nixos-config/modules/restic/system.nix

{ pkgs, config, lib, ... }:
let
  cfg = config.sbruder.restic.system;

  repository = "s3:https://s3.eu-central-1.wasabisys.com/sbruder-restic";
  excludes = [
    # Caches
    "/home/*/Downloads/"
    "/home/*/.cache/"
    "/home/*/**/cache/"
    "/home/*/.local/share/Trash" # some gui applications use it
    "/data/cache/"

    # Rust
    "/home/*/**/target/debug/"
    "/home/*/**/target/doc/"
    "/home/*/**/target/release/"
    "/home/*/**/target/rls/"
    "/home/*/**/target/tarpaulin/"
    "/home/*/**/target/wasm32-unknown-unknown/"
    "/home/*/.rustup/toolchains/"
    "/home/*/.cargo"

    # Misc
    "/home/*/mount"

    # Docker (state should be kept somewhere else)
    "/var/lib/docker/"
  ] ++ cfg.extraExcludes;
  excludesFile = pkgs.writeText "excludes.txt" (lib.concatStringsSep "\n" excludes);

  # script to use restic as user without dealing with authentication
  authScript = pkgs.writeShellScriptBin "restic-auth" ''
    . <(pass nixos/machines/${config.networking.hostName}/restic-s3 | sed 's/^/export /')
    ${pkgs.restic}/bin/restic \
      --password-command="pass nixos/machines/${config.networking.hostName}/restic-password" \
      --repo "${repository}" \
      $@
  '';
in
{
  options.sbruder.restic.system = {
    enable = lib.mkEnableOption "restic";
    timerConfig = lib.mkOption {
      type = with lib.types; attrsOf str;
      default = {
        OnCalendar = "20:00";
        RandomizedDelaySec = "2h";
      };
    };
    extraPaths = lib.mkOption {
      type = lib.types.listOf lib.types.str;
      default = [ ];
      example = [ "/data" ];
    };
    extraExcludes = lib.mkOption {
      type = lib.types.listOf lib.types.str;
      default = [ ];
    };
  };

  config = lib.mkIf cfg.enable {
    krops.secrets = {
      restic-password = { };
      restic-s3 = { };
    };

    services.restic.backups.system = {
      inherit repository;
      inherit (cfg) timerConfig;
      passwordFile = config.krops.secrets.restic-password.path;
      s3CredentialsFile = config.krops.secrets.restic-s3.path;
      paths = [
        "/home"
        "/srv"
        "/var"
      ] ++ cfg.extraPaths;
      initialize = true;
      extraBackupArgs = [
        "--exclude-caches"
        "--exclude-file=${excludesFile}"
        "--tag system"
        "--verbose"
      ];
    };

    systemd.services."restic-backups-system".serviceConfig = {
      "Nice" = 10;
      "IOSchedulingClass" = "best-effort";
      "IOSchedulingPriority" = 7;
    };

    environment.systemPackages = [
      authScript
    ];
  };
}