/*
 * 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.samza.sql.translator;

import java.time.Duration;
import java.time.Instant;
import org.apache.samza.context.ContainerContext;
import org.apache.samza.context.Context;
import org.apache.samza.metrics.Counter;
import org.apache.samza.metrics.MetricsRegistry;
import org.apache.samza.metrics.SamzaHistogram;
import org.apache.samza.operators.functions.MapFunction;
import org.apache.samza.sql.data.SamzaSqlRelMessage;


/**
 * TranslatorOutputMetricsMapFunction is a dummy map function to maintain join metrics at output
 */
class TranslatorOutputMetricsMapFunction implements MapFunction<SamzaSqlRelMessage, SamzaSqlRelMessage> {
  private transient MetricsRegistry metricsRegistry;
  private transient SamzaHistogram processingTime; // milli-seconds
  private transient Counter outputEvents;

  private final String logicalOpId;

  TranslatorOutputMetricsMapFunction(String logicalOpId) {
    this.logicalOpId = logicalOpId;
  }

  /**
   * initializes the TranslatorOutputMetricsMapFunction before any message is processed
   * @param context the {@link Context} for this task
   */
  @Override
  public void init(Context context) {
    ContainerContext containerContext = context.getContainerContext();
    metricsRegistry = containerContext.getContainerMetricsRegistry();
    processingTime = new SamzaHistogram(metricsRegistry, logicalOpId, TranslatorConstants.PROCESSING_TIME_NAME);
    outputEvents = metricsRegistry.newCounter(logicalOpId, TranslatorConstants.OUTPUT_EVENTS_NAME);
    outputEvents.clear();
  }

  /**
   * update metrics given a message
   * @param message  the input message
   * @return the same message
   */
  @Override
  public SamzaSqlRelMessage apply(SamzaSqlRelMessage message) {
    Instant endProcessing = Instant.now();
    Instant beginProcessing = Instant.ofEpochMilli(message.getSamzaSqlRelMsgMetadata().joinStartTimeMs);
    outputEvents.inc();
    processingTime.update(Duration.between(beginProcessing, endProcessing).toMillis());
    return message;
  }
} // TranslatorOutputMetricsMapFunction