#!/usr/bin/env bash

main() {
  while getopts ":l:d:t:" opt; do
    case "${opt}" in
      l)
        unset VM_FILTER
        IFS="," read -r -a VM_FILTER <<< "$OPTARG"
        ;;
      d)
        local backup_location="${OPTARG}"
        backup_location="${backup_location%/}"
        ;;
      t)
        declare -g TARGET="$OPTARG"
        ;;
      h)
        usage
        ;;
      *)
        usage
        ;;
    esac
  done

  backup_location=${backup_location:-$PWD}

  if [[ "${#VM_FILTER[*]}" -gt 0 ]]; then
    backup_vms "$backup_location" "${VM_FILTER[@]}"
  else
    backup_vms "$backup_location"
  fi
}

lxc() {
	local lxc_cmd="${TARGET:-lxc}"
	command "$lxc_cmd" "$@"
}

list_vms() {
	lxc list -c n -f csv,noheader
}

usage() {
  cat <<EOF
Usage: ${0##*/} [-l vm[,vm...]] [-d backup_dir] [-t lxc|incus] [-h]

Options:
  -l  Comma-separated list of VMs to back up
  -d  Directory where backups will be stored (default: current directory)
  -t  Manager type: lxc or incus (default: lxc)
  -h  Show this message

EOF
  exit 1
}

backup_vms() {
  local backup_location="$1"; shift
  local vms=("$@")

  # when no argument use list of all VMs
  if ((${#vms[@]} == 0)); then
    mapfile -t vms < <(list_vms)
  fi

  for vm in "${vms[@]}"; do
    [[ -n $vm ]] || continue
    start_backup "$vm" "$backup_location"
  done
}

start_backup() {
  local vm=$1
  local backup_base="$2"
  local destination="${backup_base}/${vm}"
  local backup_name="${vm}_$(date +"%Y-%m-%d_%H-%M-%S").tar.gz"

  [[ -d "$backup_base" ]] || { echo "${backup_base} is not a directory"; exit 1; }
  [[ -d "$destination" ]] || mkdir "$destination"
  [[ -f "${destination}/${backup_name}" ]] && { echo "Backup already exists"; return 2; }

  lxc export "$vm" "${destination}/${backup_name}"
}

main "$@"