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/*
 *
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright 2007-2008 Sun Microsystems, Inc. All rights reserved.
 *
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 * General Public License Version 2 only ("GPL") or the Common Development
 * and Distribution License("CDDL") (collectively, the "License").  You
 * may not use this file except in compliance with the License. You can obtain
 * a copy of the License at https://glassfish.dev.java.net/public/CDDL+GPL.html
 * or glassfish/bootstrap/legal/LICENSE.txt.  See the License for the specific
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 * file and include the License file at glassfish/bootstrap/legal/LICENSE.txt.
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package com.sun.grizzly.strategies;

import java.io.IOException;
import java.util.concurrent.Executor;
import com.sun.grizzly.Connection;
import com.sun.grizzly.IOEvent;
import com.sun.grizzly.ProcessorRunnable;
import com.sun.grizzly.Strategy;
import com.sun.grizzly.nio.NIOConnection;
import com.sun.grizzly.nio.NIOTransport;
import com.sun.grizzly.strategies.SimpleDynamicStrategy.DynamicStrategyContext;
import com.sun.grizzly.utils.CurrentThreadExecutor;
import com.sun.grizzly.utils.WorkerThreadExecutor;

/**
 * Simple dynamic strategy, which switches I/O processing strategies, basing
 * on statistics. This implementation takes in consideration number of
 * {@link SelectionKey}s, which were selected last time by {@link Selector}.
 *
 * SimpleDynamicStrategy is able to use 3 strategies underneath:
 * {@link SameThreadStrategy}, {@link LeaderFollowerStrategy},
 * {@link WorkerThreadStrategy}. And is able to switch between them basing on
 * corresponding thresholds (threshold represents the number of selected
 * {@link SelectionKey}s).
 *
 * So the strategy is getting applied following way:
 *
 * {@link SameThreadStrategy} --(leader-follower threshold)--> {@link LeaderFollowerStrategy} --(worker-thread threshold)--> {@link WorkerThreadStrategy}.
 *
 * @author Alexey Stashok
 */
public class SimpleDynamicStrategy implements Strategy {
    private SameThreadStrategy sameThreadStrategy;
    private LeaderFollowerStrategy leaderFollowerStrategy;
    private WorkerThreadStrategy workerThreadStrategy;

    private int leaderFollowerThreshold = 1;
    private int workerThreadThreshold = 32;

    public SimpleDynamicStrategy(final NIOTransport transport) {
        this(new CurrentThreadExecutor(), new WorkerThreadExecutor(transport));
    }

    public SimpleDynamicStrategy(final Executor sameThreadProcessorExecutor,
            final Executor workerThreadProcessorExecutor) {
        sameThreadStrategy = new SameThreadStrategy();
        leaderFollowerStrategy = new LeaderFollowerStrategy(
                sameThreadProcessorExecutor, workerThreadProcessorExecutor);
        workerThreadStrategy = new WorkerThreadStrategy(
                sameThreadProcessorExecutor, workerThreadProcessorExecutor);
    }

   /**
    * {@inheritDoc}
    */
    public DynamicStrategyContext prepare(final Connection connection,
            final IOEvent ioEvent) {
        return new DynamicStrategyContext(
                ((NIOConnection) connection).getSelectorRunner().getLastSelectedKeysCount());
    }

   /**
    * {@inheritDoc}
    */
    public void executeProcessor(final DynamicStrategyContext strategyContext,
            final ProcessorRunnable processorRunnable) throws IOException {
        final int lastSelectedKeysCount;
        if (strategyContext != null) {
            lastSelectedKeysCount = strategyContext.lastSelectedKeysCount;
        } else {
            workerThreadStrategy.executeProcessor(strategyContext,
                    processorRunnable);
            return;
        }

        if (lastSelectedKeysCount >= workerThreadThreshold) {
            workerThreadStrategy.executeProcessor(strategyContext,
                    processorRunnable);
        } else if (lastSelectedKeysCount >= leaderFollowerThreshold) {
            strategyContext.isTerminateThread = true;
            leaderFollowerStrategy.executeProcessor(
                    strategyContext.isTerminateThread, processorRunnable);
        } else {
            sameThreadStrategy.executeProcessor(strategyContext,
                    processorRunnable);
        }

    }

   /**
    * {@inheritDoc}
    */
    public boolean isTerminateThread(DynamicStrategyContext strategyContext) {
        return strategyContext.isTerminateThread;
    }

    /**
     * Returns the number of {@link SelectionKey}s, which should be selected
     * from a {@link Selector}, to make it apply {@link LeaderFollowerStrategy}.
     * 
     * @return the number of {@link SelectionKey}s, which should be selected
     * from a {@link Selector}, to make it apply {@link LeaderFollowerStrategy}.
     */
    public int getLeaderFollowerThreshold() {
        return leaderFollowerThreshold;
    }

    /**
     * Set the number of {@link SelectionKey}s, which should be selected
     * from a {@link Selector}, to make it apply {@link LeaderFollowerStrategy}.
     *
     * @param leaderFollowerThreshold the number of {@link SelectionKey}s,
     * which should be selected from a {@link Selector}, to make it apply
     * {@link LeaderFollowerStrategy}.
     */
    public void setLeaderFollowerThreshold(int leaderFollowerThreshold) {
        this.leaderFollowerThreshold = leaderFollowerThreshold;
        checkThresholds();
    }

    /**
     * Returns the number of {@link SelectionKey}s, which should be selected
     * from a {@link Selector}, to make it apply {@link WorkerThreadStrategy}.
     *
     * @return the number of {@link SelectionKey}s, which should be selected
     * from a {@link Selector}, to make it apply {@link WorkerThreadStrategy}.
     */
    public int getWorkerThreadThreshold() {
        return workerThreadThreshold;
    }

    /**
     * Set the number of {@link SelectionKey}s, which should be selected
     * from a {@link Selector}, to make it apply {@link WorkerThreadStrategy}.
     *
     * @param workerThreadThreshold the number of {@link SelectionKey}s,
     * which should be selected from a {@link Selector}, to make it apply
     * {@link WorkerThreadStrategy}.
     */
    public void setWorkerThreadThreshold(int workerThreadThreshold) {
        this.workerThreadThreshold = workerThreadThreshold;
        checkThresholds();
    }

    /**
     * Check if thresholds are set correctly.
     */
    private void checkThresholds() {
        if (leaderFollowerThreshold >= 0 &&
                workerThreadThreshold >= leaderFollowerThreshold) return;

        throw new IllegalStateException("Thresholds settings are incorrect");
    }

    public static final class DynamicStrategyContext {
        final int lastSelectedKeysCount;
        boolean isTerminateThread;

        public DynamicStrategyContext(int lastSelectedKeysCount) {
            this.lastSelectedKeysCount = lastSelectedKeysCount;
        }
    }
}