/*
 *
 * MariaDB Client for Java
 *
 * Copyright (c) 2012-2014 Monty Program Ab.
 * Copyright (c) 2015-2017 MariaDB Ab.
 *
 * This library is free software; you can redistribute it and/or modify it under
 * the terms of the GNU Lesser General Public License as published by the Free
 * Software Foundation; either version 2.1 of the License, or (at your option)
 * any later version.
 *
 * This library is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License
 * for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License along
 * with this library; if not, write to Monty Program Ab info@montyprogram.com.
 *
 * This particular MariaDB Client for Java file is work
 * derived from a Drizzle-JDBC. Drizzle-JDBC file which is covered by subject to
 * the following copyright and notice provisions:
 *
 * Copyright (c) 2009-2011, Marcus Eriksson
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 * Redistributions of source code must retain the above copyright notice, this list
 * of conditions and the following disclaimer.
 *
 * Redistributions in binary form must reproduce the above copyright notice, this
 * list of conditions and the following disclaimer in the documentation and/or
 * other materials provided with the distribution.
 *
 * Neither the name of the driver nor the names of its contributors may not be
 * used to endorse or promote products derived from this software without specific
 * prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS  AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
 * OF SUCH DAMAGE.
 *
 */

package org.mariadb.jdbc.internal.util.scheduler;

import java.util.concurrent.*;

/**
 * Provider for when ever an internal thread pool is needed.  This can allow library users to
 * override our default pooling behavior with possibly better and faster options.
 */
public class SchedulerServiceProviderHolder {

    /**
     * The default provider will construct a new pool on every request.
     */
    public static final SchedulerProvider DEFAULT_PROVIDER = new SchedulerProvider() {
        @Override
        public DynamicSizedSchedulerInterface getScheduler(int minimumThreads, String poolName, int maximumPoolSize) {
            return new DynamicSizedSchedulerImpl(minimumThreads, poolName, maximumPoolSize);
        }

        @Override
        public ScheduledThreadPoolExecutor getFixedSizeScheduler(int minimumThreads, String poolName) {
            return new FixedSizedSchedulerImpl(minimumThreads, poolName);
        }

        @Override
        public ScheduledThreadPoolExecutor getTimeoutScheduler() {
            ScheduledThreadPoolExecutor timeoutScheduler = new ScheduledThreadPoolExecutor(1, new MariaDbThreadFactory("MariaDb-timeout"));
            timeoutScheduler.setRemoveOnCancelPolicy(true);
            return timeoutScheduler;
        }

        @Override
        @SuppressWarnings("unchecked")
        public ThreadPoolExecutor getBulkScheduler() {
            return new ThreadPoolExecutor(5, 100, 1, TimeUnit.MINUTES, new SynchronousQueue(), new MariaDbThreadFactory("MariaDb-bulk"));
        }

    };

    private static volatile SchedulerProvider currentProvider = null;

    /**
     * Get the currently set {@link SchedulerProvider} from set invocations via
     * {@link #setSchedulerProvider(SchedulerProvider)}.  If none has been set a default provider
     * will be provided (never a {@code null} result).
     *
     * @return Provider to get scheduler pools from
     */
    public static SchedulerProvider getSchedulerProvider() {
        SchedulerProvider result = currentProvider;
        if (result == null) {
            return DEFAULT_PROVIDER;
        } else {
            return result;
        }
    }

    /**
     * Change the current set scheduler provider.  This provider will be provided in future requests
     * to {@link #getSchedulerProvider()}.
     *
     * @param newProvider New provider to use, or {@code null} to use the default provider
     */
    public static void setSchedulerProvider(SchedulerProvider newProvider) {
        currentProvider = newProvider;
    }

    /**
     * Get a Dynamic sized scheduler directly with the current set provider.
     *
     * @param initialThreadCount Number of threads scheduler is allowed to grow to
     * @param poolName           name of pool to identify threads
     * @param maximumPoolSize    maximum pool size
     * @return Scheduler capable of providing the needed thread count
     */
    public static DynamicSizedSchedulerInterface getScheduler(int initialThreadCount, String poolName, int maximumPoolSize) {
        return getSchedulerProvider().getScheduler(initialThreadCount, poolName, maximumPoolSize);
    }

    /**
     * Get a fixed sized scheduler directly with the current set provider.
     *
     * @param initialThreadCount Number of threads scheduler is allowed to grow to
     * @param poolName           name of pool to identify threads
     * @return Scheduler capable of providing the needed thread count
     */
    public static ScheduledExecutorService getFixedSizeScheduler(int initialThreadCount, String poolName) {
        return getSchedulerProvider().getFixedSizeScheduler(initialThreadCount, poolName);
    }

    /**
     * Get a scheduler to handle timeout.
     *
     * @return Scheduler capable of providing the needed thread count
     */
    public static ScheduledExecutorService getTimeoutScheduler() {
        return getSchedulerProvider().getTimeoutScheduler();
    }

    public static ThreadPoolExecutor getBulkScheduler() {
        return getSchedulerProvider().getBulkScheduler();
    }

    /**
     * <p>Provider for thread pools which allow scheduling capabilities.  It is expected that the
     * thread pools entire lifecycle (start to stop) is done through the same provider instance.</p>
     */
    public interface SchedulerProvider {
        /**
         * Request to get a scheduler with a minimum number of AVAILABLE threads.
         *
         * @param minimumThreads  Minimum number of available threads for the returned scheduler
         * @param poolName        name of pool to identify threads
         * @param maximumPoolSize maximum pool size
         * @return A new scheduler that is ready to accept tasks
         */
        DynamicSizedSchedulerInterface getScheduler(int minimumThreads, String poolName, int maximumPoolSize);

        ScheduledExecutorService getFixedSizeScheduler(int minimumThreads, String poolName);

        /**
         * Default Timeout scheduler.
         * <p>
         * This is a one Thread fixed sized scheduler.
         * This specific scheduler is using java 1.7 RemoveOnCancelPolicy, so
         * the task are removed from queue permitting to avoid memory consumption [CONJ-297]
         *
         * @return A new scheduler that is ready to accept tasks
         */
        ScheduledThreadPoolExecutor getTimeoutScheduler();

        ThreadPoolExecutor getBulkScheduler();
    }


}
