#!/usr/bin/env bash

set -euo pipefail

if [ "${1:-}" = "-h" ] || [ "${1:-}" = "--help" ] || [ $# -ne 1 ]; then
  declare -r ARGV0=$(basename "${0:-generate-keypair.sh}")
  printf 'Usage: %s SERVICE_NAME\n' "$ARGV0" >&2
  cat <<'EOF' >&2
Generate a new keypair for use in backup targets

Options:
  -h, --help        Show this help and exit
  SERVICE_NAME      The name of the service to generate a backup key for. Should not contain spaces.

Example usage:
  # Generate a new keypair for backuping some service 'my-service' state via rsync
  generate-keypair.sh my-service

EOF
  exit 1
fi

declare -r PROJECT_ROOT="$(git rev-parse --show-toplevel)"
declare -r KEYPATH="$PROJECT_ROOT/ssh_extra_keys/id_ed25519_$1_rsync_backup"

if [[ -f "$KEYPATH" ]]; then
  printf "$KEYPATH already exists...\n" >&2
  exit 1
fi

ssh-keygen -t ed25519 -b 4096 -C "$1 rsync backup" -f "$KEYPATH" -N ''