/*
 * Copyright 2016 The Netty Project
 *
 * The Netty Project licenses this file to you 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 io.netty.util.concurrent;

import io.netty.util.internal.ObjectUtil;

import java.util.concurrent.RejectedExecutionException;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.LockSupport;

Expose helper methods which create different RejectedExecutionHandlers. /**
 * Expose helper methods which create different {@link RejectedExecutionHandler}s.
 */
public final class RejectedExecutionHandlers {
    private static final RejectedExecutionHandler REJECT = new RejectedExecutionHandler() {
        @Override
        public void rejected(Runnable task, SingleThreadEventExecutor executor) {
            throw new RejectedExecutionException();
        }
    };

    private RejectedExecutionHandlers() { }

    
Returns a RejectedExecutionHandler that will always just throw a RejectedExecutionException. /**
     * Returns a {@link RejectedExecutionHandler} that will always just throw a {@link RejectedExecutionException}.
     */
    public static RejectedExecutionHandler reject() {
        return REJECT;
    }

    
Tries to backoff when the task can not be added due restrictions for an configured amount of time. This is only done if the task was added from outside of the event loop which means EventExecutor.inEventLoop() returns false. /**
     * Tries to backoff when the task can not be added due restrictions for an configured amount of time. This
     * is only done if the task was added from outside of the event loop which means
     * {@link EventExecutor#inEventLoop()} returns {@code false}.
     */
    public static RejectedExecutionHandler backoff(final int retries, long backoffAmount, TimeUnit unit) {
        ObjectUtil.checkPositive(retries, "retries");
        final long backOffNanos = unit.toNanos(backoffAmount);
        return new RejectedExecutionHandler() {
            @Override
            public void rejected(Runnable task, SingleThreadEventExecutor executor) {
                if (!executor.inEventLoop()) {
                    for (int i = 0; i < retries; i++) {
                        // Try to wake up the executor so it will empty its task queue.
                        executor.wakeup(false);

                        LockSupport.parkNanos(backOffNanos);
                        if (executor.offerTask(task)) {
                            return;
                        }
                    }
                }
                // Either we tried to add the task from within the EventLoop or we was not able to add it even with
                // backoff.
                throw new RejectedExecutionException();
            }
        };
    }
}