{
  config,
  pkgs,
  lib,
  ...
}:
{

  options = {
    _1password = {
      enable = lib.mkEnableOption {
        description = "Enable 1Password.";
        default = false;
      };
    };
  };

  config = lib.mkIf (config.gui.enable && config._1password.enable) {
    unfreePackages = [
      "1password"
      "_1password-gui"
      "1password-cli"
    ];
    home-manager.users.${config.user} = {
      home.packages = [
        pkgs._1password-cli
      ] ++ (if pkgs.stdenv.isLinux then [ pkgs._1password-gui ] else [ ]);
    };

    # https://1password.community/discussion/135462/firefox-extension-does-not-connect-to-linux-app
    # On Mac, does not apply: https://1password.community/discussion/142794/app-and-browser-integration
    # However, the button doesn't work either:
    # https://1password.community/discussion/140735/extending-support-for-trusted-web-browsers
    environment.etc."1password/custom_allowed_browsers".text = ''
      ${
        config.home-manager.users.${config.user}.programs.firefox.package
      }/Applications/Firefox.app/Contents/MacOS/firefox
      firefox
    '';
  };
}