/*
 * 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.hadoop.hdds.scm.safemode;

import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;

import org.apache.commons.lang3.tuple.Pair;
import org.apache.hadoop.hdds.HddsConfigKeys;
import org.apache.hadoop.hdds.conf.ConfigurationSource;
import org.apache.hadoop.hdds.scm.container.ContainerInfo;
import org.apache.hadoop.hdds.scm.events.SCMEvents;
import org.apache.hadoop.hdds.scm.pipeline.PipelineManager;
import org.apache.hadoop.hdds.server.events.EventPublisher;
import org.apache.hadoop.hdds.server.events.EventQueue;

import com.google.common.annotations.VisibleForTesting;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * StorageContainerManager enters safe mode on startup to allow system to
 * reach a stable state before becoming fully functional. SCM will wait
 * for certain resources to be reported before coming out of safe mode.
 *
 * SafeModeExitRule defines format to define new rules which must be satisfied
 * to exit Safe mode.
 *
 * Current SafeMode rules:
 * 1. ContainerSafeModeRule:
 * On every new datanode registration, it fires
 * {@link SCMEvents#NODE_REGISTRATION_CONT_REPORT}.  This rule handles this
 * event. This rule process this report, increment the
 * containerWithMinReplicas count when this reported replica is in the
 * containerMap. Then validates if cutoff threshold for containers is meet.
 *
 * 2. DatanodeSafeModeRule:
 * On every new datanode registration, it fires
 * {@link SCMEvents#NODE_REGISTRATION_CONT_REPORT}. This rule handles this
 * event. This rule process this report, and check if this is new node, add
 * to its reported node list. Then validate it cutoff threshold for minimum
 * number of datanode registered is met or not.
 *
 * 3. HealthyPipelineSafeModeRule:
 * Once the PipelineReportHandler processes the
 * {@link SCMEvents#PIPELINE_REPORT}, it fires
 * {@link SCMEvents#OPEN_PIPELINE}. This rule handles this
 * event. This rule processes this report, and check if pipeline is healthy
 * and increments current healthy pipeline count. Then validate it cutoff
 * threshold for healthy pipeline is met or not.
 *
 * 4. OneReplicaPipelineSafeModeRule:
 * Once the PipelineReportHandler processes the
 * {@link SCMEvents#PIPELINE_REPORT}, it fires
 * {@link SCMEvents#OPEN_PIPELINE}. This rule handles this
 * event. This rule processes this report, and add the reported pipeline to
 * reported pipeline set. Then validate it cutoff threshold for one replica
 * per pipeline is met or not.
 *
 */
public class SCMSafeModeManager implements SafeModeManager {

  private static final Logger LOG =
      LoggerFactory.getLogger(SCMSafeModeManager.class);
  private final boolean isSafeModeEnabled;
  private final long waitTime;
  private AtomicBoolean inSafeMode = new AtomicBoolean(true);
  private AtomicBoolean preCheckComplete = new AtomicBoolean(false);

  private Map<String, SafeModeExitRule> exitRules = new HashMap(1);
  private Set<String> preCheckRules = new HashSet<>(1);
  private ConfigurationSource config;
  private static final String CONT_EXIT_RULE = "ContainerSafeModeRule";
  private static final String DN_EXIT_RULE = "DataNodeSafeModeRule";
  private static final String HEALTHY_PIPELINE_EXIT_RULE =
      "HealthyPipelineSafeModeRule";
  private static final String ATLEAST_ONE_DATANODE_REPORTED_PIPELINE_EXIT_RULE =
      "AtleastOneDatanodeReportedRule";

  private Set<String> validatedRules = new HashSet<>();
  private Set<String> validatedPreCheckRules = new HashSet<>(1);

  private final EventQueue eventPublisher;
  private final PipelineManager pipelineManager;

  private final SafeModeMetrics safeModeMetrics;

  public SCMSafeModeManager(ConfigurationSource conf,
      List<ContainerInfo> allContainers, PipelineManager pipelineManager,
      EventQueue eventQueue) {
    this.config = conf;
    this.pipelineManager = pipelineManager;
    this.eventPublisher = eventQueue;
    this.isSafeModeEnabled = conf.getBoolean(
        HddsConfigKeys.HDDS_SCM_SAFEMODE_ENABLED,
        HddsConfigKeys.HDDS_SCM_SAFEMODE_ENABLED_DEFAULT);


    this.waitTime = conf.getTimeDuration(
        HddsConfigKeys.HDDS_SCM_WAIT_TIME_AFTER_SAFE_MODE_EXIT,
        HddsConfigKeys.HDDS_SCM_WAIT_TIME_AFTER_SAFE_MODE_EXIT_DEFAULT,
        TimeUnit.MILLISECONDS);

    if (isSafeModeEnabled) {
      this.safeModeMetrics = SafeModeMetrics.create();
      ContainerSafeModeRule containerSafeModeRule =
          new ContainerSafeModeRule(CONT_EXIT_RULE, eventQueue, config,
              allContainers, this);
      DataNodeSafeModeRule dataNodeSafeModeRule =
          new DataNodeSafeModeRule(DN_EXIT_RULE, eventQueue, config, this);
      exitRules.put(CONT_EXIT_RULE, containerSafeModeRule);
      exitRules.put(DN_EXIT_RULE, dataNodeSafeModeRule);
      preCheckRules.add(DN_EXIT_RULE);
      if (conf.getBoolean(
          HddsConfigKeys.HDDS_SCM_SAFEMODE_PIPELINE_AVAILABILITY_CHECK,
          HddsConfigKeys.HDDS_SCM_SAFEMODE_PIPELINE_AVAILABILITY_CHECK_DEFAULT)
          && pipelineManager != null) {
        HealthyPipelineSafeModeRule healthyPipelineSafeModeRule =
            new HealthyPipelineSafeModeRule(HEALTHY_PIPELINE_EXIT_RULE,
                eventQueue, pipelineManager,
                this, config);
        OneReplicaPipelineSafeModeRule oneReplicaPipelineSafeModeRule =
            new OneReplicaPipelineSafeModeRule(
                ATLEAST_ONE_DATANODE_REPORTED_PIPELINE_EXIT_RULE, eventQueue,
                pipelineManager, this, conf);
        exitRules.put(HEALTHY_PIPELINE_EXIT_RULE, healthyPipelineSafeModeRule);
        exitRules.put(ATLEAST_ONE_DATANODE_REPORTED_PIPELINE_EXIT_RULE,
            oneReplicaPipelineSafeModeRule);
      }
      boolean createPipelineInSafemode = conf.getBoolean(
          HddsConfigKeys.HDDS_SCM_SAFEMODE_PIPELINE_CREATION,
          HddsConfigKeys.HDDS_SCM_SAFEMODE_PIPELINE_CREATION_DEFAULT);

      if (createPipelineInSafemode) {
        pipelineManager.startPipelineCreator();
      }
    } else {
      this.safeModeMetrics = null;
      exitSafeMode(eventQueue);
    }
  }

  public void stop() {
    if (isSafeModeEnabled) {
      this.safeModeMetrics.unRegister();
    }
  }

  public SafeModeMetrics getSafeModeMetrics() {
    return safeModeMetrics;
  }

  /**
   * Emit Safe mode status.
   */
  @VisibleForTesting
  public void emitSafeModeStatus() {
    SafeModeStatus safeModeStatus =
        new SafeModeStatus(getInSafeMode(), getPreCheckComplete());
    eventPublisher.fireEvent(SCMEvents.SAFE_MODE_STATUS,
        safeModeStatus);

    // Only notify the delayed listeners if safemode remains on, as precheck
    // may have completed.
    if (safeModeStatus.isInSafeMode()) {
      eventPublisher.fireEvent(SCMEvents.DELAYED_SAFE_MODE_STATUS,
          safeModeStatus);
    } else {
      // If safemode is off, then notify the delayed listeners with a delay.
      final Thread safeModeExitThread = new Thread(() -> {
        try {
          Thread.sleep(waitTime);
        } catch (InterruptedException e) {
          Thread.currentThread().interrupt();
        }
        eventPublisher.fireEvent(SCMEvents.DELAYED_SAFE_MODE_STATUS,
            safeModeStatus);
      });

      safeModeExitThread.setDaemon(true);
      safeModeExitThread.start();
    }
  }


  public synchronized void validateSafeModeExitRules(String ruleName,
      EventPublisher eventQueue) {

    if (exitRules.get(ruleName) != null) {
      validatedRules.add(ruleName);
      if (preCheckRules.contains(ruleName)) {
        validatedPreCheckRules.add(ruleName);
      }
      LOG.info("{} rule is successfully validated", ruleName);
    } else {
      // This should never happen
      LOG.error("No Such Exit rule {}", ruleName);
    }

    if (!getPreCheckComplete()) {
      if (validatedPreCheckRules.size() == preCheckRules.size()) {
        completePreCheck(eventQueue);
      }
    }

    if (validatedRules.size() == exitRules.size()) {
      // All rules are satisfied, we can exit safe mode.
      LOG.info("ScmSafeModeManager, all rules are successfully validated");
      exitSafeMode(eventQueue);
    }

  }

  /**
   * When all the precheck rules have been validated, set preCheckComplete to
   * true and then emit the safemode status so any listeners get notified of
   * the safemode state change.
   * @param eventQueue
   */
  @VisibleForTesting
  public void completePreCheck(EventPublisher eventQueue) {
    LOG.info("All SCM safe mode pre check rules have passed");
    setPreCheckComplete(true);
    emitSafeModeStatus();
  }

  /**
   * Exit safe mode. It does following actions:
   * 1. Set safe mode status to false.
   * 2. Emits START_REPLICATION for ReplicationManager.
   * 3. Cleanup resources.
   * 4. Emit safe mode status.
   * @param eventQueue
   */
  @VisibleForTesting
  public void exitSafeMode(EventPublisher eventQueue) {
    LOG.info("SCM exiting safe mode.");
    // If safemode is exiting, then pre check must also have passed so
    // set it to true.
    setPreCheckComplete(true);
    setInSafeMode(false);

    // TODO: Remove handler registration as there is no need to listen to
    // register events anymore.

    emitSafeModeStatus();
  }

  public boolean getInSafeMode() {
    if (!isSafeModeEnabled) {
      return false;
    }
    return inSafeMode.get();
  }

  /**
   * Get the safe mode status of all rules.
   *
   * @return map of rule statuses.
   */
  public Map<String, Pair<Boolean, String>> getRuleStatus() {
    Map<String, Pair<Boolean, String>> map = new HashMap<>();
    for (SafeModeExitRule exitRule : exitRules.values()) {
      map.put(exitRule.getRuleName(),
          Pair.of(exitRule.validate(), exitRule.getStatusText()));
    }
    return map;
  }

  public boolean getPreCheckComplete() {
    return preCheckComplete.get();
  }

  /**
   * Set safe mode status.
   */
  public void setInSafeMode(boolean inSafeMode) {
    this.inSafeMode.set(inSafeMode);
  }

  public void setPreCheckComplete(boolean newState) {
    this.preCheckComplete.set(newState);
  }

  public static Logger getLogger() {
    return LOG;
  }

  @VisibleForTesting
  public double getCurrentContainerThreshold() {
    return ((ContainerSafeModeRule) exitRules.get(CONT_EXIT_RULE))
        .getCurrentContainerThreshold();
  }

  @VisibleForTesting
  public HealthyPipelineSafeModeRule getHealthyPipelineSafeModeRule() {
    return (HealthyPipelineSafeModeRule)
        exitRules.get(HEALTHY_PIPELINE_EXIT_RULE);
  }

  @VisibleForTesting
  public OneReplicaPipelineSafeModeRule getOneReplicaPipelineSafeModeRule() {
    return (OneReplicaPipelineSafeModeRule)
        exitRules.get(ATLEAST_ONE_DATANODE_REPORTED_PIPELINE_EXIT_RULE);
  }


  /**
   * Class used during SafeMode status event.
   */
  public static class SafeModeStatus {

    private boolean safeModeStatus;
    private boolean preCheckPassed;

    public SafeModeStatus(boolean safeModeState, boolean preCheckPassed) {
      this.safeModeStatus = safeModeState;
      this.preCheckPassed = preCheckPassed;
    }

    public boolean isInSafeMode() {
      return safeModeStatus;
    }

    public boolean isPreCheckComplete() {
      return preCheckPassed;
    }
  }

}