Add Nix Flake

flake.nix

@@ -0,0 +1,45 @@
+{
+  description = "Unified hosts file with base extensions.";
+  inputs.flake-utils.url = "github:numtide/flake-utils";
+  outputs = { self, nixpkgs, flake-utils }: {
+    nixosModule = { config, ... }:
+      with nixpkgs.lib;
+      let
+        cfg = config.networking.stevenBlackHosts;
+        alternatesList = (if cfg.blockFakenews then [ "fakenews" ] else []) ++
+                         (if cfg.blockGambling then [ "gambling" ] else []) ++
+                         (if cfg.blockPorn then [ "porn" ] else []) ++
+                         (if cfg.blockSocial then [ "social" ] else []);
+        alternatesPath = "alternates/" + builtins.concatStringsSep "-" alternatesList + "/";
+      in
+      {
+        options.networking.stevenBlackHosts = {
+          enable = mkEnableOption "Use Steven Black's hosts file as extra hosts.";
+          blockFakenews = mkEnableOption "Additionally block fakenews hosts.";
+          blockGambling = mkEnableOption "Additionally block gambling hosts.";
+          blockPorn = mkEnableOption "Additionally block porn hosts.";
+          blockSocial = mkEnableOption "Additionally block social hosts.";
+        };
+        config = mkIf cfg.enable {
+          networking.extraHosts =
+            builtins.readFile (
+              "${self}/" + (if alternatesList != [] then alternatesPath else "") + "hosts"
+            );
+        };
+      };
+  } // flake-utils.lib.eachDefaultSystem
+    (system:
+      let
+        pkgs = nixpkgs.legacyPackages.${system};
+      in
+      {
+        devShell = pkgs.mkShell {
+          buildInputs = with pkgs; [
+            python3
+            python3Packages.flake8
+            python3Packages.requests
+          ];
+        };
+      }
+    );
+}