{
  description = "kafka — privacy-respecting, open metasearch engine";

  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
  };

  outputs = { self, nixpkgs }:
    let
      systems = [ "x86_64-linux" "aarch64-linux" ];
      forAllSystems = f: nixpkgs.lib.genAttrs systems (system: f system);
    in
    {
      packages = forAllSystems (system:
        let
          pkgs = import nixpkgs { inherit system; };
        in
        {
          default = pkgs.buildGoModule {
            pname = "kafka";
            version = "0.1.0";
            src = ./.;

            vendorHash = "sha256-8wlKD+33s97oorCJTfHKAgE2Xp1HKXV+bSr6z29KrKM=";
            # Run: nix build .#packages.x86_64-linux.default
            # It will fail with the correct hash. Replace vendorHash with it.

            # Embed the templates and static files at build time.
            ldflags = [ "-s" "-w" ];

            # Remove stale vendor directory before buildGoModule deletes it.
            preConfigure = "rm -rf vendor || true";

            nativeCheckInputs = with pkgs; [ ];

            # Tests require network; they run in CI instead.
            checkPhase = "";

            meta = with pkgs.lib; {
              description = "Privacy-respecting, open metasearch engine";
              homepage = "https://git.ashisgreat.xyz/penal-colony/kafka";
              license = licenses.mit;
              platforms = platforms.linux ++ platforms.darwin;
            };
          };
        });

      nixosModules.default = { config, lib, pkgs, ... }:
        let
          cfg = config.services.kafka;
        in
        {
          options.services.kafka = {
            enable = lib.mkEnableOption "kafka metasearch engine";

            package = lib.mkOption {
              type = lib.types.package;
              default = self.packages.${pkgs.system}.default;
              description = "kafka package to use.";
            };

            port = lib.mkOption {
              type = lib.types.port;
              default = 8080;
              description = "Port to listen on.";
            };

            openFirewall = lib.mkOption {
              type = lib.types.bool;
              default = false;
              description = "Open the firewall port.";
            };

            baseUrl = lib.mkOption {
              type = lib.types.str;
              default = "";
              description = "Public base URL for OpenSearch XML (e.g. https://search.example.com).";
            };

            config = lib.mkOption {
              type = lib.types.path;
              default = "/etc/kafka/config.toml";
              description = "Path to config.toml file.";
            };

            user = lib.mkOption {
              type = lib.types.str;
              default = "kafka";
              description = "System user to run as.";
            };

            group = lib.mkOption {
              type = lib.types.str;
              default = "kafka";
              description = "System group to run as.";
            };

            stateDir = lib.mkOption {
              type = lib.types.path;
              default = "/var/lib/kafka";
              description = "State directory.";
            };
          };

          config = lib.mkIf cfg.enable {
            users.users.${cfg.user} = lib.mkIf (cfg.user == "kafka") {
              isSystemUser = true;
              group = cfg.group;
              home = cfg.stateDir;
              createHome = true;
            };

            users.groups.${cfg.group} = lib.mkIf (cfg.group == "kafka") { };

            systemd.services.kafka = {
              description = "kafka metasearch engine";
              after = [ "network.target" ];
              wantedBy = [ "multi-user.target" ];

              serviceConfig = {
                Type = "simple";
                User = cfg.user;
                Group = cfg.group;
                ExecStart = "${lib.getExe cfg.package} -config ${cfg.config}";
                Restart = "on-failure";
                RestartSec = "5s";
                WorkingDirectory = cfg.stateDir;
                Environment = lib.optionals (cfg.baseUrl != "") [
                  "BASE_URL=${cfg.baseUrl}"
                ];
              };
            };

            networking.firewall = lib.mkIf cfg.openFirewall {
              allowedTCPPorts = [ cfg.port ];
            };
          };
        };

      devShells = forAllSystems (system:
        let
          pkgs = import nixpkgs { inherit system; };
        in
        {
          default = pkgs.mkShell {
            buildInputs = [
              pkgs.go_1_24
              pkgs.curl
            ];
          };
        });
    };
}
