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package org.fisco.bcos.web3j.utils;

import static org.fisco.bcos.web3j.utils.Web3AsyncThreadPoolSize.web3AsyncPoolSize;

import java.util.concurrent.*;

/** Async task facilitation. */
public class Async {
  private static final ExecutorService executor = Executors.newFixedThreadPool(web3AsyncPoolSize);

  static {
    Runtime.getRuntime().addShutdownHook(new Thread(() -> shutdown(executor)));
  }

  public static  CompletableFuture run(Callable callable) {
    CompletableFuture result = new CompletableFuture<>();
    CompletableFuture.runAsync(
        () -> {
          // we need to explicitly catch any exceptions,
          // otherwise they will be silently discarded
          try {
            result.complete(callable.call());
          } catch (Throwable e) {
            result.completeExceptionally(e);
          }
        },
        executor);
    return result;
  }

  private static int getCpuCount() {
    return Runtime.getRuntime().availableProcessors();
  }

  /**
   * Provide a new ScheduledExecutorService instance.
   *
   * A shutdown hook is created to terminate the thread pool on application termination.
   *
   * @return new ScheduledExecutorService
   */
  public static ScheduledExecutorService defaultExecutorService() {
    ScheduledExecutorService scheduledExecutorService =
        Executors.newScheduledThreadPool(getCpuCount());

    Runtime.getRuntime().addShutdownHook(new Thread(() -> shutdown(scheduledExecutorService)));

    return scheduledExecutorService;
  }

  /**
   * Shutdown as per {@link ExecutorService} Javadoc recommendation.
   *
   * @param executorService executor service we wish to shut down.
   */
  private static void shutdown(ExecutorService executorService) {
    executorService.shutdown();
    try {
      if (!executorService.awaitTermination(60, TimeUnit.SECONDS)) {
        executorService.shutdownNow();
        if (!executorService.awaitTermination(60, TimeUnit.SECONDS)) {
          System.err.println("Thread pool did not terminate");
        }
      }
    } catch (InterruptedException ie) {
      executorService.shutdownNow();
      Thread.currentThread().interrupt();
    }
  }
}