{
  description =
    "Planning Poker web app. Trying to build something and learn new things";
  inputs.nixpkgs.url = "github:nixos/nixpkgs";
  inputs.flake-utils.url = "github:numtide/flake-utils";
  inputs.sbt-derivation.url = "github:zaninime/sbt-derivation/master";
  inputs.sbt-derivation.inputs.nixpkgs.follows = "nixpkgs";

  outputs = { self, nixpkgs, flake-utils, sbt-derivation }:
    flake-utils.lib.eachDefaultSystem (system:
      let
        pkgs = nixpkgs.legacyPackages.${system};
        packageName = "blanning-poker-kazbegi";
        backendName = "${packageName}-backend";
        version = "0.1.1";
        backendPackage = sbt-derivation.lib.mkSbtDerivation rec {
          inherit pkgs version;

          # ...and the rest of the arguments
          pname = "${backendName}";
          depsSha256 = "sha256-7MNlMeljYqXY4/kK4BXoycp9xUz0tGwCQvPTlE1RIQU=";
          src = pkgs.nix-gitignore.gitignoreSource [ ] ./.;
          buildPhase = ''
            sbt backend/assembly
          '';
          installPhase = ''
            mkdir -p $out/bin
            cp backend/target/scala-*/backend-assembly-*.jar $out/bin/${pname}.jar
          '';
        };
      in {
        # Development shell with things required for local dev
        devShells.default = pkgs.mkShell {
          buildInputs = [
            pkgs.nodejs
            pkgs.sbt
            pkgs.scalafmt
            pkgs.jdk
            # pkgs.nodePackages.tailwindcss
            # pkgs.nodePackages.postcss
          ];
          shellHook = ''
            echo "dev env for planning poker BWARGH started"
          '';
        };
        # Just the backend jar
        packages.backend = backendPackage;
        # Module for NixOS to allow starting backend as SystemD service
        nixosModules.backendApp = { config, pkgs, ... }:
          let
            cfg = config.services.${backendName};
            lib = pkgs.lib;
          in {
            options.services.${backendName} = {
              enable =
                lib.mkEnableOption "My frontendmentor exercise ${backendName}";

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

              host = lib.mkOption {
                type = lib.types.str;
                default = "localhost";
                description = "Host to bind to.";
              };

              useNginx = lib.mkOption {
                type = lib.types.bool;
                default = true;
                description = "Whether to use Nginx to proxy requests.";
              };
            };
            config = lib.mkIf cfg.enable {
              # users.groups."${backendName}-group" = { };
              # users.users."${backendName}-user" = {
              #   isSystemUser = true;
              #   group = "${backendName}-group";
              # };

              # systemd.services.${backendName} =
              #   let serverHost = if cfg.useNginx then "localhost" else cfg.host;
              #   in {
              #     description = "Exercise app ${backendName}";
              #     wantedBy = [ "multi-user.target" ];
              #     after = [ "network.target" ];
              #     startLimitIntervalSec = 30;
              #     startLimitBurst = 10;
              #     serviceConfig = {
              #       ExecStart =
              #         "${pkgs.jdk}/bin/java -jar ${backendPackage}/bin/${backendName}.jar -p ${
              #           toString cfg.port
              #         } --host ${serverHost}";
              #       WorkingDirectory = "${backendPackage}/bin";
              #       Restart = "on-failure";
              #       User = "${backendName}-user";
              #       Group = "${backendName}-group";
              #     };
              #   };
              # # this is only backend. Front end still configured and installed separately.
              # services.nginx.virtualHosts.${cfg.host}.locations."/api" = {
              #   proxyPass = "http://127.0.0.1:${toString cfg.port}";
              #   # this is config for websocket
              #   extraConfig = ''
              #     rewrite ^/api/(.*)$ /$1 break;
              #     proxy_set_header Host $host;
              #     proxy_set_header X-Real-IP $remote_addr;
              #     proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
              #     proxy_set_header X-Forwarded-Proto $scheme;

              #     # Add the following lines for WebSocket support
              #     proxy_http_version 1.1;
              #     proxy_set_header Upgrade $http_upgrade;
              #     proxy_set_header Connection "upgrade";
              #   '';
              # };
            };
          };
      });
  # see https://serokell.io/blog/practical-nix-flakes
}