#!/bin/bash

# snippet from https://stackoverflow.com/questions/10768160/ip-address-converter
ip2dec () {
    local a b c d ip=$@
    IFS=. read -r a b c d <<< "$ip"
    printf '%d\n' "$((a * 256 ** 3 + b * 256 ** 2 + c * 256 + d))"
}

error_exit() {
  echo "Error: $1 is not a valid IPv4 address range"
  exit 1
}

# Only run this if there is a hypen present in $1
if [[ "$1" =~ "-" ]]; then
  # This only works with real bash (<<<) - split IP addresses into array with
  # hyphen as delimiter
  readarray -d - -t strarr <<< $1

  ipaddrcheck --is-ipv4-single "${strarr[0]}"
  if [ $? -gt 0 ]; then
    error_exit $1
  fi

  ipaddrcheck --is-ipv4-single "${strarr[1]}"
  if [ $? -gt 0 ]; then
    error_exit $1
  fi

  start=$(ip2dec ${strarr[0]})
  stop=$(ip2dec ${strarr[1]})
  if [ $start -ge $stop ]; then
    error_exit $1
  fi

  exit 0
fi

error_exit $1