# -*- mode: python -*-
# virtme-mkinitramfs: Generate an initramfs image for virtme
# Copyright © 2014 Andy Lutomirski
# Licensed under the GPLv2, which is available in the virtme distribution
# as a file called LICENSE with SHA-256 hash:
# 8177f97513213526df2cf6184d8ff986c675afb514d4e68a404010521b880643

import io
import os
import shlex
import tempfile

from . import cpiowriter, util


def make_base_layout(cw):
    for d in (
        b"lib",
        b"bin",
        b"var",
        b"etc",
        b"newroot",
        b"dev",
        b"proc",
        b"tmproot",
        b"run_virtme",
        b"run_virtme/data",
        b"run_virtme/guesttools",
    ):
        cw.mkdir(d, 0o755)

    cw.symlink(b"bin", b"sbin")
    cw.symlink(b"lib", b"lib64")


def make_dev_nodes(cw):
    cw.mkchardev(b"dev/null", (1, 3), mode=0o666)
    cw.mkchardev(b"dev/kmsg", (1, 11), mode=0o666)
    cw.mkchardev(b"dev/console", (5, 1), mode=0o660)


def install_busybox(cw, config):
    with open(config.busybox, "rb") as busybox:
        cw.write_file(name=b"bin/busybox", body=busybox, mode=0o755)

    for tool in (
        "sh",
        "mount",
        "umount",
        "switch_root",
        "sleep",
        "mkdir",
        "mknod",
        "insmod",
        "cp",
        "cat",
    ):
        cw.symlink(b"busybox", (f"bin/{tool}").encode("ascii"))

    cw.mkdir(b"bin/real_progs", mode=0o755)


_LOGFUNC = """log() {
    if [[ -e /dev/kmsg ]]; then
        echo "<6>virtme initramfs: $*" >/dev/kmsg
    else
        echo "virtme initramfs: $*"
    fi
}
"""


def install_modprobe(cw):
    cw.write_file(
        name=b"bin/modprobe",
        body=b"\n".join(
            [
                b"#!/bin/sh",
                _LOGFUNC.encode("utf-8"),
                b'log "initramfs does not have module $3"',
                b"exit 1",
            ]
        ),
        mode=0o755,
    )


def install_modules(cw, modfiles):
    cw.mkdir(b"modules", 0o755)
    paths = []
    with tempfile.TemporaryDirectory() as tmpdirname:
        for mod in modfiles:
            if mod.endswith(".zst"):
                mod_file = os.path.basename(mod)
                uncompressed_mod = tmpdirname + "/" + os.path.splitext(mod_file)[0]
                os.system(f"zstd -d < {mod} > {uncompressed_mod}")
                mod = uncompressed_mod
            with open(mod, "rb") as f:
                modpath = "modules/" + os.path.basename(mod)
                paths.append(modpath)
                cw.write_file(name=modpath.encode("ascii"), body=f, mode=0o644)

    script = _LOGFUNC + "\n".join(
        f"log 'loading {os.path.basename(p)}...'; insmod {shlex.quote(p)}"
        for p in paths
    )
    cw.write_file(name=b"modules/load_all.sh", body=script.encode("ascii"), mode=0o644)


_INIT = r"""#!/bin/sh

{logfunc}

source /modules/load_all.sh

log 'mounting hostfs...'

if ! /bin/mount -n -t virtiofs -o {access} ROOTFS /newroot/ 2>/dev/null; then
  if ! /bin/mount -n -t 9p -o {access},version=9p2000.L,trans=virtio,access=any,msize=524288 /dev/root /newroot/; then
    echo "Failed to mount real root.  We are stuck."
    sleep 5
    exit 1
  fi
fi

# Can we actually use /newroot/ as root?
if ! mount -t proc -o nosuid,noexec,nodev proc /newroot/proc 2>/dev/null; then
  # QEMU 1.5 and below have a bug in virtfs that prevents mounting
  # anything on top of a virtfs mount.
  log "your host's virtfs is broken -- using a fallback tmpfs"
  need_fallback_tmpfs=1
else
  umount /newroot/proc  # Don't leave garbage behind
fi

# Find init
mount -t proc none /proc
for arg in `cat /proc/cmdline`; do
  if [[ "${{arg%%=*}}" = "init" ]]; then
    init="${{arg#init=}}"
    break
  fi
done
umount /proc

if [[ -z "$init" ]]; then
  log 'no init= option'
  exit 1
fi

log 'done; switching to real root'
exec /bin/switch_root /newroot "$init" "$@"
"""


def generate_init(config) -> bytes:
    out = io.StringIO()
    out.write(_INIT.format(logfunc=_LOGFUNC, access=config.access))
    return out.getvalue().encode("utf-8")


class Config:
    __slots__ = ["modfiles", "virtme_data", "virtme_init_path", "busybox", "access"]

    def __init__(self):
        self.modfiles: list[str] = []
        self.virtme_data: dict[bytes, bytes] = {}
        self.virtme_init_path: str | None = None
        self.busybox: str | None = None
        self.access = "ro"


def mkinitramfs(out, config) -> None:
    cw = cpiowriter.CpioWriter(out)
    make_base_layout(cw)
    make_dev_nodes(cw)
    install_busybox(cw, config)
    install_modprobe(cw)
    if config.modfiles is not None:
        install_modules(cw, config.modfiles)
    for name, contents in config.virtme_data.items():
        cw.write_file(b"run_virtme/data/" + name, body=contents, mode=0o755)
    cw.write_file(b"init", body=generate_init(config), mode=0o755)
    cw.write_trailer()


def find_busybox(root, is_native) -> str | None:
    return util.find_binary(
        ["busybox-static", "busybox.static", "busybox"], root=root, use_path=is_native
    )
