nix: add package & NixOS module

Signed-off-by: NotAShelf <raf@notashelf.dev>
Change-Id: I5bfbacb984356f912f1f40d6209f0a896a6a6964

nix/modules/nixos.nix

@@ -0,0 +1,38 @@
+self: {
+  config,
+  pkgs,
+  lib,
+  ...
+}: let
+  inherit (lib.modules) mkIf;
+  inherit (lib.options) mkOption mkEnableOption;
+  inherit (lib.types) package;
+
+  cfg = config.services.pscand;
+in {
+  options.services.pscand = {
+    enable = mkEnableOption "Pluggable System Condition Monitoring Daemon";
+    package = mkOption {
+      type = package;
+      default = self.packages.${pkgs.hostPlatform.system.pscand};
+      defaultText = "self.packages.$${pkgs.hostPlatform.system}.pscand";
+      description = "The pscand package to use";
+    };
+  };
+
+  config = mkIf cfg.enable {
+    systemd.packages = [cfg.package];
+
+    systemd.services.pscand = {
+      wantedBy = ["multi-user.target"];
+      after = ["network.target"];
+      serviceConfig = {
+        Type = "simple";
+        ExecStart = "${cfg.package}/bin/pscand";
+        Restart = "on-failure";
+        RestartSec = "5s";
+        Environment = ["${cfg.package}/lib/pscand/scanners"]; # FIXME: make this configurable
+      };
+    };
+  };
+}