sclass SingleThreadProfiler is AutoCloseable {

  // config

  settable Thread threadToSample = currentThread();

  settable int interval = 40; // 25 Hz

  settable bool skipSleeping;

  // results

  new MultiSet<S> stackTraceMultiSet;

  gettable int samples;

  // temporary

  java.util.Timer timer;

  Lock lock = lock();

  void start {

    lock lock;

    printWithMS("Starting profiler for " + threadToSample);

    stop();

    clear();

    timer = doEvery_daemon(interval, r {

      StackTraceElement[] stackTrace = threadToSample.getStackTrace();

      if (skipSleeping && !isThreadRunnable_x(stackTrace)) ret;

      lock lock;

      samples++;

      stackTraceMultiSet.add(stackTraceToString(stackTrace));

    });

  }

  public  void stop aka close() {

    lock lock;

    if (timer != null) {

      stopTimer(timer);

      timer = null;

      printWithMS("Stopped profiler for " + threadToSample);

    }

  }

  void clear() {

    lock lock;

    stackTraceMultiSet.clear();

    samples = 0;

  }

  MultiSet<S> results() {

    lock lock;

    ret cloneMultiSet(stackTraceMultiSet);

  }

  MultiSet<S> stopAndGetResults() {

    lock lock;

    stop();

    ret results();

  }

  S renderFullResults(bool mostImportantLast) {

    var traces = results();

    int n = traces.size();

    int percent = ratioToIntPercent(l(traces), samples);

    ret (samples == 0 ? "Nothing sampled"

      : percent + "% core activity [" + n2(samples, "sample") + " taken]") + "\n\n"

      + joinMap(mostImportantLast ? traces.lowestFirst() : traces.highestFirst(), trace ->

      traces.get(trace) + "/" + n + "\n" + trace + "\n\n"

    );

  }

}