# D-Bus configuration and system bus daemon.

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

let

  cfg = config.services.dbus;

  homeDir = "/run/dbus";

  configDir = pkgs.makeDBusConf {
    inherit (cfg) apparmor;
    suidHelper = "${config.security.wrapperDir}/dbus-daemon-launch-helper";
    serviceDirectories = cfg.packages;
  };

  inherit (lib) mkOption types;

in

{
  options = {

    services.dbus = {

      enable = mkOption {
        type = types.bool;
        default = false;
        internal = true;
        description = lib.mdDoc ''
          Whether to start the D-Bus message bus daemon, which is
          required by many other system services and applications.
        '';
      };

      packages = mkOption {
        type = types.listOf types.path;
        default = [ ];
        description = lib.mdDoc ''
          Packages whose D-Bus configuration files should be included in
          the configuration of the D-Bus system-wide or session-wide
          message bus.  Specifically, files in the following directories
          will be included into their respective DBus configuration paths:
          {file}`«pkg»/etc/dbus-1/system.d`
          {file}`«pkg»/share/dbus-1/system.d`
          {file}`«pkg»/share/dbus-1/system-services`
          {file}`«pkg»/etc/dbus-1/session.d`
          {file}`«pkg»/share/dbus-1/session.d`
          {file}`«pkg»/share/dbus-1/services`
        '';
      };

      apparmor = mkOption {
        type = types.enum [ "enabled" "disabled" "required" ];
        description = lib.mdDoc ''
          AppArmor mode for dbus.

          `enabled` enables mediation when it's
          supported in the kernel, `disabled`
          always disables AppArmor even with kernel support, and
          `required` fails when AppArmor was not found
          in the kernel.
        '';
        default = "disabled";
      };
    };
  };

  config = lib.mkIf cfg.enable {
    environment.systemPackages = [
      pkgs.dbus
    ];

    environment.etc."dbus-1".source = configDir;

    users.users.messagebus = {
      uid = config.ids.uids.messagebus;
      description = "D-Bus system message bus daemon user";
      home = homeDir;
      group = "messagebus";
    };

    users.groups.messagebus.gid = config.ids.gids.messagebus;

    systemd.packages = [
      pkgs.dbus
    ];

    security.wrappers.dbus-daemon-launch-helper = {
      source = "${pkgs.dbus}/libexec/dbus-daemon-launch-helper";
      owner = "root";
      group = "messagebus";
      setuid = true;
      setgid = false;
      permissions = "u+rx,g+rx,o-rx";
    };

    services.dbus.packages = [
      pkgs.dbus
      config.system.path
    ];

    systemd.services.dbus = {
      # Don't restart dbus-daemon. Bad things tend to happen if we do.
      reloadIfChanged = true;
      restartTriggers = [
        configDir
      ];
      environment = {
        LD_LIBRARY_PATH = config.system.nssModules.path;
      };
    };

    systemd.user.services.dbus = {
      # Don't restart dbus-daemon. Bad things tend to happen if we do.
      reloadIfChanged = true;
      restartTriggers = [
        configDir
      ];
    };

    systemd.user.sockets.dbus.wantedBy = [
      "sockets.target"
    ];

    environment.pathsToLink = [
      "/etc/dbus-1"
      "/share/dbus-1"
    ];
  };
}