nixos-config/system/all/borg-jobs.nix

{ config, lib, ... }: {

  options = {
    backup.dirs = lib.mkOption {
      default = [ ];
      type = with lib.types; listOf str;
      description = ''
        folders to backup
      '';
    };
    backup.exclude = lib.mkOption {
      default = [ ];
      type = with lib.types; listOf str;
      description = ''
        exclude files and folders matching a pattern.
        Theses patterns effect all folders in `backup.dirs`.
        see man borg pattern for more information
      '';
      example = [ ".git" "/home/*/.cache" ".stfolder" ];
    };
  };

  config = let

    servers = [
      {
        name = "workhorse";
        host = "workhorse.private";
      }
      {
        name = "pepe";
        host = "pepe.private";
      }
    ];

    dirs = config.backup.dirs;

    myHostname = config.networking.hostName;

    setup = server: {
      paths = config.backup.dirs;
      exclude = config.backup.exclude;
      doInit = true;
      repo = "borg@${server}:./${myHostname}";
      encryption = {
        mode = "repokey-blake2";
        # todo rename
        # passCommand = "cat ${toString <secrets/backup/repo>}";
        passCommand =
          "cat ${config.sops.secrets.backup_repository_passphrase.path}";
      };
      environment.BORG_RSH =
        "ssh -i ${toString config.sops.secrets.backup_ssh_rsa_private.path}";
      compression = "auto,lzma";
      startAt = "daily";
      prune.keep = {
        within = "10d"; # Keep all backups in the last 10 days.
        weekly = 8; # Keep 8 additional end of week archives.
        monthly = -1; # Keep end of month archive for every month
      };

    };

  in {

    sops.secrets.backup_repository_passphrase = { };
    sops.secrets.backup_ssh_rsa_private = { };

    services.borgbackup.jobs = let
      setups = map ({ name, host }: { "${name}" = setup host; }) servers;
      setupAttrs = lib.zipAttrsWith (_: vals: lib.head vals) setups;
      nonEmptySetups =
        lib.filterAttrs (_: { paths, ... }: builtins.length paths != 0)
        setupAttrs;
    in nonEmptySetups;

  };

}