make machines.sh build on Darwin

flake.nix

@@ -4,9 +4,13 @@
   inputs = {
     nixpkgs.url = "github:NixOS/nixpkgs/release-21.05";
     nixpkgs-unstable.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+    nixpkgs-darwin.url = "github:NixOS/nixpkgs/nixpkgs-21.05-darwin";
 
     nixos-hardware.url = "github:NixOS/nixos-hardware";
 
+    darwin.url = "github:LnL7/nix-darwin";
+    darwin.inputs.nixpkgs.follows = "nixpkgs-darwin";
+
     home-manager.url = "github:nix-community/home-manager/release-21.05";
     home-manager.inputs.nixpkgs.follows = "nixpkgs";
 
@@ -197,5 +201,14 @@
           inputs.home-manager.nixosModules.home-manager
         ];
       };
+
+      darwinConfigurations.flame = inputs.darwin.lib.darwinSystem {
+        modules = [
+          ({ pkgs, ... }: {
+            nix.package = pkgs.nixUnstable;
+            nixpkgs.overlays = mkOverlays "x86_64-darwin";
+          })
+        ];
+      };
     };
 }

machines.sh

@@ -1,4 +1,20 @@
 #!/usr/bin/env bash
 set -euo pipefail
 
-nixos-rebuild --flake . "$@"
+case "$(uname -s)" in
+  Linux)
+    nixos-rebuild --flake . "$@"
+    ;;
+
+  Darwin)
+    nix-shell "-p" nixUnstable --run 'nix --experimental-features "nix-command flakes" build .#darwinConfigurations.flame.system'
+    if test "$@" != "build"; then
+      ./result/sw/bin/darwin-rebuild --flake . "$@"
+    fi
+    ;;
+
+  *)
+    echo "I don't know how to build on a $(uname -s) system."
+    exit 1
+    ;;
+esac