code: /*
   * 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.skywalking.oap.server.core.query;
  
  import java.util.List;
  import java.util.Optional;
  import java.util.stream.Collectors;
  import org.apache.skywalking.oap.server.library.util.StringUtil;
  import org.apache.skywalking.oap.server.core.query.enumeration.MetricsType;
  import org.apache.skywalking.oap.server.core.source.DefaultScopeDefine;
  import org.apache.skywalking.oap.server.core.storage.annotation.ValueColumnMetadata;
  import org.apache.skywalking.oap.server.library.module.Service;
  
  /**
   * MetricsMetadataQueryService provides the metadata of metrics to other modules.
   */
  public class MetricsMetadataQueryService implements Service {
      public static MetricsType typeOfMetrics(String metricsName) {
          final Optional<ValueColumnMetadata.ValueColumn> valueColumn
              = ValueColumnMetadata.INSTANCE.readValueColumnDefinition(metricsName);
          if (valueColumn.isPresent()) {
              switch (valueColumn.get().getDataType()) {
                  case COMMON_VALUE:
                      return MetricsType.REGULAR_VALUE;
                  case LABELED_VALUE:
                      return MetricsType.LABELED_VALUE;
                  case HISTOGRAM:
                      return MetricsType.HEATMAP;
                  case SAMPLED_RECORD:
                      return MetricsType.SAMPLED_RECORD;
                  case NOT_VALUE:
                  default:
                      return MetricsType.UNKNOWN;
              }
          } else {
              return MetricsType.UNKNOWN;
          }
      }
  
      public List<MetricDefinition> listMetrics(String regex) {
          return ValueColumnMetadata.INSTANCE.getAllMetadata()
                                             .entrySet()
                                             .stream()
                                             .filter(
                                                 metadata ->
                                                     StringUtil.isNotEmpty(regex) ?
                                                         metadata.getKey().matches(regex) : true)
                                             .map(metadata -> new MetricDefinition(
                                                      metadata.getKey(),
                                                      typeOfMetrics(metadata.getKey()),
                                                      DefaultScopeDefine.catalogOf(metadata.getValue().getScopeId())
                                                  )
                                             )
                                             .collect(Collectors.toList());
      }
  }
  