os/hosts/droppie/restic-backup.nix

{pkgs, ...}: let
  shutdownWaitMinutes = 15;
  shutdownScript = pkgs.writeShellScriptBin "shutdown-wait" ''
    STATUS_FILES="/media/internal/backups-pub-solar/status"

    running=""

    for f in $STATUS_FILES; do
      declare started
      declare finished

      started=$(source $f ; echo ''${BACKUP_STARTED})
      finished=$(source $f ; echo ''${BACKUP_FINISHED})

      if [ -z "''${finished}" ]; then
        echo "backup $(dirname $f) still running"
        running="yes"
        break
      fi
    done

    if [ -n "''${running}" ] && [ "''${running}" = "yes" ]; then
      echo "backups are still running"
      exit 1
    fi

    echo "WARNING: System will be shut down within the next 15 minutes" | wall

    sleep 10

    shutdown -P +${builtins.toString shutdownWaitMinutes}
  '';
in {
  systemd.services."shutdown-after-backup" = {
    enable = true;
    serviceConfig = {
      ExecStart = "${shutdownScript}/bin/shutdown-wait";
      Type = "oneshot";
    };
  };

  systemd.timers."shutdown-after-backup" = {
    enable = true;
    timerConfig = {
      OnCalendar = "*-*-* 03..09:30:00 Etc/UTC";
    };
    wantedBy = ["timers.target"];
    partOf = ["shutdown-after-backup.service"];
  };
}