#!/bin/sh
: ${ROOT_MKFS_CMD:=mkfs.ext4 -q}
: ${ROOT_FS_TYPE:=ext4}

losetup() { /sbin/losetup "$@"; }

luks_secret()
{
  local parms=$-; # this junk keeps set -x from being too annoying
  set +x
  [ -n "$luks_secret" ] || luks_secret="$(head -c256 /dev/urandom)"
  printf %s "$luks_secret"
  case $parms in *x*) set -x; set -x ;; esac
}

floor4()
{
  # Negatives round up, but aren't used.
  echo $(($1 / 4 * 4))
}

ceil4()
{
  local x="$1"
  [ $((x % 4)) -eq 0 ] || x=$((x + 4 - x % 4))
  printf '%d\n' "$x"
}

init_samizdat()
{
  local imgfile="$1" megs="$2" keyfile="$3" dev

  init_samizdat_blockdev "$imgfile" "$megs" "$keyfile" || return
  local blockdev=/dev/mapper/samizdatcrypt uuid

  for fs in /cdrom/live/*.btrfs; do
      losetup -f "$fs" || return
  done
  modprobe btrfs || return
  btrfs device scan || return

  uuid=$(choose_uuid) || return
  [ "$uuid" ]

  mount -t btrfs -o subvol=ROOT UUID="$uuid" /root || return

  btrfs device add "$blockdev" /root || return
  mount -o rw,remount /root || return
  btrfs subvolume create /root/gpg || return
  # TODO: Restart gpg agent with stored credentials.

  # TODO: Actually, if we unconditionally added a ramdisk, we could go
  # ahead with the boot, and then do this whole thing from the installed
  # system (after pivot_root).  That way, there would be no need to
  # restart.

  # Really, the option to install could be identical to the option to
  # boot from RAM except that it would record the intent to install; or
  # else it could be removed entirely, with an option to persist added
  # as some kind of UI element.
  mv /gpg/gnupghome /root/gpg/ || return

  bootdone root-mounted
}

# Get the uuid of the filesystem with the most devices,
# excluding filesystems that don't incorporate loop devices.
# This is used to choose the latest seed -- which should have
# the most layers.
choose_uuid()
{
    local seen_loop= seen_uuid= seen_devs=
    btrfs filesystem show |
        while read line; do
            case "$line" in
                Label*)
                    seen_uuid=${line##*uuid: }
                    seen_devs=
                    seen_loop=
                    ;;
                *Total\ devices*)
                    seen_devs=${line#*Total devices }
                    seen_devs=${seen_devs%% *}
                    ;;
                *path\ /dev/loop*)
                    seen_loop=t;;
            esac
            [ "$seen_loop" ] && echo "$seen_devs $seen_uuid"
        done |
        uniq | sort -nr | head -n1 | (read _ x; echo $x)
}

open_samizdat()
{
  open_samizdat_blockdev "$@" || return
  local blockdev=/dev/mapper/samizdatcrypt fs
  for fs in /cdrom/live/*.btrfs; do
    losetup -f "$fs" || return
  done
  modprobe btrfs || return
  btrfs device scan || return
  mount -t btrfs -o subvol=ROOT "$blockdev" /root || return
  LoSetup -D
  bootdone root-mounted
}

init_samizdat_lodev()
{
  local imgfile="$1" megs=$(ceil4 "$2")
  truncate -s ${megs}M "$imgfile" || return
  dev=$(losetup -f) && losetup "$dev" "$imgfile" || return
  echo "$dev"
}

open_samizdat_blockdev()
{
  local imgfile="$1" keyfile="$2" dev
  local cryptname=samizdatcrypt
  dev=$(losetup -f) && losetup "$dev" "$imgfile" || return

  gpg2 --verify "$keyfile" || return
  # The first --decrypt merely strips the signature.  The option is
  # poorly named for that case.
  gpg2 --decrypt "$keyfile" | gpg2 --decrypt | cryptsetup --key-file - luksOpen "$dev" "$cryptname" || return

  [ -b /dev/mapper/"$cryptname" ] || return

}

init_samizdat_blockdev()
{
  local imgfile="$1" megs="$2" keyfile="$3" dev
  local cryptname=samizdatcrypt

  dev=$(init_samizdat_lodev "$imgfile" "$megs") || return

  [ ! -b /dev/mapper/"$cryptname" ] || return

  luks_secret >/dev/null
  luks_secret | gpg2 --default-recipient-self --encrypt --armor | gpg2 --clearsign --output "$keyfile" || return

  luks_secret | cryptsetup luksFormat "$dev" - || return
  cryptsetup luksDump "$dev" >&2
  luks_secret | cryptsetup --key-file - luksOpen "$dev" "$cryptname" || return

  [ -b /dev/mapper/"$cryptname" ] || return
}

majmin()
{
  local dev="$1" major minor
  eval $(stat -c 'major=%t minor=%T' "$dev") || return
  [ "$major" -a "$minor" ] || return
  printf '%d:%d\n' 0x$major 0x$minor
}

cryptdev_to_dev()
{
  local dev="$1" majmin
  majmin=$(majmin "$dev") || return
  set -- /sys/dev/block/$majmin/slaves/*
  [ $# = 1 ] || return

  cryptsetup status "$dev" |while read k v; do if [ "$k" = device: ]; then echo $v; break; fi; done
}

cryptdev_to_backing_file()
{
  local dev="$1" majmin result
  majmin="$(majmin "$dev")" || return
  set -- /sys/dev/block/$majmin/slaves/*
  [ $# = 1 ] || return
  read result < "$1"/loop/backing_file || return
  printf '%s\n' "$result"
}

lodev_to_file()
{
  local result majmin dev="$1"
  majmin="$(majmin "$dev")" || return
  read result < /sys/dev/block/$majmin/loop/backing_file || return
  printf '%s' "$result"
}

mountpoint_to_dev()
{
  local wantmp="$1" dev mp rest
  mountpoint -q "$wantmp" || return
  while read dev mp rest; do if [ "$mp" = "$wantmp" ]; then echo "$dev"; return; fi; done < /proc/mounts
  return 1
}

get_cdrom_sizelimit()
{
  # returns bytes
  local dev="$1" sectors
  sectors=$(blockdev --getsz "$dev") || return
  if dd count=2 if="$dev" bs=2048 skip=$((sectors/4 - 2)) of=/dev/null 2>/dev/null; then
    return
  else
    echo $(((sectors-8)*512))
  fi
}

init_gpg()
{
  bootwait samizdat-cdrom
  export GNUPGHOME=/gpg/gnupghome
  (umask 077; rsync --exclude '/luks-key*' --ignore-existing -rpP /cdrom/samizdat/gpg/ /gpg/)

  if samizdat-password-agent >/var/log/samizdat-password-agent.log 2>&1; then
    clear
    true
  else
    false
  fi
}

start_meter()
{
  local startmsg="$*"
  (exec >&4
  clear
  echo -n $startmsg
  set +x
  while sleep 2; do
    echo -n .
  done) &
  meterpid=$!
}

stop_meter()
{
  local endmsg="$*"
  kill $meterpid
  echo "  $endmsg" >&4
}