README: add flakes section

README.md

@@ -52,3 +52,30 @@ Impure/pure mode
 Sometimes it can be useful to build the image _outside_ of the Nix sandbox for debugging purposes.
 
 For this purpose we have an attribute called `impureMode` which outputs the shell script used by Nix inside the sandbox to build the image.
+
+
+Usage with Nix Flakes
+---------------------
+
+Build the demo by running:
+```shell
+nix build .#demoImage
+```
+
+This project's **flake.nix** exposes its functions under `lib`. To use
+in your own project, setup your flake like this:
+
+```nix
+{
+  inputs = {
+    nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
+    wfvm.url = "git+https://git.m-labs.hk/m-labs/wfvm";
+  };
+
+  outputs = { self, nixpkgs, wfvm }: {
+    packages."x86_64-linux".flaky-os = wfvm.lib.makeWindowsImage {
+      # configuration parameters go here
+    };
+  };
+}
+```

flake.nix

@@ -16,5 +16,9 @@
       lib = import ./wfvm {
         inherit pkgs;
       };
+
+      packages.${system}.demoImage = import ./wfvm/demo-image.nix {
+        inherit self;
+      };
     };
 }

wfvm/demo-image.nix

@@ -1,7 +1,17 @@
-{ pkgs ? import <nixpkgs> {}, impureMode ? false }:
+{ pkgs ? import <nixpkgs> {}
+# Whether to generate just a script to start and debug the windows installation
+, impureMode ? false
+# Flake input `self`
+, self ? null
+}:
 
 let
-  wfvm = (import ./default.nix { inherit pkgs; });
+  wfvm =
+    if self == null
+    # nix-build
+    then (import ./default.nix { inherit pkgs; })
+    # built from flake.nix
+    else self.lib;
 in
 wfvm.makeWindowsImage {
   # Build install script & skip building iso

wfvm/layers/default.nix

@@ -72,7 +72,7 @@ in
       bootstrapper = pkgs.fetchurl {
         name = "RESTRICTDIST-vs_Community.exe";
         url = "https://aka.ms/vs/16/release/vs_community.exe";
-        sha256 = "0vj6s82b1c0n6cjysx1lba7xmgmy7pmmk3apq1i4xsqwcjv80xwv";
+        sha256 = "sha256-4X8NhdcNyfHkN6eKkNz8Unvv49wRZE4CQ1vf6P1R2ic=";
       };
       # This touchy-feely "community" piece of trash seems deliberately crafted to break Wine, so we use the VM to run it.
       download-vs = wfvm.utils.wfvm-run {

wfvm/win.nix

@@ -36,8 +36,8 @@ let
   );
 
   windowsIso = if windowsImage != null then windowsImage else pkgs.requireFile rec {
-    name = "Win10_21H1_English_x64.iso";
+    name = "Win10_21H2_English_x64.iso";
-    sha256 = "1sl51lnx4r6ckh5fii7m2hi15zh8fh7cf7rjgjq9kacg8hwyh4b9";
+    sha256 = "0kr3m0bjy086whcbssagsshdxj6lffcz7wmvbh50zhrkxgq3hrbz";
     message = "Get ${name} from https://www.microsoft.com/en-us/software-download/windows10ISO";
   };