mensa-tts/module.nix

{ lib, config, pkgs, mensa-tts-pkgs, ... }:
with lib;
let
  # Shorter name to access final settings a 
  # user of hello.nix module HAS ACTUALLY SET.
  # cfg is a typical convention.
  cfg = config.services.mensa-tts;
in
{

  options.services.mensa-tts = {
    enable = mkEnableOption "mensa-tts service";

    package = mkOption {
      default = mensa-tts-pkgs.x86_64-linux.default;
      type = types.package;
      description = "mensa-tts packages to use. Needed to fix crosscompilation issues.";
    };

    user = mkOption {
      type = types.str;
      default = "mensa-tts";
      description = mdDoc "User to run the mensa-tts script.";
    };

    group = mkOption {
      type = types.str;
      default = "mensa-tts";
      description = mdDoc "Group for the mensa-tts user.";
    };

    time = mkOption {
      type = types.str;
      default = "Mon..Fri 11:10:00 Europe/Berlin";
      description = mdDoc "Time to trigger the mensa-tts service. Uses systemd OnCalendar format.";
    };

    local-address = mkOption {
      type = types.str;
      default = "127.0.0.1";
      description = mdDoc "Local address to send the UDP frames from";
    };

    local-port = mkOption {
      type = types.str;
      default = "4810";
      description = mdDoc "Local port to send the UDP frames from";
    };

    remote-address = mkOption {
      type = types.str;
      default = "127.0.0.1";
      description = mdDoc "Remote address to send the UDP frames to";
    };

    remote-port = mkOption {
      type = types.str;
      default = "3810";
      description = mdDoc "Remote port to send the UDP frames to";
    };

    cache-dir = mkOption {
      type = types.str;
      default = "/var/cache/mensa-tts";
      description = mdDoc "Directory to store temporary data";
    };

  };

  config = mkIf cfg.enable {
    environment.systemPackages = with pkgs; [
      cfg.package
    ];

    users.users = mkIf (cfg.user == "mensa-tts") {
      mensa-tts = {
        group = cfg.group;
        isNormalUser = true;
      };
    };

    users.groups = mkIf (cfg.group == "mensa-tts") {
      mensa-tts = { };
    };

    systemd.tmpfiles.rules = [
      "d '${cfg.cache-dir}' 0750 ${cfg.user} ${cfg.group} - -"
    ];

    systemd.services.mensa-tts = {
      description = "mensa-tts service";
      serviceConfig = {
        Type = "oneshot";
        User = cfg.user;
        Group = cfg.group;
        WorkingDirectory = cfg.cache-dir;
      };
      script = ''
        ${cfg.package}/bin/mensa_to_speech
        ${cfg.package}/bin/fm_feed_wav --local-addr ${cfg.local-address} \
          --local-port ${cfg.local-port} \
          --remote-addr ${cfg.remote-address} \
          --remote-port ${cfg.remote-port} \
          --wav mensa.wav
      '';
    };


    systemd.timers.mensa-tts = {
      wantedBy = [ "timers.target" ];
      timerConfig = {
        OnCalendar = cfg.time;
        Unit = "mensa-tts.service";
      };
    };
  };
}