content: /*
   * 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.bookkeeper.stats.otel;
  
  import io.opentelemetry.api.common.Attributes;
  import java.util.StringJoiner;
  import org.apache.bookkeeper.stats.Counter;
  import org.apache.bookkeeper.stats.Gauge;
  import org.apache.bookkeeper.stats.OpStatsLogger;
  import org.apache.bookkeeper.stats.StatsLogger;
  
  public class OtelStatsLogger implements StatsLogger {
  
      private final OtelMetricsProvider provider;
      private final String scope;
      private final Attributes attributes;
  
      OtelStatsLogger(OtelMetricsProvider provider, String scope, Attributes attributes) {
          this.provider = provider;
          this.scope = scope;
          this.attributes = attributes;
      }
  
      @Override
      public OpStatsLogger getOpStatsLogger(String name) {
          return provider.opStats.computeIfAbsent(scopeContext(name), sc -> new OtelOpStatsLogger(provider.meter, sc));
      }
  
      @Override
      public OpStatsLogger getThreadScopedOpStatsLogger(String name) {
          return getOpStatsLogger(name);
      }
  
      @Override
      public Counter getCounter(String name) {
          return provider.counters.computeIfAbsent(scopeContext(name), sc -> new OtelCounter(provider.meter, sc));
      }
  
      @Override
      public Counter getThreadScopedCounter(String name) {
          return getCounter(name);
      }
  
      @Override
      public <T extends Number> void registerGauge(String name, Gauge<T> gauge) {
          provider.meter.gaugeBuilder(completeName(name))
                  .buildWithCallback(observableDoubleMeasurement -> {
                      double v = gauge.getSample().doubleValue();
                      observableDoubleMeasurement.record(v, attributes);
                  });
      }
  
      @Override
      public <T extends Number> void unregisterGauge(String name, Gauge<T> gauge) {
          // no-op
      }
  
      @Override
      public StatsLogger scope(String name) {
          return new OtelStatsLogger(provider, completeName(name), attributes);
      }
  
      @Override
      public void removeScope(String name, StatsLogger statsLogger) {
          // no-op
      }
  
      @Override
      public StatsLogger scopeLabel(String labelName, String labelValue) {
          Attributes newAttributes = Attributes.builder()
                  .putAll(attributes)
                  .put(labelName, labelValue)
                  .build();
          return new OtelStatsLogger(provider, scope, newAttributes);
      }
  
      private ScopeContext scopeContext(String name) {
          return new ScopeContext(completeName(name), attributes);
      }
  
      private String completeName(String name) {
          String metricName = scope.isEmpty()
                  ? name
                  : new StringJoiner(".").add(scope).add(name).toString();
  
          return metricName;
      }
  }
  