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.oal.rt.parser;
  
  import com.google.common.reflect.ClassPath;
  import java.io.IOException;
  import java.util.HashMap;
  import java.util.Map;
  import java.util.Set;
  import lombok.AllArgsConstructor;
  import lombok.Getter;
  import org.apache.commons.lang3.StringUtils;
  import org.apache.skywalking.oap.server.core.analysis.metrics.annotation.BooleanValueFilterMatcher;
  import org.apache.skywalking.oap.server.core.analysis.metrics.annotation.FilterMatcher;
  
  @SuppressWarnings("UnstableApiUsage")
  public enum FilterMatchers {
      INSTANCE;
  
      FilterMatchers() {
          try {
              init();
          } catch (IOException e) {
              throw new RuntimeException(e);
          }
      }
  
      private final Map<String, MatcherInfo> matchersKeyedByType = new HashMap<>();
  
      private void init() throws IOException {
          final ClassPath classpath = ClassPath.from(FilterMatchers.class.getClassLoader());
          final Set<ClassPath.ClassInfo> classes = classpath.getTopLevelClassesRecursive("org.apache.skywalking");
          for (ClassPath.ClassInfo classInfo : classes) {
              final Class<?> clazz = classInfo.load();
  
              final FilterMatcher plainFilterMatcher = clazz.getAnnotation(FilterMatcher.class);
              final BooleanValueFilterMatcher booleanFilterMatcher = clazz.getAnnotation(BooleanValueFilterMatcher.class);
              if (plainFilterMatcher != null && booleanFilterMatcher != null) {
                  throw new IllegalStateException(
                      "A matcher class can not be annotated with both @FilterMatcher and @BooleanValueFilterMatcher"
                  );
              }
  
              if (plainFilterMatcher != null) {
                  for (final String type : plainFilterMatcher.value()) {
                      matchersKeyedByType.put(type, new MatcherInfo(clazz, false));
                  }
                  if (plainFilterMatcher.value().length == 0) {
                      final String defaultTypeName = StringUtils.uncapitalize(clazz.getSimpleName());
                      matchersKeyedByType.put(defaultTypeName, new MatcherInfo(clazz, false));
                  }
              }
  
              if (booleanFilterMatcher != null) {
                  for (final String type : booleanFilterMatcher.value()) {
                      matchersKeyedByType.put(type, new MatcherInfo(clazz, true));
                  }
                  if (booleanFilterMatcher.value().length == 0) {
                      final String defaultTypeName = StringUtils.uncapitalize(clazz.getSimpleName());
                      matchersKeyedByType.put(defaultTypeName, new MatcherInfo(clazz, true));
                  }
              }
          }
      }
  
      public MatcherInfo find(final String type) {
          if (!matchersKeyedByType.containsKey(type)) {
              throw new IllegalArgumentException("filter expression [" + type + "] not found");
          }
          return matchersKeyedByType.get(type);
      }
  
      @Getter
      @AllArgsConstructor
      public static class MatcherInfo {
          private final Class<?> matcher;
          private final boolean isBooleanType;
      }
  }
  