{
  lib,
  gensokyo-zone,
  ...
}: let
  inherit (gensokyo-zone.lib) mapAlmostOptionDefaults mkAlmostOptionDefault;
  inherit (lib.modules) mkIf;
  inherit (lib.attrsets) mapAttrs;
  inherit (lib.lists) all imap0;
  inherit (lib.trivial) id;
in {
  config.exports.services.home-assistant = {config, ...}: let
    mkAssertion = f: nixosConfig: let
      cfg = nixosConfig.services.home-assistant;
    in
      f nixosConfig cfg;
    assertPort = nixosConfig: cfg: {
      assertion = config.ports.default.port == cfg.config.http.server_port;
      message = "port mismatch";
    };
    assertHomekitPort = let
      portName = i: "homekit${toString i}";
      mkAssertPort = i: homekit: config.ports.${portName i}.port or null == homekit.port;
    in
      nixosConfig: cfg: {
        assertion = all id (imap0 mkAssertPort cfg.config.homekit);
        message = "homekit port mismatch";
      };
  in {
    id = mkAlmostOptionDefault "home";
    displayName = mkAlmostOptionDefault "Home Assistant";
    prometheus.exporter.metricsPath = "/api/prometheus";
    nixos = {
      serviceAttr = "home-assistant";
      assertions = mkIf config.enable [
        (mkAssertion assertPort)
        (mkAssertion assertHomekitPort)
      ];
    };
    defaults.port.listen = mkAlmostOptionDefault "lan";
    ports = {
      default = {
        port = mkAlmostOptionDefault 8123;
        protocol = "http";
        status.enable = true;
        prometheus.exporter.enable = mkAlmostOptionDefault true;
      };
      homekit0 = {
        port = mkAlmostOptionDefault 21063;
        transport = "tcp";
      };
      # TODO: cast udp port range 32768 to 60999
    };
  };
}