use mkSystem

flake.nix

@@ -58,63 +58,46 @@
       inputs.nixpkgs.follows = "nixpkgs";
     };
   };
-  outputs = inputs @ {
+  outputs = {
     nixpkgs,
     nixos-cosmic,
     nix-index-database,
     darwin,
     ...
-  }: let
+  } @ inputs: let
     overlays = [
       inputs.zig.overlays.default
       inputs.rust-overlay.overlays.default
       inputs.chinese-fonts-overlay.overlays.default
       inputs.nh.overlays.default
     ];
-    inherit (nixpkgs) lib;
-    mkIfElse = p: yes: no:
-      lib.mkMerge [
-        (lib.mkIf p yes)
-        (lib.mkIf (!p) no)
-      ];
+
+    mkSystem = import ./lib/mkSystem.nix {
+      inherit overlays nixpkgs inputs;
+    };
 
     user = "nmarks";
-
-    shared_modules = [
-      # {nixpkgs.overlays = overlays;}
-      # {programs.nix-index-database.comma.enable = true;}
-      # nixindex
-      # homemanagerModules
-      {
-        _module.args = {
-          inherit user;
-          inherit mkIfElse;
-        };
-      }
-    ];
   in {
-    nixosConfigurations = {
-      nixos = lib.nixosSystem {
-        system = "x86_64-linux";
-        modules =
-          [
-            ./hosts/desktop/configuration.nix
-            nixos-cosmic.nixosModules.default
-          ]
-          ++ shared_modules;
-        specialArgs = inputs;
-      };
+    nixosConfigurations.nixos = mkSystem "nixos" {
+      system = "x86_64-linux";
+      inherit user;
+      extraModules = [
+        nixos-cosmic.nixosModules.default
+      ];
     };
-    darwinConfigurations = {
-      "Natalies-MacBook-Air" = darwin.lib.darwinSystem {
-        system = "aarch64-darwin";
-        specialArgs = inputs;
-        modules =
-          [
-            ./hosts/laptop/configuration.nix
-          ]
-          ++ shared_modules;
-      };
+    darwinConfigurations."Natalies-MacBook-Air" = mkSystem "Natalies-MacBook-Air" {
+      system = "aarch64-darwin";
+      inherit user;
+      darwin = true;
     };
+    # darwinConfigurations = {
+    #   "Natalies-MacBook-Air" = darwin.lib.darwinSystem {
+    #     system = "aarch64-darwin";
+    #     specialArgs = inputs;
+    #     modules = [
+    #       ./hosts/laptop/configuration.nix
+    #     ];
+    #   };
+    # };
   };
 }

lib/mkSystem.nix

@@ -0,0 +1,70 @@
+# This function creates a NixOS system based on our VM setup for a
+# particular architecture.
+{
+  nixpkgs,
+  overlays,
+  inputs,
+}: name: {
+  system,
+  user,
+  darwin ? false,
+  extraModules ? [],
+}: let
+  # True if this is a WSL system.
+  # True if Linux, which is a heuristic for not being Darwin.
+  mkIfElse = p: yes: no:
+    nixpkgs.lib.mkMerge [
+      (nixpkgs.lib.mkIf p yes)
+      (nixpkgs.lib.mkIf (!p) no)
+    ];
+
+  nixindex = mkIfElse darwin inputs.nix-index-database.darwinModules.nix-index inputs.nix-index-database.nixosModules.nix-index;
+
+  host = mkIfElse darwin "laptop" "desktop";
+
+  # The config files for this system.
+
+  hostConfig = ../hosts/${host}/configuration.nix;
+
+  # NixOS vs nix-darwin functions
+  systemFunc = mkIfElse darwin inputs.darwin.lib.darwinSystem nixpkgs.lib.nixosSystem;
+  home-manager =
+    if darwin
+    then inputs.home-manager.darwinModules
+    else inputs.home-manager.nixosModules;
+in
+  systemFunc rec {
+    inherit system;
+
+    modules =
+      [
+        # Apply our overlays. Overlays are keyed by system type so we have
+        # to go through and apply our system type. We do this first so
+        # the overlays are available globally.
+        {nixpkgs.overlays = overlays;}
+        {inputs.programs.nix-index-database.comma.enable = true;}
+        hostConfig
+        nixindex
+        home-manager.home-manager
+        {
+          home-manager = {
+            useGlobalPkgs = true;
+            useUserPackages = true;
+            backupFileExtension = "hm-backup";
+            extraSpecialArgs = {inherit inputs;};
+          };
+        }
+
+        # We expose some extra arguments so that our modules can parameterize
+        # better based on these values.
+        {
+          config._module.args = {
+            currentSystem = system;
+            currentSystemName = name;
+            currentSystemUser = user;
+            inherit inputs;
+          };
+        }
+      ]
+      ++ extraModules;
+  }

modules/shared/extras.nix

@@ -2,13 +2,8 @@
   pkgs,
   config,
   inputs,
-  hostName,
-  mkIfElse,
-  darwin,
   ...
 }: {
   networking = {
-    inherit hostName;
-    networkmanager = !darwin;
   };
 }

modules/shared/home-manager.nix

@@ -1,8 +0,0 @@
-{inputs, ...}: {
-  home-manager = {
-    useGlobalPkgs = true;
-    useUserPackages = true;
-    backupFileExtension = "hm-backup";
-    extraSpecialArgs = {inherit inputs;};
-  };
-}

modules/shared/modules.nix

@@ -1,13 +0,0 @@
-{
-  pkgs,
-  inputs,
-  config,
-  ...
-}: {
-  imports = [
-    # {pkgs.overlays = overlays;}
-    {programs.nix-index-database.comma.enable = true;}
-    config.nixindex
-    config.homemanagerModules
-  ];
-}

modules/shared/vars.nix

@@ -1,23 +0,0 @@
-{
-  inputs,
-  pkgs,
-  config,
-  lib,
-  mkIfElse,
-  ...
-}: let
-  darwin = pkgs.stdenv.isDarwin;
-  homemanagerModules = mkIfElse darwin inputs.home-manager.darwinModules inputs.home-manager.nixosModules;
-  nixindex = mkIfElse darwin inputs.nix-index-database.darwinModules.nix-index inputs.nix-index-database.nixosModules.nix-index;
-in {
-  config.var = {
-    inherit darwin homemanagerModules nixindex;
-  };
-
-  options = {
-    var = lib.mkOption {
-      type = lib.types.attrs;
-      default = {};
-    };
-  };
-}