nix: Add a NixOS module

Signed-off-by: Gergely Nagy <me@gergo.csillger.hu>

flake.nix

@@ -89,5 +89,7 @@
             "export RUSTFLAGS='--cfg tokio_unstable';" + self.checks.${pkgs.system}.pre-commit-check.shellHook;
         };
       });
+
+      nixosModules.default = import ./nix/nixos-module.nix { inherit self; };
     };
 }

nix/nixos-module.nix

@@ -0,0 +1,90 @@
+# SPDX-FileCopyrightText: 2025 Gergely Nagy
+# SPDX-FileContributor: Gergely Nagy
+#
+# SPDX-License-Identifier: MIT
+{ self }:
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
+let
+  cfg = config.services.iocaine;
+  defaultPackage = self.packages.${pkgs.hostPlatform.system}.iocaine;
+  tomlFormat = pkgs.formats.toml { };
+  configFile = tomlFormat.generate "iocaine.toml" cfg.config;
+in
+{
+  options.services.iocaine = {
+    enable = lib.mkEnableOption "iocaine, the deadliest poison known to AI";
+    package = lib.mkOption {
+      type = lib.types.package;
+      default = defaultPackage;
+      description = "The iocaine package to use.";
+    };
+    config = lib.mkOption {
+      inherit (tomlFormat) type;
+      default = { };
+      description = "THe configuration for iocaine.";
+    };
+  };
+
+  config = lib.mkIf cfg.enable {
+    assertions = [
+      {
+        assertion = cfg.config.sources.markov or null != null;
+        message = ''
+          You have to define at least one Markov source (`services.iocaine.config.sources.markov`) for iocaine.
+        '';
+      }
+      {
+        assertion = cfg.config.sources.words or null != null;
+        message = ''
+          You have to define a word list source (`services.iocaine.config.sources.words`) for iocaine.
+        '';
+      }
+    ];
+
+    systemd.services.iocaine = {
+      description = "iocaine, the deadliest poison known to AI";
+      restartTriggers = [ configFile ];
+      wantedBy = [ "multi-user.target" ];
+      after = [ "network.target" ];
+      environment = {
+        HOME = "%S/home";
+      };
+
+      serviceConfig = {
+        Type = "simple";
+        ExecStart = "${pkgs.lib.getExe cfg.package} --config-file ${configFile}";
+        Restart = "on-failure";
+        DynamicUser = true;
+
+        StateDirectory = "iocaine";
+        WorkingDirectory = "/var/lib/iocaine";
+
+        ProtectSystem = "strict";
+        SystemCallArchitectures = "native";
+        MemoryDenyWriteExecute = true;
+        NoNewPrivileges = true;
+        PrivateTmp = true;
+        PrivateDevices = true;
+        RestrictAddressFamilies = [
+          "AF_INET"
+          "AF_INET6"
+        ];
+        RestrictNamespaces = true;
+        RestrictRealtime = true;
+        DevicePolicy = "closed";
+        ProtectClock = true;
+        ProtectHostname = true;
+        ProtectProc = "invisible";
+        ProtectControlGroups = true;
+        ProtectKernelModules = true;
+        ProtectKernelTunables = true;
+        LockPersonality = true;
+      };
+    };
+  };
+}