dotfiles.nix/home/services/tarsnap.nix

{
  config,
  pkgs,
  lib,
  ...
}:
{
  # set configuration in ~ so tarsnap cli works interactively
  home.file.".tarsnaprc".text = ''
    cachedir ${config.xdg.cacheHome}
    keyfile ${config.xdg.configHome}/tarsnap/read-write-delete.key
    nodump
    print-stats
    checkpoint-bytes 1G
    humanize-numbers
  '';
  # tarsnap periodic backup configuration
  launchd.agents.tarsnap =
    let
      logPath = "${config.xdg.stateHome}/tarsnap";
      tarsnapBackup = pkgs.writeShellScriptBin "tarsnap-backup-helper" ''
        date=$(date -u +%Y-%m-%dT%H:%M:%SZ)
        echo
        echo "Running tarsnap backup for $date"
        ${lib.getExe pkgs.tarsnap} -c \
          --configfile ${config.home.homeDirectory}/.tarsnaprc \
          --keyfile ${config.xdg.configHome}/tarsnap/write-only.key \
          -f $(uname -n)-$date \
          ${config.home.homeDirectory}/{dotfiles.nix,Desktop,Development,Documents}
      '';
    in
    {
      enable = true;
      config = {
        Label = "com.tarsnap.tarsnap";
        StandardErrorPath = "${logPath}/error.log";
        StandardOutPath = "${logPath}/out.log";
        StartCalendarInterval = [
          {
            # every sunday
            Weekday = 0;
            # at midnight
            Hour = 0;
            Minute = 0;
          }
        ];
        Program = lib.getExe tarsnapBackup;
      };
    };
}