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

let
  inherit (lib)
    mkEnableOption mkIf mkOption types
    recursiveUpdate;

  cfg = config.networking.wireless.iwd;
  ini = pkgs.formats.ini { };
  defaults = {
    # without UseDefaultInterface, sometimes wlan0 simply goes AWOL with NetworkManager
    # https://iwd.wiki.kernel.org/interface_lifecycle#interface_management_in_iwd
    General.UseDefaultInterface = with config.networking.networkmanager; (enable && (wifi.backend == "iwd"));
  };
  configFile = ini.generate "main.conf" (recursiveUpdate defaults cfg.settings);

in
{
  options.networking.wireless.iwd = {
    enable = mkEnableOption (lib.mdDoc "iwd");

    package = mkOption {
      type = types.package;
      default = pkgs.iwd;
      defaultText = lib.literalExpression "pkgs.iwd";
      description = lib.mdDoc ''
        The iwd package to use.
      '';
    };

    settings = mkOption {
      type = ini.type;
      default = { };

      example = {
        Settings.AutoConnect = true;

        Network = {
          EnableIPv6 = true;
          RoutePriorityOffset = 300;
        };
      };

      description = lib.mdDoc ''
        Options passed to iwd.
        See [here](https://iwd.wiki.kernel.org/networkconfigurationsettings) for supported options.
      '';
    };
  };

  config = lib.mkMerge [
    (mkIf cfg.enable {
      assertions = [{
        assertion = !config.networking.wireless.enable;
        message = ''
          Only one wireless daemon is allowed at the time: networking.wireless.enable and networking.wireless.iwd.enable are mutually exclusive.
        '';
      }];

      environment.etc."iwd/${configFile.name}".source = configFile;

      # for iwctl
      environment.systemPackages = [ cfg.package ];
      services.dbus.packages = [ cfg.package ];
      systemd.packages = [ cfg.package ];

      systemd.network.links."80-iwd" = {
        matchConfig.Type = "wlan";
        linkConfig.NamePolicy = "keep kernel";
      };

      systemd.services.iwd = {
        wantedBy = [ "multi-user.target" ];
        restartTriggers = [ configFile ];
      };
    })

    (
      let
        needResolv = cfg.enable
          && lib.hasAttrByPath [ "Network" "NameResolvingService" ] cfg.settings
          && cfg.settings.Network.NameResolvingService == "resolvconf";
      in
      mkIf needResolv {
        environment.systemPackages = [ pkgs.openresolv ];

        systemd.services.iwd = {
          path = [ pkgs.openresolv ];
          serviceConfig.ReadWritePaths = "/etc/resolv.conf";
        };
      }
    )
  ];

  meta.maintainers = with lib.maintainers; [ dtzWill ];
}