{ config, lib, pkgs, ... }:

with lib;
let cfg = config.fudo.games.valheim;
in {
  options.fudo.games.valheim = with types; {
    enable = mkEnableOption "Enable dedicated Valheim server.";

    state-directory = mkOption {
      type = str;
      description = "Directory at which to store Valheim state data.";
      default = "/var/lib/valheim";
    };

    port = mkOption {
      type = port;
      description = "Port on which to listen for connections.";
      default = 2456;
    };

    password = mkOption {
      type = str;
      description = "Password required by connecting users.";
    };
  };

  config = mkIf cfg.enable {
    users.users.valheim = {
      home = cfg.state-directory;
      createHome = true;
      isSystemUser = true;
    };

    systemd.services.fudo-valheim = {
      wantedBy = [ "multi-user.target" ];
      serviceConfig = {
        ExecStartPre = ''
          [[ -d ${cfg.state-directory}/state ]] || mkdir ${cfg.state-directory}/state
          ${pkgs.steamcmd}/bin/steamcmd \
            +login anonymous \
            +force_install_dir ${cfg.state-directory}/state \
            +app_update 896660 \
            +quit
        '';

        ExecStart = ''
          ${pkgs.glibc}/lib/ld-linux-x86-64.so.2 ./valheim_server.x86_64 \
            -name "CoCo Valheim" \
            -port ${toString cfg.port} \
            -world "Dedicated" \
            -password ${cfg.password} \
            -public 1
        '';
        Nice = -5;
        Restart = "always";
        User = "valheim";
        StateDirectory = "${cfg.state-directory}/state";
        WorkingDirectory = cfg.state-directory;
      };
      environment = { LD_LIBRARY_PATH = "linux64:${pkgs.glibc}/lib"; };
    };
  };
}