{ config, lib, ... }:
let
  inherit (lib)
    mkEnableOption
    mkIf
    mkOption
    optionalAttrs
  ;

  cfg = config.my.services.transmission;

  domain = config.networking.domain;
  webuiDomain = "transmission.${domain}";

  transmissionRpcPort = 9091;
  transmissionPeerPort = 30251;

  downloadBase = "/media/torrents/";
in
{
  options.my.services.transmission = let inherit (lib) types; in {
    enable = mkEnableOption "Transmission torrent client";

    username = mkOption {
      type = types.str;
      default = "alarsyo";
      example = "username";
      description = "Name of the transmission RPC user";
    };

    secretConfigFile = mkOption {
      type = types.nullOr types.path;
      default = null;
      example = "/var/run/secrets/transmission-secrets";
      description = "Path to secrets file to append to configuration";
    };
  };

  config = mkIf cfg.enable {
    services.transmission = {
      enable = true;
      group = "media";

      settings = {
        download-dir = "${downloadBase}/complete";
        incomplete-dir = "${downloadBase}/incomplete";

        peer-port = transmissionPeerPort;

        rpc-enabled = true;
        rpc-port = transmissionRpcPort;
        rpc-authentication-required = false;

        rpc-whitelist-enabled = true;
        rpc-whitelist = "127.0.0.1";

        rpc-host-whitelist-enabled = true;
        rpc-host-whitelist = webuiDomain;
      };

      # automatically allow transmission.settings.peer-port
      openFirewall = true;
    } // (optionalAttrs (cfg.secretConfigFile != null) {
      credentialsFile = cfg.secretConfigFile;
    });

    services.nginx.virtualHosts."${webuiDomain}" = {
      forceSSL = true;
      useACMEHost = domain;

      locations."/".proxyPass = "http://127.0.0.1:${toString transmissionRpcPort}";

      listen = [
        # FIXME: hardcoded tailscale IP
        {
          addr = "100.80.61.67";
          port = 443;
          ssl = true;
        }
        {
          addr = "100.80.61.67";
          port = 80;
          ssl = false;
        }
      ];
    };
  };
}