nixpkgs/modules/services/system/dbus.nix

# D-Bus system-wide daemon.
{pkgs, config, ...}:

###### interface
let
  inherit (pkgs.lib) mkOption;

  options = {
    services = {
      dbus = {

        enable = mkOption {
          default = true;
          description = "
            Whether to start the D-Bus message bus daemon.  It is required
            by the HAL service.
          ";
          merge = pkgs.lib.mergeEnableOption;
        };

        services = mkOption {
          default = [];
          description = ".. fill me ..";
        };

      };
    };
  };
in

###### implementation
let
  cfg = config.services.dbus;
  services = cfg.services;
  inherit (pkgs.lib) mkIf;

  inherit (pkgs) stdenv dbus;

  homeDir = "/var/run/dbus";

  # Take the standard system configuration file, except that we don't
  # want to fork (Upstart will monitor the daemon).
  configFile = stdenv.mkDerivation {
    name = "dbus-conf";
    buildCommand = "
      ensureDir $out
      ln -s ${dbus}/etc/dbus-1/system.conf $out/system.conf

      ensureDir $out/system.d
      for i in ${toString services}; do
        ln -s $i/etc/dbus-1/system.d/* $out/system.d/
      done
    ";
  };

  user = {
    name = "messagebus";
    uid = (import ../../../system/ids.nix).uids.messagebus;
    description = "D-Bus system message bus daemon user";
    home = homeDir;
  };

  job = {
    name = "dbus";
  
    job = ''
      description "D-Bus system message bus daemon"

      start on startup
      stop on shutdown

      start script

          mkdir -m 0755 -p ${homeDir}
          chown messagebus ${homeDir}

          mkdir -m 0755 -p /var/lib/dbus
          ${dbus.tools}/bin/dbus-uuidgen --ensure
 
          rm -f ${homeDir}/pid
          ${dbus}/bin/dbus-daemon --config-file=${configFile}/system.conf
      end script

      respawn sleep 1000000

      stop script
          pid=$(cat ${homeDir}/pid)
          if test -n "$pid"; then
              kill -9 $pid
          fi
      end script
    '';
  };

in

mkIf cfg.enable {
  require = [
    # ../upstart-jobs/default.nix # config.services.extraJobs
    # ../system/user.nix # users.*
    # ? # config.environment.extraPackages
    options
  ];

  environment = {
    extraPackages = [dbus.daemon dbus.tools];
  };

  users = {
    extraUsers = [user];
  };

  services = {
    extraJobs = [job];
  };
}