/*
 * Licensed to the Apache Software Foundation (ASF) under one or more contributor license
 * agreements. See the NOTICE file distributed with this work for additional information regarding
 * copyright ownership. The ASF 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 org.apache.geode.internal.admin;

import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Set;
import java.util.TimerTask;

import org.apache.logging.log4j.Logger;

import org.apache.geode.CancelException;
import org.apache.geode.StatisticDescriptor;
import org.apache.geode.Statistics;
import org.apache.geode.StatisticsType;
import org.apache.geode.admin.jmx.internal.StatAlertsAggregator;
import org.apache.geode.annotations.internal.MakeNotStatic;
import org.apache.geode.distributed.internal.ClusterDistributionManager;
import org.apache.geode.distributed.internal.InternalDistributedSystem;
import org.apache.geode.internal.SystemTimer;
import org.apache.geode.internal.SystemTimer.SystemTimerTask;
import org.apache.geode.internal.admin.remote.AlertsNotificationMessage;
import org.apache.geode.internal.admin.remote.UpdateAlertDefinitionMessage;
import org.apache.geode.internal.admin.statalerts.DummyStatisticInfoImpl;
import org.apache.geode.internal.admin.statalerts.StatisticInfo;
import org.apache.geode.internal.admin.statalerts.StatisticInfoImpl;
import org.apache.geode.logging.internal.log4j.api.LogService;

/**
 * The alert manager maintains the list of alert definitions (added by client e.g GFMon 2.0).
 *
 * It retrieved the value of statistic( defined in alert definition) and notify alert aggregator
 * sitting on admin VM
 *
 * @see StatAlertDefinition
 * @see StatAlert
 *
 *
 * @since GemFire 5.7
 */
public class StatAlertsManager {
  private static final Logger logger = LogService.getLogger();

  /**
   * Instance for current DM
   *
   * Guarded by StatAlertsManager.class
   */
  @MakeNotStatic
  private static StatAlertsManager alertManager;

  /**
   * Guarded by this
   */
  private long refreshInterval;

  /**
   * Guarded by this.alertDefinitionsMap
   */
  @MakeNotStatic
  protected final HashMap alertDefinitionsMap = new HashMap();

  /**
   * Guarded by this
   */
  private SystemTimer timer;

  /**
   * Guarded by this
   */
  private boolean refreshAtFixedRate;

  /**
   * Provides life cycle support
   */
  protected final ClusterDistributionManager dm;

  private StatAlertsManager(ClusterDistributionManager dm) {
    this.dm = dm;
    logger.info("StatAlertsManager created");
  }

  /**
   * @return singleton instance of StatAlertsManager
   */
  public static synchronized StatAlertsManager getInstance(ClusterDistributionManager dm) {
    // As per current implementation set up request will be send only once ,
    // when member joined to Admin distributed system
    // we don't need to care about race condition
    if (alertManager != null && alertManager.dm == dm) {
      return alertManager;
    }
    if (alertManager != null) {
      alertManager.close();
    }

    /*
     * Throw DistributedSystemDisconnectedException if cancel operation is in progress
     */
    dm.getCancelCriterion().checkCancelInProgress(null);

    alertManager = new StatAlertsManager(dm);
    return alertManager;
  }

  /**
   * Nullifies the StatAlertsManager instance.
   */
  private static synchronized void closeInstance() {
    StatAlertsManager.alertManager = null;
  }

  /**
   *
   * Update the alert's definition map
   *
   * @param defns Alert definitions
   * @param actionCode Action to be performed like add , remove or update alert's definition
   *
   * @see UpdateAlertDefinitionMessage
   */
  public void updateAlertDefinition(StatAlertDefinition[] defns, int actionCode) {
    if (logger.isDebugEnabled()) {
      logger.debug("Entered StatAlertsManager.updateAlertDefinition *****");
    }
    synchronized (alertDefinitionsMap) {
      if (actionCode == UpdateAlertDefinitionMessage.REMOVE_ALERT_DEFINITION) {
        for (int i = 0; i < defns.length; i++) {
          alertDefinitionsMap.remove(Integer.valueOf(defns[i].getId()));
          if (logger.isDebugEnabled()) {
            logger.debug("Removed StatAlertDefinition: {}", defns[i].getName());
          }
        }
      } else {
        StatAlertDefinition[] alertDefns = this.createMemberStatAlertDefinition(dm, defns);
        StatAlertDefinition defn;
        for (int i = 0; i < alertDefns.length; i++) {
          defn = alertDefns[i];
          alertDefinitionsMap.put(Integer.valueOf(defns[i].getId()), defn);
        }
      }
    } // synchronized

    if (logger.isDebugEnabled()) {
      logger.debug("Exiting StatAlertsManager.updateAlertDefinition *****");
    }
  }

  private synchronized void rescheduleTimer() {
    // cancel the old timer. Although cancelled, old task might execute one last
    // time
    if (timer != null)
      timer.cancel();

    // Get the swarm. Currently rather UGLY.
    InternalDistributedSystem system = dm.getSystem();
    if (system == null || system.getDistributionManager() != dm) {
      throw new org.apache.geode.distributed.DistributedSystemDisconnectedException(
          "This manager has been cancelled");
    }
    // start and schedule new timer
    timer = new SystemTimer(system /* swarm */, true);

    EvaluateAlertDefnsTask task = new EvaluateAlertDefnsTask();
    if (refreshAtFixedRate) {
      timer.scheduleAtFixedRate(task, 0, refreshInterval);
    } else {
      timer.schedule(task, 0, refreshInterval);
    }
  }

  /**
   * Set refresh time interval also cancel the previous {@link TimerTask} and create new timer task
   * based on ner refresh time interval
   *
   * @param interval Refresh time interval
   */
  public synchronized void setRefreshTimeInterval(long interval) {
    refreshInterval = interval;
    rescheduleTimer();
  }

  /**
   *
   * @return time interval alert generation
   */
  public synchronized long getRefreshTimeInterval() {
    return refreshInterval;
  }

  /**
   * @return true if refresh for timer has to be fixed rate see scheduleAtFixedRate method of
   *         {@link TimerTask}
   */
  public synchronized boolean isRefreshAtFixedRate() {
    return refreshAtFixedRate;
  }

  /**
   * set true if refresh for timer has to be fixed rate see scheduleAtFixedRate method of
   * {@link TimerTask}
   *
   * TODO never called
   *
   */
  public synchronized void setRefreshAtFixedRate(boolean refreshAtFixedRate) {
    this.refreshAtFixedRate = refreshAtFixedRate;
    rescheduleTimer();
  }

  /**
   * Query all the statistic defined by alert definition and notify alerts aggregator if at least
   * one statistic value crosses the threshold defined in alert definition
   *
   */
  protected StatAlert[] getAlerts() {
    Set alerts = new HashSet();

    synchronized (alertDefinitionsMap) {
      Set keyset = alertDefinitionsMap.keySet();
      Iterator iter = keyset.iterator();
      StatAlert alert;
      Date now = new Date();
      while (iter.hasNext()) {
        Integer key = (Integer) iter.next();
        StatAlertDefinition defn = (StatAlertDefinition) alertDefinitionsMap.get(key);
        alert = defn.evaluateAndAlert();
        if (alert != null) {
          alert.setTime(now);
          alerts.add(alert);
          if (logger.isDebugEnabled()) {
            logger.debug("getAlerts:  found alert {}", alert);
          }
        }
      } // while
    } // synchronized
    return (StatAlert[]) alerts.toArray(new StatAlert[0]);
  }

  /**
   * Convert {@link StatAlertDefinition }(Created by client like GFMon2.0) with
   * {@link DummyStatisticInfoImpl} to StatAlertDefinition with {@link StatisticInfoImpl}
   */
  private StatAlertDefinition[] createMemberStatAlertDefinition(ClusterDistributionManager dm,
      StatAlertDefinition[] defns) {
    dm.getCancelCriterion().checkCancelInProgress(null);

    Statistics[] statistics;
    StatisticsType type;
    StatisticDescriptor desc;
    String textId;
    boolean skipDefinition = false;
    List result = new ArrayList();

    for (int i = 0; i < defns.length; i++) {
      skipDefinition = false;
      StatAlertDefinition defn = defns[i];
      StatisticInfo[] statInfos = defn.getStatisticInfo();
      for (int ii = 0; ii < statInfos.length && !skipDefinition; ii++) {
        textId = statInfos[ii].getStatisticsTextId();

        // TODO If none by TextID, use StatType and getAll.
        statistics = dm.getSystem().findStatisticsByTextId(textId);
        if (statistics.length == 0) {
          logger.error(
              "StatAlertsManager.createMemberStatAlertDefinition :: statistics with given textId={}, NOT found.",
              textId);
          skipDefinition = true;
          // break;
          continue; // To print all errors
        }

        type = statistics[0].getType();
        desc = type.nameToDescriptor(statInfos[ii].getStatisticName());
        // Replace the actual StatInfo object
        statInfos[ii] = new StatisticInfoImpl(statistics[0], desc);
        if (logger.isDebugEnabled()) {
          logger.debug("StatAlertsManager.createMemberStatAlertDefinition: created statInfo {}",
              statInfos[ii]);
        }
      } // for

      if (!skipDefinition) {
        defn.setStatisticInfo(statInfos);
        result.add(defn);
        if (logger.isDebugEnabled()) {
          logger.debug("StatAlertsManager.createMemberStatAlertDefinition :: {}",
              defns[i].getStringRepresentation());
        }
      } else {
        if (logger.isDebugEnabled()) {
          logger.debug(
              "StatAlertsManager.createMemberStatAlertDefinition :: StatAlertDefinition {} is excluded",
              defn.getName());
        }
      }
    } // for

    return (StatAlertDefinition[]) result.toArray(new StatAlertDefinition[0]);
  }

  /**
   * Shut down this instance
   */
  protected synchronized void close() {
    // nullify the manager instance first
    closeInstance();

    // cancel the old timer. Although canceled, old task might execute one last
    // time
    if (timer != null) {
      timer.cancel();
    }
    timer = null;
  }

  /**
   * Timer task to send all the alerts raised to {@link StatAlertsAggregator}
   *
   */
  class EvaluateAlertDefnsTask extends SystemTimerTask {
    /**
     * Collect all the alerts raised and send it to {@link StatAlertsAggregator}
     */
    @Override
    public void run2() {
      final boolean isDebugEnabled = logger.isDebugEnabled();

      synchronized (StatAlertsManager.this) {
        if (dm.getCancelCriterion().isCancelInProgress()) {
          return;
        }

        // start alert notification are supposed to send to all the
        // admin agents exists in the system.
        // For the DS without agent, alert manager should not create
        // any alert notifications
        Set adminMemberSet = dm.getAdminMemberSet();
        if (adminMemberSet == null || adminMemberSet.isEmpty())
          return;

        if (isDebugEnabled) {
          logger.debug("EvaluateAlertDefnsTask: starting");
        }
        try {
          StatAlert[] alerts = getAlerts();
          if (alerts.length == 0) {
            if (isDebugEnabled) {
              logger.debug("EvaluateAlertsDefnsTask: no alerts");
            }
            return;
          }

          AlertsNotificationMessage request = new AlertsNotificationMessage();
          request.setAlerts(alerts);
          if (isDebugEnabled) {
            Iterator iterator = adminMemberSet.iterator();
            while (iterator.hasNext()) {
              logger.debug("EvaluateAlertDefnsTask: sending {} alerts to {}", alerts.length,
                  iterator.next());
            }
          }
          request.setRecipients(adminMemberSet);
          dm.putOutgoing(request);
        } catch (CancelException e) {
          logger.debug("EvaluateAlertDefnsTask: system closed: {}", e.getMessage(), e);
          close();
        } catch (Exception e) {
          logger.error("EvaluateAlertDefnsTask failed with an exception",
              e);
          close();
        }
        if (isDebugEnabled) {
          logger.debug("EvaluateAlertDefnsTask: done ");
        }
      }
    } // run
  } // EvaluateAlertDefnsTask
}