/**
 * Copyright (C) 2014-2016 LinkedIn Corp. (pinot-core@linkedin.com)
 *
 * Licensed 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 com.linkedin.pinot.routing;

import com.linkedin.pinot.common.config.AbstractTableConfig;
import com.linkedin.pinot.common.config.TableNameBuilder;
import com.linkedin.pinot.common.metadata.ZKMetadataProvider;
import com.linkedin.pinot.common.metadata.segment.OfflineSegmentZKMetadata;
import com.linkedin.pinot.common.utils.CommonConstants.Helix.TableType;
import com.linkedin.pinot.common.utils.time.TimeUtils;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.TimeUnit;
import org.apache.helix.ZNRecord;
import org.apache.helix.model.ExternalView;
import org.apache.helix.store.zk.ZkHelixPropertyStore;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;


public class HelixExternalViewBasedTimeBoundaryService implements TimeBoundaryService {

  private static final Logger LOGGER = LoggerFactory.getLogger(HelixExternalViewBasedTimeBoundaryService.class);

  private static final String DAYS_SINCE_EPOCH = "daysSinceEpoch";
  private static final String HOURS_SINCE_EPOCH = "hoursSinceEpoch";
  private static final String MINUTES_SINCE_EPOCH = "minutesSinceEpoch";
  private static final String SECONDS_SINCE_EPOCH = "secondsSinceEpoch";

  private final ZkHelixPropertyStore<ZNRecord> _propertyStore;
  private final Map<String, TimeBoundaryInfo> _timeBoundaryInfoMap = new HashMap<String, TimeBoundaryInfo>();

  public HelixExternalViewBasedTimeBoundaryService(ZkHelixPropertyStore<ZNRecord> propertyStore) {
    _propertyStore = propertyStore;
  }

  public synchronized void updateTimeBoundaryService(ExternalView externalView) {
    if (_propertyStore == null) {
      return;
    }
    String tableName = externalView.getResourceName();
    // Do nothing for realtime table.
    if (TableNameBuilder.getTableTypeFromTableName(tableName) == TableType.REALTIME) {
      return;
    }

    Set<String> offlineSegmentsServing = externalView.getPartitionSet();
    if (offlineSegmentsServing.isEmpty()) {
      LOGGER.info("Skipping updating time boundary service for table '{}' with no offline segments.", tableName);
      return;
    }

    AbstractTableConfig offlineTableConfig = ZKMetadataProvider.getOfflineTableConfig(_propertyStore, tableName);
    String timeType = offlineTableConfig.getValidationConfig().getTimeType();
    TimeUnit tableTimeUnit = getTimeUnitFromString(timeType);
    if (tableTimeUnit == null) {
      LOGGER.info("Skipping updating time boundary service for table '{}' with null timeUnit, config time type: {}.",
          tableName, timeType);
      return;
    }

    // Bulk reading all segment zk-metadata at once is more efficient than reading one at a time.
    List<OfflineSegmentZKMetadata> segmentZKMetadataList =
        ZKMetadataProvider.getOfflineSegmentZKMetadataListForTable(_propertyStore, tableName);

    long maxTimeValue = computeMaxSegmentEndTimeForTable(segmentZKMetadataList, tableTimeUnit);
    TimeBoundaryInfo timeBoundaryInfo = new TimeBoundaryInfo();
    timeBoundaryInfo.setTimeColumn(offlineTableConfig.getValidationConfig().getTimeColumnName());

    timeBoundaryInfo.setTimeValue(Long.toString(maxTimeValue));
    _timeBoundaryInfoMap.put(tableName, timeBoundaryInfo);

    LOGGER.info("Updated time boundary service for table '{}', maxTime: {}", tableName, maxTimeValue);
  }

  /**
   * Compute maximum end time across a list of segment zk-metadata.
   *
   * @param segmentZKMetadataList List of Segment zk metadata for which to compute the max end time.
   * @param tableTimeUnit Time Unit for table
   * @return Max end time across all segments.
   */
  private long computeMaxSegmentEndTimeForTable(List<OfflineSegmentZKMetadata> segmentZKMetadataList,
      TimeUnit tableTimeUnit) {
    long maxTimeValue = -1;

    for (OfflineSegmentZKMetadata metadata : segmentZKMetadataList) {
      long endTime = metadata.getEndTime();
      if (endTime <= 0) {
        continue;
      }

      // Convert all segment times to table's time unit, before comparison.
      TimeUnit segmentTimeUnit = metadata.getTimeUnit();
      if (segmentTimeUnit != null) {
        endTime = tableTimeUnit.convert(endTime, segmentTimeUnit);
      }
      maxTimeValue = Math.max(maxTimeValue, endTime);
    }
    return maxTimeValue;
  }

  private TimeUnit getTimeUnitFromString(String timeTypeString) {
    // If input data does not have a time column, no need to fire an exception.
    if ((timeTypeString == null) || timeTypeString.isEmpty()) {
      return null;
    }

    TimeUnit timeUnit = TimeUtils.timeUnitFromString(timeTypeString);

    // Check legacy time formats
    if (timeUnit == null) {
      if (timeTypeString.equalsIgnoreCase(DAYS_SINCE_EPOCH)) {
        timeUnit = TimeUnit.DAYS;
      }
      if (timeTypeString.equalsIgnoreCase(HOURS_SINCE_EPOCH)) {
        timeUnit = TimeUnit.HOURS;
      }
      if (timeTypeString.equalsIgnoreCase(MINUTES_SINCE_EPOCH)) {
        timeUnit = TimeUnit.MINUTES;
      }
      if (timeTypeString.equalsIgnoreCase(SECONDS_SINCE_EPOCH)) {
        timeUnit = TimeUnit.SECONDS;
      }
    }

    if (timeUnit == null) {
      throw new RuntimeException("Not supported time type for: " + timeTypeString);
    }
    return timeUnit;
  }

  @Override
  public void remove(String tableName) {
    _timeBoundaryInfoMap.remove(tableName);
  }

  @Override
  public TimeBoundaryInfo getTimeBoundaryInfoFor(String table) {
    return _timeBoundaryInfoMap.get(table);
  }
}