{
  pkgs,
  lib,
  config,
  ...
}: let
  inherit (lib) mkIf mkEnableOption mkOption types concatStringsSep typeOf;
  cfg = config.programs.culr;
in {
  options.programs.culr = {
    enable = mkEnableOption "culr";
    pattern = mkOption {
      type = with types; either str (listOf int);
      default = [];
      description = "colourising pattern";
    };
    palette = mkOption {
      type = with types; listOf str;
      default = [];
      description = "palette to use in comma separated RGB hex eg. #0f0f0f";
    };
  };

  config = mkIf cfg.enable {
    environment.systemPackages = let inherit (pkgs) culr; in [culr];
    environment.sessionVariables = {
      CULR_PATTERN = let
        serialise = {
          list = list: concatStringsSep ";";
          str = s: s;
        };
      in
        mkIf (cfg.pattern != "" && cfg.pattern != [])
        serialise.${typeOf cfg.pattern}
        cfg.pattern;
      CULR_PALETTE = mkIf (cfg.palette != []) (concatStringsSep ";" cfg.palette);
    };
  };
}