/**
   * This is called when JPM runs in the background to start jobs
   *
   * @throws Exception
   */
  public void daemon() throws Exception {
    Runtime.getRuntime()
        .addShutdownHook(
            new Thread("Daemon shutdown") {
              public void run() {

                for (Service service : startedByDaemon) {
                  try {
                    reporter.error("Stopping " + service);
                    service.stop();
                    reporter.error("Stopped " + service);
                  } catch (Exception e) {
                    // Ignore
                  }
                }
              }
            });
    List<ServiceData> services = getServices();
    Map<String, ServiceData> map = new HashMap<String, ServiceData>();
    for (ServiceData d : services) {
      map.put(d.name, d);
    }
    List<ServiceData> start = new ArrayList<ServiceData>();
    Set<ServiceData> set = new HashSet<ServiceData>();
    for (ServiceData sd : services) {
      checkStartup(map, start, sd, set);
    }

    if (start.isEmpty()) reporter.warning("No services to start");

    for (ServiceData sd : start) {
      try {
        Service service = getService(sd.name);
        reporter.trace("Starting " + service);
        String result = service.start();
        if (result != null) reporter.error("Started error " + result);
        else startedByDaemon.add(service);
        reporter.trace("Started " + service);
      } catch (Exception e) {
        reporter.error("Cannot start daemon %s, due to %s", sd.name, e);
      }
    }

    while (true) {
      for (Service sd : startedByDaemon) {
        try {
          if (!sd.isRunning()) {
            reporter.error("Starting due to failure " + sd);
            String result = sd.start();
            if (result != null) reporter.error("Started error " + result);
          }
        } catch (Exception e) {
          reporter.error("Cannot start daemon %s, due to %s", sd, e);
        }
      }
      Thread.sleep(10000);
    }
  }
  public Map<String, Revision> latest(Collection<Revision> list) {
    Map<String, Revision> programs = new HashMap<String, Library.Revision>();

    for (Revision r : list) {
      String coordinates = r.groupId + ":" + r.artifactId;
      if (r.classifier != null) coordinates += ":" + r.classifier;

      if (r.groupId.equals(Library.SHA_GROUP)) continue;

      Revision current = programs.get(coordinates);
      if (current == null) programs.put(coordinates, r);
      else {
        // who is better?
        if (compare(r, current) >= 0) programs.put(coordinates, r);
      }
    }
    return programs;
  }
  /**
   * @param data
   * @param target
   * @throws Exception
   * @throws IOException
   */
  public String createCommand(CommandData data, boolean force) throws Exception, IOException {

    // TODO
    // if (Data.validate(data) != null)
    // return "Invalid command data: " + Data.validate(data);

    Map<String, String> map = null;
    if (data.trace) {
      map = new HashMap<String, String>();
      map.put("java.security.manager", "aQute.jpm.service.TraceSecurityManager");
      reporter.trace("tracing");
    }
    String s = platform.createCommand(data, map, force, service.getAbsolutePath());
    if (s == null) storeData(new File(commandDir, data.name), data);
    return s;
  }