factorio: automate updating server

hosts/monolith/factorio-server.nix

@@ -2,14 +2,7 @@
 {
   services.factorio = {
     enable = true;
-    package = pkgs.unstable.factorio-headless.overrideAttrs (_: rec {
+    package = pkgs.factorio-headless; # I override this in ./pkgs
-      version = "2.0.12";
-      src = pkgs.fetchurl {
-        name = "factorio_headless_x64-${version}.tar.xz";
-        url = "https://www.factorio.com/get-download/${version}/headless/linux64";
-        hash = "sha256-0vgg5eJ6ZEFO0TUixNsByCs8YyPGOArgqnXbT5RIjTE=";
-      };
-    });
     public = true;
     lan = true;
     openFirewall = true;

pkgs/default.nix

@@ -8,4 +8,7 @@ rec {
   emmet-cli = pkgs.callPackage ./emmet-cli.nix { };
   material-wifi-icons = pkgs.callPackage ./material-wifi-icons.nix { };
   gnome-pass-search-provider = pkgs.callPackage ./gnome-pass-search-provider.nix { };
+  factorio-headless = pkgs.callPackage ./factorio-headless {
+    inherit (pkgs.unstable) factorio-headless;
+  };
 }

pkgs/factorio-headless/default.nix

@@ -0,0 +1,10 @@
+{ factorio-headless, pkgs }:
+
+factorio-headless.overrideAttrs (_: rec {
+  version = "2.0.13";
+  src = pkgs.fetchurl {
+    name = "factorio_headless_x64-${version}.tar.xz";
+    url = "https://www.factorio.com/get-download/${version}/headless/linux64";
+    hash = "sha256-J7NpAaOeWTrfKEGMAoYULGx6n4PRVpY8c2m9QFolx9E=";
+  };
+})

pkgs/factorio-headless/update.sh

@@ -0,0 +1,14 @@
+#!/bin/sh
+
+set -xe
+
+cd "$(dirname $0)"
+
+current_version="$(rg '^.*?version\s*=\s*"(.+)".*?$' --replace '$1' ./default.nix)"
+current_hash="$(rg '^.*?hash\s*=\s*"(.+)".*?$' --replace '$1' ./default.nix)"
+
+new_version="$(curl https://factorio.com/api/latest-releases | jq -r .stable.headless)"
+new_hash="$(nix-hash --to-sri --type sha256 $(nix-prefetch-url --type sha256 https://www.factorio.com/get-download/${new_version}/headless/linux64))"
+
+sd "$current_version" "$new_version" ./default.nix
+sd "$current_hash" "$new_hash" ./default.nix