{ config, pkgs, lib, ... }:
{
  # Nix configuration ------------------------------------------------------------------------------

  nix.binaryCaches = [
    "https://cache.nixos.org/"
    "https://hydra.iohk.io"
    "https://nix-community.cachix.org"
  ];
  nix.binaryCachePublicKeys = [
    "cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY="
    "hydra.iohk.io:f/Ea+s+dFdN+3Y/G+FDgSq+a5NEWhJGzdjvKNGv0/EQ="
    "nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs="
  ];
  nix.trustedUsers = [
    "@admin"
  ];
  users.nix.configureBuildUsers = true;

  nix.buildCores = 1;
  nix.maxJobs = 8;

  # Enable experimental nix command and flakes
  # nix.package = pkgs.nixUnstable;
  nix.extraOptions = ''
    auto-optimise-store = true
    experimental-features = nix-command flakes
  '' + lib.optionalString (pkgs.system == "aarch64-darwin") ''
    extra-platforms = x86_64-darwin aarch64-darwin
  '';

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

  # Make Fish the default shell
  programs.fish.enable = true;
  programs.fish.useBabelfish = true;
  programs.fish.babelfishPackage = pkgs.babelfish;
  # Needed to address bug where $PATH is not properly set for fish:
  # https://github.com/LnL7/nix-darwin/issues/122
  programs.fish.shellInit = ''
    for p in (string split : ${config.environment.systemPath})
      if not contains $p $fish_user_paths
        set -g fish_user_paths $fish_user_paths $p
      end
    end
  '';
  environment.variables.SHELL = "${pkgs.fish}/bin/fish";
  environment.loginShell = "${pkgs.fish}/bin/fish";

  # Install and setup ZSH to work with nix(-darwin) as well
  programs.zsh.enable = true;

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

}