/*
 * Copyright 2012 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.handler.traffic;

import io.netty.channel.ChannelHandler.Sharable;
import io.netty.util.concurrent.EventExecutor;

import java.util.concurrent.ScheduledExecutorService;

/**
 * This implementation of the {@link AbstractTrafficShapingHandler} is for global
 * traffic shaping, that is to say a global limitation of the bandwidth, whatever
 * the number of opened channels.<br><br>
 *
 * The general use should be as follow:<br>
 * <ul>
 * <li>Create your unique GlobalTrafficShapingHandler like:<br><br>
 * <tt>GlobalTrafficShapingHandler myHandler = new GlobalTrafficShapingHandler(executor);</tt><br><br>
 * The executor could be the underlying IO worker pool<br>
 * <tt>pipeline.addLast(myHandler);</tt><br><br>
 *
 * <b>Note that this handler has a Pipeline Coverage of "all" which means only one such handler must be created
 * and shared among all channels as the counter must be shared among all channels.</b><br><br>
 *
 * Other arguments can be passed like write or read limitation (in bytes/s where 0 means no limitation)
 * or the check interval (in millisecond) that represents the delay between two computations of the
 * bandwidth and so the call back of the doAccounting method (0 means no accounting at all).<br><br>
 *
 * A value of 0 means no accounting for checkInterval. If you need traffic shaping but no such accounting,
 * it is recommended to set a positive value, even if it is high since the precision of the
 * Traffic Shaping depends on the period where the traffic is computed. The highest the interval,
 * the less precise the traffic shaping will be. It is suggested as higher value something close
 * to 5 or 10 minutes.<br>
 * </li>
 * </ul><br>
 *
 * Be sure to call {@link #release()} once this handler is not needed anymore to release all internal resources.
 * This will not shutdown the {@link EventExecutor} as it may be shared, so you need to do this by your own.
 */
@Sharable
public class GlobalTrafficShapingHandler extends AbstractTrafficShapingHandler {
    /**
     * Create the global TrafficCounter
     */
    void createGlobalTrafficCounter(ScheduledExecutorService executor) {
        if (executor == null) {
            throw new NullPointerException("executor");
        }
        TrafficCounter tc = new TrafficCounter(this, executor, "GlobalTC",
                    checkInterval);
        setTrafficCounter(tc);
        tc.start();
    }

    /**
     * Create a new instance
     *
     * @param executor
     *          the {@link ScheduledExecutorService} to use for the {@link TrafficCounter}
     * @param writeLimit
     *          0 or a limit in bytes/s
     * @param readLimit
     *          0 or a limit in bytes/s
     * @param checkInterval
     *          The delay between two computations of performances for
     *            channels or 0 if no stats are to be computed
     */
    public GlobalTrafficShapingHandler(ScheduledExecutorService executor, long writeLimit,
            long readLimit, long checkInterval) {
        super(writeLimit, readLimit, checkInterval);
        createGlobalTrafficCounter(executor);
    }

    /**
     * Create a new instance
     *
     * @param executor
     *          the {@link ScheduledExecutorService} to use for the {@link TrafficCounter}
     * @param writeLimit
     *          0 or a limit in bytes/s
     * @param readLimit
     *          0 or a limit in bytes/s
     */
    public GlobalTrafficShapingHandler(ScheduledExecutorService executor, long writeLimit,
            long readLimit) {
        super(writeLimit, readLimit);
        createGlobalTrafficCounter(executor);
    }

    /**
     * Create a new instance
     *
     * @param executor
     *          the {@link ScheduledExecutorService} to use for the {@link TrafficCounter}
     * @param checkInterval
     *          The delay between two computations of performances for
     *            channels or 0 if no stats are to be computed
     */
    public GlobalTrafficShapingHandler(ScheduledExecutorService executor, long checkInterval) {
        super(checkInterval);
        createGlobalTrafficCounter(executor);
    }

    /**
     * Create a new instance
     *
     * @param executor
     *          the {@link ScheduledExecutorService} to use for the {@link TrafficCounter}
     */
    public GlobalTrafficShapingHandler(EventExecutor executor) {
        createGlobalTrafficCounter(executor);
    }

    /**
     * Release all internal resources of this instance
     */
    public final void release() {
        if (trafficCounter != null) {
            trafficCounter.stop();
        }
    }
}