Add oura and fourmolu to the dev shell

flake.nix

@@ -0,0 +1,52 @@
+{
+  inputs = {
+    raw-oura.url = "github:Renegatto/oura?rev=3be6b2883d41ced958c4d462b5e899e05cdf9b6a";
+    flake-utils.follows = "raw-oura/flake-utils";
+    rust-overlay.follows = "raw-oura/rust-overlay";
+    nixpkgs.follows = "raw-oura/nixpkgs";
+    crane = {
+      url = "github:ipetkov/crane";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
+  };
+
+  outputs = {
+    self,
+    raw-oura,
+    crane,
+    flake-utils,
+    rust-overlay,
+    nixpkgs,
+    ...
+  }: let
+    supportedSystems = ["x86_64-linux" "x86_64-darwin" "aarch64-linux"];
+    overlays = [ (import rust-overlay) ];
+    pkgs = import nixpkgs {
+      inherit overlays;
+      system = "x86_64-linux";
+    };
+    # oura: Derivation
+    oura =
+      let
+        # oura.nix:
+        #   {inputs: {crane: NixInput, oura: NixInput}} ->
+        #   { perSystem: {pkgs: any} ->
+        #     {  packages: { oura-${string}: Package } }
+        #   }
+        make-oura = import ./oura.nix {inputs = {inherit crane; oura = raw-oura;};};
+      in builtins.head (builtins.attrValues (make-oura.perSystem {inherit pkgs;}).packages);
+
+  in flake-utils.lib.eachSystem supportedSystems
+    (
+      system: {
+        devShells = {
+          default =
+            pkgs.mkShell {
+            nativeBuildInputs = [
+              oura
+              pkgs.haskellPackages.fourmolu
+            ];
+          };
+       };
+    });
+}

oura.nix

@@ -0,0 +1,19 @@
+# {inputs: {crane: NixInput, oura: NixInput}} ->
+# { perSystem: {pkgs: any} -> {  packages: { oura: Package } }
+# }
+{inputs}: {
+  perSystem = {pkgs}: let
+    craneLib = inputs.crane.mkLib pkgs;
+    oura = craneLib.buildPackage {
+      cargoExtraArgs = "--all-features"; # Enable all bundled plugins
+      env = {
+        OPENSSL_NO_VENDOR = "1"; # Use system openssl
+      };
+      nativeBuildInputs = [pkgs.pkg-config];
+      buildInputs = [pkgs.openssl];
+      src = craneLib.cleanCargoSource inputs.oura;
+    };
+  in {
+    packages = { inherit oura; };
+  };
+}