, dir=False) -> None:
    """Verify access to a file or directory."""
    try:
        p.open().close()
    except IsADirectoryError:
        if dir:
            return
        raise

def mandatory_variable(name):
    try:
        return os.environ[name]
    except KeyError as e:
        raise KeyError(f'${name} must be set in the environment') from e

def parse_args(args=None):
    p = argparse.ArgumentParser(
        description='kernel-install plugin to build a Unified Kernel Image',
        allow_abbrev=False,
        usage='60-ukify.install COMMAND KERNEL_VERSION ENTRY_DIR KERNEL_IMAGE INITRD…',
    )

    # Suppress printing of usage synopsis on errors
    p.error = lambda message: p.exit(2, f'{p.prog}: error: {message}\n')

    p.add_argument('command',
                   metavar='COMMAND',
                   help="The action to perform. Only 'add' is supported.")
    p.add_argument('kernel_version',
                   metavar='KERNEL_VERSION',
                   help='Kernel version string')
    p.add_argument('entry_dir',
                   metavar='ENTRY_DIR',
                   type=Path,
                   nargs='?',
                   help='Type#1 entry directory (ignored)')
    p.add_argument('kernel_image',
                   metavar='KERNEL_IMAGE',
                   type=Path,
                   nargs='?',
                   help='Kernel binary')
    p.add_argument('initrd',
                   metavar='INITRD…',
                   type=Path,
                   nargs='*',
                   help='Initrd files')
    p.add_argument('--version',
                   action='version',
                   version=f'systemd {__version__}')

    opts = p.parse_args(args)

    if opts.command == 'add':
        opts.staging_area = Path(mandatory_variable('KERNEL_INSTALL_STAGING_AREA'))
        path_is_readable(opts.staging_area, dir=True)

        opts.entry_token = mandatory_variable('KERNEL_INSTALL_ENTRY_TOKEN')
        opts.machine_id = mandatory_variable('KERNEL_INSTALL_MACHINE_ID')

    return opts

def we_are_wanted() -> bool:
    KERNEL_INSTALL_LAYOUT = os.getenv('KERNEL_INSTALL_LAYOUT')

    if KERNEL_INSTALL_LAYOUT != 'uki':
        log(f'{KERNEL_INSTALL_LAYOUT=}, quitting.')
        return False

    KERNEL_INSTALL_UKI_GENERATOR = os.getenv('KERNEL_INSTALL_UKI_GENERATOR')

    if KERNEL_INSTALL_UKI_GENERATOR != 'ukify':
        log(f'{KERNEL_INSTALL_UKI_GENERATOR=}, quitting.')
        return False

    log('KERNEL_INSTALL_LAYOUT and KERNEL_INSTALL_UKI_GENERATOR are good')
    return True


def config_file_location() -> Optional[Path]:
    if root := os.getenv('KERNEL_INSTALL_CONF_ROOT'):
        p = Path(root) / 'uki.conf'
    else:
        p = Path('/etc/kernel/uki.conf')
    if p.exists():
        return p
    return None


def kernel_cmdline_base() -> list[str]:
    if root := os.getenv('KERNEL_INSTALL_CONF_ROOT'):
        return Path(root).joinpath('cmdline').read_text().split()

    for cmdline in ('/etc/kernel/cmdline',
                    '/usr/lib/kernel/cmdline'):
        try:
            return Path(cmdline).read_text().split()
        except FileNotFoundError:
            continue

    options = Path('/proc/cmdline').read_text().split()
    return [opt for opt in options
            if not opt.startswith(('BOOT_IMAGE=', 'initrd='))]


def kernel_cmdline(opts) -> str:
    options = kernel_cmdline_base()

    # If the boot entries are named after the machine ID, then suffix the kernel
    # command line with the machine ID we use, so that the machine ID remains
    # stable, even during factory reset, in the initrd (where the system's machine
    # ID is not directly accessible yet), and if the root file system is volatile.
    if (opts.entry_token == opts.machine_id and
        not any(opt.startswith('systemd.machine_id=') for opt in options)):
        options += [f'systemd.machine_id={opts.machine_id}']

    # TODO: we unconditionally set the cmdline here, ignoring the setting in
    #       the config file. Should we not do that?

    # Prepend a space so that '@' does not get misinterpreted
    return ' ' + ' '.join(options)


def call_ukify(opts):
    # Punish me harder.
    # We want this:
    #   ukify = importlib.machinery.SourceFileLoader('ukify', UKIFY).load_module()
    # but it throws a DeprecationWarning.
    # https://stackoverflow.com/questions/67631/how-can-i-import-a-module-dynamically-given-the-full-path
    # https://github.com/python/cpython/issues/65635
    # offer "explanations", but to actually load a python file without a .py extension,
    # the "solution" is 4+ incomprehensible lines.
    # The solution with runpy gives a dictionary, which isn't great, but will do.
    ukify = runpy.run_path(UKIFY, run_name='ukify')

    # Create "empty" namespace. We want to override just a few settings,
    # so it doesn't make sense to duplicate all the fields. We use a hack
    # to pre-populate the namespace like argparse would, all defaults.
    # We need to specify the two mandatory arguments to not get an error.
    opts2 = ukify['create_parser']().parse_args(('A','B'))

    opts2.config = config_file_location()
    opts2.uname = opts.kernel_version
    opts2.linux = opts.kernel_image
    opts2.initrd = opts.initrd
    # Note that 'uki.efi' is the name required by 90-uki-copy.install.
    opts2.output = opts.staging_area / 'uki.efi'

    opts2.cmdline = kernel_cmdline(opts)
    if BOOT_STUB:
        opts2.stub = BOOT_STUB

    # opts2.summary = True

    ukify['apply_config'](opts2)
    ukify['finalize_options'](opts2)
    ukify['check_inputs'](opts2)
    ukify['make_uki'](opts2)

    log(f'{opts2.output} has been created')


def main():
    opts = parse_args()
    if opts.command != 'add':
        return
    if not we_are_wanted():
        return

    call_ukify(opts)


if __name__ == '__main__':
    main()