#! @python3@/bin/python3 -B
import argparse
import ctypes
import datetime
import errno
import glob
import os
import os.path
import re
import shutil
import subprocess
import sys
import tempfile
import warnings
from typing import NamedTuple

from packaging import version

libc = ctypes.CDLL("libc.so.6")

class SystemIdentifier(NamedTuple):
    profile: Optional[str]
    generation: int
    specialisation: Optional[str]


def copy_if_not_exists(source: str, dest: str) -> None:
    if not os.path.exists(dest):
        shutil.copyfile(source, dest)


def generation_dir(profile: Optional[str], generation: int) -> str:
    if profile:
        return "/nix/var/nix/profiles/system-profiles/%s-%d-link" % (profile, generation)
    else:
        return "/nix/var/nix/profiles/system-%d-link" % (generation)

def system_dir(profile: Optional[str], generation: int, specialisation: Optional[str]) -> str:
    d = generation_dir(profile, generation)
    if specialisation:
        return os.path.join(d, "specialisation", specialisation)
    else:
        return d

BOOT_ENTRY = """title {title}
version Generation {generation} {description}
linux {kernel}
initrd {initrd}
options {kernel_params}
"""

def generation_conf_filename(profile: Optional[str], generation: int, specialisation: Optional[str]) -> str:
    pieces = [
        "nixos",
        profile or None,
        "generation",
        str(generation),
        f"specialisation-{specialisation}" if specialisation else None,
    ]
    return "-".join(p for p in pieces if p) + ".conf"


def write_loader_conf(profile: Optional[str], generation: int, specialisation: Optional[str]) -> None:
    with open("@efiSysMountPoint@/loader/loader.conf.tmp", 'w') as f:
        if "@timeout@" != "":
            f.write("timeout @timeout@\n")
        f.write("default %s\n" % generation_conf_filename(profile, generation, specialisation))
        if not @editor@:
            f.write("editor 0\n")
        f.write("console-mode @consoleMode@\n")
    os.rename("@efiSysMountPoint@/loader/loader.conf.tmp", "@efiSysMountPoint@/loader/loader.conf")


def profile_path(profile: Optional[str], generation: int, specialisation: Optional[str], name: str) -> str:
    return os.path.realpath("%s/%s" % (system_dir(profile, generation, specialisation), name))


def copy_from_profile(profile: Optional[str], generation: int, specialisation: Optional[str], name: str, dry_run: bool = False) -> str:
    store_file_path = profile_path(profile, generation, specialisation, name)
    suffix = os.path.basename(store_file_path)
    store_dir = os.path.basename(os.path.dirname(store_file_path))
    efi_file_path = "/efi/nixos/%s-%s.efi" % (store_dir, suffix)
    if not dry_run:
        copy_if_not_exists(store_file_path, "@efiSysMountPoint@%s" % (efi_file_path))
    return efi_file_path


def describe_generation(profile: Optional[str], generation: int, specialisation: Optional[str]) -> str:
    try:
        with open(profile_path(profile, generation, specialisation, "nixos-version")) as f:
            nixos_version = f.read()
    except IOError:
        nixos_version = "Unknown"

    kernel_dir = os.path.dirname(profile_path(profile, generation, specialisation, "kernel"))
    module_dir = glob.glob("%s/lib/modules/*" % kernel_dir)[0]
    kernel_version = os.path.basename(module_dir)

    build_time = int(os.path.getctime(system_dir(profile, generation, specialisation)))
    build_date = datetime.datetime.fromtimestamp(build_time).strftime('%F')

    description = "@distroName@ {}, Linux Kernel {}, Built on {}".format(
        nixos_version, kernel_version, build_date
    )

    return description


def write_entry(profile: Optional[str], generation: int, specialisation: Optional[str],
                machine_id: str, current: bool) -> None:
    kernel = copy_from_profile(profile, generation, specialisation, "kernel")
    initrd = copy_from_profile(profile, generation, specialisation, "initrd")

    title = "@distroName@{profile}{specialisation}".format(
        profile=" [" + profile + "]" if profile else "",
        specialisation=" (%s)" % specialisation if specialisation else "")

    try:
        append_initrd_secrets = profile_path(profile, generation, specialisation, "append-initrd-secrets")
        subprocess.check_call([append_initrd_secrets, "@efiSysMountPoint@%s" % (initrd)])
    except FileNotFoundError:
        pass
    except subprocess.CalledProcessError:
        if current:
            print("failed to create initrd secrets!", file=sys.stderr)
            sys.exit(1)
        else:
            print("warning: failed to create initrd secrets "
                  f'for "{title} - Configuration {generation}", an older generation', file=sys.stderr)
            print("note: this is normal after having removed "
                  "or renamed a file in `boot.initrd.secrets`", file=sys.stderr)
    entry_file = "@efiSysMountPoint@/loader/entries/%s" % (
        generation_conf_filename(profile, generation, specialisation))
    tmp_path = "%s.tmp" % (entry_file)
    kernel_params = "init=%s " % profile_path(profile, generation, specialisation, "init")

    with open(profile_path(profile, generation, specialisation, "kernel-params")) as params_file:
        kernel_params = kernel_params + params_file.read()
    with open(tmp_path, 'w') as f:
        f.write(BOOT_ENTRY.format(title=title,
                    generation=generation,
                    kernel=kernel,
                    initrd=initrd,
                    kernel_params=kernel_params,
                    description=describe_generation(profile, generation, specialisation)))
        if machine_id is not None:
            f.write("machine-id %s\n" % machine_id)
    os.rename(tmp_path, entry_file)


def mkdir_p(path: str) -> None:
    try:
        os.makedirs(path)
    except OSError as e:
        if e.errno != errno.EEXIST or not os.path.isdir(path):
            raise


def get_generations(profile: Optional[str] = None) -> List[SystemIdentifier]:
    gen_list = subprocess.check_output([
        "@nix@/bin/nix-env",
        "--list-generations",
        "-p",
        "/nix/var/nix/profiles/%s" % ("system-profiles/" + profile if profile else "system"),
        "--option", "build-users-group", ""],
        universal_newlines=True)
    gen_lines = gen_list.split('\n')
    gen_lines.pop()

    configurationLimit = @configurationLimit@
    configurations = [
        SystemIdentifier(
            profile=profile,
            generation=int(line.split()[0]),
            specialisation=None
        )
        for line in gen_lines
    ]
    return configurations[-configurationLimit:]


def get_specialisations(profile: Optional[str], generation: int, _: Optional[str]) -> List[SystemIdentifier]:
    specialisations_dir = os.path.join(
            system_dir(profile, generation, None), "specialisation")
    if not os.path.exists(specialisations_dir):
        return []
    return [SystemIdentifier(profile, generation, spec) for spec in os.listdir(specialisations_dir)]


def remove_old_entries(gens: List[SystemIdentifier]) -> None:
    rex_profile = re.compile("^@efiSysMountPoint@/loader/entries/nixos-(.*)-generation-.*\.conf$")
    rex_generation = re.compile("^@efiSysMountPoint@/loader/entries/nixos.*-generation-([0-9]+)(-specialisation-.*)?\.conf$")
    known_paths = []
    for gen in gens:
        known_paths.append(copy_from_profile(*gen, "kernel", True))
        known_paths.append(copy_from_profile(*gen, "initrd", True))
    for path in glob.iglob("@efiSysMountPoint@/loader/entries/nixos*-generation-[1-9]*.conf"):
        if rex_profile.match(path):
            prof = rex_profile.sub(r"\1", path)
        else:
            prof = None
        try:
            gen_number = int(rex_generation.sub(r"\1", path))
        except ValueError:
            continue
        if not (prof, gen_number, None) in gens:
            os.unlink(path)
    for path in glob.iglob("@efiSysMountPoint@/efi/nixos/*"):
        if not path in known_paths and not os.path.isdir(path):
            os.unlink(path)


def get_profiles() -> List[str]:
    if os.path.isdir("/nix/var/nix/profiles/system-profiles/"):
        return [x
            for x in os.listdir("/nix/var/nix/profiles/system-profiles/")
            if not x.endswith("-link")]
    else:
        return []

def main() -> None:
    parser = argparse.ArgumentParser(description='Update @distroName@-related systemd-boot files')
    parser.add_argument('default_config', metavar='DEFAULT-CONFIG', help='The default @distroName@ config to boot')
    args = parser.parse_args()

    try:
        with open("/etc/machine-id") as machine_file:
            machine_id = machine_file.readlines()[0]
    except IOError as e:
        if e.errno != errno.ENOENT:
            raise
        # Since systemd version 232 a machine ID is required and it might not
        # be there on newly installed systems, so let's generate one so that
        # bootctl can find it and we can also pass it to write_entry() later.
        cmd = ["@systemd@/bin/systemd-machine-id-setup", "--print"]
        machine_id = subprocess.run(
          cmd, text=True, check=True, stdout=subprocess.PIPE
        ).stdout.rstrip()

    if os.getenv("NIXOS_INSTALL_GRUB") == "1":
        warnings.warn("NIXOS_INSTALL_GRUB env var deprecated, use NIXOS_INSTALL_BOOTLOADER", DeprecationWarning)
        os.environ["NIXOS_INSTALL_BOOTLOADER"] = "1"

    # flags to pass to bootctl install/update
    bootctl_flags = []

    if "@canTouchEfiVariables@" != "1":
        bootctl_flags.append("--no-variables")

    if "@graceful@" == "1":
        bootctl_flags.append("--graceful")

    if os.getenv("NIXOS_INSTALL_BOOTLOADER") == "1":
        # bootctl uses fopen() with modes "wxe" and fails if the file exists.
        if os.path.exists("@efiSysMountPoint@/loader/loader.conf"):
            os.unlink("@efiSysMountPoint@/loader/loader.conf")

        subprocess.check_call(["@systemd@/bin/bootctl", "--esp-path=@efiSysMountPoint@"] + bootctl_flags + ["install"])
    else:
        # Update bootloader to latest if needed
        available_out = subprocess.check_output(["@systemd@/bin/bootctl", "--version"], universal_newlines=True).split()[2]
        installed_out = subprocess.check_output(["@systemd@/bin/bootctl", "--esp-path=@efiSysMountPoint@", "status"], universal_newlines=True)

        # See status_binaries() in systemd bootctl.c for code which generates this
        installed_match = re.search(r"^\W+File:.*/EFI/(?:BOOT|systemd)/.*\.efi \(systemd-boot ([\d.]+[^)]*)\)$",
                      installed_out, re.IGNORECASE | re.MULTILINE)

        available_match = re.search(r"^\((.*)\)$", available_out)

        if installed_match is None:
            raise Exception("could not find any previously installed systemd-boot")

        if available_match is None:
            raise Exception("could not determine systemd-boot version")

        installed_version = version.parse(installed_match.group(1))
        available_version = version.parse(available_match.group(1))

        # systemd 252 has a regression that leaves some machines unbootable, so we skip that update.
        # The fix is in 252.2
        # See https://github.com/systemd/systemd/issues/25363 and https://github.com/NixOS/nixpkgs/pull/201558#issuecomment-1348603263
        if installed_version < available_version:
            if version.parse('252') <= available_version < version.parse('252.2'):
                print("skipping systemd-boot update to %s because of known regression" % available_version)
            else:
                print("updating systemd-boot from %s to %s" % (installed_version, available_version))
                subprocess.check_call(["@systemd@/bin/bootctl", "--esp-path=@efiSysMountPoint@"] + bootctl_flags + ["update"])

    mkdir_p("@efiSysMountPoint@/efi/nixos")
    mkdir_p("@efiSysMountPoint@/loader/entries")

    gens = get_generations()
    for profile in get_profiles():
        gens += get_generations(profile)
    remove_old_entries(gens)
    for gen in gens:
        try:
            is_default = os.path.dirname(profile_path(*gen, "init")) == args.default_config
            write_entry(*gen, machine_id, current=is_default)
            for specialisation in get_specialisations(*gen):
                write_entry(*specialisation, machine_id, current=is_default)
            if is_default:
                write_loader_conf(*gen)
        except OSError as e:
            # See https://github.com/NixOS/nixpkgs/issues/114552
            if e.errno == errno.EINVAL:
                profile = f"profile '{gen.profile}'" if gen.profile else "default profile"
                print("ignoring {} in the list of boot entries because of the following error:\n{}".format(profile, e), file=sys.stderr)
            else:
                raise e

    for root, _, files in os.walk('@efiSysMountPoint@/efi/nixos/.extra-files', topdown=False):
        relative_root = root.removeprefix("@efiSysMountPoint@/efi/nixos/.extra-files").removeprefix("/")
        actual_root = os.path.join("@efiSysMountPoint@", relative_root)

        for file in files:
            actual_file = os.path.join(actual_root, file)

            if os.path.exists(actual_file):
                os.unlink(actual_file)
            os.unlink(os.path.join(root, file))

        if not len(os.listdir(actual_root)):
            os.rmdir(actual_root)
        os.rmdir(root)

    mkdir_p("@efiSysMountPoint@/efi/nixos/.extra-files")

    subprocess.check_call("@copyExtraFiles@")

    # Since fat32 provides little recovery facilities after a crash,
    # it can leave the system in an unbootable state, when a crash/outage
    # happens shortly after an update. To decrease the likelihood of this
    # event sync the efi filesystem after each update.
    rc = libc.syncfs(os.open("@efiSysMountPoint@", os.O_RDONLY))
    if rc != 0:
        print("could not sync @efiSysMountPoint@: {}".format(os.strerror(rc)), file=sys.stderr)


if __name__ == '__main__':
    main()