#!/bin/bash

shopt -s extglob

m4_include(common)

write_source() {
  local src=$1 spec= label= uuid= comment=()

  label=$(blkid -s LABEL -o value "$1" 2>/dev/null)
  uuid=$(blkid -s UUID -o value "$1" 2>/dev/null)

  # bind mounts do not have a UUID!

  case $bytag in
    '')
      [[ $uuid ]] && comment=("UUID=$uuid")
      [[ $label ]] && comment+=("LABEL=$label")
      ;;
    LABEL)
      spec=$label
      [[ $uuid ]] && comment=("$src" "UUID=$uuid")
      ;;
    UUID)
      spec=$uuid
      comment=("$src")
      [[ $label ]] && comment+=("LABEL=$label")
      ;;
    *)
      [[ $uuid ]] && comment=("$1" "UUID=$uuid")
      [[ $label ]] && comment+=("LABEL=$label")
      [[ $bytag ]] && spec=$(blkid -s "$bytag" -o value "$1")
      ;;
  esac

  [[ $comment ]] && printf '# %s\n' "${comment[*]}"

  if [[ $spec ]]; then
    printf '%-20s' "$bytag=$spec"
  else
    printf '%-20s' "$(mangle "$src")"
  fi
}

usage() {
  cat <<EOF
usage: ${0##*/} [options] root

  Options:
    -L             Use labels for source identifiers (shortcut for -t LABEL)
    -p             Avoid printing pseudofs mounts
    -t TAG         Use TAG for source identifiers
    -U             Use UUIDs for source identifiers (shortcut for -t UUID)

    -h             Print this help message

genfstab generates output suitable for addition to an fstab file based on the
devices mounted under the mountpoint specified by the given root.

EOF
}

if [[ -z $1 || $1 = @(-h|--help) ]]; then
  usage
  exit $(( $# ? 0 : 1 ))
fi

while getopts ':Lpt:U' flag; do
  case $flag in
    L)
      bytag=LABEL
      ;;
    U)
      bytag=UUID
      ;;
    p)
      nopseudofs=1
      ;;
    t)
      bytag=${OPTARG^^}
      ;;
    :)
      die '%s: option requires an argument -- '\''%s'\' "${0##*/}" "$OPTARG"
      ;;
    ?)
      die '%s: invalid option -- '\''%s'\' "${0##*/}" "$OPTARG"
      ;;
  esac
done
shift $(( OPTIND - 1 ))

(( $# )) || die "No root directory specified"
root=$1; shift

if ! mountpoint -q "$root"; then
  die "$root is not a mountpoint"
fi

if (( bylabel && byuuid )); then
  die "cannot specify both -U and -L"
fi

# handle block devices
findmnt -Recvruno SOURCE,TARGET,FSTYPE,OPTIONS,FSROOT "$root" |
    while read -r src target fstype opts fsroot; do
  # default 5th and 6th columns
  dump=0 pass=2

  src=$(unmangle "$src")
  target=$(unmangle "$target")
  target=${target#$root}

  if (( !foundroot )) && findmnt "$src" "$root" >/dev/null; then
    # this is root. we can't possibly have more than one...
    pass=1 foundroot=1
  fi

  # we don't fsck pseudofs
  if fstype_is_pseudofs "$fstype"; then
    (( nopseudofs )) && continue
    pass=0
  fi

  if [[ $fsroot != / ]]; then
    if [[ $fstype = btrfs ]]; then
      opts+=,subvol=${fsroot#/}
    else
      # it's a bind mount
      src=$(findmnt -funcevo TARGET "$src")$fsroot
      if [[ $src -ef $target ]]; then
        # hrmm, this is weird. we're probably looking at a file or directory
        # that was bound into a chroot from the host machine. Ignore it,
        # because this won't actually be a valid mount. Worst case, the user
        # just re-adds it.
        continue
      fi
      fstype=none
      opts+=,bind
      pass=0
    fi
  fi

  # write one line
  write_source "$src"
  printf '\t%-10s' "/$(mangle "${target#/}")" "$fstype" "$opts"
  printf '\t%s %s' "$dump" "$pass"
  printf '\n\n'
done

# handle swaps devices
{
  # ignore header
  read

  while read -r device type _ _ prio; do
    options=defaults
    if [[ $prio != -1 ]]; then
      options+=,pri=$prio
    fi

    # skip files marked deleted by the kernel
    [[ $device = *'\\040(deleted)' ]] && continue

    if [[ $type = file ]]; then
      printf '%-20s' "$device"
    elif [[ $device = /dev/dm-+([0-9]) ]]; then
      # device mapper doesn't allow characters we need to worry
      # about being mangled, and it does the escaping of dashes
      # for us in sysfs.
      write_source "$(dm_name_for_devnode "$device")"
    else
      write_source "$(unmangle "$device")"
    fi

    printf '\t%-10s\t%-10s\t%-10s\t0 0\n\n' 'none' 'swap' "$options"
  done
} </proc/swaps

# vim: et ts=2 sw=2 ft=sh: