{ pkgs, ... }:
{

  nix = {
    package = pkgs.nix;
    settings.sandbox = true;
    extraOptions = ''
      experimental-features = nix-command flakes
    '';
  };

  # Right now the documentation build is broken.
  # TODO(jwall): Add this back when they work again.
  documentation.enable = false;

  # I'm not a zealot about this one.
  nixpkgs.config.allowUnfree = true;

  nixpkgs.overlays = [
   (self: super: {
     neovim = super.neovim.override {
       viAlias = true;
       vimAlias = true;
     };
   })
  ];

  launchd.user.agents.ipfs = {
    serviceConfig = {
      ProgramArguments = [
        "${pkgs.kubo}/bin/ipfs"
        "daemon"
        "--init"
      ];
      KeepAlive = true;
      RunAtLoad = true;
    };
  };

  # TODO launchd.user.agents.prometheus;
  # Use a custom configuration.nix location.
  # $ darwin-rebuild switch -I darwin-config=$HOME/.config/nixpkgs/darwin/configuration.nix
  # environment.darwinConfig = "$HOME/.config/nixpkgs/darwin/configuration.nix";

  # Auto upgrade nix package and the daemon service.
  services.nix-daemon.enable = true;

  #services.spacebar.enable = true;
  #services.spacebar.package = "${pkgs.spacebar}";

  # Create /etc/bashrc that loads the nix-darwin environment.
  # programs.bash.enable = true;  # default shell on catalina
  # programs.fish.enable = true;

  # Used for backwards compatibility, please read the changelog before changing.
  # $ darwin-rebuild changelog
  system.stateVersion = 4;
}