/**
 * Utility for running code on the main launch thread at the next available
 * opportunity. There is no guaranteed order that work from various mods will be
 * run, but your own work will be run sequentially.
 * <p>
 * <strong>Use of this class after startup is not possible.</strong> At that
 * point, {@link IThreadListener} should be used instead.
 */
public class DeferredWorkQueue
{
    static final ConcurrentLinkedDeque<Runnable> deferredWorkQueue = new ConcurrentLinkedDeque<>();
    private static final Executor deferredExecutor = r -> deferredWorkQueue.add(r);

    private static Throwable lastExceptionRaised;
    private static int exceptionsRaised;

    private static <T> T handleException(Throwable t) {
        LogManager.getLogger(DeferredWorkQueue.class).error("Encountered exception executing deferred work", t);
        lastExceptionRaised = t;
        exceptionsRaised++;
        return null;
    }

    public static CompletableFuture<Void> runLater(Runnable workToEnqueue) {
        return CompletableFuture.runAsync(workToEnqueue, deferredExecutor).exceptionally(DeferredWorkQueue::handleException);
    }

    public static <T> CompletableFuture<T> getLater(Supplier<T> workToEnqueue) {
        return CompletableFuture.supplyAsync(workToEnqueue, deferredExecutor).exceptionally(DeferredWorkQueue::handleException);
    }

    public static <T> CompletableFuture<T> getLaterUnchecked(Callable<T> workToEnqueue) {
        return getLater(() -> {
            try {
                return workToEnqueue.call();
            } catch (Exception e) {
                throw new CompletionException(e);
            }
        });
    }

    static void runTasks() {
        exceptionsRaised = 0;
        lastExceptionRaised = null;
        deferredWorkQueue.forEach(Runnable::run);
        if (lastExceptionRaised != null) {
            throw new LoaderException(exceptionsRaised
                    + " exceptions were raised during processing async tasks. The last can be seen in this crash report. All errors were reported in the log.",
                    lastExceptionRaised);
        }
    }
}