#!/bin/bash

set -o errexit

readonly LSB_RELEASE="/etc/lsb-release"
readonly BOARD_NAME_KEY="CHROMEOS_RELEASE_BOARD"
readonly APPID_KEY="CHROMEOS_BOARD_APPID"

mount_rw() {
  mount -o remount,rw /
}

mount_ro() {
  mount -o remount,ro /
}

die() {
  echo "$@"
  mount_ro
  exit 1
}

get_board() {
  grep "$BOARD_NAME_KEY" "$LSB_RELEASE" | awk -F '=' '{print $2}'
}

set_appid() {
  local appid="$1"
  if [[ -z "$appid" ]]; then
    die "No valid appid detected, abort."
  fi
  sed -i "s|^\($APPID_KEY\)={.*}$|\1={$appid}|" "$LSB_RELEASE"
  echo -e "\nModified appid to $appid successfully, all done.\n\n"
}

check_user() {
  if [[ $EUID -ne 0 ]]; then
    echo "Please run this script as root or prepend sudo, abort."
    exit 1
  fi
}

main() {
  check_user
  mount_rw
  local board

  board="$(get_board)"
  case "$board" in
    "surface-pro4")
      echo -e "\nSurface Pro 4 detected, proceed..."
      set_appid "C8975970-2856-498A-8938-3570D7756CAF"
      ;;
    "surface-pro5")
      echo -e "\nSurface Pro 5 detected, proceed..."
      set_appid "CF167F7B-C4AD-42F1-82F4-0598D0785ABE"
      ;;
    "surface-pro6")
      echo -e "\nSurface Pro 6 detected, proceed..."
      set_appid "8E7644B3-3941-4E22-BC82-6625F947972F"
      ;;
    *) die "No modification required, abort."
      ;;
  esac

  mount_ro
}

main "$@"