content: /*
   * Copyright (C) 2012-2016 Markus Junginger, greenrobot (http://greenrobot.org)
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.greenrobot.eventbus.util;
  
  import org.greenrobot.eventbus.EventBus;
  
  import java.lang.reflect.Constructor;
  import java.util.concurrent.Executor;
  import java.util.concurrent.Executors;
  import java.util.logging.Level;
  
  /**
   * Executes an {@link RunnableEx} using a thread pool. Thrown exceptions are propagated by posting
   * failure events. By default, uses {@link ThrowableFailureEvent}.
   *
   * <p>Set a custom event type using {@link Builder#failureEventType(Class)}. The failure event class
   * must have a constructor with one parameter of type {@link Throwable}. If using ProGuard or R8
   * make sure the constructor of the failure event class is kept, it is accessed via reflection. E.g.
   * add a rule like
   *
   * <pre>
   * -keepclassmembers class com.example.CustomThrowableFailureEvent {
   *     &lt;init&gt;(java.lang.Throwable);
   * }
   * </pre>
   */
  public class AsyncExecutor {
  
    public static class Builder {
      private Executor threadPool;
      private Class<?> failureEventType;
      private EventBus eventBus;
  
      private Builder() {}
  
      public Builder threadPool(Executor threadPool) {
        this.threadPool = threadPool;
        return this;
      }
  
      public Builder failureEventType(Class<?> failureEventType) {
        this.failureEventType = failureEventType;
        return this;
      }
  
      public Builder eventBus(EventBus eventBus) {
        this.eventBus = eventBus;
        return this;
      }
  
      public AsyncExecutor build() {
        return buildForScope(null);
      }
  
      public AsyncExecutor buildForScope(Object executionContext) {
        if (eventBus == null) {
          eventBus = EventBus.getDefault();
        }
        if (threadPool == null) {
          threadPool = Executors.newCachedThreadPool();
        }
        if (failureEventType == null) {
          failureEventType = ThrowableFailureEvent.class;
        }
        return new AsyncExecutor(threadPool, eventBus, failureEventType, executionContext);
      }
    }
  
    /** Like {@link Runnable}, but the run method may throw an exception. */
    public interface RunnableEx {
      void run() throws Exception;
    }
  
    public static Builder builder() {
      return new Builder();
    }
  
    public static AsyncExecutor create() {
      return new Builder().build();
    }
  
    private final Executor threadPool;
    private final Constructor<?> failureEventConstructor;
    private final EventBus eventBus;
    private final Object scope;
  
    private AsyncExecutor(
        Executor threadPool, EventBus eventBus, Class<?> failureEventType, Object scope) {
      this.threadPool = threadPool;
      this.eventBus = eventBus;
      this.scope = scope;
      try {
        failureEventConstructor = failureEventType.getConstructor(Throwable.class);
      } catch (NoSuchMethodException e) {
        throw new RuntimeException(
            "Failure event class must have a constructor with one parameter of type Throwable", e);
      }
    }
  
    /** Posts an failure event if the given {@link RunnableEx} throws an Exception. */
    public void execute(final RunnableEx runnable) {
      threadPool.execute(
          () -> {
            try {
              runnable.run();
            } catch (Exception e) {
              Object event;
              try {
                event = failureEventConstructor.newInstance(e);
              } catch (Exception e1) {
                eventBus.getLogger().log(Level.SEVERE, "Original exception:", e);
                throw new RuntimeException("Could not create failure event", e1);
              }
              if (event instanceof HasExecutionScope) {
                ((HasExecutionScope) event).setExecutionScope(scope);
              }
              eventBus.post(event);
            }
          });
    }
  }
  