#!/bin/bash --posix

set -e

IP=""
INBOUND_PORT=""
FORWARD_PORT=""

usage() {
  printf "%s" "Usage:
    --ip
        The ip address to forward data to
        Example:
          --ip 192.168.10.11
    --inbound-port
        The port that data will be received on
        Example:
          --inbound-port 22
    --forward-port
        The port that data will be forwarded to
        Example:
          --forward-port 2020

    All above flags must be passed with arguments"
}

error() {
  printf '%s\n' "$1" >&2
  exit 1
}

while :; do
  case $1 in
  -h | -\? | --help)
    usage # Display a usage synopsis.
    exit
    ;;
  --) # End of all options.
    shift
    break
    ;;
  --ip)
    shift
    [[ "${1}" == "" ]] && error "--ip requires an argument"
    IP=${1}
    ;;
  --inbound-port)
    shift
    [[ "${1}" == "" ]] && error "--inbound-port requires an argument"
    INBOUND_PORT=${1}
    ;;
  --forward-port)
    shift
    [[ "${1}" == "" ]] && error "--forward-port requires an argument"
    FORWARD_PORT=${1}
    ;;
  -?*)
    printf 'Unknown option: %s\n' "$1" >&2
    usage
    ;;
  *) # Default case: No more options, so break out of the loop.
    break ;;
  esac

  shift
done

[[ "${IP}" == "" ]] && error "--ip requires an argument"
[[ "${FORWARD_PORT}" == "" ]] && error "--forward-port requires an argument"
[[ "${INBOUND_PORT}" == "" ]] && error "--inbound-port requires an argument"

firewall-cmd --permanent --add-forward-port=port="${INBOUND_PORT}":proto=tcp:toaddr="${IP}":toport="${FORWARD_PORT}"
firewall-cmd --permanent --add-port="${INBOUND_PORT}"/tcp
firewall-cmd --add-masquerade --permanent
firewall-cmd --reload

echo "Routing all data on ${INBOUND_PORT} to ${IP}:${FORWARD_PORT}"