/*
 *
 * 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.failover.thread;

import org.mariadb.jdbc.internal.failover.Listener;
import org.mariadb.jdbc.internal.util.scheduler.SchedulerServiceProviderHolder;

import java.util.Iterator;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicLong;

public class ConnectionValidator {
    private static final ScheduledExecutorService fixedSizedScheduler = SchedulerServiceProviderHolder.getFixedSizeScheduler(1, "validator");
    private static final int MINIMUM_CHECK_DELAY_MILLIS = 100;

    private final ConcurrentLinkedQueue<Listener> queue = new ConcurrentLinkedQueue<>();
    private final AtomicLong currentScheduledFrequency = new AtomicLong(-1);
    private final ListenerChecker checker = new ListenerChecker();

    /**
     * Add listener to validation list.
     *
     * @param listener            listener
     * @param listenerCheckMillis schedule time
     */
    public void addListener(Listener listener, long listenerCheckMillis) {
        queue.add(listener);

        long newFrequency = Math.min(MINIMUM_CHECK_DELAY_MILLIS, listenerCheckMillis);

        //first listener
        if (currentScheduledFrequency.get() == -1) {
            if (currentScheduledFrequency.compareAndSet(-1, newFrequency)) {
                fixedSizedScheduler.schedule(checker, listenerCheckMillis, TimeUnit.MILLISECONDS);
            }
        } else {
            long frequency = currentScheduledFrequency.get();
            if (frequency > newFrequency) {
                currentScheduledFrequency.compareAndSet(frequency, newFrequency);
            }
        }

    }

    /**
     * Remove listener to validation list.
     *
     * @param listener listener
     */
    public void removeListener(Listener listener) {
        queue.remove(listener);

        if (queue.isEmpty()) {
            synchronized (queue) {
                if (currentScheduledFrequency.get() > 0 && queue.isEmpty()) {
                    currentScheduledFrequency.set(-1);
                }
            }

        }
    }

    private class ListenerChecker implements Runnable {

        @Override
        public void run() {
            try {
                doRun();
            } finally {
                long delay = currentScheduledFrequency.get();
                if (delay > 0) {
                    fixedSizedScheduler.schedule(this, delay, TimeUnit.MILLISECONDS);
                }
            }
        }

        private void doRun() {
            Listener listener;
            Iterator<Listener> tmpQueue = queue.iterator();
            long now = -1;
            while (tmpQueue.hasNext()) {
                listener = tmpQueue.next();
                if (!listener.isExplicitClosed()) {
                    long durationNanos = (now == -1 ? now = System.nanoTime() : now) - listener.getLastQueryNanos();
                    long durationSeconds = TimeUnit.NANOSECONDS.toSeconds(durationNanos);
                    if (durationSeconds >= listener.getUrlParser().getOptions().validConnectionTimeout
                            && !listener.isMasterHostFail()) {
                        boolean masterFail = false;
                        if (listener.isMasterConnected()) {
                            listener.checkMasterStatus(null);
                        } else {
                            masterFail = true;
                        }

                        if (masterFail && listener.setMasterHostFail()) {
                            try {
                                listener.primaryFail(null, null, false);
                            } catch (Throwable t) {
                                //do nothing
                            }
                        }
                    }
                }
            }
        }
    }
}
