#!/bin/bash

set -e

display=:10
interface=0.0.0.0
cert_group=ssl-cert
xstartup_script=~/.vnc/xstartup
de_was_selected_file="$HOME/.vnc/.kasmvncserver-easy-start-de-was-selected"

action=start

manual_xstartup_choice="Manually edit xstartup"
declare -A all_desktop_environments=(
  [Cinnamon]=cinnamon-session
  [Mate]="XDG_CURRENT_DESKTOP=MATE dbus-launch --exit-with-session mate-session"
  [LXDE]=lxsession [Lxqt]=startlxqt
  [KDE]=startkde
  [Gnome]="XDG_CURRENT_DESKTOP=GNOME dbus-launch --exit-with-session /usr/bin/gnome-session"
  [XFCE]=xfce4-session)

readarray -t sorted_desktop_environments < <(for de in "${!all_desktop_environments[@]}"; do echo "$de"; done | sort)

all_desktop_environments[$manual_xstartup_choice]=""
sorted_desktop_environments+=("$manual_xstartup_choice")

detected_desktop_environments=()
declare -A numbered_desktop_environments

debug() {
  if [ -z "$debug" ]; then return; fi

  echo "$@"
}

print_detected_desktop_environments() {
  declare -i i=1

  echo "Please choose Desktop Environment to run:"
  for detected_de in "${detected_desktop_environments[@]}"; do
    echo "[$i] $detected_de"
    numbered_desktop_environments[$i]=$detected_de
    i+=1
  done
}

detect_desktop_environments() {
  for de_name in "${sorted_desktop_environments[@]}"; do
    if [[ "$de_name" = "$manual_xstartup_choice" ]]; then
      detected_desktop_environments+=("$de_name")
      continue;
    fi

    local executable=${all_desktop_environments[$de_name]}
    executable=($executable)
    executable=${executable[-1]}

    if detect_desktop_environment "$de_name" "$executable"; then
      detected_desktop_environments+=("$de_name")
    fi
  done
}

ask_user_to_choose_de() {
  while : ; do
    print_detected_desktop_environments
    read -r de_number_to_run
    de_name_from_number "$de_number_to_run"
    if [[ -n "$de_name" ]]; then
      break;
    fi

    echo "Incorrect number: $de_number_to_run"
    echo
  done
}

remember_de_choice() {
  touch "$de_was_selected_file"
}

de_was_selected() {
  [[ -f "$de_was_selected_file" ]]
}

detect_desktop_environment() {
  local de_name="$1"
  local executable="$2"

  if command -v "$executable" &>/dev/null; then
    return 0
  fi

  return 1
}

did_user_forbid_replacing_xstartup() {
  grep -q -v KasmVNC-safe-to-replace-this-file "$xstartup_script"
}

de_cmd_from_name() {
  de_cmd=${all_desktop_environments[$de_name]}
}

de_name_from_number() {
  local de_number_to_run="$1"

  de_name=${numbered_desktop_environments[$de_number_to_run]}
}

setup_de_to_run_via_xstartup() {
  generate_xstartup "$de_name"
}

generate_xstartup() {
  local de_name="$1"

  de_cmd_from_name

  cat <<-SCRIPT > "$xstartup_script"
    #!/bin/sh
    exec $de_cmd
SCRIPT
  chmod +x "$xstartup_script"
}

enable_debug() {
  debug=1
  log_option="-log *:stderr:100"
}

kill_vnc_server() {
  vncserver -kill $display
}

process_cli_options() {
  for option in "$@"; do
    case "$option" in
      --help)
        show_help
        exit
        ;;
      -d)
        enable_debug
        ;;
      -kill)
        kill_vnc_server
        exit
        ;;
      -select-de)
        action=select-de-and-start
        ;;
      *)
        echo >&2 "Unsupported argument: $option"
        exit 1
    esac
  done
}

user_asked_to_select_de() {
  [[ "$action" = "select-de-and-start" ]]
}
show_help() {
  cat >&2 <<-USAGE
Usage: `basename $0` [options]
  -d          Debug output
  -kill       Kill vncserver
  -select-de  Select desktop environent to run
  --help      show this help
USAGE
}

process_cli_options "$@"

if groups | grep -qvw ssl-cert; then
  cat <<-EOF
    Can't access TLS certificate.
    Please add your user to $cert_group via 'addgroup <user> ssl-cert'
EOF
  exit 1
fi

if user_asked_to_select_de || ! de_was_selected; then
  detect_desktop_environments
  ask_user_to_choose_de
  debug "You selected $de_name desktop environment"
  if [[ "$de_name" != "$manual_xstartup_choice" ]]; then
    setup_de_to_run_via_xstartup
  fi
  remember_de_choice
fi

vncserver $display -interface $interface
vncserver -kill $display
vncserver $display -depth 24 -geometry 1280x1050 -websocketPort 8443 \
  -cert /etc/ssl/certs/ssl-cert-snakeoil.pem \
  -key /etc/ssl/private/ssl-cert-snakeoil.key -sslOnly -FrameRate=24 \
  -interface $interface -httpd /usr/share/kasmvnc/www $log_option