/*
 * Copyright 2017-2020 The OpenTracing Authors
 *
 * 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 io.opentracing.contrib.kafka;

import io.opentracing.References;
import io.opentracing.Span;
import io.opentracing.SpanContext;
import io.opentracing.Tracer;
import io.opentracing.propagation.Format;
import io.opentracing.tag.Tags;
import java.util.Collection;
import java.util.Collections;
import java.util.function.BiFunction;
import org.apache.kafka.clients.consumer.ConsumerRecord;
import org.apache.kafka.clients.producer.ProducerRecord;
import org.apache.kafka.common.header.Headers;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class TracingKafkaUtils {

  private static final Logger logger = LoggerFactory.getLogger(TracingKafkaUtils.class);
  public static final String TO_PREFIX = "To_";
  public static final String FROM_PREFIX = "From_";

  /**
   * Extract Span Context from record headers
   *
   * @param headers record headers
   * @return span context
   */
  public static SpanContext extractSpanContext(Headers headers, Tracer tracer) {
    return tracer
        .extract(Format.Builtin.TEXT_MAP, new HeadersMapExtractAdapter(headers));
  }

  /**
   * Inject Span Context to record headers
   *
   * @param spanContext Span Context
   * @param headers record headers
   */
  public static void inject(SpanContext spanContext, Headers headers,
      Tracer tracer) {
    tracer.inject(spanContext, Format.Builtin.TEXT_MAP, new HeadersMapInjectAdapter(headers));
  }

  public static <K, V> Span buildAndInjectSpan(ProducerRecord<K, V> record, Tracer tracer) {
    return buildAndInjectSpan(record, tracer, ClientSpanNameProvider.PRODUCER_OPERATION_NAME, null,
        Collections.singletonList(SpanDecorator.STANDARD_TAGS));
  }

  public static <K, V> Span buildAndInjectSpan(ProducerRecord<K, V> record, Tracer tracer,
      BiFunction<String, ProducerRecord, String> producerSpanNameProvider,
      SpanContext parent) {
    return buildAndInjectSpan(record, tracer, producerSpanNameProvider, parent,
        Collections.singletonList(SpanDecorator.STANDARD_TAGS));
  }

  static <K, V> Span buildAndInjectSpan(ProducerRecord<K, V> record, Tracer tracer,
      BiFunction<String, ProducerRecord, String> producerSpanNameProvider,
      SpanContext parent, Collection<SpanDecorator> spanDecorators) {
    String producerOper =
        TO_PREFIX + record.topic(); // <======== It provides better readability in the UI
    Tracer.SpanBuilder spanBuilder = tracer
        .buildSpan(producerSpanNameProvider.apply(producerOper, record))
        .withTag(Tags.SPAN_KIND.getKey(), Tags.SPAN_KIND_PRODUCER);

    SpanContext spanContext = TracingKafkaUtils.extractSpanContext(record.headers(), tracer);

    if (spanContext != null) {
      spanBuilder.asChildOf(spanContext);
    } else if (parent != null) {
      spanBuilder.asChildOf(parent);
    }

    Span span = spanBuilder.start();

    for (SpanDecorator decorator : spanDecorators) {
      decorator.onSend(record, span);
    }

    try {
      TracingKafkaUtils.inject(span.context(), record.headers(), tracer);
    } catch (Exception e) {
      // it can happen if headers are read only (when record is sent second time)
      logger.error("failed to inject span context. sending record second time?", e);
    }

    return span;
  }

  public static <K, V> void buildAndFinishChildSpan(ConsumerRecord<K, V> record, Tracer tracer) {
    buildAndFinishChildSpan(record, tracer, ClientSpanNameProvider.CONSUMER_OPERATION_NAME,
        Collections.singletonList(SpanDecorator.STANDARD_TAGS));
  }

  public static <K, V> void buildAndFinishChildSpan(ConsumerRecord<K, V> record, Tracer tracer,
      BiFunction<String, ConsumerRecord, String> consumerSpanNameProvider) {
    buildAndFinishChildSpan(record, tracer, consumerSpanNameProvider,
        Collections.singletonList(SpanDecorator.STANDARD_TAGS));
  }

  static <K, V> void buildAndFinishChildSpan(ConsumerRecord<K, V> record, Tracer tracer,
      BiFunction<String, ConsumerRecord, String> consumerSpanNameProvider,
      Collection<SpanDecorator> spanDecorators) {
    SpanContext parentContext = TracingKafkaUtils.extractSpanContext(record.headers(), tracer);
    String consumerOper =
        FROM_PREFIX + record.topic(); // <====== It provides better readability in the UI
    Tracer.SpanBuilder spanBuilder = tracer
        .buildSpan(consumerSpanNameProvider.apply(consumerOper, record))
        .withTag(Tags.SPAN_KIND.getKey(), Tags.SPAN_KIND_CONSUMER);

    if (parentContext != null) {
      spanBuilder.addReference(References.FOLLOWS_FROM, parentContext);
    }

    Span span = spanBuilder.start();

    for (SpanDecorator decorator : spanDecorators) {
      decorator.onResponse(record, span);
    }

    span.finish();

    // Inject created span context into record headers for extraction by client to continue span chain
    inject(span.context(), record.headers(), tracer);
  }
}