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

  nix = {
    package = pkgs.nix;
    # SEE: https://github.com/NixOS/nix/issues/4119#issuecomment-1734738812
    settings.sandbox = "relaxed";
    extraOptions = ''
      experimental-features = nix-command flakes repl-flake
      extra-platforms = x86_64-darwin aarch64-darwin x86_64-linux
    '';
  };

  # 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;
     };
   })
  ];

  # TODO(zaphar): Move this to a module.
  launchd.user.agents.ipfs = {
    serviceConfig = {
      ProgramArguments = [
        "${pkgs.kubo}/bin/ipfs"
        "daemon"
        "--init"
      ];
      KeepAlive = true;
      RunAtLoad = true;
    };
  };

  services.node-exporter.enable = true;
  services.prometheus.enable = true;
  services.heracles.enable = true;
  services.heracles.settings = [
        {
            title = "Metrics";
            span = {
                end = "now";
                duration = "1d";
                step_duration = "5min";
            };
            graphs = [
                {
                    title = "CPU and Mem Used";
                    query_type = "Range";
                    plots = [
                        { # CPU plot
                            source = "http://${config.services.prometheus.listen}";
                            query = ''
                              sum by (job,instance, mode)(irate(node_cpu_seconds_total[5m]))
                              / ignoring(mode) group_left
                              sum by (job,instance)(irate(node_cpu_seconds_total[5m]))
                            '';
                            meta = {
                                name_format = "`\${labels.instance} - \${labels.mode}`";
                                d3_tick_format = "~%";
                            };
                        }
                        { # Memory Usage
                            source = "http://${config.services.prometheus.listen}";
                            query = ''
                              (node_memory_wired_bytes
                               + node_memory_compressed_bytes
                               + node_memory_active_bytes)
                              / node_memory_total_bytes
                            '';
                            meta = {
                                name_format = "`\${labels.instance} - Memory`";
                                d3_tick_format = "~%";
                            };
                        }
                    ];
                }
            ];
        }
    ];

  # 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;

   system.defaults = {
     finder.AppleShowAllExtensions = true;
   };
   system.systemBuilderArgs = lib.mkIf (config.nix.settings.sandbox == "relaxed") {
      sandboxProfile = ''
        (allow file-read* file-write* process-exec mach-lookup (subpath "${builtins.storeDir}"))
      '';
    };
  # Used for backwards compatibility, please read the changelog before changing.
  # $ darwin-rebuild changelog
  system.stateVersion = 4;
}