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/*
 * Copyright 2014-2019 Netflix, Inc.
 *
 * 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.netflix.spectator.atlas.impl;

import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.SerializerProvider;
import com.netflix.spectator.api.Id;
import com.netflix.spectator.api.Measurement;

import java.io.IOException;
import java.util.function.Function;

/**
 * Jackson serializer for measurements. Values will be converted to a
 * valid set as they are written out by replacing invalid characters with
 * an '_'.
 *
 * Classes in this package are only intended for use internally within spectator. They may
 * change at any time and without notice.
 */
public class MeasurementSerializer extends JsonSerializer {

  private final Function fixTagString;

  /**
   * Create a new instance of the serializer.
   *
   * @param fixTagString
   *     Function that fixes characters used for tag keys and values.
   */
  public MeasurementSerializer(Function fixTagString) {
    super();
    this.fixTagString = fixTagString;
  }

  @Override
  public void serialize(
      Measurement value,
      JsonGenerator gen,
      SerializerProvider serializers) throws IOException {
    Id id = value.id();
    gen.writeStartObject();
    gen.writeObjectFieldStart("tags");
    gen.writeStringField("name", fixTagString.apply(id.name()));
    boolean explicitDsType = false;
    int n = id.size();
    for (int i = 1; i < n; ++i) {
      final String k = fixTagString.apply(id.getKey(i));
      final String v = fixTagString.apply(id.getValue(i));
      if (!"name".equals(k)) {
        if ("atlas.dstype".equals(k)) {
          explicitDsType = true;
        }
        gen.writeStringField(k, v);
      }
    }

    // If the dstype has not been explicitly set, then the value must be coming in
    // as a gauge. Go ahead and explicitly mark it as such because the backend will
    // default to a rate.
    if (!explicitDsType) {
      gen.writeStringField("atlas.dstype", "gauge");
    }
    gen.writeEndObject();
    gen.writeNumberField("timestamp", value.timestamp());
    gen.writeNumberField("value", value.value());
    gen.writeEndObject();
  }
}