#!/bin/bash

set -eE -o pipefail
trap 'echo "$0:$LINENO:error: \"$BASH_COMMAND\" returned $?" >&2' ERR



usage() {
  cat <<EOF
Usage: ${0##*/} [OPTION]
If grub var set, act like pxe rom and pxe-kexec to faiserver

-f|--force  do kexec if we can reach faiserver
-h|--help  Print help and exit.

Note: Uses GNU getopt options parsing style
EOF
  exit $1
}



# Keep it short so we don't delay too much wnen we don't have networking.
# In practice, on my home network, on an x200, it took 15 seconds, so
# give it an extra 10 seconds, which seems fairly short as I write this.
NETWORK_TIMOUT_SECS=25
did_fai_check=false

m() { printf "%s\n" "$*";  "$@"; }

try-kexec() {
  deadline=$(( `date +%s` + NETWORK_TIMOUT_SECS ))
  while ! timeout -s 9 3 nc -zu faiserver 69; do
    if (( `date +%s` > deadline )); then
      echo "fai-check: hit $NETWORK_TIMOUT_SECS s tftp server timeout"
      return 0
    fi
    sleep 1
  done
  m pxe-kexec -n --ignore-whitelist -l fai-generated faiserver ||:
}

case $1 in
  -f|--force)
    try-kexec
    exit
    ;;
esac


first=true
for dev in $(btrfs fi show / | sed -rn 's#^\s*devid\s.*\s([^0-9 ]+)\S+$#\1#p' \
               |sort); do

  # Decide which is my grub_ext partition. see partition.DEFAULT file
  # for details
  if [[ $(blockdev --getsize64 ${dev}4) == 8388608 ]]; then
    # Old partition scheme
    grub_extn=${dev}4
  elif [[ $(blockdev --getsize64 ${dev}5) == 8388608 ]]; then
    # Old partition scheme
    grub_extn=${dev}5
  else
    grub_extn=${dev}7
  fi
  mount $grub_extn /mnt
  if $first; then
    if [[ -e /mnt/grubenv ]]; then
      set -x
      source <(grub-editenv /mnt/grubenv list)
      set +x
    fi
    first=false
    # we could just as well check if last_boot != /debianbullseye_bootstrap
    # the intent with this one is just a little clearer.
    if [[ $did_fai_check == true ]]; then
      grub-editenv /mnt/grubenv set did_fai_check=os_true
      # our service does not wait for network-online.target,
      # because it will wait for too long when we don't have a network
      # connection. So, we wait for 10 seconds.
      # ref: https://www.freedesktop.org/wiki/Software/systemd/NetworkTarget/
      try-kexec ||:
    fi
  else
    # we make sure there is only 1 grubenv,
    # so grub can just find the first one, in whatever order
    # if looks at them, which may not be the same as us.
    # If the disk dies, we just lose the default boot option,
    # we will have to do manual steps to replace it anyways.
    rm -f /mnt/gruvenv
  fi
  umount /mnt
done

# the check for last_boot is not needed afaik, just sanity check.
if [[ $did_fai_check == true && $last_boot != /debianbullseye_bootstrap ]]; then
  # no need to reboot if we actually want to boot into this os.
  reboot
fi