docs: update Nix usage instructions

Signed-off-by: NotAShelf <raf@notashelf.dev>
Change-Id: I8717b49f21f777003787a663feb0467a6a6a6964

README.md

@@ -232,6 +232,40 @@ npm start
 
 </details>
 
+<details>
+<summary>Nix</summary>
+
+**Flake** (NixOS or flake-enabled systems):
+
+```nix
+{
+  inputs.troutbot.url = "github:notashelf/troutbot";
+
+  outputs = { self, nixpkgs, troutbot }: {
+    nixosConfigurations.myhost = nixpkgs.lib.nixosSystem {
+      modules = [
+        troutbot.nixosModules.troutbot
+        {
+          services.troutbot = {
+            enable = true;
+            environmentFile = "/path/to/.env"; # use Agenix if possible
+            configPath = "/path/to/config.ts" # use Agenix if possible
+          };
+        }
+      ];
+    };
+  };
+};
+```
+
+**Run directly**:
+
+```bash
+nix run github:notashelf/troutbot
+```
+
+</details>
+
 <details>
 <summary>Docker</summary>
 

flake.lock

@@ -0,0 +1,27 @@
+{
+  "nodes": {
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1769461804,
+        "narHash": "sha256-msG8SU5WsBUfVVa/9RPLaymvi5bI8edTavbIq3vRlhI=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "bfc1b8a4574108ceef22f02bafcf6611380c100d",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixos-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

flake.nix

@@ -0,0 +1,36 @@
+{
+  description = "Troutbot - GitHub webhook bot";
+
+  inputs.nixpkgs.url = "github:NixOS/nixpkgs?ref=nixos-unstable";
+
+  outputs = {
+    self,
+    nixpkgs,
+  }: let
+    systems = [
+      "x86_64-linux"
+      "aarch64-linux"
+      "x86_64-darwin"
+      "aarch64-darwin"
+    ];
+
+    forEachSystem = f: nixpkgs.lib.genAttrs systems (system: f nixpkgs.legacyPackages.${system});
+  in {
+    nixosModules = {
+      troutbot = import ./nix/modules/nixos.nix self;
+      default = self.nixosModules.troutbot;
+    };
+
+    packages = forEachSystem (pkgs: {
+      troutbot = pkgs.callPackage ./nix/package.nix {};
+      default = self.packages.${pkgs.hostPlatform.system}.troutbot;
+    });
+
+    devShells = forEachSystem (pkgs: {
+      default = pkgs.mkShell {
+        name = "troutbot-dev";
+        packages = [pkgs.nodejs-slim pkgs.pnpm];
+      };
+    });
+  };
+}

nix/modules/nixos.nix

@@ -0,0 +1,83 @@
+self: {
+  config,
+  pkgs,
+  lib,
+  ...
+}: let
+  inherit (lib.modules) mkIf;
+  inherit (lib.options) mkOption mkEnableOption literalExpression;
+  inherit (lib.types) nullOr str port package;
+
+  defaultPackage = self.packages.${pkgs.stdenv.hostPlatform.system}.troutbot;
+  cfg = config.services.troutbot;
+in {
+  options.services.troutbot = {
+    enable = mkEnableOption "troutbot";
+
+    package = mkOption {
+      type = nullOr package;
+      default = defaultPackage;
+      defaultText = literalExpression "inputs.troutbot.packages.${pkgs.stdenv.hostPlatform.system}.troutbot";
+      description = ''
+        The Troutbot package to use.
+
+        By default, this option will use the `packages.default` as exposed by this flake.
+      '';
+    };
+
+    user = mkOption {
+      type = str;
+      default = "troutbot";
+    };
+
+    group = mkOption {
+      type = str;
+      default = "troutbot";
+    };
+
+    port = mkOption {
+      type = port;
+      default = 3000;
+    };
+
+    environmentFile = mkOption {
+      type = nullOr str;
+      default = null;
+    };
+
+    configPath = mkOption {
+      type = nullOr str;
+      default = null;
+    };
+  };
+
+  config = mkIf cfg.enable {
+    users.users.${cfg.user} = {
+      isSystemUser = true;
+      group = cfg.group;
+    };
+
+    users.groups.${cfg.group} = {};
+
+    systemd.services.troutbot = {
+      description = "Troutbot";
+      after = ["network.target"];
+      wantedBy = ["multi-user.target"];
+      serviceConfig = {
+        Type = "simple";
+        User = cfg.user;
+        Group = cfg.group;
+        ExecStart = "${lib.getExe cfg.package}";
+        Restart = "on-failure";
+        EnvironmentFile = cfg.environmentFile;
+        NODE_ENV = "production";
+        CONFIG_PATH = cfg.configPath;
+        PORT = toString cfg.port;
+        ProtectSystem = "strict";
+        ProtectHome = true;
+        PrivateTmp = true;
+        NoNewPrivileges = true;
+      };
+    };
+  };
+}

nix/package.nix

@@ -0,0 +1,71 @@
+{
+  lib,
+  stdenv,
+  nodejs,
+  pnpmConfigHook,
+  fetchPnpmDeps,
+  pnpm,
+  makeBinaryWrapper,
+}:
+stdenv.mkDerivation (finalAttrs: {
+  pname = "troutbot";
+  version = "0-unstable-2026-01-30";
+
+  src = lib.fileset.toSource {
+    root = ../.;
+    fileset = lib.fileset.unions [
+      ../src
+      ../config.example.ts
+      ../package.json
+      ../pnpm-lock.yaml
+      ../tsconfig.json
+    ];
+  };
+
+  strictDeps = true;
+  nativeBuildInputs = [
+    nodejs # in case scripts are run outside of a pnpm call
+    pnpmConfigHook
+    pnpm # at least required by pnpmConfigHook, if not other (custom) phases
+
+    makeBinaryWrapper
+  ];
+
+  pnpmDeps = fetchPnpmDeps {
+    inherit (finalAttrs) pname version src;
+    fetcherVersion = 3;
+    hash = "sha256-y8LV1D+EgGcZ79lmxS20dqYBPEfk4atma+RWf7pJI30=";
+  };
+
+  buildPhase = ''
+    runHook preBuild
+
+    pnpm run build --outDir dist
+
+    runHook postBuild
+  '';
+
+  installPhase = ''
+    runHook preInstall
+
+    mkdir -p $out/{bin,share}
+
+    # Copy transpiled result
+    cp -rv dist/* $out/share
+
+    # Copy the example config
+    install -Dm755 config.example.ts $out/share
+
+    makeWrapper ${lib.getExe nodejs} $out/bin/troutbot \
+      --set-default NODE_ENV production \
+      --add-flags "$out/share/index.js"
+
+    runHook postInstall
+  '';
+
+  meta = {
+    description = "The ultimate trout population helper";
+    license = lib.licenses.eupl12;
+    maintainers = with lib.maintainers; [NotAShelf];
+  };
+})