/*
 *
 * MariaDB Client for Java
 *
 * Copyright (c) 2012-2014 Monty Program Ab.
 * Copyright (c) 2015-2020 MariaDB Corporation 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 java.util.Iterator;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicLong;
import org.mariadb.jdbc.internal.failover.Listener;
import org.mariadb.jdbc.internal.util.scheduler.SchedulerServiceProviderHolder;

public class ConnectionValidator {

  private static final int MINIMUM_CHECK_DELAY_MILLIS = 100;
  private final ScheduledExecutorService fixedSizedScheduler =
      SchedulerServiceProviderHolder.getFixedSizeScheduler(1, "validator");
  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, false);
              } catch (Throwable t) {
                // do nothing
              }
            }
          }
        }
      }
    }
  }
}
