#!/usr/bin/env bash
set -euo pipefail

usage() {
  echo "usage: $0 backup <data-file> <backup-dir> | restore <backup-file> <data-file>" >&2
  exit 2
}

[ "$#" -eq 3 ] || usage
command=$1
source=$2
target=$3

case "$command" in
backup)
  [ -f "$source" ] || {
    echo "data file does not exist: $source" >&2
    exit 1
  }
  mkdir -p "$target"
  name="$(basename "$source").$(date -u +%Y%m%dT%H%M%SZ).manual.json"
  temporary="$target/.wxagent-backup-$$.tmp"
  trap 'rm -f "$temporary"' EXIT
  install -m 600 "$source" "$temporary"
  mv -f "$temporary" "$target/$name"
  sha256sum "$target/$name"
  ;;
restore)
  [ -f "$source" ] || {
    echo "backup file does not exist: $source" >&2
    exit 1
  }
  directory=$(dirname "$target")
  mkdir -p "$directory"
  lock="$target.lock"
  exec 9>"$lock"
  flock -n 9 || {
    echo "data file is in use; stop the active control plane first" >&2
    exit 1
  }
  temporary="$directory/.wxagent-restore-$$.tmp"
  trap 'rm -f "$temporary"' EXIT
  install -m 600 "$source" "$temporary"
  python3 -m json.tool "$temporary" >/dev/null
  mv -f "$temporary" "$target"
  sha256sum "$target"
  ;;
*)
  usage
  ;;
esac