msg() {
  # check if messages are to be printed using color
  unset ALL_OFF BOLD BLUE GREEN RED YELLOW
  # prefer terminal safe colored and bold text when tput is supported
  if tput setaf 0 &>/dev/null; then
    ALL_OFF="$(tput sgr0)"
    BOLD="$(tput bold)"
    BLUE="${BOLD}$(tput setaf 4)"
    GREEN="${BOLD}$(tput setaf 2)"
    RED="${BOLD}$(tput setaf 1)"
    YELLOW="${BOLD}$(tput setaf 3)"
  else
    ALL_OFF="\e[0m"
    BOLD="\e[1m"
    BLUE="${BOLD}\e[34m"
    GREEN="${BOLD}\e[32m"
    RED="${BOLD}\e[31m"
    YELLOW="${BOLD}\e[33m"
  fi

  local mesg=$1; shift
  printf "${RED}  ->${ALL_OFF}${BOLD} ${mesg}${ALL_OFF}\n" "$@" >&2
}

flash_uboot() {
  msg "A new U-Boot version needs to be flashed onto /dev/mmcblk0."
  msg "Do you want to do this now? [y|N]"
  read -r shouldwe
  if [[ $shouldwe =~ ^([yY][eE][sS]|[yY])$ ]]; then
    dd if=/dev/zero of=/dev/mmcblk0 bs=1k count=1023 seek=1 status=noxfer
    dd if=/boot/rksd_loader.img of=/dev/mmcblk0 seek=64 conv=notrunc
  else
    msg "You can do this later by running:"
    msg "# dd if=/dev/zero of=/dev/mmcblk0 bs=1k count=1023 seek=1 status=noxfer"
    msg "# dd if=/boot/rksd_loader.img of=/dev/mmcblk0 seek=64 conv=notrunc"
    msg "# if you are using the emmc interface, take care to use the correct device identifier! (probably mmcblk1)"
  fi
}

## arg 1:  the new package version
post_install() {
  mkimage -A arm -O linux -T script -C none -n "U-Boot boot script" -d "/boot/boot.txt" "/boot/boot.scr"
  flash_uboot
}

## arg 1:  the new package version
## arg 2:  the old package version
post_upgrade() {
  post_install
}