dyn-gandi/nix/module.nix

inputs: {
  config,
  lib,
  pkgs,
  system,
  ...
}: let
  cfg = config.dyn-gandi;
  package = inputs.self.packages.${pkgs.stdenv.hostPlatform.system}.default;
  inherit (lib) mkIf mkEnableOption mkOption types;

  format = pkgs.formats.json {};
  configFile = format.generate "config.json" cfg.settings;
in {
  options.dyn-gandi = {
    enable = mkEnableOption "dyn-gandi";

    timer = lib.mkOption {
      type = types.nullOr types.int;
      default = null;
      description = lib.mdDoc ''
        The time intervall in seconds the script should be repeated.
      '';
    };

    settings = mkOption {
      type = with types; let
        valueType = nullOr (oneOf [
          # TODO: restrict type to actual config file structure
          bool
          int
          float
          str
          path
          (attrsOf valueType)
          (listOf valueType)
        ]);
      in
        valueType;
      default = throw "Please specify dyn-gandi.settings";
    };
  };

  config = mkIf cfg.enable {
    environment.systemPackages = [package];

    systemd.services.dyn-gandi = mkIf (cfg.timer
      != null) {
      script = "${package}/bin/dyn-gandi --config ${configFile}";

      serviceConfig = {
        Type = "oneshot";
      };
    };

    systemd.timers.dyn-gandi = mkIf (cfg.timer
      != null) {
      wantedBy = ["timers.target"];
      timerConfig = {
        OnBootSec = "0s";
        OnUnitActiveSec = "${toString cfg.timer}s";
        Unit = "dyn-gandi.service";
      };
    };
  };
}