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.meter.analyzer.prometheus.rule;
  
  import java.io.File;
  
  import java.io.FileReader;
  import java.io.IOException;
  import java.io.Reader;
  
  import java.nio.file.FileSystems;
  import java.nio.file.Files;
  import java.nio.file.Path;
  
  import java.util.Collections;
  import java.util.List;
  import java.util.Map;
  import java.util.Objects;
  import java.util.stream.Collectors;
  
  import java.util.stream.Stream;
  
  import org.apache.skywalking.oap.server.core.UnexpectedException;
  import org.apache.skywalking.oap.server.library.util.ResourceUtils;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  import org.yaml.snakeyaml.Yaml;
  
  /**
   * Rules is factory to instance {@link Rule} from a local file.
   */
  public class Rules {
      private static final Logger LOG = LoggerFactory.getLogger(Rule.class);
  
      public static List<Rule> loadRules(final String path) throws IOException {
          return loadRules(path, Collections.emptyList());
      }
  
      public static List<Rule> loadRules(final String path, List<String> enabledRules) throws IOException {
  
          final Path root = ResourceUtils.getPath(path);
  
          Map<String, Boolean> formedEnabledRules = enabledRules
                  .stream()
                  .map(rule -> {
                      rule = rule.trim();
                      if (rule.startsWith("/")) {
                          rule = rule.substring(1);
                      }
                      if (!rule.endsWith(".yaml") && !rule.endsWith(".yml")) {
                          return rule + "{.yaml,.yml}";
                      }
                      return rule;
                  })
                  .collect(Collectors.toMap(rule -> rule, $ -> false));
          List<Rule> rules;
          try (Stream<Path> stream = Files.walk(root)) {
              rules = stream
                      .filter(it -> formedEnabledRules.keySet().stream()
                                      .anyMatch(rule -> {
                                          boolean matches = FileSystems.getDefault().getPathMatcher("glob:" + rule)
                                                  .matches(root.relativize(it));
                                          if (matches) {
                                              formedEnabledRules.put(rule, true);
                                          }
                                          return matches;
                                      }))
                      .map(pathPointer -> {
                          // Use relativized file path without suffix as the rule name.
                          String relativizePath = root.relativize(pathPointer).toString();
                          String ruleName = relativizePath.substring(0, relativizePath.lastIndexOf("."));
                          return getRulesFromFile(ruleName, pathPointer);
                      })
                      .filter(Objects::nonNull)
                      .collect(Collectors.toList()) ;
          }
  
          if (formedEnabledRules.containsValue(false)) {
              List<String> rulesNotFound = formedEnabledRules.keySet().stream()
                      .filter(rule -> !formedEnabledRules.get(rule))
                      .collect(Collectors.toList());
              throw new UnexpectedException("Some configuration files of enabled rules are not found, enabled rules: " + rulesNotFound);
          }
          return rules;
      }
  
      private static Rule getRulesFromFile(String ruleName, Path path) {
          File file = path.toFile();
          if (!file.isFile() || file.isHidden()) {
              return null;
          }
          try (Reader r = new FileReader(file)) {
              Rule rule = new Yaml().loadAs(r, Rule.class);
              if (rule == null) {
                  return null;
              }
              rule.setName(ruleName);
              return rule;
          } catch (IOException e) {
              throw new UnexpectedException("Load rule file" + file.getName() + " failed", e);
          }
      }
  }
  