nix-config-tn/nixos/lib/default.nix

{ lib, ... }:

with lib;
rec {

  firstOrDefault = first: default: if first != null then first else default;
  existsOrDefault = x: set: default: if builtins.hasAttr x set then builtins.getAttr x set else default;

  # main service builder
  mkService = options: (
    let
      user = existsOrDefault "user" options "568";
      group = existsOrDefault "group" options "568";

      enableBackups = (lib.attrsets.hasAttrByPath [ "persistence" "folder" ] options)
        && (lib.attrsets.attrByPath [ "persistence" "enable" ] true options);
      # nix doesnt have an exhausive list of options for oci
      # so here i try to get a robust list of security options for containers
      # because everyone needs more tinfoild hat right?  RIGHT?

      containerExtraOptions = lib.optionals (lib.attrsets.attrByPath [ "container" "caps" "privileged" ] false options) [ "--privileged" ]
        ++ lib.optionals (lib.attrsets.attrByPath [ "container" "caps" "readOnly" ] false options) [ "--read-only" ]
        ++ lib.optionals (lib.attrsets.attrByPath [ "container" "caps" "tmpfs" ] false options) [ (map (folders: "--tmpfs=${folders}") tmpfsFolders) ]
        ++ lib.optionals (lib.attrsets.attrByPath [ "container" "caps" "noNewPrivileges" ] false options) [ "--security-opt=no-new-privileges" ]
        ++ lib.optionals (lib.attrsets.attrByPath [ "container" "caps" "dropAll" ] false options) [ "--cap-drop=ALL" ]
      ;
    in
    {
      virtualisation.oci-containers.containers.${options.app} = mkIf options.container.enable {
        image = "${options.container.image}";
        user = "${user}:${group}";
        environment = {
          TZ = options.timeZone;
        } // options.container.env;
        environmentFiles = lib.attrsets.attrByPath [ "container" "envFiles" ] [ ] options;
        volumes = [ "/etc/localtime:/etc/localtime:ro" ] ++
          lib.optionals (lib.attrsets.hasAttrByPath [ "container" "persistentFolderMount" ] options) [
            "${options.persistence.folder}:${options.container.persistentFolderMount}:rw"
          ] ++ lib.attrsets.attrByPath [ "container" "volumes" ] [ ] options;
        extraOptions = containerExtraOptions;
      };
      systemd.tmpfiles.rules = lib.optionals (lib.attrsets.hasAttrByPath [ "persistence" "folder" ] options) [ "d ${options.persistence.folder} 0750 ${user} ${group} -" ];
    }
  );
}