{ lib, config, pkgs, ... }: {
  options = {
    promptSymbol = lib.mkOption {
      type = lib.types.str;
      description = "Prompt prefix symbol.";
    };
  };

  config = {
    programs.fish = lib.mkIf config.programs.fish.enable {
      promptInit = ''
        function fish_prompt
          echo -n '${config.promptSymbol} '
          if fish_is_root_user
            set_color red
          else
            set_color brgreen
          end
          echo -n (prompt_pwd)
          set_color normal
          echo -n ' > '
        end
        function fish_right_prompt
          set_color bryellow
          echo -n (${pkgs.git}/bin/git branch --show-current 2>/dev/null)
        end
      '';
      shellInit = ''
        set -g fish_greeting
        set -g fish_prompt_pwd_full_dirs 999
      '';
    };
  };
}