#!/bin/bash

usage() {
  cat <<EOF
Usage:
  $(basename "$0") [OPTION...]

Options:
  -h  Print this help
  -i  Path to SSH identity file
  -d  Domain or IP to EC2 instance
  -r  Reboot after building the system
  -b  Switch to new system on next boot

EOF
}

dialog() {
  echo "Please open $(tput bold)https://nixos.org/download#nixos-amazon$(tput sgr0) and follow the
instructions to launch an EC2 instance.

$(tput bold)Note: it's recommended to use a disk size of >=20GB.$(tput sgr0)"
  echo

  read -r -p "Domain or IP of launched EC2 instance: " host
  echo
}

while getopts d:i:hrb opt; do
  case "$opt" in
    i)
      identityFile="${OPTARG}"
      ;;
    d)
      domain="${OPTARG}"
      ;;
    r)
      reboot=true
      ;;
    b)
      boot=true
      ;;
    h)
      usage
      exit 0
      ;;
    \?)
      usage >&2
      exit 64
      ;;
  esac
done

shift $((OPTIND - 1))

if [ -z "${identityFile}" ]; then
  echo "missing option: -i is required" >&2
  usage >&2
  exit 64
fi

if [ -z "$(type -P 'scp')" ] || [ -z "$(type -P 'ssh')" ]; then
  echo "missing dependency: scp or ssh not found in \$PATH" >&2
  exit 64
fi

if [ -z "${domain}" ]; then
  dialog
else
  host="${domain}"
fi

echo "$(tput bold)Copying configuration to ${host}...$(tput sgr0)"
scp -i "${identityFile}" ./configuration.nix root@"${host}":/etc/nixos/configuration.nix

echo "$(tput bold)Building system...$(tput sgr0)"
if [ "${boot}" = true ]; then
  ssh -i "${identityFile}" root@"${host}" "nixos-rebuild boot --upgrade"
else
  ssh -i "${identityFile}" root@"${host}" "nixos-rebuild switch --upgrade"
fi

if [ "${reboot}" = true ]; then
  echo "$(tput bold)Rebooting system...$(tput sgr0)"
  ssh -i "${identityFile}" root@"${host}" "systemctl reboot"
fi