#!/usr/bin/env bash

UUID="1429a4c6-78f5-4f46-98bc-894106b52399"
mountpoint=""

usage() {
  cat <<EOF >&2
Attach GPG master key
---

$0 [action] [--debug] [--help]

mount or unmount encrypted device based on UUID and attach GnuPG private keys
to private key directory. Actions can be

 - 'mount' to mount USB device and attach keys
 - 'unmount' to remove private keys attached and unmount USB device
EOF
}

error() {
  local message
  printf -v message "\e[31mERROR:\e[0m %s\n" "$1"
  >&2 printf "%b" "${message}"
  show_stack_trace
}

show_stack_trace() {
  if [[ $DEBUG -eq 1 ]]; then
    local message
    message="└─ \e[1mStack trace\e[0m:\n"
    for ((i = 2; i < ${#FUNCNAME[@]} - 1; i++)); do
      if [[ $i = $((${#FUNCNAME[@]} - 2)) ]]; then
        message="${message}   └"
      else
        message="${message}   ├"
      fi
      message="${message}─ source:\e[3;34m${BASH_SOURCE[$i]}\e[0m"
      message="${message} function:\e[3;34m${FUNCNAME[$i]}\e[0m"
      message="${message} line:\e[3;34m${BASH_LINENO[$i - 1]}\e[0m\n"
    done
    >&2 printf "%b" "${message}"
  fi
}

debug() {
  local message
  if [[ $DEBUG -eq 1 ]]; then
    printf -v message "\e[3;34mDEBUG:\e[0m %s\n" "$*"
    >&2 printf "%b" "$message"
    show_stack_trace
  fi
}

# shellcheck disable=SC2317
process_args() {
  while :; do
    case $1 in
    -h | --help)
      usage
      exit 0
      ;;
    m | mount)
      action="mount"
      ;;
    u | umount | unmount)
      action="unmount"
      ;;
    -d | --debug)
      DEBUG=1
      ;;
    *)
      break
      ;;
    esac
    shift
  done
}

main() {
  if [ ! -L "/dev/disk/by-uuid/${UUID}" ]; then
    error "disk with UUID ${UUID} not found"
    exit 10
  fi
  if [ -z "${GNUPGHOME}" ]; then
    error "GNUPGHOME env variable not set, can't determine gnuph home directory"
    exit 11
  fi
  key_destination="${GNUPGHOME}/private-keys-v1.d"

  case "$action" in
  "mount")
    debug "Mount encryted key"
    if ! udisksctl unlock -b /dev/disk/by-uuid/${UUID}; then
      error "Unlock disk ${UUID} failed"
      exit 10
    fi
    mountpoint=$(udisksctl mount -b /dev/mapper/luks-${UUID} | awk '{print $4}')

    while read -r key_file; do

      debug "Create symlink for ${key_file}"
      base=$(basename "$key_file")

      #create symlink to key file if not exist
      if [ ! -e "${key_destination}/${base}" ]; then
        ln -s "$key_file" "${key_destination}/${base}"
      fi
    done < <(find "${mountpoint%.}/.gpg_master/" -type f -name "*.key")
    ;;

  "unmount")
    debug "unmount encrypted key"
    while read -r key_file; do
      debug "Remove key \`${key_file}\`"
      rm "$key_file"
    done < <(find "${key_destination}" -type l -name "*.key")

    if ! udisksctl unmount -b /dev/mapper/luks-${UUID} 2 &>/dev/null; then
      error "Can't unmount volume \`luks-${UUID}\`"
    fi

    if ! udisksctl lock -b /dev/disk/by-uuid/${UUID} 2 &>/dev/null; then
      error "Can't lock device \`${UUID}\`"
    fi
    ;;
  *)
    error "What do you want, mount or unmount:"
    usage
    exit 1
    ;;
  esac
}

process_args "$@"
main
exit 0