{
  config,
  pkgs,
  lib,
  ...
}:
{
  programs.fish = {
    enable = true;
    useBabelfish = true;
    interactiveShellInit = ''
      set --global fish_greeting ""
    '';
    shellAliases = lib.mkMerge [
      {
        ip6 = "ip -6";
      }
      (lib.mkIf pkgs.stdenv.isLinux {
        ping6 = "ping -6";
      })
    ];
    promptInit = ''
      if ! functions --query tide
        fish_config prompt choose astronaut
      end
    '';
  };
  users = lib.optionalAttrs pkgs.stdenv.isLinux {
    defaultUserShell = config.programs.fish.package;
    users.root.shell = "/bin/sh";
  };

  programs.bash = {
    interactiveShellInit = ''
      # check if parent process is not fish && make nested shells work properly
      if grep -qv fish /proc/$PPID/comm && [[ $SHLVL == [12] ]]; then
          # set $SHELL for better integration with programs like nix shell, tmux, etc.
          SHELL=${pkgs.fish}/bin/fish exec fish
      fi
    '';
  };
}