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// Copyright 2012 Square, Inc.
package io.logspace.jvm.agent.shaded.tape;

/**
 * Persistent task queue. Not safe for concurrent use.
 *
 * @param  The type of tasks in the queue.
 */
public class TaskQueue implements ObjectQueue {

  private final TaskInjector taskInjector;
  private final ObjectQueue delegate;

  public TaskQueue(ObjectQueue delegate) {
    this(delegate, null);
  }

  public TaskQueue(ObjectQueue delegate, TaskInjector taskInjector) {
    this.delegate = delegate;
    this.taskInjector = taskInjector;
  }

  /**
   * {@inheritDoc}
   *
   * Overridden to inject members into Tasks.
   */
  @Override public T peek() {
    T task = delegate.peek();
    if (task != null && taskInjector != null) {
      taskInjector.injectMembers(task);
    }
    return task;
  }

  @Override public int size() {
    return delegate.size();
  }

  @Override public void add(T entry) {
    delegate.add(entry);
  }

  @Override public void remove() {
    delegate.remove();
  }

  @Override public void setListener(final Listener listener) {
    if (listener != null) {
      // Intercept event delivery to pass the correct TaskQueue instance to listener.
      delegate.setListener(new Listener() {
        @Override
        public void onAdd(ObjectQueue queue, T entry) {
          listener.onAdd(TaskQueue.this, entry);
        }

        @Override
        public void onRemove(ObjectQueue queue) {
          listener.onRemove(TaskQueue.this);
        }
      });
    } else {
      delegate.setListener(null);
    }
  }
}