#!/bin/bash
## vim:sw=2:sts=2:ts=2:et:spell:
##
## Copyright (C) 2023 - 2023 ENCRYPTED SUPPORT LP <adrelanos@whonix.org>
## See the file COPYING for copying conditions.
##########################
## BEGIN DEFAULT VALUES ##
##########################

if test "${BASH_SOURCE-}" != "${0}"; then
  ## Script was sourced.
  ## This is useful for other programs / scripts to be able to `source` the
  ## functions of this script for code re-use. dist-installer-gui will do this.
  dist_installer_cli_was_sourced="true"
else
  ## Script was executed.
  dist_installer_cli_was_sourced="false"
  # shellcheck disable=SC2317
  set -o errexit
  set -o nounset
fi


set_globals() {
  ## Version is commit based: https://github.com/Whonix/usability-misc
  version="20.3-1"
  me="${0##*/}"
  # shellcheck disable=SC2034
  all_args="${*}"
  start_time="$(date +%s)"

  dialog_title="License agreement (scroll with arrows)"
  license="
Please do NOT continue unless you understand everything!
 DISCLAIMER OF WARRANTY.
 .
 THE PROGRAM IS PROVIDED WITHOUT ANY WARRANTIES, WHETHER EXPRESSED OR IMPLIED,
 INCLUDING, WITHOUT LIMITATION, IMPLIED WARRANTIES OF FITNESS FOR A PARTICULAR
 PURPOSE, NON-INFRINGEMENT, TITLE AND MERCHANTABILITY.  THE PROGRAM IS BEING
 DELIVERED OR MADE AVAILABLE 'AS IS', 'WITH ALL FAULTS' AND WITHOUT WARRANTY OR
 REPRESENTATION.  THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE
 PROGRAM IS WITH YOU.  SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF
 ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
 .
 LIMITATION OF LIABILITY.
 .
 UNDER NO CIRCUMSTANCES SHALL ANY COPYRIGHT HOLDER OR ITS AFFILIATES, OR ANY
 OTHER PARTY WHO MODIFIES AND/OR CONVEYS THE PROGRAM AS PERMITTED ABOVE, BE
 LIABLE TO YOU, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, FOR ANY
 DAMAGES OR OTHER LIABILITY, INCLUDING ANY GENERAL, DIRECT, INDIRECT, SPECIAL,
 INCIDENTAL, CONSEQUENTIAL OR PUNITIVE DAMAGES ARISING FROM, OUT OF OR IN
 CONNECTION WITH THE USE OR INABILITY TO USE THE PROGRAM OR OTHER DEALINGS WITH
 THE PROGRAM(INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED
 INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE
 PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), WHETHER OR NOT ANY COPYRIGHT HOLDER
 OR SUCH OTHER PARTY RECEIVES NOTICE OF ANY SUCH DAMAGES AND WHETHER OR NOT SUCH
 DAMAGES COULD HAVE BEEN FORESEEN.
 .
 INDEMNIFICATION.
 .
 IF YOU CONVEY A COVERED WORK AND AGREE WITH ANY RECIPIENT
 OF THAT COVERED WORK THAT YOU WILL ASSUME ANY LIABILITY FOR THAT COVERED WORK,
 YOU HEREBY AGREE TO INDEMNIFY, DEFEND AND HOLD HARMLESS THE OTHER LICENSORS AND
 AUTHORS OF THAT COVERED WORK FOR ANY DAMAGES, DEMANDS, CLAIMS, LOSSES, CAUSES OF
 ACTION, LAWSUITS, JUDGMENTS EXPENSES (INCLUDING WITHOUT LIMITATION REASONABLE
 ATTORNEYS' FEES AND EXPENSES) OR ANY OTHER LIABILITY ARISING FROM, RELATED TO OR
 IN CONNECTION WITH YOUR ASSUMPTIONS OF LIABILITY.
If the disclaimer of warranty and limitation of liability provided
above cannot be given local legal effect according to their terms,
reviewing courts shall apply local law that most closely approximates
an absolute waiver of all civil liability in connection with the
Program, unless a warranty or assumption of liability accompanies a
copy of the Program in return for a fee.
"

  ## https://www.whonix.org/wiki/Main/Project_Signing_Key#cite_note-7
  adrelanos_signify="untrusted comment: Patrick Schleizer adrelanos@whonix.org signify public key
  RWQ6KRormNEETq+M8IysxRe/HAWlqZRlO8u7ACIiv5poAW0ztsirOjCQ"
  ## https://www.whonix.org/wiki/KVM/Project_Signing_Key#cite_note-4
  hulahoop_signify="untrusted comment: signify public key
  RWT2GZDQkp1NtTAC1IoQHUsyb/AQ2LIQF82cygQU+riOpPWSq730A/rq"

  ## https://www.virtualbox.org/wiki/Linux_Downloads
  oracle_pgp="-----BEGIN PGP PUBLIC KEY BLOCK-----
Version: GnuPG v1.4.12 (GNU/Linux)

mQINBFcZ9OEBEACSvycoAEIKJnyyIpZ9cZLCWa+rHjXJzPymndnPOwZr9lksZVYs
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6XQ69VLtkNPgiWzVMclg+qW1pA8ptXqXLMxi4h5EmE5GOhsihuwkwhhBmFqGT1RJ
EGlc/uiHWQskOW3nhQ3Epd6xhCUImy8Eu83YRxS6QriH6K8z5LgRSdg9nwARAQAB
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a04IlbXiT46V9jjJFnNem/Co0u+2e2J3oReNmHvbb62OC57rqeBxqBplXg9tvJk/
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k74BcWD9PZVadSMN7FWZzMfVsbTMmUA22tuDKD6hrF6ysCelex4YO44kSH7dhXu5
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KQ5/86JaIPN+JJLHJoO2EBQC08Cw3oxTDFVcWZ/IWvEFeqyqRSyoFMoDkjLYsqHS
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Y3B83Y34PxuSIq2kokIGo8JhqfqPB/ohtTLHg/o9RhP8xmfvALRD
=Rv7/
-----END PGP PUBLIC KEY BLOCK-----"
}

## colors
get_colors(){
  ## Disable colors if some environment variables are present.
  if test -n "${NO_COLOR:-}" || test -n "${ANSI_COLORS_DISABLED:-}"; then
    # shellcheck disable=SC2034
    nocolor=""
    bold=""
    nobold=""
    underline=""
    nounderline=""
    red=""
    green=""
    yellow=""
    #blue=""
    magenta=""
    cyan=""
    return 0
  fi

  # shellcheck disable=SC2034
  nocolor="\033[0m"
  bold="\033[1m"
  nobold="\033[22m"
  underline="\033[4m"
  nounderline="\033[24m"
  red="\033[31m"
  green="\033[32m"
  yellow="\033[33m"
  #blue="\033[34m"
  magenta="\033[35m"
  cyan="\033[36m"
}


########################
## END DEFAULT VALUES ##
########################

################
## BEGIN MISC ##
################
## This is just a simple wrapper around 'command -v' to avoid
## spamming '>/dev/null' throughout this function. This also guards
## against aliases and functions.
## https://github.com/dylanaraps/pfetch/blob/pfetch#L53
has(){
  _cmd="$(command -v "${1}")" 2>/dev/null || return 1
  [ -x "${_cmd}" ] || return 1
}

dirname() {
  ## Usage: dirname "path"

  ## If '$1' is empty set 'dir' to '.', else '$1'.
  dir=${1:-.}

  ## Strip all trailing forward-slashes '/' from
  ## the end of the string.
  #
  ## "${dir##*[!/]}": Remove all non-forward-slashes
  ## from the start of the string, leaving us with only
  ## the trailing slashes.
  ## "${dir%%"${}"}": Remove the result of the above
  ## substitution (a string of forward slashes) from the
  ## end of the original string.
  dir=${dir%%"${dir##*[!/]}"}

  ## If the variable *does not* contain any forward slashes
  ## set its value to '.'.
  [ "${dir##*/*}" ] && dir=.

  ## Remove everything *after* the last forward-slash '/'.
  dir=${dir%/*}

  ## Again, strip all trailing forward-slashes '/' from
  ## the end of the string (see above).
  dir=${dir%%"${dir##*[!/]}"}

  ## Print the resulting string and if it is empty,
  ## print '/'.
  printf '%s\n' "${dir:-/}"
}


## Capitalize only the first char of a string.
capitalize_first_char(){
  echo "${1:-}" | awk '{$1=toupper(substr($1,0,1))substr($1,2)}1'
}


## Block running as root.
not_as_root(){
  test "$(id -u)" = "0" && die 1 "\
${underline}Non-Root Check:${nounderline} Running as root detected.
  - You are currently running this installer with root privileges.
  - This installer should not be run as root.
  - Please run as normal user."
  return 0
}


## Wrapper that supports su, sudo, doas
root_cmd(){
  test -z "${1:-}" && die 1 "${underline}root_cmd function:${nounderline} Failed to pass arguments to root_cmd."
  : "${root_cmd_loglevel:=notice}"
  case "${sucmd}" in
    su)
      ## Thanks to Congelli501 for su to not mess with quotes.
      ## https://stackoverflow.com/a/32966744/2605155
      cmd="$(which -- "${1}")"
      shift
      log_run "$root_cmd_loglevel" su root -s "${cmd}" -- "${@}"
      ;;
    sudo)
      log_run "$root_cmd_loglevel" sudo -- "${@}"
      ;;
    doas)
      log_run "$root_cmd_loglevel" doas -u root -- "${@}"
      ;;
    *)
      die 1 "${underline}root_cmd function:${nounderline} root_cmd does not support sucmd: '${sucmd}'"
      ;;
  esac
}


## Check if variable is integer
is_integer(){
  printf %d "${1}" >/dev/null 2>&1 || return 1
}


## Checks if the target is valid.
## Address range from 0.0.0.0 to 255.255.255.255. Port ranges from 0 to 65535
## this is not perfect but it is better than nothing
is_addr_port(){
  addr_port="${1}"
  port="${addr_port##*:}"
  addr="${addr_port%%:*}"

  ## Support only IPv4 x.x.x.x:y
  if [ "$(echo "${addr_port}" | tr -cd "." | wc -c)" != 3 ] ||
    [ "$(echo "${addr_port}" | tr -cd ":" | wc -c)" != 1 ] ||
    [ "${port}" = "${addr}" ]; then
    die 2 "${underline}is_addr_port test:${nounderline} Invalid address:port assignment: ${addr_port}"
  fi

  is_integer "${port}" ||
    die 2 "${underline}is_addr_port test:${nounderline} Invalid port '${port}', not an integer."

  if [ "${port}" -gt 0 ] && [ "${port}" -le 65535 ]; then
    true "is_addr_port test: Valid port: '${port}'"
  else
    die 2 "${underline}is_addr_port test:${nounderline} Invalid port '${port}', not within range: 0-65535."
  fi

  for quad in $(printf '%s\n' "${addr}" | tr "." " "); do
    is_integer "${quad}" ||
      die 2 "${underline}is_addr_port test:${nounderline} Invalid address '${addr}', '${quad}' is not an integer."
    if [ "${quad}" -ge 0 ] && [ "${quad}" -le 255 ]; then
      true "Valid quad '${quad}'"
    else
      die 2 "${underline}is_addr_port test:${nounderline} Invalid address '${addr}', '${quad}' not within range: 0-255."
    fi
  done
}


## Get host os and other necessary information.
get_os(){
  ## Source: pfetch: https://github.com/dylanaraps/pfetch/blob/master/pfetch
  os="$(uname -s)"
  kernel="$(uname -r)"
  arch="$(uname -m)"

  distro=""
  distro_version=""
  debian_testing_or_unstable_detected=""
  case ${os} in
    Linux*)
      if has lsb_release; then
        distro=$(lsb_release --short --description || lsb_release -sd)
        distro_version=$(lsb_release --short --release || lsb_release -sr)
      elif test -f /etc/os-release; then
        while IFS='=' read -r key val; do
          case "${key}" in
            (PRETTY_NAME) distro=${val}
              ;;
            (VERSION_ID) distro_version=${val}
              ;;
          esac
        done < /etc/os-release
      else
        has crux && distro=$(crux)
        has guix && distro='Guix System'
      fi
      distro=${distro##[\"\']}
      distro=${distro%%[\"\']}
      case ${PATH} in (*/bedrock/cross/*) distro='Bedrock Linux' ;; esac
      if [ "${WSLENV:-}" ]; then
        distro="${distro}${WSLENV+ on Windows 10 [WSL2]}"
      elif [ -z "${kernel%%*-Microsoft}" ]; then
        distro="${distro} on Windows 10 [WSL1]"
      fi
    ;;
    Haiku) distro=$(uname -sv);;
    Minix|DragonFly) distro="${os} ${kernel}";;
    SunOS) IFS='(' read -r distro _ < /etc/release;;
    OpenBSD*) distro="$(uname -sr)";;
    FreeBSD) distro="${os} $(freebsd-version)";;
    *) distro="${os} ${kernel}";;
  esac

  ## Debian testing /etc/os-release does not contain VERSION_ID.
  if echo "${distro}" | grep --quiet "/sid" ; then
    debian_testing_or_unstable_detected=true
  fi

  distro_derivative_name_pretty="(No derivative detected.)"
  distro_derivative_version="(No derivative detected.)"
  if test -f /usr/share/kicksecure/marker; then
    distro_derivative_name_pretty="Kicksecure"
    distro_derivative_version=$(cat /etc/kicksecure_version)
  elif test -f /usr/share/whonix/marker; then
    distro_derivative_name_pretty="Whonix"
    distro_derivative_version=$(cat /etc/whonix_version)
  fi

  log notice "Architecture detected: '${arch}'"
  log notice "System detected: '${os}'"
  log notice "Distribution/Derivative name detected: '${distro}' / '${distro_derivative_name_pretty}'"
  log notice "Distribution/Derivative version detected: '${distro_version}' / '${distro_derivative_version}'"

  if [ "$debian_testing_or_unstable_detected" = "true" ]; then
    log notice "Debian testing or unstable detection: 'success'"
    if test "${oracle_repo}" = "1"; then
      log error "You are attempting to use '--oracle-repo' on Debian testing. This is impossible."
      if test "${ci}" = "1"; then
        die 0 "${underline}Distribution Test Result:${nounderline} Oracle doesn't provide a Debian testing or unstable repository. Skipped on CI to avoid breaking the CI testing."
      else
        die 101 "${underline}Distribution Test Result:${nounderline} Oracle doesn't provide a Debian testing or unstable repository."
      fi
    fi
    log info "Not attempting to use '--oracle-repo' on Debian testing, good."
    ## In Debian testing distro_version was previously observed as 'n/a' or empty, because
    ## Debian testing /etc/os-release does not contain VERSION_ID.
    return 0
  fi
  log info "Debian testing or unstable detection: 'not detected'"

  ## This at last so the user can hopefully post his system info from the
  ## logs before the error below.
  if [ -z "${distro_version}" ]; then
    if test -f /etc/os-release; then
      log notice "Contents of /etc/os-release:"
      cat /etc/os-release || true
    else
      log notice "/etc/os-release file not found."
    fi
    die 101 "${underline}Distribution Check:${nounderline} Failed to find distribution version."
    ## it will fail later on get_host_pkgs if the system is not supported.
    ## but distro version needs to be checked here because it can occur
    ## frequently when the release of the distribution is still unstable.
    ## Also because we check for distribution version to abort if necessary.
  fi

  distro_version_without_dot="$(echo "${distro_version}" | tr -d ".")"
  is_integer "${distro_version_without_dot}" ||
     die 101 "${underline}Distribution Check:${nounderline} Distribution version without dot is still not a number: '${distro_version_without_dot}'"
}


get_distro() {
  true "distro: ${distro}"
  case "${os}" in
    Linux*)
      case "${distro}" in
        "Debian"*|"Kali"*|"Tails"*|"Kicksecure"|"Whonix")
          debian_derivative_detected=1
          ;;
        "Linux Mint"*|"LinuxMint"*|"mint"*)
          ubuntu_derivative_detected=1
          debian_derivative_detected=1
          ;;
        *"buntu"*)
          ubuntu_derivative_detected=1
          debian_derivative_detected=1
          if [ "${distro_version_without_dot}" -lt 2204 ]; then
            die 101 "${underline}Distribution Check:${nounderline} Minimal '${distro}' required version is '22.04', yours is '${distro_version}'."
          fi
          ;;
        "Fedora"*|"CentOS"*|"rhel"*|"Redhat"*|"Red hat")
          fedora_derivative_detected=1
          ;;
        "Arch"*|"Artix"*|"ArcoLinux"*)
          claim_unsupported_distro known "${distro}"
          ;;
        *)
          claim_unsupported_distro unknown "${distro}"
          ;;
      esac
    ;;
    "OpenBSD"*)
      claim_unsupported_distro known "${distro}"
      ;;
    "NetBSD"*)
      claim_unsupported_distro known "${distro}"
      ;;
    "FreeBSD"*|"HardenedBSD"*|"DragonFly"*)
      claim_unsupported_distro known "${distro}"
      ;;
    *)
      claim_unsupported_distro unknown "${distro}"
      ;;
  esac

  if [ ! "$fedora_derivative_detected" = "1" ]; then
    return 0
  fi
  if ! test "${ci}" = "1"; then
    return 0
  fi
  if [ ! "${onion}" = "1" ]; then
    return 0
  fi

  die 0 "${underline}Distribution Test Result:${nounderline} Fedora on CI does not run the Tor systemd service. Skipped on CI to avoid breaking the CI testing."
}


check_not_qubes_template() {
  if ! test -f /run/qubes/this-is-templatevm; then
    true "INFO: Not running inside a Qubes Template."
    return 0
  fi

  qubes_template_detected=true
  user_warned_potential_startup_issue=true
  log warn "${underline}QubesOS Template Detection Test:${nounderline} 'Template detected'
- The installer has detected being run inside a Qubes Template."

  if test "${virtualbox_only}" = "1"; then
    true "INFO: Running inside a Qubes Template. Continuing via '--virtualbox-only' option."
    return 0
  fi

  ## Downloading non-Qubes VM images in Qubes Template makes no sense. Not even for development purposes.
  ## Installing VirtualBox inside Qubes however makes sense for development purposes.
  ## For example, this permits building non-Qubes VM images inside Qubes VMs.
  die 1 "${underline}QubesOS Template Detection Test:${nounderline} Only virtualbox-installer-cli ('--virtualbox-only') allowed in Qubes Template."
}

##############
## END MISC ##
##############

##########################
## BEGIN OPTION PARSING ##
##########################

## Begin parsing options.
## function should be called before the case statement to assign the options
## to a temporary variable
begin_optparse(){
  ## options ended
  test -z "${1:-}" && return 1
  shift_n=""
  ## save opt orig for error message to understand which opt failed
  opt_orig="${1}"
  # shellcheck disable=SC2034
  ## need to pass the second positional parameter cause maybe it is an argument
  arg_possible="${2}"
  clean_opt "${1}" || return 1
}


## Get arguments from options that require them.
## if option requires argument, check if it was provided, if true, assign the
## arg to the opt. If $arg was already assigned, and if valid, will use it for
## the key value
## usage: get_arg key
get_arg(){
  true "BEGIN get_arg(): '${*}'"
  ## if argument is empty or starts with '-', fail as it possibly is an option
  case "${arg:-}" in
    ""|-*)
      die 2 "Option '${opt_orig}' requires an argument."
      ;;
  esac
  set_arg "${1}" "${arg}"

  ## shift positional argument two times, as this option demands argument,
  ## unless they are separated by equal sign '='
  ## shift_n default value was assigned when trimming dashes '--' from the
  ## options. If shift_n is equal to zero, '--option arg', if shift_n is not
  ## equal to zero, '--option=arg'
  if test -z "${shift_n}"; then
    shift_n=2
  fi
  true "END get_arg(): '${*}'"
}


## Single source to set opts, can later be used to print the options parsed
## usage: set_arg variable value
set_arg(){
  ## Check if variable had already a value assigned. Expanding to empty value
  ## is necessary to avoid eval failing because of unset parameter if variable
  ## didn't have a value assigned before.
  # shellcheck disable=SC2016
  eval previous_value="$(printf '${%s:-}' "${1}")"

  ## Escaping quotes is needed because else it fails if the argument is quoted
  # shellcheck disable=SC2140
  eval "${1}"="\"${2}\""

  ## variable used for --getopt
  if test -z "${arg_saved:-}"; then
    arg_saved="${1}=\"${2}\""
  else
    if test -z "${previous_value:-}"; then
      ## If didn't add to the end of the list
      arg_saved="${arg_saved}\n${1}=\"${2}\""
    else
      ## If had, replace existing value.
      arg_saved="$(printf %s"${arg_saved}" | sed "s|^${1}=.*$|${1}=\"${2}\"|")"
    fi
  fi
  true "END set_arg(): '${*}'"
}


## Clean options.
## '--option=value' should shift once and '--option value' should shift twice
## but at this point it is not possible to be sure if option requires an
## argument, reset shift to zero, at the end, if it is still 0, it will be
## assigned to one, has to be zero here so we can check later if option
## argument is separated by space ' ' or equal sign '='
clean_opt(){
  case "${opt_orig}" in
    "")
      ## options ended
      return 1
      ;;
    --)
      ## stop option parsing
      shift 1
      return 1
      ;;
    --*=*)
      ## long option '--sleep=1'
      opt="${opt_orig%=*}"
      opt="${opt#*--}"
      arg="${opt_orig#*=}"
      shift_n=1
      ;;
    -*=*)
      ## short option '-s=1'
      opt="${opt_orig%=*}"
      opt="${opt#*-}"
      arg="${opt_orig#*=}"
      shift_n=1
      ;;
    --*)
      ## long option '--sleep 1'
      opt="${opt_orig#*--}"
      arg="${arg_possible}"
      ;;
    -*)
      ## short option '-s 1'
      opt="${opt_orig#*-}"
      arg="${arg_possible}"
      ;;
    *)
      ## not an option
      usage 2
      ;;
  esac
}


## Check if argument is within range
## usage:
## $ range_arg key "1" "2" "3" "4" "5"
## $ range_arg key "a" "b" "c" "A" "B" "C"
range_arg(){
  key="${1:-}"
  eval var='$'"${key}"
  shift 1
  list="${*:-}"
  #range="${list#"${1} "}"
  if [ -n "${var:-}" ]; then
    success=0
    for tests in ${list:-}; do
      ## only evaluate if matches all chars
      [ "${var:-}" = "${tests}" ] && success=1 && break
    done
    ## if not within range, fail and show the fixed range that can be used
    if [ ${success} -eq 0 ]; then
      die 2 "Option '${key}' cannot be '${var:-}'. Possible values: '${list}'"
    fi
  fi
}


## check if option has value, if not, error out
## this is intended to be used with required options
check_opt_filled(){
  key="${1}"
  eval val='$'"${key:-}"
  ! test -n "${val}" && die 2 "${key} is missing."
}
########################
## END OPTION PARSING ##
########################

###################
## BEGIN LOGGING ##
###################

## Logging mechanism with easy customization of message format as well as
## standardization on how the messages are delivered.
## usage: log [info|notice|warn|error] "X occurred."
log(){
  ## Avoid clogging output if log() is working alright.
  if test "${xtrace}" = "1"; then
    true "Removing xtrace for log() function."
    set +o xtrace
  fi
  log_type="${1}"
  ## capitalize log level
  log_type_up="$(echo "${log_type}" | tr "[:lower:]" "[:upper:]")"
  shift 1
  ## escape printf reserved char '%'
  # shellcheck disable=SC2001
  log_content="$(echo "${*}" | sed "s/%/%%/g")"
  ## set formatting based on log level
  case "${log_type}" in
    bug)
      log_color="${yellow}"
      ;;
    error)
      log_color="${red}"
      ;;
    warn)
      log_color="${magenta}"
      ;;
    info)
      log_color="${cyan}"
      ;;
    notice)
      log_color="${green}"
      ;;
    null)
      true
      ;;
    *)
      log bug "Unsupported log type specified: '${log_type}'"
      die 1 "Please report this bug."
  esac
  ## uniform log format
  log_color="${bold}${log_color}"
  log_full="${me}: [${log_color}${log_type_up}${nocolor}]: ${log_content}"
  ## error logs are the minimum and should always be printed, even if
  ## failing to assign a correct log type
  ## send bugs and error to stdout and stderr
  case "${log_type}" in
    bug)
      #printf %s"${log_full:+$log_full }Please report this bug.\n" 1>&2
      printf %s"${log_full}" 1>&2
      return 0
      ;;
    error)
      printf %s"${log_full}\n" 1>&2
      return 0
      ;;
    null)
      true
      ;;
  esac
  ## reverse importance order is required, excluding 'error'
  all_log_levels="warn notice info debug null"
  if echo " ${all_log_levels} " | grep -o ".* ${log_level} " \
    | grep -q " ${log_type}"
  then
    case "${log_type}" in
      warn)
        ## send warning to stdout and stderr
        printf %s"${log_full}\n" 1>&2
        ;;
      null)
        true
        ;;
      *)
        printf %s"${log_full}\n"
        ;;
    esac
  fi

  if test "${xtrace}" = "1"; then
    set -o xtrace
  fi
}


## For one liners 'log error; die'
## 'log' should not handle exits, because then it would not be possible
## to log consecutive errors on multiple lines, making die more suitable
## usage: die # "msg"
## where '#' is the exit code.
die(){
  log error "${2}"
  if test "${allow_errors}" = "1"; then
    log warn "Skipping termination because of with code '${1}' due to 'allow_errors' setting."
    return 0
  fi
  case "${1}" in
    106|107)
      true
      ;;
    *)
      log error "Installer aborting."
      ;;
  esac
  exit "${1}"
}


## Wrapper to log command before running to avoid duplication of code
log_run(){
  level="${1}"
  shift
  ## Extra spaces appearing when breaking log_run on multiple lines.
  command_without_extrarenous_spaces="$(echo "${@}" | tr -s " ")"
  if test "${dry_run}" = "1"; then
    log "${level}" "Skipping command: $ ${command_without_extrarenous_spaces}"
    return 0
  fi

  ## TODO: Still an issue? CI expects no output from root_cmd() which calls log_run().

  if test "${run_background}" = "1"; then
    log "${level}" "Background command starting: $ ${command_without_extrarenous_spaces} &"
    "${@}" &
    background_pid="$!"
    disown "$background_pid"
  else
    log "${level}" "Command executing: $ ${command_without_extrarenous_spaces}"
    "${@}" || return 1
  fi
}


## Useful to get runtime mid run to log easily
get_elapsed_time(){
  printf '%s\n' "$(($(date +%s) - start_time))"
}


## Log elapsed time, the name explains itself.
log_time(){
  log info "Time elapsed: $(get_elapsed_time)s."
}


## Wrapper to end the exit trap.
end_exit(){
  ## Reset exit trap.
  trap - EXIT HUP INT QUIT ABRT ALRM TERM
  ## Kill tail PID.
  if test -n "${tail_pid:-}"; then
    ## Sleep less than a second so the file descriptors have enough time to
    ## output all the logs to the screen before the background job is killed.
    sleep 0.3
    # shellcheck disable=SC2086
    kill -9 ${tail_pid}
  fi
  ## Exit with desired exit code.
  exit "${last_exit}"
}


## Handle exit trap with line it failed and its exit code.
handle_exit(){
  true "BEGIN handle_exit() with args: $*"
  last_exit="${1}"
  line_number="${2:-0}"
  log_time
  ## Exit without errors.
  test "${last_exit}" = "0" && end_exit
  ## Virtual Machine expected start issues.
  test "${last_exit}" = "106" && end_exit
  ## Virtual Machine unexpected start issues.
  test "${last_exit}" = "107" && end_exit
  ## Exit with errors.
  # shellcheck disable=SC3028
  if test -n "${BASH_COMMAND:-}"; then
    # shellcheck disable=SC2039,3028,3054
    log notice "Executed script, function, command executed: '${0}' '${FUNCNAME[1]}' '${BASH_COMMAND}'"
  else
    log notice "Executed script: '${0}'"
  fi
  ## some shells have a bug that displays line 1 as LINENO
  if test "${line_number}" -gt 2; then
    log error "Installer aborted due to an error."
    log error "No need to panic. Nothing is broken. Just some rare condition has been hit."
    log error "A solution likely exists for this issue."
    log error "If the issue does not recur on retry, it can be safely ignored as transient."
    log error "Consult ${guest_pretty} News and the User Help Forum for assistance."
    log error "Please report this bug if it has not been already."
    echo ""
    log error "An error occurred at line: '${line_number}'"
    ## ideas from https://unix.stackexchange.com/questions/39623/trap-err-and-echoing-the-error-line
    ## Simple version that doesn't indicate the error line.
    # pr -tn "${0}" | tail -n+$((line_number - 3)) | head -n3
    ## Easy version for wasting resources and better readability.
    line_above="$(pr -tn "${0}" | tail -n+$((line_number - 4)) | head -n4)"
    line_error="$(pr -tn "${0}" | tail -n+$((line_number)) | head -n1)"
    line_below="$(pr -tn "${0}" | tail -n+$((line_number + 1)) | head -n4)"
    printf '%s\n*%s\n%s\n' "${line_above}" "${line_error}" "${line_below}"
    ## Too complex.
    # awk 'NR>L-4 && NR<L+4 { printf " %-5d%3s %s\n",NR,(NR==L?">>>":""),$0 }' L="${line_number}" "${0}" >&2
    echo ""
    log error "Please include the user log and the debug log in your bug report."
    log error "(For file locations where to find these logs, see above.)"
    echo ""
  else
    if [ "${last_exit}" -gt 128 ] && [ "${last_exit}" -lt 193 ]; then
      signal_code=$((last_exit-128))
      signal_caught="$(kill -l "${signal_code}")"
      log error "Signal received: '${signal_caught}'"
    fi
  fi
  ## Print exit code.
  log error "Installer exited with code: '${last_exit}'"
  end_exit
}


#################
## END LOGGING ##
#################

###########################
## BEGIN SCRIPT SPECIFIC ##
###########################

claim_unsupported_distro(){
  status="${1}"
  distro="${2}"
  log error "At this time, your Operating System is unsupported by the ${guest_pretty} Installer."
  log error "Visit the following URL to check support for manual installation:"
  log error "    ${url_version_domain}/wiki/Virtualbox"
  die 101 "${underline}Distribution Check:${nounderline} Unsupported (${status} '${distro}') system."
}

## Get necessary packages for your host system to be able to set the guest.
get_host_pkgs(){
    log notice "Package Installation: installation of hypervisor-required packages... Please wait, as this could take a while..."
    if [ "$ubuntu_derivative_detected" = "1" ]; then
      install_package_debian_common
      install_virtualbox_ubuntu
    elif [ "$debian_derivative_detected" = "1" ]; then
      install_package_debian_common
      install_virtualbox_debian
    elif [ "$fedora_derivative_detected" = "1" ]; then
      install_package_fedora_common
      install_virtualbox_fedora
    else
      die 1 "Operating system not found in get_host_pkgs. Please report this bug. Debug log required."
    fi
}


get_independent_host_pkgs(){
  ## Platform independent packages
  if has signify-openbsd; then
    ## fix Debian unconventional naming
    signify(){
      # shellcheck disable=SC2317
      signify-openbsd "${@}"
    }
  fi

  has timeout || die 1 "${underline}Packages Installed Check:${nounderline} Timeout utility is missing."
  has curl || install_pkg curl
  has rsync || install_pkg rsync
  has mokutil || install_pkg mokutil
  has pgrep || install_pkg procps

  ## Install openssl and ca-certificates.
  ## openssl is required:
  ## Otherwise there will be an error message by rsync-ssl:
  ## Failed to find on your path: openssl stunnel4 stunnel
  ## ca-certificates is required:
  ## Otherwise rsync-ssl will fail TLS verification.
  ## XXX: Strictly speaking packages openssl ca-certificates are only required
  ##      if using clearnet. I.e. not required when using --onion.
  install_pkg openssl ca-certificates

  while true; do
    has systemd-detect-virt && nested_virt_tool="systemd-detect-virt" && break
    test_pkg virt-what && nested_virt_tool="virt-what" && break
    install_pkg virt-what && nested_virt_tool="virt-what" && break
    break
  done
}


nested_virtualization_test() {
  #nested_virtualization_detected=""
  if test -z "${nested_virt_tool:-}"; then
    ## No hard fail, not a requirement, good to have only.
    user_warned_potential_startup_issue=true
    log warn "${underline}Nested Virtualization Test:${nounderline} Detection tool for nested virtualization is missing."
  else
    if test "${dry_run}" = "1"; then
      log notice "Nested Virtualization Test: Skipping test due to dry_run mode."
    else
      ## Check if we are a guest of virtualization.
      if root_cmd "${nested_virt_tool:-}" >/dev/null 2>&1; then
        #nested_virtualization_detected=true
        user_warned_potential_startup_issue=true
        log warn "${underline}Nested Virtualization Test:${nounderline} Nested virtualization detected.
  - This might be a user error.
  - This installer is designed to run on the host operating system.
  - This installer is not designed to be run inside virtual machines.
  - For more information about nested virtualization, refer to:
  ${url_version_domain}/wiki/Nested_Virtualization"
      fi
    fi
  fi

  if test -f /usr/share/qubes/marker-vm; then
    #nested_virtualization_detected=true
    user_warned_potential_startup_issue=true
    log warn "${underline}QubesOS Detection Test:${nounderline} 'Qubes detected'
  - The installer is not designed for execution within Qubes.
  - Useful only for development purposes.
  - It is recommended to use Qubes-Whonix instead."
  fi
}


secure_boot_test() {
  local mokutil_output
  if mokutil_output=$(mokutil --sb-state 2>&1) ; then
    secure_boot_status="'enabled' (mokutil_output: '$mokutil_output')"
  else
    secure_boot_status="'disabled' (mokutil_output: '$mokutil_output')"
  fi
  log info "Secure Boot Check Result: $secure_boot_status Ok."
}


kernel_modules_load() {
  local modules_disabled
  ## Does usually not require root but might on some hardened systems.
  if ! modules_disabled=$(root_cmd_loglevel=null root_cmd cat /proc/sys/kernel/modules_disabled) ; then
    kernel_modules_can_be_load=maybe
    user_warned_potential_startup_issue=true
    log warn "${underline}Kernel Module Load Check Result:${nounderline} 'failed' (failed to cat /proc/sys/kernel/modules_disabled)"
    return 0
  fi
  if [ "$modules_disabled" = "0" ]; then
    kernel_modules_can_be_load=true
    log info "Kernel Module Load Check Result: 'yes' - modules can be load. (sysctl kernel.modules_disabled=0 is set.)"
    return 0
  fi
  kernel_modules_can_be_load=false
  log info "${underline}Kernel Module Load Check Result:${nounderline} 'no' - modules cannot be load. (sysctl kernel.modules_disabled=1 is set.)"
}


kernel_modules_signed_only() {
  local sig_enforce
  ## Does usually not require root but might on some hardened systems.
  if ! sig_enforce=$(root_cmd_loglevel=null root_cmd cat /sys/module/module/parameters/sig_enforce) ; then
    modules_signed_only=maybe
    user_warned_potential_startup_issue=true
    log warn "${underline}Kernel Module Signature Enforcement Check Result:${nounderline} 'failed' (failed to cat /sys/module/module/parameters/sig_enforce)"
    return 0
  fi
  if [ "$sig_enforce" = "Y" ]; then
    modules_signed_only=true
    log info "Kernel Module Signature Enforcement Check Result: 'yes' - only signed modules can be load. (kernel parameter module.sig_enforce=1 might be set.)"
    return 0
  fi
  modules_signed_only=false
  log info "Kernel Module Signature Enforcement Check Result: 'no' - unsigned modules can be load."
}


need_reboot_check_first() {
  ## Debian: /var/run/reboot-required
  ## Fedora: Does not have this.
  if ! test -f /var/run/reboot-required ; then
    log info "Reboot Check Result: File /var/run/reboot-required does not exist, good."
    return 0
  fi

  ## Building for an old kernel might result in missing kernel headers for that kernel
  ## In result, VirtualBox would fail to start.
  die 1 "${underline}Reboot Check Result:${nounderline} Your system reports that a reboot is required.

Please reboot your system and restart this installer.

Debugging information: file /var/run/reboot-required exists."
}


need_reboot_check_second() {
  true "fedora_derivative_detected: $fedora_derivative_detected"
  if [ ! "$fedora_derivative_detected" = "1" ]; then
    return 0
  fi

  ## Fedora 38: Part of dnf-utils. Not installed by default (on CI).
  ## Fedora 39: Part of dnf-plugins-core. Not installed by default (on CI).
  ## Therefore this can only run after install_package_fedora_common.
  if root_cmd /usr/bin/needs-restarting --reboothint ; then
    true "INFO: No reboot required."
    return 0
  fi

  if test "${ci}" = "1"; then
    true "INFO: Ignore need_reboot_check_second because running on CI."
    return 0
  fi

  die 1 "${underline}Reboot Check Result:${nounderline} Your system reports that a reboot is required.

Please reboot your system and restart this installer.

Debugging information: needs-restarting reported that a reboot is required."
}


update_sources(){
  log notice "Updating package list..."

  ## global console_write_command
  if tty >/dev/null >&1 ; then
    console_write_command="tee /dev/tty"
  else
    ## github actions CI issue:
    ## tee: /dev/tty: No such device or address
    ## https://github.com/actions/runner/issues/241
    console_write_command="cat"
  fi

  #root_cmd ${pkg_mngr_update} 2>&1 || true
  #update_sources_error
  ## result: OK: command_without_extrarenous_spaces="sudo -- apt-get update --yes --error-on=any"
  ## But if root_cmd is run in a subshell using $(root_cmd ...) then command_without_extrarenous_spaces
  ## won't be updated.

  local simulate_only_maybe=""
  if test "${noupdate}" = "1"; then
    ## Too slow to run over and over again during testing.
    simulate_only_maybe=true
    log warn "Package List Update: Simulate only, via '--noupdate' option."
  fi

  # shellcheck disable=SC2086
  if update_output=$(root_cmd ${simulate_only_maybe} ${pkg_mngr_update} 2>&1 | $console_write_command) ; then
    true "INFO: Exit code is zero but that does not guarantee in case of dnf that there is no error."
    if echo "$update_output" | grep --quiet --ignore-case "Error:" ; then
      log error "${underline}Package List Update:${nounderline} Exit code was 0 but 'Error:' found in output."
      update_sources_error
    else
      true "INFO: No error found in update output, ok."
      return 0
    fi
  else
    log error "${underline}Package List Update:${nounderline} Non-zero exit code. Stop."
    update_sources_error
  fi
}


package_manager_issue_extra_help_text="The user is advised to attempt to debug this with the following steps:
1. Run above command as root (with sudo).
2. If there is an issue, use search engines, documentation and if needed
   contact the support of your operating system.
3. Once this has been fixed fixed, re-run this installer."


update_sources_error() {
  die 1 "${underline}Package List Update:${nounderline} Could not update package lists.
  - This issue is most likely not caused by this installer.
  - This is most likely a package manager configuration or network issue.

This is the command which the installer has just run that failed:

${sucmd} ${pkg_mngr_update}

${package_manager_issue_extra_help_text}"
}


check_upgrades_simulation() {
  # shellcheck disable=SC2086
  if upgrade_simulate_output=$(root_cmd ${pkg_mngr_upgrade_check} ${install_pkg_fasttrack_extra_args_maybe} 2>&1 | $console_write_command) ; then
    true "INFO: Exit code is zero but that does not guarantee in case of dnf that there is no error."
    if echo "$upgrade_simulate_output" | grep --quiet --ignore-case "Error:" ; then
      log error "${underline}Package Upgrade Simulation:${nounderline} Exit code was 0 but 'Error:' found in output."
      upgrade_simulate_sources_error
    fi
  else
    log error "${underline}Package Upgrade Simulation:${nounderline} Non-zero exit code. Stop."
    upgrade_simulate_sources_error
  fi

  true "INFO: No error found in upgrade_simulate_output output, ok."
  local number_upgradable
  number_upgradable="$(${pkg_mngr_upgradable_check} 2>/dev/null| wc -l)"
  ## First line is just reports.
  number_upgradable="$((number_upgradable-1))"

  if test "${dry_run}" = "1"; then
    number_upgradable=0
  fi

  if [ "$number_upgradable" = "0" ]; then
    log info "Package Upgrade Simulation: No packages require upgrading, ok."
    return 0
  fi

  if test "${noupdate}" = "1"; then
    log warn "Package Upgrade Simulation: Package upgrades available but proceeding anyhow via '--noupdate' option."
    return 0
  fi

  die 1 "${underline}Package Upgrade Simulation:${nounderline} Package upgrades available.

'${number_upgradable}' packages can be upgraded.

Please upgrade your operating system first. Otherwise this installer cannot proceed.

${sucmd} ${pkg_mngr_upgrade_install} ${install_pkg_fasttrack_extra_args_maybe}

${package_manager_issue_extra_help_text}"

}

upgrade_simulate_sources_error() {
  die 1 "${underline}Package Upgrade Simulation:${nounderline} Failed.
  - This issue is most likely not caused by this installer.
  - This is most likely a package manager configuration or network issue.

This is the command which the installer has just run that failed:

${sucmd} ${pkg_mngr_upgrade_check} ${install_pkg_fasttrack_extra_args_maybe}

${package_manager_issue_extra_help_text}"
}


## Install package only if not installed already.
install_pkg(){
  pkgs="${*}"
  special_args=""
  pkg_not_installed=""

  for arg in ${pkgs}; do
    case "${arg}" in
      --target-release=*)
        special_args="${special_args} ${arg}"
        ;;
      *)
        ## Test if package exists as a binary or a library, using different tools.
        # shellcheck disable=SC2086
        if ${pkg_mngr_check_installed} "${arg}" >/dev/null 2>&1; then
          log info "Package already installed: '${arg}'"
          continue
        fi
        if has "${arg}"; then
          log info "Program already installed: '${arg}'"
          continue
        fi

        pkg_not_installed="${pkg_not_installed} ${arg}"
        ;;
    esac
  done

  if test -n "${pkg_not_installed}"; then
    if test "${dry_run}" = "1"; then
      log notice "Skipping installation of the following packages via '--dry-run' option: '${pkg_not_installed}'"
      return 0
    fi

    log notice "Installing package(s): '${pkg_not_installed}'"
    log info "special_args: '${special_args}'"

    # shellcheck disable=SC2086
    if ! root_cmd ${pkg_mngr_install} ${special_args} ${pkg_not_installed} ; then
      if echo "${pkg_not_installed}" | grep --quiet --ignore-case virtualbox ; then
        virtualbox_installation_failure_debug
      fi
      die 1 "${underline}Package Installation:${nounderline} Failed to install package: '${pkg_not_installed}'"
    fi

    ## Test if installation succeeded.
    test_pkg "${pkg_not_installed}"
  fi
}


## Used to test for a 2nd time if packages exist or not, if not,
## install_pkg() failed above and best thing to do is abort because of missing
## dependencies.
test_pkg(){
  pkgs="${*}"
  pkg_not_installed=""
  for pkg in ${pkgs}; do
    if ! has "${pkg}" &&
      ! ${pkg_mngr_check_installed} "${pkg}" >/dev/null 2>&1
    then
      pkg_not_installed="${pkg_not_installed} ${pkg}"
    fi
  done

  if test -n "${pkg_not_installed}"; then
    if test "${dry_run}" = "1"; then
      log error "Failed to locate package(s) and ignoring via '--dry-run' option: '${pkg_not_installed}'"
    else
      log error "Failed to locate package(s): '${pkg_not_installed}'"
      return 1
    fi
  fi
}


check_vm_running_general() {
  case "${guest}" in
    whonix)
        check_vm_running_virtualbox "${guest_full_vm_name_gateway}"
        check_vm_running_virtualbox "${guest_full_vm_name_workstation}"
      ;;
    kicksecure)
        check_vm_running_virtualbox "${guest_full_vm_name_kicksecure}"
      ;;
  esac
}


## Abort if user wants to reimport a VM that is running.
## This function is called before attempting to reimport an image.
check_vm_running_virtualbox(){
  vm="${1}"
  ## Paused state should be considered as running. Instead of grepping
  ## possible states, grep VM from list of running VMs.
  # vboxmanage list runningvms | grep -q "^\"${vm}\" "
  if vboxmanage showvminfo "${vm}" 2>&1 | \
    grep -qE "^State:[[:space:]]+(running|paused)"
  then
    log error "Cannot proceed. You have the following VM running: ${vm}"
    die 1 "${underline}VM Running Check:${nounderline} Please turn it off before re-running this installer."
  fi
}


## Check if VM exists on VirtualBox
check_vm_registered_virtualbox(){
  local extra_message
  extra_message="$1"

  case "${guest}" in
    whonix)
      ## Test if machine exists.
      workstation_exists=0
      gateway_exists=0
      if vboxmanage showvminfo "${guest_full_vm_name_gateway}" >/dev/null 2>&1 ; then
        gateway_exists=1
        log info "Existing VM Check Result $extra_message: guest '${guest_full_vm_name_gateway}' exists."
      fi
      if vboxmanage showvminfo "${guest_full_vm_name_workstation}" >/dev/null 2>&1 ; then
        workstation_exists=1
        log info "Existing VM Check Result $extra_message: guest '${guest_full_vm_name_workstation}' exists."
      fi
      ## Find discrepancies.
      if test "${workstation_exists}" = "0" && test "${gateway_exists}" = "1" ; then
        log info "Existing VM Check Result $extra_message: Gateway exists but Workstation doesn't."
      fi
      if test "${workstation_exists}" = "1" && test "${gateway_exists}" = "0" ; then
        log info "Existing VM Check Result $extra_message: Workstation exists but Gateway doesn't."
      fi
      vm_or_vms_already_existing_test_result=false
      if test "${workstation_exists}" = "1" || test "${gateway_exists}" = "1" ; then
        ## If either one of the guests exists, proceed.
        vm_or_vms_already_existing_test_result=true
      fi
      if test "${vm_or_vms_already_existing_test_result}" = "false" ; then
        ## Both guests are still non-existing. Therefore return from this function.
        log info "Existing VM Check Result $extra_message: None existing yet, ok."
        return 0
      fi
      log notice "Existing VM Check Result $extra_message: Virtual Machine(s) have been imported previously."
      ;;
    kicksecure)
      vm_or_vms_already_existing_test_result=false
      if ! vboxmanage showvminfo "${guest_full_vm_name_kicksecure}" >/dev/null 2>&1 ; then
        log info "Existing VM Check Result $extra_message: None existing yet, ok."
        return 0
      fi
      log notice "Existing VM Check Result $extra_message: Virtual Machine(s) were imported previously."
      vm_or_vms_already_existing_test_result=true
      ;;
  esac
}


## Check if VM exists using hypervisor tools.
check_vm_exists_general(){
  if test "${virtualbox_only}" = "1"; then
    return 0
  fi

  if [ "${hypervisor}" = "kvm" ]; then
    return 0
  fi

  check_vm_registered_virtualbox "$1"
}


check_vm_file_exists_virtualbox_general() {
  ## '/home/user/VirtualBox VMs/Kicksecure-Xfce/Kicksecure-Xfce.vbox'
  ## '/home/user/VirtualBox VMs/Whonix-Gateway-Xfce/Whonix-Gateway-Xfce.vbox'
  ## '/home/user/VirtualBox VMs/Whonix-Workstation-Xfce/Whonix-Workstation-Xfce.vbox'

  if [ -z "${HOME+x}" ]; then
    log warn "VM Import Check: Skip testing if there is an extraneous '.vbox' file because environment variable HOME is unset."
    return 0
  fi

  local file_name_list=()
  case "${guest}" in
    whonix)
      if test "${import_only}" = "gateway" ; then
        file_name_list+=("$HOME/VirtualBox VMs/${guest_full_vm_name_gateway}/${guest_full_vm_name_gateway}.vbox")
      elif test "${import_only}" = "workstation" ; then
        file_name_list+=("$HOME/VirtualBox VMs/${guest_full_vm_name_workstation}/${guest_full_vm_name_workstation}.vbox")
      else
        file_name_list+=("$HOME/VirtualBox VMs/${guest_full_vm_name_gateway}/${guest_full_vm_name_gateway}.vbox")
        file_name_list+=("$HOME/VirtualBox VMs/${guest_full_vm_name_workstation}/${guest_full_vm_name_workstation}.vbox")
      fi
    ;;
    kicksecure)
      file_name_list+=("$HOME/VirtualBox VMs/${guest_full_vm_name_kicksecure}/${guest_full_vm_name_kicksecure}.vbox")
    ;;
  esac

  local file_name_item
  for file_name_item in "${file_name_list[@]}" ; do
    if test -e "$file_name_item" ; then
      log warn "VM Import Check: Inconsistent state.
This might have happened by previously using VirtualBox GUI 'Remove...' with 'Remove only' instead of 'Delete all files'.
File '$file_name_item' exists but there is no associated VM registered in VirtualBox."
      if test -z "${import_only}"; then
        die 1 "VM Import Check: Aborting because of inconsistent state and missing '--import-only' option."
      fi
      if test "${destroy_existing_guest}" != "1"; then
        die 1 "VM Import Check: Aborting because ofinconsistent state and missing '--destroy-existing-guest' option."
      fi
      log warn "VM superfluous '.vbox' File Deletion: Removing file '$file_name_item' via '--import-only=${import_only}' and '--destroy-existing-guest' option."
      log_run warn rm -f -- "${file_name_item}"
    fi
  done
}


vm_delete_kicksecure() {
  if test "${vm_or_vms_already_existing_test_result}" = "true"; then
    log_run notice vboxmanage unregistervm "${guest_full_vm_name_kicksecure}" --delete
  else
    log notice "VM Deletion: Kicksecure VM does not exist, no need to delete, ok."
  fi
}


vm_delete_gateway() {
  if test "${gateway_exists}" = "1"; then
    log_run notice vboxmanage unregistervm "${guest_full_vm_name_gateway}" --delete
  else
    log notice "VM Deletion: Gateway VM does not exist, no need to delete, ok."
  fi
}


vm_delete_workstation() {
  if test "${workstation_exists}" = "1"; then
    log_run notice vboxmanage unregistervm "${guest_full_vm_name_workstation}" --delete
  else
    log notice "VM Deletion: Workstation VM does not exist, no need to delete, ok."
  fi
}


vm_delete_maybe() {
  case "${guest}" in
    whonix)
      if test "${destroy_existing_guest}" = "1"; then
        ## '--destroy-existing-guest' option is set.
        if test "${import_only}" = "gateway" ; then
          log warn "VM Deletion: 'yes' - Deleting previously imported gateway via '--import-only=gateway' option... (If it exists.)"
          vm_delete_gateway
        elif test "${import_only}" = "workstation" ; then
          log warn "VM Deletion: 'yes' - Deleting previously imported workstation via '--import-only=workstation' option... (If it exists.)"
          vm_delete_workstation
        elif test "${import_only}" = "both" ; then
          log warn "VM Deletion: 'yes' - Deleting previously imported gateway via '--import-only=both' option... (If it exists.)"
          vm_delete_gateway
          log warn "VM Deletion: 'yes' - Deleting previously imported workstation via '--import-only=both' option... (If it exists.)"
          vm_delete_workstation
        else
          die 1 "VM Deletion: 'no' - Not deleting previously any imported VMs because '--import-only' option is not set..."
        fi
      else
        ## '--destroy-existing-guest' option not yet.
        if test -n "${import_only}" ; then
          if test "${gateway_exists}" = "1" && test "${import_only}" = "gateway" ; then
            die 1 "${underline}Existing VM Check Result:${nounderline} '--import-only' option was set to 'gateway', but it already exists and '--destroy-existing-guest' option was not set."
          elif test "${workstation_exists}" = "1" && test "${import_only}" = "workstation" ; then
            die 1 "${underline}Existing VM Check Result:${nounderline} '--import-only' option was set to 'workstation', but it already exists and '--destroy-existing-guest' option was not set."
          fi
        else
          log info "Existing VM Check: Neither '--destroy-existing-guest' nor '--import-only' option was set, ok."
        fi
      fi
      ;;
    kicksecure)
      if test "${destroy_existing_guest}" = "1"; then
        ## If VMs exists and '--destroy-existing-guest' is set, remove VMs as they are gonna
        ## be imported later by main.
        log warn "VM Deletion: 'yes' - Deleting previously imported Virtual Machine(s) via '--destroy-existing-guest' option. (If it exists.)"
        vm_delete_kicksecure
      else
        log notice "VM Deletion: 'no' - Not deleting previously any imported VMs because neither using '--destroy-existing-guest' option."
      fi
      ;;
  esac
}


## Check if guest should start or not
check_guest_boot(){
  if test "${virtualbox_only}" = "1"; then
    return 0
  fi
  if [ "${hypervisor}" = "kvm" ]; then
    return 0
  fi

  ## Refresh variables vm_or_vms_already_existing_test_result, gateway_exists and workstation_exists.
  check_vm_exists_general "(check after import)"

  case "${guest}" in
    whonix)
      if test "${gateway_exists}" = "1" ; then
        log notice "Available guest: '${guest_full_vm_name_gateway}'"
      fi
      if test "${workstation_exists}" = "1" ; then
        log notice "Available guest: '${guest_full_vm_name_workstation}'"
      fi
      ;;
    kicksecure)
      log notice "Available guest: '${guest_full_vm_name_kicksecure}'"
      ;;
  esac

  if [ "$kernel_module_has_been_load" = "false" ]; then
    ## Kernel modules have not been load.
    user_warned_potential_startup_issue=true
    log warn "Debugging information:
Secure Boot Status: '$secure_boot_status'
Kernel module has been load: '$kernel_module_has_been_load'
Kernel module can be load: '$kernel_modules_can_be_load' (modules can be load. (sysctl kernel.modules_disabled=0 is set.)
Only signed kernel modules can be load: '$modules_signed_only'
Kernel module vboxdrv signer: '$kernel_module_signer'
kernel_module_modprobe_output ($sucmd modprobe vboxdrv): '$kernel_module_modprobe_output'"

    if [ "$kernel_modules_can_be_load" = "true" ]; then
      log error "${underline}VirtualBox Installation Result:${nounderline} ${red}${bold}'FAIL'${nobold}${nocolor} - because kernel modules have not been load yet.
  - Kernel modules can be load in theory, should be loaded by now, but are not.
  - This is a VirtualBox installation issue."
      if ! test "${ci}" = "1"; then
        virtualbox_start_failed
      fi
    else
      log error "${underline}VirtualBox Installation Result:${nounderline} ${red}${bold}'REBOOT REQUIRED'${nobold}${nocolor} - because kernel module loading is disabled on your system:
  - The system administrator might have disabled module loading.
  - Module loading might have been disabled by Kicksecure package security-misc.
  - You can re-run this installer again after reboot."
      if ! test "${ci}" = "1"; then
        virtualbox_start_failed
      fi
    fi
  fi

  log notice "${underline}VirtualBox Installation Result:${nounderline} 'success'"

  log info "VM Start: Checking if user wants to start Virtual Machine(s) now..."

  if test "${qubes_template_detected}" = "true"; then
    log notice "${underline}VirtualBox Startup Check:${nounderline} Not starting VirtualBox because running inside a Qubes Template."
    ## Avoid needlessly starting VirtualBox inside a Qubes Template.
    ## That would not be useful, would create unnecessary files inside the Template's home folder and might be confusing.
    ## What instead might be useful for development purposes is to install VirtualBox inside a Qubes Template for the purpose
    ## of using a Qubes App Qube for building VirtualBox VM images.
    ## Run end_installer here, because no VMs were downloaded anyhow if a Qubes Template was detected.
    end_installer
  elif test "${no_boot}" = "1"; then
    log notice "${underline}VirtualBox Startup Check:${nounderline} User declined to start VirtualBox via '--no-boot' option."
    log notice "VirtualBox can be started manually."
    ## Not running end_installer here, because that happens below and we want the following output messages.
    #end_installer
  elif test "${non_interactive}" = "1"; then
    log notice "${underline}VirtualBox Startup Check:${nounderline} Starting VirtualBox automatically via '--non-interactive' option."
    if test "${virtualbox_only}" = "1"; then
      start_virtualbox_gui
      end_installer
    fi
  else
    if test "${virtualbox_only}" = "1"; then
      log notice "${bold}Question:${nobold} Do you want to start VirtualBox now? [y/n] (default: yes): "
    else
      log notice "${bold}Question:${nobold} Do you want to start VirtualBox and the ${guest_pretty} Virtual Machine(s) now? [y/n] (default: yes): "
    fi
    printf '%s' "Your answer: "
    local response
    read -r response
    log notice "User replied: '${response}'"
    case ${response} in
      ""|[Yy]|[Yy][Ee][Ss])
        log notice "${underline}VirtualBox Startup Check:${nounderline} User accepted to start VirtualBox."
        if test "${virtualbox_only}" = "1"; then
          start_virtualbox_gui
          end_installer
        fi
        ;;
      *)
        log notice "${underline}VirtualBox Startup Check:${nounderline} User declined to start VirtualBox."
        end_installer
        ;;
    esac
  fi

  log info "Virtual Machine(s) already exist."
  if test "${redownload}" != "1"; then
    log notice "Hint: If you would like to redownload the image, read about '--redownload' option (safe)."
  fi
  if test "${destroy_existing_guest}" != "1"; then
    log notice "Hint: If you would like to delete a VM and re-import, read about '--destroy-existing-guest' option (danger)."
  fi

  if test "${no_boot}" = "1"; then
    ## Skip guest boot
    log notice "${underline}VM Startup Check:${nounderline} User declined to start Virtual Machine(s) via '--no-boot' option."
    log notice "Virtual Machine(s) can be started manually."
    end_installer
  fi

  if test "${non_interactive}" = "1"; then
    ## start guest without interaction
    log notice "${underline}VM Startup Check:${nounderline} VM start agreed by the user via '--non-interactive' setting."
    ## Try to start VMs before trying to start VirtualBox Manager,
    ## because if it fails, it is less confusing to avoid starting VirtualBox Manager.
    start_guest
    start_virtualbox_gui
    end_installer
  fi

  case ${response} in
    ""|[Yy]|[Yy][Ee][Ss])
      log notice "${underline}VM Startup Check:${nounderline} User accepted to start Virtual Machine(s)."
      start_guest
      start_virtualbox_gui
      ;;
    *)
      log notice "${underline}VM Startup Check:${nounderline} User declined to start Virtual Machine(s)."
      log notice "The following Virtual Machine(s) can be started manually: '${guest_pretty}'"
      ;;
  esac
  end_installer
}


import_guest(){
  if test "${virtualbox_only}" = "1"; then
    return 0
  fi

  if test "${no_import}" = "1"; then
    log notice "VM Import: Not importing guest via '--import-only' option."
    end_installer
  fi

  case "${hypervisor}" in
    virtualbox)
      import_virtualbox
      ;;
    kvm)
      import_kvm
      ;;
  esac
}


extract_vm_name_from_virtualbox_ova() {
  local output="$1"
  local system_number="$2"
  local a b c d
  a=$(echo "$output" | grep --max-count=1 --after-context=4 "Virtual system $system_number:")
  b=$(echo "$a" | grep "Suggested VM name")
  c=$(echo "$b" | grep -oP '"\K[^"]+')
  ## Take first word only because VirtualBox would suggest name "Whonix-Gateway-Xfce 1" in case,
  ## a VM "Whonix-Gateway-Xfce" is already registered in VirtualBox.
  d=$(echo "$c" | awk '{print $1}')
  echo "$d"
}


## Import VirtualBox images
import_virtualbox(){
  ## Check how many systems to import.
  ## vsys 0: gateway
  ## vsys 1: workstation

  case "${guest}" in
    whonix)
      ## if importing whonix, import 2 virtual systems
      vbox_arg_normal="--vsys 0 --eula accept --vsys 1 --eula accept"
    ;;
    kicksecure)
      vbox_arg_normal="--vsys 0 --eula accept"
    ;;
  esac

  vbox_arg_general="${vbox_arg_normal}"
  vm_purge="purgeme"

  case "${import_only}" in
    workstation)
      vbox_arg_importonly="--vsys 0 --eula accept --vmname ${vm_purge} --vsys 1 --eula accept"
      vbox_arg_general="${vbox_arg_importonly}"
      ;;
    gateway)
      vbox_arg_importonly="--vsys 0 --eula accept --vsys 1 --eula accept --vmname ${vm_purge}"
      vbox_arg_general="${vbox_arg_importonly}"
      ;;
    "")
      ;;
  esac

  local do_continue
  if test "${vm_or_vms_already_existing_test_result}" = "true" ; then
    if test -n "${import_only}"; then
      do_continue=yes
      log info "VM Import Check Result: Continue via '--import-only' option."
    else
      do_continue=no
      log info "VM Import Check Result: Skipping import because at least 1 VM already exists but '--import-only' option is not set."
    fi
  else
    do_continue=yes
    log info "VM Import Check Result: Continue because no VM(s) exist yet."
  fi
  if [ "$do_continue" = "no" ]; then
    log notice "VM Import Check Result: Skipping to import, because Virtual Machine(s) have been imported previously and not using '--import-only' option."
    return 0
  fi

  check_vm_file_exists_virtualbox_general

  local output
  # TODO: vboxmanage localce needs to be C so output can be grepped.
  #lc_all="$LC_ALL"
  #export LC_ALL=C
  # shellcheck disable=SC2086
  output=$(log_run notice vboxmanage import "${directory_prefix}/${guest_file}.${guest_file_ext}" ${vbox_arg_normal} --dry-run) || \
    die 105 "${underline}VM Import:${nounderline} Failed to import virtual machines."
  log info "OUTPUT: $output"
  #export LC_ALL="$lc_all"

  case "${guest}" in
    whonix)
      vsys_0_actual=$(extract_vm_name_from_virtualbox_ova "$output" 0) || true
      vsys_1_actual=$(extract_vm_name_from_virtualbox_ova "$output" 1) || true
      if [ ! "${guest_full_vm_name_gateway}" = "${vsys_0_actual}" ]; then
        die 105 "${underline}VM Import:${nounderline} BUG: vsys0 is actually '${vsys_0_actual}', not '${guest_full_vm_name_gateway}'."
      fi
      if [ ! "${guest_full_vm_name_workstation}" = "$vsys_1_actual" ]; then
        die 105 "${underline}VM Import:${nounderline} BUG: vsys1 is actually '${vsys_1_actual}', not '${guest_full_vm_name_workstation}'."
      fi
      log info "vsys_0_actual: ${vsys_0_actual}"
      log info "vsys_1_actual: ${vsys_1_actual}"
    ;;
    kicksecure)
      vsys_0_actual=$(extract_vm_name_from_virtualbox_ova "$output" 0) || true
      if [ ! "${guest_full_vm_name_kicksecure}" = "${vsys_0_actual}" ]; then
        die 105 "${underline}VM Import:${nounderline} BUG: vsys0 is actually '${vsys_0_actual}', not '${guest_full_vm_name_kicksecure}'."
      fi
      log info "vsys_0_actual: ${vsys_0_actual}"
    ;;
  esac

  log notice "VM Import: Importing Virtual Machine(s)..."

  ## import VirtualBox image
  # shellcheck disable=SC2086
  log_run notice vboxmanage import "${directory_prefix}/${guest_file}.${guest_file_ext}" ${vbox_arg_general} || \
    die 105 "${underline}VM Import:${nounderline} Failed to import virtual machines."

  ## VirtualBox does not accept any command to import a single virtual system
  ## out from an ova with multiple ones.
  ## https://forums.virtualbox.org/viewtopic.php?f=1&t=107965
  if test -n "${import_only}" && test "${import_only}" != "both"; then
    log_run notice vboxmanage unregistervm "${vm_purge}" --delete ||
      die 1 "${underline}VM Import:${nounderline} Failed to remove extraneous VM '${vm_purge}'."
  fi

  log notice "VM Import: 'success'"
  log notice "You can now open the VirtualBox application and start using: '${guest_pretty}'"
}


## Import KVM images
import_kvm(){
  ## placeholder
  log notice "KVM import feature does not exist. Ending run."
  exit 0
}


start_guest(){
  if test "${virtualbox_only}" = "1"; then
    return 0
  fi
  case "${hypervisor}" in
    virtualbox)
      start_virtualbox_vm
      ;;
    kvm)
      start_kvm_vm
      ;;
  esac
}


## Start the hypervisor with the desired guest
start_virtualbox_vm() {
  log notice "Virtual Machine Startup: Starting Virtual Machine(s)..."
  ## 'virtualbox' is called after 'vboxmanage' because it hangs till the app
  ## is closed, while 'vboxmanage startvm' exits after starting the VMs.
  case "${guest}" in
    whonix)
      if test "${gateway_exists}" = "1" ; then
        log_run notice vboxmanage startvm "${guest_full_vm_name_gateway}" || virtualbox_start_failed
      fi
      if test "${workstation_exists}" = "1" ; then
        log_run notice vboxmanage startvm "${guest_full_vm_name_workstation}" || virtualbox_start_failed
      fi
      ;;
    kicksecure)
      log_run notice vboxmanage startvm "${guest_full_vm_name_kicksecure}" || virtualbox_start_failed
      ;;
  esac
  log notice "${underline}Virtual Machine Startup Result:${nounderline} 'success'"
}


start_virtualbox_gui() {
  if pgrep 'VirtualBox$' >/dev/null ; then
    log notice "VirtualBox Manager Startup Result: Not starting duplicate VirtualBox GUI because already running."
    return 0
  fi

  run_background=1
  log_run notice virtualbox
  if ! test "${dry_run}" = "1"; then
    log notice "VirtualBox Manager Startup Result: Launched VirtualBox GUI into the background. (pid: '$background_pid')"
  fi
  run_background=""
}


virtualbox_start_failed() {
  local likely_cause
  likely_cause=""
  if [ "$user_warned_potential_startup_issue" = "true" ]; then
    likely_cause="- This is likely happening due to the warnings that have been reported above."
  fi
  die 106 "${underline}Virtual Machine Startup Result:${nounderline} ${red}${bold}FAIL${nobold}${nocolor}
  $likely_cause
  - The installer succeeded with download and import, but
  - failed to start the virtual machines (VMs).
  - The root cause for this issue is likely not the installer.
  - This issue would likely also happen if the user tried to manually start the VMs.
  - Resolving these issues (as per documentation hyperlinks above) would likely resolve this issue.
  ${url_version_domain}/wiki/VirtualBox/Troubleshooting"
}


## Detect if repository is configured in the sources list.
get_pattern_sources_debian(){
  file="${1}"
  pattern="${2}"
  grep -v "#" "${file}" | grep -q -E "${pattern}" || return 1
}

write_sources_debian(){
  url="${1}"
  file="${2}"
  echo "${url}" | root_cmd tee "${file}" ||
    die 1 "${underline}Sources List Writer:${nounderline} Failed to write to file: '${file}'"
}


## https://stackoverflow.com/a/54239534
## "apt list --installed $pkg" does not fail if package is not installed.
check_installed_debian(){
  status="$(dpkg-query --show --showformat='${db:Status-Status}' "$1" 2>&1)"
  if test "$?" != 0 || test "$status" != "installed"; then
    return 1
  fi
  return 0
}


install_package_fedora_common(){
  pkg_mngr="dnf"
  pkg_mngr_install="${pkg_mngr} install --assumeyes --setopt=install_weak_deps=False"
  ## Fedora lacks an equivalent to Debian's '--error-on=any'.
  #pkg_mngr_update="${pkg_mngr} update --assumeyes"
  ## 'dnf makecache' does exit non-zero if a repository is unavailable.
  ## --assumeyes good or bad idea? For now not needed. So not using.
  #pkg_mngr_update="${pkg_mngr} makecache"
  pkg_mngr_update="${pkg_mngr} --assumeyes update"
  pkg_mngr_check_installed="${pkg_mngr} list installed"
  pkg_mngr_upgrade_check="/bin/true 'dnf does not seem to support an alternative to apt-get full-upgrade --simulate, skipping.'"
  pkg_mngr_upgradable_check="/bin/true 'dnf does not seem to support an alternative to apt-get full-upgrade --simulate, skipping.'"
  pkg_mngr_upgrade_install="${pkg_mngr} upgrade"

  update_sources
  #check_upgrades_simulation

  if test "${virtualbox_only}" = "1"; then
    return 0
  fi

  ## TODO: remove dnf-utils when removing Fedora 38 support from CI.
  install_pkg torsocks redhat-lsb-core dnf-plugins-core dnf-utils
  install_signify signify
}


install_package_debian_common(){
  pkg_mngr="apt-get"
  pkg_mngr_install="${pkg_mngr} install --yes --no-install-recommends"
  pkg_mngr_update="${pkg_mngr} update --yes --error-on=any"
  pkg_mngr_check_installed="check_installed_debian"
  pkg_mngr_upgrade_check="${pkg_mngr} full-upgrade --simulate"
  pkg_mngr_upgradable_check="apt list --upgradable"
  pkg_mngr_upgrade_install="${pkg_mngr} full-upgrade"

  ## 'dpkg --audit' does not return non-zero exit code on failure.
  dpkg_audit_output="$(dpkg --audit 2>&1)"
  if test -n "${dpkg_audit_output}"; then
    die 1 "${underline}DPKG Audit Test Result:${nounderline} ${red}${bold}'FAIL'${nobold}${nocolor}
- What happened in simple terms? This installer has performed a check to ensure it's sane to proceed, which has failed.
- What exactly happened? The command 'dpkg --audit' generated output, signaling a system issue.
- What was the expected behavior? The 'dpkg --audit' command should execute without producing any output.
- Is this installer to blame for the issue? It's unlikely that this installer is the root cause of the issue.
- So, what might have caused it? The issue likely originates from pre-existing DPKG / APT package management system issues on your machine.
- What steps should you take now? Start by running the following command yourself:

dpkg --audit

- What should you do after that? Analyze the output of the command to identify and address the underlying problem. Once resolved, you can re-run this installer.

- Do you have any suggestions? The following link might offer helpful insights:

https://www.kicksecure.com/wiki/Operating_System_Software_and_Updates#Broken_APT

If that doesn't resolve the issue, consider reaching out to your operating system's support team for assistance."
  fi

  ## Dumping all sources.list files could have privacy implications.
  ## Hence only doing it for '--dev'.
  if test "${dev}" = "1"; then
    if [ -f /etc/apt/sources.list ]; then
      cat /etc/apt/sources.list
    fi
    for file in /etc/apt/sources.list.d/*; do
      if [ -f "$file" ]; then
        cat "$file"
      fi
    done
  fi

  update_sources
  check_upgrades_simulation

  install_pkg lsb-release

  if test "${virtualbox_only}" = "1"; then
    return 0
  fi

  install_pkg torsocks
  install_signify signify-openbsd
}


add_user_to_vbox_group(){
  id_of_user="$(id --name --user)" || die 1 "${underline}Linux user ID check:${nounderline} Failed to run: 'id --name --user'"
  if id -nG "${id_of_user}" | grep -qw "${virtualbox_linux_user_group}\$"; then
    log info "Linux Group Configuration: Account '${id_of_user}' is already a member of the Linux group 'vboxusers'."
    return 0
  fi

  if test "${debian_derivative_detected}" = "1"; then
    root_cmd adduser "${id_of_user}" "${virtualbox_linux_user_group}" || \
      die 1 "${underline}Linux Group Configuration: adduser to Linux user group virtualbox:${nounderline} Failed to add user '$id_of_user' to group '${virtualbox_linux_user_group}'."
  else
    root_cmd usermod --append --groups "${virtualbox_linux_user_group}" "${id_of_user}" || \
      die 1 "${underline}Linux Group Configuration: adduser to Linux user group virtualbox:${nounderline} Failed to add user '$id_of_user' to group '${virtualbox_linux_user_group}'."
  fi
}


## End installation of VirtualBox on Fedora and derived systems.
install_virtualbox_fedora_common_end(){
  if ! has vboxmanage ; then
    if test "${dry_run}" = "1"; then
      log error "Failed to locate 'vboxmanage' program. Ignoring via '--dry-run' option."
    else
      die 1 "${underline}vboxmanage test:${nounderline} Failed to locate 'vboxmanage' program."
    fi
  fi

  add_user_to_vbox_group
}


## End installation of VirtualBox on Debian and derived systems.
install_virtualbox_debian_common_end(){
  if ! has vboxmanage ; then
    if test "${dry_run}" = "1"; then
      log error "Failed to locate 'vboxmanage' program. - Ignoring via '--dry-run' option."
    else
      die 1 "${underline}vboxmanage test:${nounderline} Failed to locate 'vboxmanage' program."
    fi
  fi

  add_user_to_vbox_group
}


kernel_modules_check() {
  if ! [ "${hypervisor}" = "virtualbox" ]; then
    return 0
  fi

  if ! test -e /dev/vboxdrv ; then
    kernel_module_has_been_load=false
    user_warned_potential_startup_issue=true
    log warn "${underline}VirtualBox Kernel Module Loaded Test Result${nounderline}: 'no' - file /dev/vboxdrv does not exist. This probably means that the vboxdrv kernel module has not been load yet."
  else
    kernel_module_has_been_load=true
    log info "VirtualBox Kernel Module Loaded Test Result: 'yes' - file /dev/vboxdrv exists."
  fi

  ## Debugging.
  log info "Command executing: $ $sucmd -- modinfo --field signer vboxdrv"
  if kernel_module_signer=$(root_cmd_loglevel=null root_cmd modinfo --field signer vboxdrv 2>&1) ; then
    log info "VirtualBox Kernel Module Signer: '$kernel_module_signer'"
  else
    user_warned_potential_startup_issue=true
    log warn "${underline}VirtualBox Kernel Module Signer${nounderline}: '$kernel_module_signer'"
  fi

  ## Debugging.
  ## modprobe should be automatic but if it fails, figure out why.
  log notice "Command executing: $ $sucmd -- modprobe vboxdrv"
  if kernel_module_modprobe_output=$(root_cmd_loglevel=null root_cmd modprobe vboxdrv 2>&1) ; then
    log info "VirtualBox Kernel Module modprobe output: '$kernel_module_modprobe_output'"
  else
    user_warned_potential_startup_issue=true
    log warn "${underline}VirtualBox Kernel modprobe output${nounderline}: '$kernel_module_modprobe_output'"
  fi
}


install_repositories_for_virtualbox_on_debian(){
  distro_codename_real=$(lsb_release --short --codename)
  distro_codename_common_use="${distro_codename_real}"

#   log info "VirtualBox Package Availability Test: Checking if package 'virtualbox-qt' is already installable from an already enabled repository..."
#   if ${pkg_mngr_install} --simulate install virtualbox-qt 1>/dev/null 2>/dev/null ; then
#     ## Package 'virtualbox' is installable on Debian unstable ("sid").
#     log notice "VirtualBox Package Availability Test Result: 'success' - Package 'virtualbox-qt' is already installable from an already enabled repository. No need to add any extra repositories."
#     return 0
#   fi
#   log info "VirtualBox Package Availability Test Result: Not yet Available. Enabling additional repository..."

  if test "${dev}" = "1"; then
    distro_codename_kicksecure_use="${distro_codename_common_use}-developers"
  else
    distro_codename_kicksecure_use="${distro_codename_common_use}"
  fi

  oracle_found=""
  oracle_clearnet="download.virtualbox.org"
  #oracle_onion=""
  oracle_file_debsource="/etc/apt/sources.list.d/oracle.list"
  oracle_prefix_debsource="deb [signed-by=/usr/share/keyrings/oracle-virtualbox-2016.asc] "
  oracle_suffix_debsource="/virtualbox/debian ${distro_codename_common_use} contrib"

  unstable_found=""
  unstable_clearnet="deb.debian.org"
  unstable_onion="2s4yqjx5ul6okpp3f2gaunr2syex5jgbfpfvhxxbbjwnrsvbk5v3qbid.onion"
  unstable_file_debsource="/etc/apt/sources.list.d/unstable.list"
  ## CI /etc/apt/sources.list.d/debian.sources uses:
  ## Signed-By: /usr/share/keyrings/debian-archive-keyring.gpg
  ## So we have to use signed-by here too, otherwise we get an apt-get error:
  ## E: Conflicting values set for option Signed-By regarding source
  unstable_prefix_debsource="deb [signed-by=/usr/share/keyrings/debian-archive-keyring.gpg] "
  unstable_suffix_debsource="/debian/ unstable main contrib non-free"

  backports_found=""
  backports_clearnet="deb.debian.org"
  backports_onion="2s4yqjx5ul6okpp3f2gaunr2syex5jgbfpfvhxxbbjwnrsvbk5v3qbid.onion"
  backports_file_debsource="/etc/apt/sources.list.d/backports.list"
  backports_prefix_debsource="deb "
  backports_suffix_debsource="/debian/ ${distro_codename_common_use}-backports main contrib non-free"

  fasttrack_found=""
  fasttrack_clearnet="fasttrack.debian.net"
  fasttrack_onion="5phjdr2nmprmhdhw4fdqfxvpvt363jyoeppewju2oqllec7ymnolieyd.onion"
  fasttrack_file_debsource="/etc/apt/sources.list.d/fasttrack.list"
  fasttrack_prefix_debsource="deb "
  fasttrack_suffix_debsource="/debian/ ${distro_codename_common_use}-fasttrack main contrib non-free"

  kicksecure_found=""
  kicksecure_clearnet="deb.kicksecure.com"
  kicksecure_onion="deb.w5j6stm77zs6652pgsij4awcjeel3eco7kvipheu6mtr623eyyehj4yd.onion"
  kicksecure_file_debsource="/etc/apt/sources.list.d/derivative.list"
  kicksecure_prefix_debsource="deb [signed-by=/usr/share/keyrings/derivative.asc] "
  kicksecure_suffix_debsource=" ${distro_codename_kicksecure_use} main contrib non-free"

  apt_torified=""
  apt_onion=""

  ## TODO:
  ## - handle case if using Debian mirrors
  ## - add support for Deb822-style Format parsing
  ## - write sources.list files in one-line-style format or Deb822-style format?
  ##   https://forums.kicksecure.com/t/apt-sources-list-one-line-format-versus-deb822-style-format/267
  ## - unit tests

  for file in /etc/apt/sources.list /etc/apt/sources.list.d/*.list; do
    test -f "${file}" || continue

    if get_pattern_sources_debian "${file}" "${oracle_clearnet}"
    then
      oracle_found=1
    fi

    if get_pattern_sources_debian "${file}" "${kicksecure_clearnet}|${kicksecure_onion}"
    then
      kicksecure_found=1
    fi

    if get_pattern_sources_debian "${file}" "(${unstable_clearnet}|${unstable_onion})/debian.* (unstable|sid)"
    then
      unstable_found=1
    fi

    ## Need to check if not only unstable repository or sid codename is enabled but also check if the 'contrib' suite is enabled,
    ## because VirtualBox is only available from 'contrib'.
    if get_pattern_sources_debian "${file}" "(${unstable_clearnet}|${unstable_onion})/debian.* (unstable|sid).*contrib"
    then
      unstable_found_with_contrib=1
    fi

    if get_pattern_sources_debian "${file}" "(${backports_clearnet}|${backports_onion})/debian/? ${distro_codename_common_use}-backports"
    then
      backports_found=1
    fi

    if get_pattern_sources_debian "${file}" "${fasttrack_clearnet}|${fasttrack_onion}"
    then
      fasttrack_found=1
    fi

    if get_pattern_sources_debian "${file}" "tor://|tor\+"; then
      apt_torified=1
    fi

    if get_pattern_sources_debian "${file}" "\.onion"; then
      apt_onion=1
    fi
  done

  if test "${apt_torified}" = "1"; then
    ## If apt-transport-tor is not installed, we shouldn't, because we got
    ## a false positive that updates should be torified. This can happen if
    ## user configured the sources list to be torified but hasn't installed
    ## apt-transport-tor. It is better to abort, the user should configure
    ## tor by other means to ensure a working connection (bridges, proxy etc).
    log info "APT is supposed to be torified, checking if package apt-transport-tor is installed."
    test_pkg apt-transport-tor ||
      die 1 "${underline}Torified APT Test Result:${nounderline} APT is supposed to be torified, but package apt-transport-tor is not installed. Please install."
  fi

  ## If user has onion repositories configured, prefer it.
  if test "${apt_onion}"; then
    protocol_prefix_debsource="tor+http://"
    connection_type_debsource="onion"
    if test "${oracle_repo}" = "1"; then
      log warn "Oracle doesn't provide onion repositories."
      oracle_domain_debsource="${oracle_clearnet}"
      if test "${apt_torified}"; then
        log warn "Fallback Oracle repository to torified clearnet"
        protocol_prefix_debsource="tor+https://"
      else
        log warn "Fallback Oracle repository to clearnet"
        protocol_prefix_debsource="https://"
      fi
    fi
    kicksecure_domain_debsource="${kicksecure_onion}"
    unstable_domain_debsource="${unstable_onion}"
    fasttrack_domain_debsource="${fasttrack_onion}"
    backports_domain_debsource="${backports_onion}"
  ## If user has torified repositories configured, prefer it.
  elif test "${apt_torified}"; then
    protocol_prefix_debsource="tor+https://"
    connection_type_debsource="torified clearnet"
    oracle_domain_debsource="${oracle_clearnet}"
    kicksecure_domain_debsource="${kicksecure_clearnet}"
    unstable_domain_debsource="${unstable_clearnet}"
    fasttrack_domain_debsource="${fasttrack_clearnet}"
    backports_domain_debsource="${backports_clearnet}"
  ## If user doesn't have torified repositories, use clearnet one.
  else
    protocol_prefix_debsource="https://"
    connection_type_debsource="clearnet"
    oracle_domain_debsource="${oracle_clearnet}"
    kicksecure_domain_debsource="${kicksecure_clearnet}"
    unstable_domain_debsource="${unstable_clearnet}"
    fasttrack_domain_debsource="${fasttrack_clearnet}"
    backports_domain_debsource="${backports_clearnet}"
  fi

  kicksecure_url="${kicksecure_prefix_debsource} ${protocol_prefix_debsource}${kicksecure_domain_debsource}${kicksecure_suffix_debsource}"
  unstable_url="${unstable_prefix_debsource} ${protocol_prefix_debsource}${unstable_domain_debsource}${unstable_suffix_debsource}"
  fasttrack_url="${fasttrack_prefix_debsource} ${protocol_prefix_debsource}${fasttrack_domain_debsource}${fasttrack_suffix_debsource}"
  backports_url="${backports_prefix_debsource} ${protocol_prefix_debsource}${backports_domain_debsource}${backports_suffix_debsource}"

  if test "${oracle_repo}" = "1"; then
    oracle_url="${oracle_prefix_debsource} ${protocol_prefix_debsource}${oracle_domain_debsource}${oracle_suffix_debsource}"
    install_oracle_repository_debian
    return 0
  fi

  log info "Installing packages required for 'backports' and 'fasttrack' repository..."
  install_pkg ca-certificates fasttrack-archive-keyring

  case "${distro_codename_real}" in
    bullseye)
      install_backports_and_fasttrack_repository_debian
      return 0
      ;;
    bookworm)
      install_backports_and_fasttrack_repository_debian
      return 0
      ;;
    trixie)
      install_unstable_repository_debian
      return 0
      ;;
  esac

  die 1 "${underline}Repository Add:${nounderline} Unsupported distribution codename: '${distro_codename_real}'!"
}


install_oracle_repository_fedora(){
  oracle_found=""
  if dnf repolist --all virtualbox | grep -q "."; then
    oracle_found="1"
  fi
  if dnf repolist --disabled virtualbox | grep -q "."; then
    dnf config-manager --set-enabled virtualbox
  fi
  if test "${oracle_found}" = "1"; then
    log info "Oracle Repository: Skipped adding Oracle repository because it was already found."
  else
    log notice "Oracle Repository: Adding Oracle's clearnet repository to /etc/yum.repos.d/oracle.repo"
    if test -f /etc/pki/rpm-gpg/RPM-GPG-KEY-oracle; then
      log info "Oracle Repository: Key /etc/pki/rpm-gpg/RPM-GPG-KEY-oracle already exists."
    else
      echo "${oracle_pgp}" | \
        tee "${log_dir_cur}/oracle-virtualbox-2016.asc" >/dev/null
      echo "${oracle_pgp}" | \
        root_cmd tee /etc/pki/rpm-gpg/RPM-GPG-KEY-oracle >/dev/null
      ## Optional: the key will be imported when trying to use the repository
      root_cmd rpm --import /etc/pki/rpm-gpg/RPM-GPG-KEY-oracle
    fi

    ## Based on:
    ## https://download.virtualbox.org/virtualbox/rpm/fedora/virtualbox.repo
    # shellcheck disable=SC2016
    echo '[virtualbox]
name=Fedora $releasever - $basearch - VirtualBox
baseurl=https://download.virtualbox.org/virtualbox/rpm/fedora/$releasever/$basearch
enabled=1
gpgcheck=1
repo_gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-oracle
' | root_cmd tee /etc/yum.repos.d/oracle.repo

    ## dnf does not have a command to accept add the key to its database.
    ## https://bugzilla.redhat.com/show_bug.cgi?id=1768206
    ## Workaround to accept the key with --assumeyes without accepting other things.
    ## Does not work.
    #root_cmd dnf --assumeyes --cacheonly search VirtualBox
    #root_cmd dnf --assumeyes module list
  fi
}


install_oracle_repository_debian(){
  if test "${oracle_found}" = "1"; then
    log info "Oracle Repository: Skipped adding Oracle repository because it was already found."
  else
    log notice "Oracle Repository: Adding Oracle's ${connection_type_debsource} repository to ${oracle_file_debsource}"
    if test -f /usr/share/keyrings/oracle.asc ; then
      log info "Oracle Repository: Key /usr/share/keyrings/oracle.asc already exists."
    else
      echo "${oracle_pgp}" | \
        tee "${log_dir_cur}/oracle-virtualbox-2016.asc" >/dev/null
      echo "${oracle_pgp}" | \
        root_cmd tee /usr/share/keyrings/oracle-virtualbox-2016.asc >/dev/null
    fi
    write_sources_debian "${oracle_url}" "${oracle_file_debsource}"
  fi
}


install_kicksecure_repository_debian() {
  ## Contains file:
  ## /usr/share/extrepo/offline-data/debian/bullseye/whonix.asc
  ## Same as: kicksecure.asc
  ## (Which is not yet in the extrepo-offline-data package as of Debian 12.0.)
  install_pkg extrepo-offline-data
  ## Not using extrepo directly because it does not support torified and/or onion repositories:
  ## https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1037254

  if test -f /usr/share/keyrings/derivative.asc ; then
    log info "Kicksecure Repository: Key /usr/share/keyrings/derivative.asc already exists."
    log info "Kicksecure Repository: Not copying /usr/share/extrepo/offline-data/debian/bullseye/whonix.asc to /usr/share/keyrings/derivative.asc."
  else
    root_cmd cp --verbose /usr/share/extrepo/offline-data/debian/bullseye/whonix.asc /usr/share/keyrings/derivative.asc
  fi

  if test "${kicksecure_found}" = "1"; then
    log info "Kicksecure Repository: Skipped adding Kicksecure repository because it was already found."
  else
    log notice "Kicksecure Repository: Adding Kicksecure's ${connection_type_debsource} repository to ${kicksecure_file_debsource}"
    write_sources_debian "${kicksecure_url}" "${kicksecure_file_debsource}"
  fi
}


install_unstable_repository_debian() {
  if test "${unstable_found}" = "1" && test "${unstable_found_with_contrib}" = "1"; then
    log info "APT Repository Configuration: Skipped adding additional APT repositories because 'unstable' (with 'contrib') were already found."
    return 0
  fi

  log notice "APT Preferences Configuration Writer: Adding APT pinning configuration to prefer testing over unstable."
  file="/etc/apt/preferences.d/40-installer-dist-pinning"
  echo "\
## This file was created by: $0
## It can be safely deleted if you know what you are doing.

Package: *
Pin: release a=testing
Pin-Priority: 700

Package: *
Pin: release a=unstable
Pin-Priority: 650
" | root_cmd tee "$file" ||
    die 1 "${underline}APT Preferences Configuration Writer:${nounderline} Failed to write to file: '$file'"

  log notice "APT Repository Configuration: Adding 'unstable' ${connection_type_debsource} repository to ${unstable_file_debsource}"
  write_sources_debian "${unstable_url}" "${unstable_file_debsource}"
}


install_backports_and_fasttrack_repository_debian() {
  if test "${backports_found}" = "1"; then
    log info "APT Repository Configuration: Skipped adding 'backports' repository because it was already found."
  else
    log notice "APT Repository Configuration: Adding 'backports' ${connection_type_debsource} repository to ${backports_file_debsource}"
    write_sources_debian "${backports_url}" "${backports_file_debsource}"
  fi

  if test "${fasttrack_found}" = "1"; then
    log info "APT Repository Configuration: Skipped adding 'fasttrack' repository because it was already found."
  else
    log notice "APT Repository Configuration: Adding 'fasttrack' ${connection_type_debsource} repository to ${fasttrack_file_debsource}"
    write_sources_debian "${fasttrack_url}" "${fasttrack_file_debsource}"
  fi

  ## virtualbox-guest-additions-iso is available from Debian stable and fasttrack.
  ## Debian stable version however is outdated.
  ## If not using APT with option '--target-release=bookworm-fasttrack' then
  ## APT would download an outdated version from Debian stable instead the
  ## newer version from Debian fasttrack.
  install_pkg_fasttrack_extra_args_maybe="--target-release=${distro_codename_common_use}-fasttrack"
}


virtualbox_installation_failure_debug() {
  virtualbox_dkms_main_folder=/var/lib/dkms/virtualbox

  if ! test -d "$virtualbox_dkms_main_folder" ; then
    log notice "VirtualBox Installation Debug: folder '$virtualbox_dkms_main_folder' does not exist."
    return 0
  fi

  ## TODO: review
  # shellcheck disable=SC2012
  log_run notice ls --format=single-column --sort=time "$virtualbox_dkms_main_folder"
  # shellcheck disable=SC2012
  latest_folder=$(ls --format=single-column --sort=time "$virtualbox_dkms_main_folder" | head --lines=1)
  if [ "$latest_folder" = "" ]; then
    log notice "VirtualBox Installation Debug: latest_folder in '$virtualbox_dkms_main_folder' is empty, could not be determined."
    log_run notice ls -la "$virtualbox_dkms_main_folder" || true
    return 0
  fi

  log notice "VirtualBox Installation Debug: latest_folder: '$latest_folder'"

  virtualbox_dkms_latest_folder="${virtualbox_dkms_main_folder}/${latest_folder}"

  if ! test -d "$virtualbox_dkms_latest_folder" ; then
    log notice "VirtualBox Installation Debug: virtualbox_dkms_latest_folder '$virtualbox_dkms_latest_folder' is not a directory."
    log_run notice ls -la "$virtualbox_dkms_latest_folder" || true
    return 0
  fi

  make_log="${virtualbox_dkms_latest_folder}/build/make.log"

  if ! test -f "$make_log" ; then
    log notice "VirtualBox Installation Debug: make_log '$make_log' does not exist."
    log_run notice ls -la "$virtualbox_dkms_latest_folder" || true
    return 0
  fi

  if ! test -r "$make_log" ; then
    log notice "VirtualBox Installation Debug: make_log '$make_log' not readable."
    log_run notice ls -la "$virtualbox_dkms_latest_folder" || true
    log_run notice ls -la "$make_log" || true
    return 0
  fi

  log_run notice cat "$make_log" || true
}


## Install VirtualBox on Fedora
install_virtualbox_fedora(){
  install_pkg kernel-headers kernel-devel dkms

  get_virtualbox_version_fedora(){
    ## Too many issues with auto detection. Therefore hardcoded.
    virtualbox_qt_package_name="VirtualBox-7.0"
    return 0

#     log info "VirtualBox Version Detection: Running 'dnf search VirtualBox-*'. This can take a while..."
#     ## --cacheonly does not work.
#     ## Maybe dnf would need to be run with root_cmd.
#     virtualbox_version=$(dnf search "VirtualBox-*")
#     virtualbox_version=$(echo "$virtualbox_version" | grep "^VirtualBox-[[:digit:]]\{1,2\}\.[[:digit:]]\{1,2\}\.")
#     virtualbox_version=$(echo "$virtualbox_version" | tail -1)
#     virtualbox_version=$(echo "$virtualbox_version" | cut -d " " -f1)
#     virtualbox_version=$(echo "$virtualbox_version" | cut -d "-" -f2-)
#     virtualbox_version=$(echo "$virtualbox_version" | cut -d "." -f1)
#     virtualbox_qt_package_name=VirtualBox-"${virtualbox_version}"
#     if test -z "$virtualbox_version"; then
#       ## return non-zero late to avoid unbound variable virtualbox_qt_package_name.
#       return 1
#     fi
  }

  has_virtualbox_qt=0
  if get_virtualbox_version_fedora ; then
    test_pkg "${virtualbox_qt_package_name}" 2>/dev/null && has_virtualbox_qt=1
  else
    true "INFO: get_virtualbox_version_fedora failed the first time which is normal is the repository has not been enabled yet."
  fi

  ## Guard against adding extraneous repositories.
  if test "${has_virtualbox_qt}" != "1"; then
    log notice "VirtualBox Installation: Preparing to install VirtualBox..."
    install_oracle_repository_fedora
    ## Does not work.
    #root_cmd dnf makecache --assumeyes '--disablerepo=*' --enablerepo=virtualbox
    update_sources
    #check_upgrades_simulation
    get_virtualbox_version_fedora || die 2 "\
${underline}VirtualBox Package Version Detection:${nounderline} 'FAIL'"
  fi

  ## This is to make sure loglevel info message is shown:
  ## Package already installed: $virtualbox_qt_package_name
  install_pkg "$virtualbox_qt_package_name"

  install_virtualbox_fedora_common_end
}


## Install VirtualBox on Debian
## See also comments for install_virtualbox_fedora.
install_virtualbox_debian(){
  get_virtualbox_version_debian(){
    if test "${oracle_repo}" = "1"; then
      virtualbox_version=$(apt-cache search --names-only --quiet "^virtualbox-[[:digit:]]{1,2}\.[[:digit:]]{1,2}$")
      virtualbox_version=$(echo "$virtualbox_version" | tail -1)
      virtualbox_version=$(echo "$virtualbox_version" | cut -d " " -f1)
      virtualbox_version=$(echo "$virtualbox_version" | cut -d "-" -f2-)
      virtualbox_qt_package_name=virtualbox-"${virtualbox_version}"
      ## Package virtualbox-guest-additions-iso is unavailable from Oracle repository.
      virtualbox_guest_additions_iso_package_name=""
      if test -z "$virtualbox_version"; then
        ## return non-zero late to avoid unbound variable virtualbox_qt_package_name.
        return 1
      fi
    else
      virtualbox_qt_package_name=virtualbox-qt
      ## virtualbox-guest-additions-iso is Freedom Software:
      ## https://www.kicksecure.com/wiki/Dev/VirtualBox#VirtualBox_Guest_Additions_ISO_Freedom_vs_Non-Freedom
      ## Provides file: /usr/share/virtualbox/VBoxGuestAdditions.iso
      ## Useful to easily install VirtualBox guest additions in custom VirtualBox VMs.
      virtualbox_guest_additions_iso_package_name="virtualbox-guest-additions-iso"
    fi
  }

  if test "${oracle_repo}" = "1"; then
    ## Workaround for undeclared dependencies bug by virtualbox.org (Oracle) repository.
    ##
    ## udev:
    ## https://www.virtualbox.org/ticket/21804
    ##
    ## gcc:
    ## virtualbox-"${virtualbox_version}" by virtualbox.org (Oracle) `Recommends:` `gcc`
    ## Otherwise kernel modules will not be compiled during installation.
    install_pkg gcc udev
  fi

  linux_image="linux-image-$(dpkg --print-architecture)"
  linux_headers="linux-headers-$(dpkg --print-architecture)"
  ## Doing here and now below because we $install_pkg_fasttrack_extra_args_maybe should not be used here.
  install_pkg "${linux_image}" "${linux_headers}"

  log notice "VirtualBox Installation: Preparing to install VirtualBox..."
  install_repositories_for_virtualbox_on_debian
  update_sources
  check_upgrades_simulation
  get_virtualbox_version_debian || die 2 "${underline}VirtualBox Package Version Detection:${nounderline} 'FAIL'"

  ## Cannot quote $virtualbox_guest_additions_iso_package_name because is unset in case of using oracle_repo.
  # shellcheck disable=SC2086
  install_pkg $install_pkg_fasttrack_extra_args_maybe "$virtualbox_qt_package_name" $virtualbox_guest_additions_iso_package_name
  install_virtualbox_debian_common_end
}


## Install VirtualBox on Ubuntu
install_virtualbox_ubuntu(){
  install_pkg virtualbox-qt virtualbox-guest-additions-iso linux-image-generic linux-headers-generic
  install_virtualbox_debian_common_end
}


## Helper to install signify on different systems.
install_signify(){
  pkg_name="${1:-signify}"
  has "${pkg_name}" && return 0
  install_pkg "${pkg_name}"
}


## Test if user accepts the license, if not, abort.
check_license(){
  if [ "${non_interactive}" = "1" ]; then
    log notice "License Check: 'success' - User agreement confirmed via '--non-interactive' option."
    return 0
  fi

  log notice "The license will be shown in 5 seconds."
  log notice "(Use '-n' or '--non-interactive' for non-interactive mode.)"

  test "${dry_run}" != "1" && sleep 5

  local dialog_box
  dialog_box=""
  ## 'whiptail' is the Debian version of Dialog with much less features.
  ## Dialog types problems:
  ## - whiptail does not allow to set default option with scrolltext on.
  ## - dialog leaves empty lines on exit.
  while true; do
    has dialog && dialog_box="dialog" && break
    has whiptail && dialog_box="whiptail" && break
    break
  done

  case "${dialog_box}" in
    dialog)
      ## output-fd to stdout because currently 'main 2>&1 | tee file' if used
      ## and makes the dialog fail to recognize the characters as it is
      ## receiving from stderr and writing to stdout.
      dialog --erase-on-exit --no-shadow \
        --title "${dialog_title}" \
        --yes-label "Agree" \
        --no-label "Disagree" \
        --output-fd 1 \
        --yesno "${license}" 640 480 || return 1
      log notice "${underline}License Check:${nounderline} 'success' - User has accepted the license."
      ;;
    whiptail)
      ## When text is too long and scrolltext is needed, the yesno box
      ## does not display a default item. (note: --default-item is for items
      ## in the box to be selected as menu for example, not for buttons).
      whiptail \
        --scrolltext \
        --title "${dialog_title}" \
        --yes-button "Agree" \
        --no-button "Disagree" \
        --yesno "${license}" 24 80 || return 1
      log notice "${underline}License Check:${nounderline} 'success' - User has accepted the license."
      ;;
    *)
      printf '%s\n' "${license}"
      printf '%s' "Do you accept the license(s)? (yes/no): "
      read -r license_agreement
      case "${license_agreement}" in
        [yY][eE][sS])
          log notice "${underline}License Check:${nounderline} 'success' - User has accepted the license."
          ;;
        *)
          log warn "${underline}License Check:${nounderline} User replied: '${license_agreement}'"
          return 1
          ;;
      esac
      ;;
  esac
}


get_su_cmd(){
  while true; do
    has sudo && sucmd=sudo && break
    has doas && sucmd=doas && break
    has su && sucmd=su && break
    test -z "${sucmd}" && {
      die 1 "${underline}get_su_cmd:${nounderline} Failed to find program to run commands with administrative (\"root\") privileges. This installer requires either one of the following programs to be installed:
- sudo (recommended)
- doas
- su"
    }
    case "${sucmd}" in
      sudo) :;;
      *) log warn "Using sucmd '$sucmd'. Consider installation of sudo instead to cache your passwords instead of typing them every time.";;
    esac
  done

  log info "Testing root_cmd function..."
  root_cmd echo "test" ||
    die 1 "${underline}get_su_cmd:${nounderline} Failed to run test command as root."

  if test "${ci}" = "1"; then
    root_output="$(timeout --kill-after 5 5 sudo --non-interactive -- test -d /usr 2>&1)"
    if test -n "${root_output}"; then
      log error "sudo output: '${root_output}'"
      die 1 "${underline}get_su_cmd:${nounderline} Unexpected non-empty output for sudo test in CI mode."
    fi
    return 0
  fi

  ## Other su cmds do not have an option that does the same.
  if test "${sucmd}" = "sudo"; then
    if ! timeout --kill-after 5 5 sudo --non-interactive -- test -d /usr; then
      log warn "Credential Caching Status: 'No' - Without credential caching, this installer will prompt for sudo authorization multiple times. Consider configuring sudo credential caching to streamline the installation process."
      return 0
    fi
    ## Used by dist-installer-gui.
    # shellcheck disable=SC2034
    credential_caching_status=yes
    log info "Credential Caching Status: 'Yes'"
    root_output="$(timeout --kill-after 5 5 sudo -- test -d /usr 2>&1)"
    if test -n "${root_output}"; then
      log error "sudo output: '${root_output}'"
      die 1 "${underline}get_su_cmd:${nounderline} Unexpected non-empty output for sudo test in normal mode."
    fi
  fi
}

get_checkhash_cmd(){
  if test "${virtualbox_only}" = "1"; then
    return 0
  fi
  while true; do
    has sha512sum && checkhash="sha512sum --check --strict --warn" && break
    has shasum && checkhash="shasum --algorithm 512 --check --strict --warn" && break
    ## TODO: Does it have an equivalent to --check? Compatible file format?
    #has sha512 && checkhash="sha512 -c" && break
    #has digest && checkhash="digest -a sha512 -c" && break
    ## TODO: How to make openssl check the file without workarounds?
    #has openssl && checkhash="openssl dgst -sha512 -r" && break
    test -z "${checkhash}" && {
      die 1 "${underline}get_checkhash_cmd:${nounderline} Failed to find program that checks SHA512 hash sum."
    }
  done
}

get_transfer_cmd(){
  ## curl|rsync
  transfer_utility=rsync
  case "${transfer_utility}" in
    rsync)
      rsync=1
      ;;
    curl)
      curl=1
      ;;
  esac
  ## 45m
  transfer_max_time_large_file="2700"
  ## 3m
  transfer_max_time_small_file="180"
  ## 10m
  transfer_io_timeout="600"
  ## 3m
  transfer_connect_timeout="180"
  transfer_size_test_connection="200K"
  transfer_size_small_file="2K"
  transfer_size_large_file="3G"
  case ${transfer_utility} in
    curl)
      ## Maximum time in seconds that we allow the whole operation to take.
      ## Option works but as rsync doesn't have it, we are using timeout
      ## utility from coreutils.
      #transfer_max_time_opt="--max-time"
      ## Curl does not have I/O timeout.
      transfer_io_timeout_opt=""
      ## Maximum time in seconds that we allow curl's connection to take.
      ## This only limits the connection phase, so if curl's connect in the
      ## given period, it will continue.
      transfer_connect_timeout_opt="--connect-timeout ${transfer_connect_timeout}"
      ## curl max-filesize is not a definitive barrier:
      ## The file size is not always known prior to download, and for
      ## such files this option has no effect even if the file transfer ends
      ## up  being  larger than this given limit.
      transfer_size_opt="--max-filesize"
      transfer_dryrun_opt=""
      transfer_output_dir_opt="--output-dir"
      transfer_output_file_opt="--remote-name"
      transfer_verbosity_opt=""
      transfer_speed_optimization_opt=""
      ;;
    rsync*)
      ## Rsync does not have an option to set maximum time for of operation.
      ## Option works but as rsync doesn't have it, we are using timeout
      ## utility from coreutils.
      #transfer_max_time_opt=""
      ## If no data is transferred in the specified time, rsync will exit.
      transfer_io_timeout_opt="--timeout ${transfer_io_timeout}"
      ## Amount of time the client will wait for its connection to a server
      ## to succeed.
      ## Error when using this option:
      ##   The --contimeout option may only be used when connecting to an
      ##   rsync daemon.
      #transfer_connect_timeout_opt="--contimeout ${transfer_connect_timeout}"
      transfer_size_opt="--max-size"
      transfer_dryrun_opt="--dry-run"
      transfer_output_dir_opt=""
      transfer_output_file_opt=""
      transfer_verbosity_opt="--no-motd --progress --verbose --verbose"
      transfer_speed_optimization_opt="--compress --partial"
      ;;
  esac
}

## Get utilities from a pool of known utilities and use the first one found.
get_utilities(){
  get_su_cmd
  get_checkhash_cmd
  get_transfer_cmd
}


## Set default traps
set_trap(){
  log info "Current PATH: '${PATH}'"
  ## Sometimes ps is not available, default to sh.
  curr_shell="$(cat /proc/$$/comm)"
  ## Get current shell from current process
  ## If the process if the file name, get its shell from shebang
  ## sometimes the process name is the base name of the script with some
  ## missing letters.
  case "${0##*/}" in
    ${curr_shell}*)
      ## necessary glob because /bin/sh makes the file name
      ## appear with one letter less
      shebang="$(head -1 "${0}")"
      curr_shell="${shebang##*/}"
      ;;
  esac
  ## TODO: This is not shown on CI.
  log info "Current shell: '${curr_shell}'"
  case "${curr_shell}" in
    *bash|*ksh|*zsh)
      # shellcheck disable=SC2039
      if test "${curr_shell}" = "bash"; then
        # shellcheck disable=SC2039,3040
        set -o errtrace
        set -o pipefail
      fi
      # shellcheck disable=SC2039,3047
      trap 'handle_exit $? ${LINENO:-}' ERR
      ;;
  esac
  trap 'handle_exit $? ${LINENO:-}' EXIT HUP INT QUIT ABRT ALRM TERM
}


## Check if system status is supported
get_system_stat(){
  if [ "${arch}" != "x86_64" ]; then
    die 101 "${underline}Architecture Check:${nounderline} Only supported architecture is 'x86_64', yours is: '${arch}'."
  fi

  ## https://www.whonix.org/wiki/RAM#Whonix_RAM_and_VRAM_Defaults
  ## TODO
  ## min_ram_mb not used currently because less than total 4GB is too low
  ## already
  # shellcheck disable=SC2034
  case "${interface}" in
    xfce)
      min_ram_mb="3328"
      ;;
    cli)
      min_ram_mb="1024"
      ;;
  esac
  if test "${virtualbox_only}" = "1"; then
    # shellcheck disable=SC2034
    min_ram_mb="1024"
  fi

  ## 4GB RAM machine reports 3844Mi and 4031MB
  ## /proc/meminfo replies in kB
  ## https://ux.stackexchange.com/a/13850
  total_mem_kB="$(awk '/MemTotal/{print $2}' /proc/meminfo)"
  ## convert kB to MB
  total_mem="$((total_mem_kB/1000))"
  ## capped to 4200MB to report that 4GB RAM on the host is too little
  if [ "${total_mem}" -lt "4200" ]; then
    user_warned_potential_startup_issue=true
    log warn "${underline}Minimum RAM Check:${nounderline} Your systems has a low amount of total RAM: '${total_mem} MB'"
    if test "${virtualbox_only}" != "1"; then
      log warn "  - For more information, refer to:"
      log warn "  ${url_version_domain}/wiki/RAM"
    fi
  fi

  df_output="$(df --output=avail -BG "${directory_prefix}")"
  free_space_available="$(echo "$df_output" |
                awk '/G$/{print substr($1, 1, length($1)-1)}')"

  ## TODO: do not hardcode 10 GB - Kicksecure vs Whonix
  free_space_required="10"
  ## Free space require set to approximately double the image size (2023-03-21)
  case "${guest}" in
    whonix)
      case "${interface}" in
        xfce)
          free_space_required="5"
          ;;
        cli)
          free_space_required="3"
          ;;
      esac
      ;;
    kicksecure)
      case "${interface}" in
        xfce)
          free_space_required="2"
          ;;
        cli)
          free_space_required="1"
          ;;
      esac
      ;;
  esac

  if test "${virtualbox_only}" = "1"; then
    free_space_required="1"
  fi

  if test "${dev}" = "1"; then
    free_space_required="1"
  fi

  if [ "${free_space_available}" -lt "$free_space_required" ]; then
    die 101 "\
${underline}Free Disk Space Check Result:${nounderline} Insufficient free disk space!

  - available: '${free_space_available}G'
  - required : '${free_space_required}G'

Debugging information:
- Command to test the available free space on ${directory_prefix}:
df --output=avail -BG \"${directory_prefix}\"
- Available free space result:
$df_output"
  fi
}


## Sanity checks that should be called before execution of main
pre_check(){
  get_os
  get_distro
  check_not_qubes_template
  get_system_stat
  need_reboot_check_first
  get_host_pkgs
  need_reboot_check_second
  get_independent_host_pkgs
  kernel_modules_check
  nested_virtualization_test
  secure_boot_test
  kernel_modules_load
  kernel_modules_signed_only

  ## onion=1 -- Always torify onion connections.
  ## onion=* -- Only torify clearnet if SOCKS proxy is specified.
  case "${onion}" in
    1) torify_conn;;
    *) test -n "${socks_proxy}" && torify_conn;;
  esac

  ## Functions below are difficult to emulate
  if test "${dry_run}" = "1"; then
    log info "Skipping rest or pre_check() because via '--dry-run' option."
    return 0
  fi

  get_virtualization
}


## Generate SOCKS credentials for stream isolation
get_proxy_cred(){
  test "${transfer_utility}" != "curl" && return 0
  test -z "${transfer_proxy_suffix:-}" && return 0
  proxy_user="anonym"
  proxy_pass="${1:?}"
  printf '%s' "--proxy-user ${proxy_user}:${proxy_pass}"
}


## Test if can connect to SOCKS proxy and expect the correct Tor reply.
check_tor_proxy(){
  log notice "Testing SOCKS proxy: '${proxy}'"
  expected_response_header="HTTP/1.0 501 Tor is not an HTTP Proxy"
  log info "Expected response header:"
  log info "'$expected_response_header'"
  cmd_check_proxy="env UTW_DEV_PASSTHROUGH=1 curl --silent --show-error --max-time 3 --head http://${proxy}"
  log info "Command used to check if proxy is functional:"
  log info "$cmd_check_proxy"
  # shellcheck disable=SC2086
  actual_response_header="$(${cmd_check_proxy} 2>&1)"
  parsed_response_header=$(echo "${actual_response_header}" | head -1)
  parsed_response_header=$(echo "${parsed_response_header}" | tr -d "\r")
  ## Globs are necessary to match patterns in the event the header has more
  ## characters them expected but still has the expected string.
  ## Rsync header response example:
  ##   bad response from proxy -- HTTP/1.0 501 Tor is not an HTTP Proxy
  case "${parsed_response_header}" in
    *"${expected_response_header}"*)
      log info "Received header:"
      log info "'${parsed_response_header}'"
      log notice "Connected to Tor SOCKS proxy successfully."
      return 0
      ;;
    *)
      log error "\
Unexpected proxy response, maybe not a Tor proxy?

Debugging information:
- Command used to check if proxy is functional:
'$cmd_check_proxy'

- Expected response header:
'$expected_response_header'

- Actual received header:
'${actual_response_header}'

- Parsed received header:
'${parsed_response_header}'"
      return 1
  esac
}


## Set transference proxy depending on transfer utility.
## usage: set_transfer_proxy ${proxy}
set_transfer_proxy(){
  proxy_port="${1##*:}"
  proxy_addr="${1%%:*}"
  ## Used for transfers that only curl can do.
  curl_transfer_proxy="--proxy socks5h://${1}"
  ## Set transfer proxy per utility.
  case "${transfer_utility}" in
    curl)
      transfer_proxy_prefix=""
      transfer_proxy_suffix="--proxy socks5h://${1}"
      ;;
    rsync*)
      transfer_proxy_suffix=""
      transfer_proxy_prefix="torsocks --isolate --address ${proxy_addr} --port ${proxy_port}"
      ;;
  esac
}


## Useful to test if it is a SOCKS proxy before attempting to make requests.
## If connection to proxy fails, abort to avoid leaks.
torify_conn(){
  if ! has tor; then
    log warn "System tor binary (little-t-tor) was not found on the system."
    log warn "Unless your SOCKS connection is made available by the Tor Browser"
    log warn "  or by your uplink network, the proxy check mail fail."
    log warn "The installer with torified connections depends on a working SOCKS proxy,"
    log warn "  it won't configure the proxy, only establish the connection."
    log warn "If the proxy connection fails, try installation of the 'tor' package on your system."
  fi
  ## curl and many other viable applications do not support SOCKS proxy to
  ## connect with Unix Domain Socket:
  ##   https://curl.se/mail/archive-2021-03/0013.html
  if test -n "${socks_proxy:-}"; then
    proxy="${socks_proxy}"
    set_transfer_proxy "${proxy}"
  elif test -n "${TOR_SOCKS_PORT:-}"; then
    proxy="${TOR_SOCKS_HOST:-127.0.0.1}:${TOR_SOCKS_PORT}"
    set_transfer_proxy "${proxy}"
  else
    ## Stream Isolation will be enforced get_proxy_cred()
    log warn "Missing SOCKS proxy for torified connections."
    log warn "Trying Tor defaults: system Tor (little-t-tor) (port: 9050) and TBB (Tor Browser Bundle) (port: 9150)."
    proxy="127.0.0.1:9050"
    set_transfer_proxy ${proxy}
    if ! check_tor_proxy; then
      proxy="127.0.0.1:9150"
      set_transfer_proxy ${proxy}
    else
      return 0
    fi
  fi
  check_tor_proxy || die 2 "\
${underline}Check Tor Proxy:${nounderline} 'FAIL'

Unable to connect to Tor SOCKS proxy.

  - This issue is unlikely caused by this installer.
  - It is more probable that the problem stems from absent software, improper configuration, or network issues.

Please note that in order to torify connections, an already functional Tor connection is needed:

  - A) A pre-installed and running system Tor (little-t-tor), or,
  - B) A pre-installed and running TBB (Tor Browser Bundle).

Additional details:

  - This installer does not support setting up a functional Tor connection. This task needs to be performed by the system administrator.
  - When running the above cmd_check_proxy manually, ensure it includes the expected_response_header."
}


## Set version by user input or by querying the API
get_version(){
  log notice "Version Detection: Detecting guest version..."
  if test -n "${guest_version:-}"; then
    log notice "Version Detection: 'skipped' - Autodetection using API not required via '--dry_run' or '--dev' option."
    return 0
  fi
  log info "Version Detection: Acquiring guest version using API..."
  log info "Version Detection: API host: ${1}"
  cmd_raw_version="curl ${curl_transfer_proxy:-} $(get_proxy_cred version) \
      ${curl_opt_ssl:-} \
      --max-time ${transfer_max_time_small_file} \
      --max-filesize ${transfer_size_small_file} \
      --url ${1}"
  ## this is necessary because we log will not be printed as the command is
  ## assigned to a variable at 'raw_version=$()'.
  if test "${dry_run}" = "1"; then
    # shellcheck disable=SC2086
    log_run notice ${cmd_raw_version}
    return 0
  fi
  # shellcheck disable=SC2086
  raw_version="$(${cmd_raw_version})"
  ## First line only.
  guest_version="$(echo "$raw_version" | head -n 1)"
  # shellcheck disable=SC2046,SC2086
  guest_version="$(printf '%s\n' "${guest_version}" | sed "s/<.*//")"
  ## Distrust the API version
  ## Block anything that is not made purely out of numbers and dots
  ## Not printing queried version to avoid it showing a very long version
  ## that could inhibit the user from seeing the error message.
  ## The user would still see a failed exit code.
  [ "${guest_version%%*[^0-9.]*}" ] ||
    die 1 "${underline}Version Check Result:${nounderline} Invalid guest version: contains unexpected characters."
  ## block string containing more than 12 chars
  [ "${#guest_version}" -le 12 ] ||
    die 1 "${underline}Version Check Result:${nounderline} Invalid guest version: contains more than 12 characters."
}


## Helper for download_files() to make it less repetitive.
## usage: get_file small|large $url
get_file(){
  size="${1}"
  url="${2}"
  ## Round is only used to get a different password every time.
  test -z "${round:-}" && round=10
  round=$((round+1))

  case "${size}" in
    small)
      download_opt_prefix="timeout --foreground ${transfer_max_time_small_file}"
      download_opt="${transfer_size_opt} ${transfer_size_small_file}"
      ;;
    large)
      download_opt_prefix="timeout --foreground ${transfer_max_time_large_file}"
      download_opt="${transfer_speed_optimization_opt} ${transfer_size_opt} ${transfer_size_large_file}"
      ;;
    *)
      log bug "Missing size option for get_file()."
      ;;
  esac
  # shellcheck disable=SC2046,SC2086
  download_opt_full="${download_opt_prefix} ${transfer_proxy_prefix:-} ${transfer_utility} ${transfer_verbosity_opt} ${transfer_proxy_suffix:-} $(get_proxy_cred ${round}) ${transfer_connect_timeout_opt:-} ${transfer_io_timeout_opt:-} ${download_opt} ${transfer_output_file_opt} ${url} ${transfer_output_dir_opt} ${directory_prefix}"

  # shellcheck disable=SC2086
  log_run notice ${download_opt_full} || return 1
}


files_already_downloaded_check() {
  test -f "${directory_prefix}/${guest_file}.${guest_file_ext}"
  test -f "${directory_prefix}/${guest_file}.${guest_file_ext}.sha512sums.sig"
  test -f "${directory_prefix}/${guest_file}.${guest_file_ext}.sha512sums"
}


## Check if files were already downloaded, if not, try to download everything
## and only if succeeds, set download flag.
download_files(){
  log_time

  log notice "Download: Files will be stored in the directory: '${directory_prefix}'"
  get_file large "${url_guest_file}.${guest_file_ext}" || return 1
  get_file small "${url_guest_file}.${guest_file_ext}.sha512sums.sig" || return 1
  get_file small "${url_guest_file}.${guest_file_ext}.sha512sums" || return 1

  log info "Download: Checking if files exists locally..."

  if ! files_already_downloaded_check ; then
    die 103 "${underline}Download:${nounderline} Failed to download files."
  fi

  log_time
}


## https://en.wikipedia.org/wiki/X86_virtualization
get_virtualization(){
  local virt_flag brand

  ## Check if virtualization is enabled.
  ## Check CPU flags for capability
  virt_flag="$(root_cmd grep -m1 -w '^flags[[:blank:]]*:' /proc/cpuinfo | grep -wo -E '(vmx|svm)' || true)"

  case "${virt_flag:=none}" in
    vmx) brand=intel;;
    svm) brand=amd;;
    *) brand=unknown;;
  esac

#  if compgen -G "/sys/kernel/iommu_groups/*/devices/*" > /dev/null; then
#    log notice "${brand}'s I/O Virtualization Technology is enabled in the BIOS/UEFI"
#  else
#    log warn "${brand}'s I/O Virtualization Technology is not enabled in the BIOS/UEFI"
#  fi

  case "${virt_flag:=}" in
    vmx|svm)
      log notice "Virtualization Support Test Result: 'success'"
      log info "cpu_brand: '${brand}' virt_flag: '${virt_flag}'"
      virt_detection_success=true
      return 0
      ;;
    none)
      user_warned_potential_startup_issue=true
      log warn "${underline}Virtualization Support Test:${nounderline} ${red}${bold}'FAIL'${nobold}${nocolor} - No virtualization flag found."
      virt_detection_success=false
      ;;
    *)
      user_warned_potential_startup_issue=true
      log warn "${underline}Virtualization Support Test:${nounderline} ${red}${bold}'FAIL'${nobold}${nocolor} - Unknown virtualization flag. (Use '--log-level=info' for potentially privacy sensitive details.)"
      log info "cpu_brand: '${brand}' virt_flag: '${virt_flag}'"
      virt_detection_success=false
      ;;
  esac

  if [ "$virt_detection_success" = "false" ]; then
    user_warned_potential_startup_issue=true
    log warn "  - The virtualization detection feature of this installer may not be flawless and could potentially fail to detect virtualization support (this is known as a 'false negative')."
    if [ "${hypervisor}" = "virtualbox" ]; then
      log warn "  - Refer to user documentation on how to enable virtualization:"
      log warn "  ${url_version_domain}/wiki/VirtualBox/Troubleshooting#Enable_VT-x_in_BIOS"
    fi
    return 0
    ## Let's not hard fail here, let the user do it later.
    #return 101
  fi

  ## msr is blocked by security-misc. If no other solution is found,
  ## remove the rest of of this function.
  ## $ modprobe msr
  ## /bin/disabled-msr-by-security-misc: ERROR: This CPU MSR kernel module is disabled by package security-misc by default. See the configuration file /etc/modprobe.d/30_security-misc.conf | args:
  ## modprobe: ERROR: ../libkmod/libkmod-module.c:990 command_do() Error running install command '/bin/disabled-msr-by-security-misc' for module msr: retcode 1
  ## modprobe: ERROR: could not insert 'msr': Invalid argument

  install_pkg msr-tools
  # https://bazaar.launchpad.net/~cpu-checker-dev/cpu-checker/trunk/view/head:/kvm-ok
  # kvm-ok - check whether the CPU we're running on supports KVM acceleration
  # Copyright (C) 2008-2010 Canonical Ltd.
  #
  # Authors:
  #  Dustin Kirkland <kirkland@canonical.com>
  #  Kees Cook <kees.cook@canonical.com>
  #
  # This program is free software: you can redistribute it and/or modify
  # it under the terms of the GNU General Public License version 3,
  # as published by the Free Software Foundation.
  #
  # This program is distributed in the hope that it will be useful,
  # but WITHOUT ANY WARRANTY; without even the implied warranty of
  # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  # GNU General Public License for more details.
  #
  # You should have received a copy of the GNU General Public License
  # along with this program.  If not, see <http://www.gnu.org/licenses/>.

  ## Print verdict
  verdict() {
    case "${1}" in
      0)
        log notice "Virtualization can be used."
        log warn "Virtualization availability can be a false negative."
        return 0
        ;;
      1)
        user_warned_potential_startup_issue=true
        log warn "Virtualization can NOT be used."
        log warn "Virtualization availability can be a false negative."
        return 0
        ## let's not hard fail here, let the user do it later.
        #return 1
        ;;
      2)
        user_warned_potential_startup_issue=true
        log warn "Virtualization can be used, but not enabled."
        log warn "Virtualization availability can be a false negative."
        return 0
        ## let's not hard fail here, let the user do it later.
        #return 1
        ;;
    esac
  }

  ## Check CPU flags for capability
  virt=$(root_cmd grep -m1 -w '^flags[[:blank:]]*:' /proc/cpuinfo |
         grep -wo -E '(vmx|svm)') || true
  if test -z "${virt}"; then
    log error "Your CPU does not support Virtualization."
    verdict 1
  fi
  [ "${virt}" = "vmx" ] && brand="intel"
  [ "${virt}" = "svm" ] && brand="amd"

  ## Now, check that the device exists
  if test -e /dev/kvm; then
    log notice "Device /dev/kvm exists"
    verdict 0
  else
    user_warned_potential_startup_issue=true
    log warn "Device /dev/kvm does not exist"
    log warn "hint: '${sucmd} modprobe kvm_$brand'"
  fi

  ## Prepare MSR access
  msr="/dev/cpu/0/msr"
  if root_cmd test ! -r "${msr}"; then
    root_cmd modprobe msr ||
      die 1 "${underline}modprobe:${nounderline} Could not add module 'msr' to the kernel."
  fi
  if root_cmd test ! -r "${msr}"; then
    log error "Cannot read: '${msr}'"
    return 1
  fi

  log notice "Your CPU supports Virtualization extensions."

  virt_disabled=0
  ## check brand-specific registers
  if [ "${virt}" = "vmx" ]; then
    virt_bit=$(root_cmd rdmsr --bitfield 0:0 0x3a 2>/dev/null || true)
    if [ "${virt_bit}" = "1" ]; then
      ## and FEATURE_CONTROL_VMXON_ENABLED_OUTSIDE_SMX clear (no tboot)
      virt_bit=$(root_cmd rdmsr --bitfield 2:2 0x3a 2>/dev/null || true)
      [ "${virt_bit}" = "0" ] && virt_disabled=1
    fi
  elif [ "${virt}" = "svm" ]; then
    virt_bit=$(root_cmd rdmsr --bitfield 4:4 0xc0010114 2>/dev/null || true)
    [ "${virt_bit}" = "1" ] && virt_disabled=1
  else
    log error "Unknown virtualization extension: '${virt}'"
    verdict 1
  fi

  if [ "${virt_disabled}" -eq 1 ]; then
    user_warned_potential_startup_issue=true
    log warn "'${virt}' is disabled by your BIOS"
    log warn "Enter your BIOS setup and enable Virtualization Technology (VT),"
    log warn "      and then reboot your system."
    verdict 2
  fi

  verdict 0
}

#########################
## END SCRIPT SPECIFIC ##
#########################

################
## BEGIN MAIN ##
################
get_download_links(){
  ## Set upstream links as base, especially for API.
  ## clearnet project domain
  site_clearnet_whonix="whonix.org"
  ## onion project domain
  site_onion_whonix="dds6qkxpwdeubwucdiaord2xgbbeyds25rbsgr73tbfpqpt4a6vjwsyd.onion"
  ## clearnet project domain
  site_clearnet_kicksecure="kicksecure.com"
  ## onion project domain
  site_onion_kicksecure="w5j6stm77zs6652pgsij4awcjeel3eco7kvipheu6mtr623eyyehj4yd.onion"

  case "${guest}" in
    whonix)
      site_clearnet="${site_clearnet_whonix}"
      site_onion="${site_onion_whonix}"
      ;;
    kicksecure)
      site_clearnet="${site_clearnet_kicksecure}"
      site_onion="${site_onion_kicksecure}"
      ;;
    *)
      ## Variables need to be set for --virtualbox-only.
      site_clearnet="${site_onion_kicksecure}"
      site_onion="${site_clearnet_kicksecure}"
      ;;
  esac

  if test -z "${mirror}"; then
    ## No mirror chosen, use default values.
    mirror=0
  fi

  ## ${variable+string} means use string as value if variable is not empty.
  ## get download links by mirror of choice.
  case "${mirror}" in
    0)
      site_download_clearnet="${curl+download.}${site_clearnet}${rsync+/${guest}}"
      site_download_onion="${curl+download.}${site_onion}${rsync+/${guest}}"
      ;;
    1)
      site_download_clearnet="mirrors.dotsrc.org/${guest}"
      site_download_onion="dotsrccccbidkzg7oc7oj4ugxrlfbt64qebyunxbrgqhxiwj3nl6vcad.onion/${guest}"
      ;;
    2)
      site_download_clearnet="quantum-mirror.hu/mirrors/pub/${guest}"
      site_download_onion=""
      ;;
    *)
      ## range_arg should have catch this error before, just safeguarding.
      log bug "Invalid mirror number: '${mirror}'"
      ;;
  esac

  case "${transfer_utility}" in
    curl)
      protocol_prefix_clearnet="https"
      protocol_prefix_onion="http"
      ;;
    rsync)
      protocol_prefix_clearnet="rsync"
      protocol_prefix_onion="rsync"
      ;;
  esac

  ## clearnet download url
  url_download_clearnet="${protocol_prefix_clearnet}://${site_download_clearnet}"
  ## onion download url
  url_download_onion="${protocol_prefix_onion}://${site_download_onion}"

  case "${onion}" in
    1)
      log info "Onion preferred."
      curl_opt_ssl=""
      ## Used to test internet connection.
      url_origin="${protocol_prefix_onion}://www.${site_onion}"
      ## URL to download files from.
      test -n "${site_download_onion}" ||
        die 1 "${underline}Mirror Selection:${nounderline} Mirror ${mirror} doesn't provide an onion service."
      url_download="${url_download_onion}"
      ## Used to query version number.
      url_version_domain="http://www.${site_onion}"
      ;;

    *)
      log info "Clearnet preferred."
      test "${transfer_utility}" = "rsync" && transfer_utility="rsync-ssl"
      curl_opt_ssl="--tlsv1.3 --proto =https"
      ## Used to test internet connection.
      url_origin="${protocol_prefix_clearnet}://www.${site_clearnet}"
      ## URL to download files from.
      url_download="${url_download_clearnet}"
      ## Used to query version number.
      url_version_domain="https://www.${site_clearnet}"
      ;;
  esac


  case "${hypervisor}" in
    virtualbox)
      if test "${testers}" = "1"; then
        url_version_template="VersionTesters"
      else
        url_version_template="VersionNew"
      fi
      ## image signer
      signify_key="${adrelanos_signify}"
      signify_signer="adrelanos"
      ## url directory to find files of the selected hypervisor
      url_domain="${url_download}/ova"
      ## image file extension
      guest_file_ext="ova"
      ## function to call when importing guest
      ;;

    kvm)
      if test "${testers}" = "1"; then
        die 1 "${underline}Version Selection:${nounderline} KVM does not have testers version."
        #url_version_template=""
      else
        url_version_template="Version_KVM"
      fi
      ## image signer
      signify_key="${hulahoop_signify}"
      signify_signer="hulahoop"
      ## url directory to find files of the selected hypervisor
      url_domain="${url_download}/libvirt"
      ## image file extension
      guest_file_ext="Intel_AMD64.qcow2.libvirt.xz"
      ## function to call when importing guest
      ## TODO
      ;;
  esac

  url_version_prefix="w/index.php?title=Template:"
  url_version_suffix="&stable=0&action=raw"
  url_version="${url_version_domain}/${url_version_prefix}${url_version_template}${url_version_suffix}"
}


## Test if files should be downloaded
should_download(){
  if test "${virtualbox_only}" = "1"; then
    ## 'return 1' so the result of should_download is "no".
    return 1
  fi
  if test "${dry_run}" = "1"; then
    log notice "Download: Creating download flag via '--dry-run' option."
    log_run notice touch "${download_flag}"
    return 0
  fi

  if test "${redownload}" = "1"; then
    ## Do not print further messages as it was already printed before.
    ## Occurs if the should_download() function was called more than once.
    test "${download_msg_done:-}" = "1" && return 0
    download_msg_done=1
    ## Download if redownload option is set.
    log notice "Download: Re-downloading files via '--redownload' option."
    return 0
  elif test -f "${download_flag:-}"; then
    ## Do not download if flag exists.
    log notice "Download: Skipping download because download and integrity check previously succeeded."
    return 1
  fi
  ## Download as no obstacles prohibit it.
  return 0
}


## Check signature of signed checksum.
check_signature(){
  signify_checksum_file="${1}"
  log info "Signify key:\n${signify_key}"
  log info "Verifying file: '${signify_checksum_file}'"
  signify_pub_file="${log_dir_cur}/${signify_signer}.pub"
  echo "${signify_key}" | tee "${signify_pub_file}" >/dev/null

  log_run info signify -V -p "${signify_pub_file}" \
    -m "${signify_checksum_file}" || return 1

  log info "Signify Signature Verification: 'success'"
}


## Check hash sum.
check_hash(){
  shafile="${1}"
  dir="$(dirname "${shafile}")"
  log info "Checking SHA512 checksum: '${shafile}"
  ## $checkhash needs to be executed on the same folder as the compared file.
  log info "Changing to directory: '${dir}'"
  cd "${dir}"
  # shellcheck disable=SC2086
  log_run info ${checkhash} "${shafile}" || return 1
  log info "SHA512 Hash Verification: 'success'"
}


check_signature_test(){
  log info "Unit testing signature, expecting non-zero exit code."
  rm -f "${directory_prefix}/${guest_file}.${guest_file_ext}.sha512sums.test"
  cp "${directory_prefix}/${guest_file}.${guest_file_ext}.sha512sums" "${directory_prefix}/${guest_file}.${guest_file_ext}.sha512sums.test"
  echo "" | tee "${directory_prefix}/${guest_file}.${guest_file_ext}.sha512sums.test" >/dev/null
  if ! check_signature "${directory_prefix}/${guest_file}.${guest_file_ext}.sha512sums.test" 2>/dev/null; then
    rm -f "${directory_prefix}/${guest_file}.${guest_file_ext}.sha512sums.test"
    log info "Received expected non-zero exit code from unit test."
  else
    rm -f "${directory_prefix}/${guest_file}.${guest_file_ext}.sha512sums.test"
    die 104 "${underline}SHA512 Hash Verification (unit test):${nounderline} 'FAIL' - received a zero as exit code, expected non-zero."
  fi
}


check_hash_test(){
  log info "Unit testing checksum, expecting non-zero exit code."
  rm -f "${directory_prefix}/${guest_file}.${guest_file_ext}.sha512sums.test"
  cp "${directory_prefix}/${guest_file}.${guest_file_ext}.sha512sums" "${directory_prefix}/${guest_file}.${guest_file_ext}.sha512sums.test"
  echo "" | tee "${directory_prefix}/${guest_file}.${guest_file_ext}.sha512sums.test" >/dev/null
  if ! check_hash "${directory_prefix}/${guest_file}.${guest_file_ext}.sha512sums.test" 2>/dev/null; then
    rm -f "${directory_prefix}/${guest_file}.${guest_file_ext}.sha512sums.test"
    log info "Received expected non-zero exit code from unit test."
  else
    rm -f "${directory_prefix}/${guest_file}.${guest_file_ext}.sha512sums.test"
    die 104 "${underline}SHA512 Hash Verification (unit test):${nounderline} 'FAIL' - received a zero as exit code, expected non-zero."
  fi
}

## Check integrity of files
check_integrity(){
  if test "${virtualbox_only}" = "1"; then
    return 0
  fi

  if test "${dry_run}" = "1"; then
    log notice "Integrity Check: Skipping integrity checks via '--dry-run' option."
    return 0
  fi
  log notice "Integrity Check: Performing integrity checks..."
  check_signature "${directory_prefix}/${guest_file}.${guest_file_ext}.sha512sums" || die 104 "${underline}Signify Signature Verification:${nounderline} 'FAIL'"
  check_hash "${directory_prefix}/${guest_file}.${guest_file_ext}.sha512sums" \
    || die 104 "${underline}SHA512 Hash Verification:${nounderline} 'FAIL'"

  check_signature_test
  check_hash_test

  log_run info touch "${download_flag}"

  log notice "Integrity Check Result: 'success'"
}


## Self explanatory name, make everything after option parsing.
main(){
  ###############
  ## BEGIN PRE ##
  ###############
  log notice "Saving user log to: '${log_file_user}'"
  if test -f "${log_file_debug}"; then
    log notice "Saving debug log to: '${log_file_debug}'"
  fi
  log info "Starting main function."

  guest_pretty="$(capitalize_first_char "${guest}")"

  case "${guest}" in
    whonix)
      guest_full_vm_name_gateway="${guest_pretty}-Gateway-${interface_name}"
      guest_full_vm_name_workstation="${guest_pretty}-Workstation-${interface_name}"
      ;;
    kicksecure)
      guest_full_vm_name_kicksecure="${guest_pretty}-${interface_name}"
      ;;
  esac

  case "${hypervisor}" in
    virtualbox)
      hypervisor_pretty="VirtualBox"
      ;;
    kvm)
      hypervisor_pretty="KVM"
      ;;
    *)
      hypervisor_pretty="${hypervisor}"
      ;;
  esac

  log info "Parsed options:"
  for item in ${arg_saved}; do
    log info "  ${item}"
  done

  if test "${virtualbox_only}" = "1"; then
    log notice "${underline}Installer:${nounderline} ${bold}'VirtualBox Installer'${nobold}"
  else
    log notice "${underline}Installer:${nounderline} ${bold}'${guest_pretty} ${interface_name} for ${hypervisor_pretty} Installer'${nobold}"
  fi
  if test "${non_interactive}" != "1"; then
    log notice "If you wish to cancel installation, press Ctrl+C."
  fi
  ## The license function sleeps for some seconds to give time to abort
  check_license || die 100 "${underline}License Check:${nounderline} User declined the license."

  pre_check

  log_time

  #############
  ## END PRE ##
  #############

  ####################
  ## BEGIN DOWNLOAD ##
  ####################
  ## Skip making internet requests if flag already exists and user
  ## specified the desired version.
  ## If version is set, use it now to set the download flag path.
  if test -n "${guest_version}"; then
    guest_file="${guest_pretty}-${interface_name}-${guest_version}"
    download_flag="${directory_prefix}/${guest_file}.${guest_file_ext}.flag"
  fi


  if should_download; then
    if test "${dry_run}" != "1"; then
      log notice "Connectivity Test: Testing internet connection to '${url_origin}'..."
      cmd_check_internet="timeout --foreground ${transfer_max_time_small_file} ${transfer_proxy_prefix:-} ${transfer_utility} ${transfer_proxy_suffix:-} ${transfer_dryrun_opt} ${transfer_size_opt} ${transfer_size_test_connection} ${url_origin}"
      log info "Executing: $ ${cmd_check_internet}"
      ${cmd_check_internet} >/dev/null ||
        die $? "${underline}Connectivity Test Result:${nounderline} 'FAIL' - Cannot connect, perhaps no internet?"
      log notice "Connectivity Test Result: 'success'"
    fi
    get_version "${url_version}"
    log notice "Version Detection Result: '${guest_version}'"
    guest_file="${guest_pretty}-${interface_name}-${guest_version}"
    download_flag="${directory_prefix}/${guest_file}.${guest_file_ext}.flag"
    url_domain="${url_domain}/${guest_version:?}"
    url_guest_file="${url_domain}/${guest_file}"

    ## Check again for download flag after version was queried.
    if should_download; then
      download_files || die 103 "${underline}Download:${nounderline} Failed to download files."
    fi
  else
    if test "${virtualbox_only}" = "1"; then
      true "INFO: Skip showing version via '--virtualbox-only' option."
    else
      log notice "Version Detection Result: '${guest_version}'"
    fi
  fi
  ##################
  ## END DOWNLOAD ##
  ##################

  ##########################################
  ## BEGIN VERIFICATION, IMPORT AND START ##
  ##########################################
  check_integrity
  check_vm_running_general
  check_vm_exists_general "(check before import)"
  vm_delete_maybe
  import_guest
  check_guest_boot
  ########################################
  ## END VERIFICATION, IMPORT AND START ##
  ########################################
}


## Print usage message and exit with set exit code, depending if usage was
## called by [-h|--help] or because user tried and invalid option.
usage(){
  printf %s"Usage: ${me} [options...]

User Options:
 -g, --guest=<guest> Specify the guest. Options: kicksecure, whonix (default)
 -u, --guest-version=<version>
                     Specify guest version, or query from API if not provided.
 -i, --interface=<interface>
                     Choose the interface. Options: cli, xfce (default)
 -m, --hypervisor=<platform>
                     Select the virtualization platform. Options: kvm, virtualbox (default)
 --oracle-repo       Use Oracle's repository for VirtualBox
 -o, --onion         Enable downloading files via onion.
 -s, --socks-proxy=<proxy>
                     Set TCP SOCKS proxy for onion client connections.
                       (Defaults to TOR_SOCKS_HOST:TOR_SOCKS_PORT; if unset,
                       attempts to use TBB (Tor Browser Bundle) proxy at port 9150,
                       or system Tor (little-t-tor) proxy at port 9050.)
 -l, --log-level=<level>
                     Choose log verbosity. Options: debug, info,
                       notice (default), warn, error.
 -V, --version       Display version information and exit.
 -h, --help          Show this help message and exit.

Developer options:
 --no-show-errors    Suppress error messages.
 --allow-errors      Continue execution despite errors. Dirty mode. Use with caution.
 --mirror=<number>   Choose a download mirror by index. Defaults to mirror 0 for
                       clearnet and mirror 0 for onion if unspecified.
                       Mirror indices:
                         0 [DE] download.whonix.org (onion available)
                         1 [DK] mirrors.dotsrc.org (onion available)
                         2 [HU] quantum-mirror.hu
 --redownload        Re-download the guest image, even if previously successful.
 --import-only=<vm>  Select specific VM to import. Only if guest is Whonix.
                       Options: workstation, gateway.
 --no-import         Skip guest import. Default behavior is to import.
 --destroy-existing-guest Deletes any existing virtual machine(s) and re-imports them.
                       Warning: This action poses a risk of data loss as it involves
                       a complete reinstallation of the VM(s). Proceed with caution.
 -k, --no-boot       Do not boot the guest after setup. Default is to start.
 -P, --directory-prefix=<dir>
                    Specify the absolute path for the directory where
                      files will be saved. Ensure that the directory already exists
                      and is readable and writable by the user. If this directory
                      is changed and previously downloaded files are not moved
                      to the new directory, the download will restart. Default:
                      \$HOME/dist-installer-cli-download.
 -n, --non-interactive
                     Enable non-interactive mode; license will be accepted.
 -D, --dev           Activate development mode. Downloads an empty image.
 --noupdate          Skip package manager list update. For development only.
 --ci                Enable Continuous Integration (CI) mode.
 --testers           Download the tester's version.
 -d, --dry-run       Simulate execution; log commands without executing.
 --virtualbox-only   Restrict actions to downloading and installing VirtualBox.
 -t, --getopt        Display parsed options and exit.
File name:
  The default file name is dist-installer-cli. Basic options can be set by using
  file name following the format 'guest-installer-interface'.
  Names not adhering to this format or the default are rejected.
  Command-line options take precedence over file name settings.
"
  exit "${1:-0}"
}


## Set default values for variables.
set_default(){
  last_exit=0
  guest_pretty=""
  get_colors
  xtrace=""
  directory_prefix=""
  set_arg directory_prefix "${HOME}/dist-installer-cli-download"
  guest=""
  set_arg guest whonix
  hypervisor=""
  set_arg hypervisor virtualbox
  interface=""
  set_arg interface xfce
  oracle_repo=""
  log_level=""
  set_arg log_level notice
  guest_version=""
  socks_proxy=""
  onion=""
  non_interactive=""
  dev=""
  noupdate=""
  dry_run=""
  getversion=""
  getopt=""
  ci=""
  no_import=""
  no_boot=""
  redownload=""
  import_only=""
  destroy_existing_guest=""
  testers=""
  allow_errors=""
  mirror=""
  virtualbox_only=""
  url_version_domain=""
  run_background=""
  background_pid=""
  debian_derivative_detected=""
  ubuntu_derivative_detected=""
  fedora_derivative_detected=""
  virtualbox_linux_user_group="vboxusers"
  # shellcheck disable=SC2034
  credential_caching_status=""
  qubes_template_detected=""
  install_pkg_fasttrack_extra_args_maybe=""
  user_warned_potential_startup_issue=""
}


## Parse script name.
parse_name(){
  ## if using default file name, ignore the rest
  test "${me}" = "dist-installer-cli" && return 0
  ## check if file name is valid
  case "${me}" in
    whonix-xfce-installer-cli | whonix-cli-installer-cli | \
      kicksecure-xfce-installer-cli | kicksecure-cli-installer-cli )
      log info "Valid script name to set options: '${me}'"
      ;;
    virtualbox-installer-cli )
      log info "Valid script name to set options: '${me}'"
      set_arg virtualbox_only 1
      set_arg hypervisor virtualbox
      return 0
      ;;
    *)
      log error "Invalid script name: '${me}'"
      log error "If you don't know why this happened, rename this script to"
      log error "  dist-installer-cli and use command-line options instead."
      return 2
  esac
  ## assign values according to script name
  set_arg guest "$(echo "${me}" | cut -d "-" -f1)"
  set_arg interface "$(echo "${me}" | cut -d "-" -f2)"
  log info "Assigned guest and interface according to script name: '${me}'"
  return 0
}


## Parse command-line options.
parse_opt(){
  #test -z "${1:-}" && usage 2
  while true; do
    begin_optparse "${1:-}" "${2:-}" || break
    # shellcheck disable=SC2034
    case "${opt}" in
      P|directory-prefix)
        get_arg directory_prefix
        ;;
      o|onion)
        set_arg onion 1
        ;;
      s|socks-proxy)
        get_arg socks_proxy
        ;;
      l|log-level)
        get_arg log_level
        ;;
      g|guest)
        get_arg guest
        ;;
      u|guest-version)
        get_arg guest_version
        ;;
      i|interface)
        get_arg interface
        ;;
      m|hypervisor)
        get_arg hypervisor
        ;;
      oracle-repo)
        set_arg oracle_repo 1
        ;;
      mirror)
        get_arg mirror
        ;;
      import-only)
        get_arg import_only
        ;;
      allow-errors)
        set_arg allow_errors 1
        ;;
      redownload)
        set_arg redownload 1
        ;;
      destroy-existing-guest)
        set_arg destroy_existing_guest 1
        ;;
      n|non-interactive)
        set_arg non_interactive 1
        ;;
      k|no-boot)
        set_arg no_boot 1
        ;;
      no-import)
        set_arg no_import 1
        ;;
      D|dev)
        set_arg dev 1
        ;;
      noupdate)
        set_arg noupdate 1
        ;;
      testers)
        set_arg testers 1
        ;;
      t|getopt)
        set_arg getopt 1
        ;;
      ci)
        set_arg ci 1
        ;;
      d|dry-run)
        set_arg dry_run 1
        ;;
      virtualbox-only)
        set_arg virtualbox_only 1
        set_arg hypervisor virtualbox
        set_arg guest none
        ;;
      V|version)
        set_arg getversion 1
        ;;
      h|help)
        usage 0
        ;;
      *)
        die 2 "Invalid option: '${opt_orig}'"
        ;;
    esac
    shift "${shift_n:-1}"
  done

  ## Put last newline after last argument of arg_saved.
  arg_saved="$(printf %s"${arg_saved}\n")"
  ## Test if options are valid
  range_arg log_level error warn notice info debug
  if [ "${log_level}" = "debug" ]; then
    xtrace=1
    set -o xtrace
  fi
  range_arg guest none whonix kicksecure
  range_arg interface cli xfce
  range_arg hypervisor kvm virtualbox
  range_arg import_only workstation gateway both

  case "${interface}" in
    xfce)
      ## Whonix 17 and above uses Xfce instead of XFCE.
      interface_name="Xfce"
      ;;
    cli)
      interface_name="CLI"
      ;;
  esac

  if test "${guest}" != "whonix"; then
    ## Guest is not 'whonix'. I.e. is 'kicksecure'
    if test -n "${import_only}"; then
      die 1 "The option '--import-only' option can only be set when the guest is 'whonix'."
    fi
  fi

  test -n "${mirror}" && range_arg mirror 0 1 2

  test -n "${socks_proxy}" && is_addr_port "${socks_proxy}"

  if test -n "${directory_prefix}"; then
    ## Remove trailing slash from directory.
    directory_prefix="${directory_prefix%*/}"
    ## Only accept an absolute path.
    if [ "${directory_prefix}" = "${directory_prefix#/}" ]; then
      log error "Invalid directory prefix: '${directory_prefix}'"
      die 1 "Directory prefix can not be a relative path, must be an absolute path."
    fi

    ## Test if parent directory exists.
    directory_prefix_parent="$(dirname "${directory_prefix}")"
    if ! test -d "${directory_prefix_parent}"; then
      die 1 "Directory doesn't exist: '${directory_prefix_parent}'"
    fi
    ## Not possible to check if parent dir is writable because if the prefix
    ## is set to '~/', the parent '/home' is not writable.

    log info "Creating directory: '${directory_prefix}'"
    mkdir -p "${directory_prefix}" ||
      die 1 "Failed to created directory: '${directory_prefix}'"
    test -w "${directory_prefix}" ||
      die 1 "Directory isn't writable: '${directory_prefix}'"
    test -r "${directory_prefix}" ||
      die 1 "Directory isn't readable: '${directory_prefix}'"

    log_dir_main="${directory_prefix}/logs"

    ## Log to incrementing integer to avoid leaking other information such
    ## as PID or date (even if UTC).
    if ! test -d "${log_dir_main}/1"; then
      log_dir_cur="${log_dir_main}/1"
    else
      last_run_integer="$(echo "${log_dir_main}"/* | awk '{print NF}')"
      cur_run_integer=$((last_run_integer+1))
      log_dir_cur="${log_dir_main}/${cur_run_integer}"
    fi
    log_file_user="${log_dir_cur}/user.log"
    log_file_debug="${log_dir_cur}/debug.log"

    ## If the commands below fail, it should have failed earlier for the
    ## parent directory permissions, not below.
    mkdir -p "${log_dir_cur}"
    cp "${0}" "${log_dir_cur}"
    touch "${log_file_user}"
  fi

  # shellcheck disable=SC2194
  if test "${getopt}" = "1"; then
    printf '%s\n' "${arg_saved}"
    exit 0
  fi
  if test "${getversion}" = "1"; then
    printf '%s\n' "${me} ${version}"
    exit 0
  fi
  if test "${dev}" = "1"; then
    if test -z "${guest_version}"; then
      log notice "Version Detection: Setting dev software version."
      guest_version="17.0.3.4"
    fi
  fi
  if test "${dry_run}" = "1"; then
    if test -z "${guest_version}"; then
      log notice "Simulation: dry_run set, commands will be printed but not executed."
      log notice "Version Detection: Using simulated software version because of dry_run."
      guest_version="17.0.3.4"
    fi
  fi
  if test "${allow_errors}" = "1"; then
    set +o errexit
    # shellcheck disable=SC2039,3040
    test "${curr_shell}" = "bash" && set +o errtrace
  fi

  log info "Option Parsing: 'success'"
}


## Logging mechanism.
## Bash supports process substitution and saving xtrace to a file, which is a
## simpler way to log to file and console.
log_term_and_file(){
  ## Discover if terminal is attached to stdout
  if ! test -t 1; then
    log warn "Output is not being sent to the terminal because terminal is not connected to stdout."
    return 0
  fi

  touch "${log_file_user}"
  touch "${log_file_debug}"
  ## By appending '&' at the end, log_file_user would remain empty.
  true "exec > >(tee -a \"${log_file_user}\") 2> >(tee -a \"${log_file_debug}\" >&2)"
  exec > >(tee -a "${log_file_user}") 2> >(tee -a "${log_file_debug}" >&2)
  ## Bash has built-in feature to redirect xtrace to the specified file.
  # shellcheck disable=SC2039
  true "exec 9>>${log_file_debug}"
  exec 9>>"${log_file_debug}"
  export BASH_XTRACEFD=9
  set -o xtrace
  xtrace=1
}


end_installer() {
  log notice "Installer Result: ${green}${bold}'SUCCESS'${nobold}${nocolor}"
  end_exit
}


## Wrapper to call all necessary functions in one.
run_installer(){
  set_globals "${@}"
  ## Set default values.
  set_default
  not_as_root
  ## Set trap for common signals.
  set_trap
  ## Parse script name for wanted values.
  parse_name
  ## Parse command-line options.
  parse_opt "${@}"
  ## Logging mechanism.
  log_term_and_file

  get_utilities
  get_download_links

  ## Start main function.
  main
}


if [ "$dist_installer_cli_was_sourced" = "true" ]; then
  true "INFO: Not running the install script because it was sourced by another script."
else
  true "INFO: Running the install script because it was executed."
  run_installer "${@}"
fi