{ config, lib, ... }:

let
  cfg = config.my.defaults;
  mkCmdOption = description: lib.mkOption {
    type = lib.types.nullOr lib.types.str;
    default = null;
    inherit description;
  };
in
{
  options.my.defaults = {
    terminal = mkCmdOption "Command for the default terminal ($TERMINAL).";
    browser  = mkCmdOption "Command for the default browser ($BROWSER).";
    editor   = mkCmdOption "Command for the default editor ($EDITOR and $VISUAL).";
  };

  config.home.sessionVariables = lib.mkMerge [
    (lib.mkIf (cfg.terminal != null) { TERMINAL = cfg.terminal; })
    (lib.mkIf (cfg.browser != null)  { BROWSER = cfg.browser; })
    (lib.mkIf (cfg.editor != null)   { EDITOR = cfg.editor; VISUAL = cfg.editor; })
  ];
}