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;
  
  import com.google.common.base.Preconditions;
  import com.google.common.base.Strings;
  import com.google.common.collect.ImmutableMap;
  import io.vavr.control.Try;
  import java.util.List;
  import java.util.StringJoiner;
  import java.util.stream.Stream;
  import lombok.extern.slf4j.Slf4j;
  import org.apache.commons.lang3.StringUtils;
  import org.apache.skywalking.oap.meter.analyzer.dsl.DSL;
  import org.apache.skywalking.oap.meter.analyzer.dsl.Expression;
  import org.apache.skywalking.oap.meter.analyzer.dsl.ExpressionParsingException;
  import org.apache.skywalking.oap.meter.analyzer.dsl.Result;
  import org.apache.skywalking.oap.meter.analyzer.dsl.SampleFamily;
  import org.apache.skywalking.oap.server.core.analysis.meter.MeterSystem;
  
  import static java.util.stream.Collectors.toList;
  
  /**
   * MetricConvert converts {@link SampleFamily} collection to meter-system metrics, then store them to backend storage.
   */
  @Slf4j
  public class MetricConvert {
  
      public static <T> Stream<T> log(Try<T> t, String debugMessage) {
          return t
              .onSuccess(i -> log.debug(debugMessage + " :{}", i))
              .onFailure(e -> log.debug(debugMessage + " failed", e))
              .toJavaStream();
      }
  
      private final List<Analyzer> analyzers;
  
      public MetricConvert(MetricRuleConfig rule, MeterSystem service) {
          Preconditions.checkState(!Strings.isNullOrEmpty(rule.getMetricPrefix()));
          // init expression script
          if (StringUtils.isNotEmpty(rule.getInitExp())) {
              handleInitExp(rule.getInitExp());
          }
          this.analyzers = rule.getMetricsRules().stream().map(
              r -> buildAnalyzer(
                  formatMetricName(rule, r.getName()),
                  rule.getFilter(),
                  formatExp(rule.getExpPrefix(), rule.getExpSuffix(), r.getExp()),
                  service
              )
          ).collect(toList());
      }
  
      Analyzer buildAnalyzer(final String metricsName,
                             final String filter,
                             final String exp,
                             final MeterSystem service) {
          return Analyzer.build(
              metricsName,
              filter,
              exp,
              service
          );
      }
  
      private String formatExp(final String expPrefix, String expSuffix, String exp) {
          String ret = exp;
          if (!Strings.isNullOrEmpty(expPrefix)) {
              ret = String.format("(%s.%s)", StringUtils.substringBefore(exp, "."), expPrefix);
              final String after = StringUtils.substringAfter(exp, ".");
              if (!Strings.isNullOrEmpty(after)) {
                  ret = String.format("(%s.%s)", ret, after);
              }
          }
          if (!Strings.isNullOrEmpty(expSuffix)) {
              ret = String.format("(%s).%s", ret, expSuffix);
          }
          return ret;
      }
  
      /**
       * toMeter transforms {@link SampleFamily} collection  to meter-system metrics.
       *
       * @param sampleFamilies {@link SampleFamily} collection.
       */
      public void toMeter(final ImmutableMap<String, SampleFamily> sampleFamilies) {
          Preconditions.checkNotNull(sampleFamilies);
          if (sampleFamilies.size() < 1) {
              return;
          }
          for (Analyzer each : analyzers) {
              try {
                  each.analyse(sampleFamilies);
              } catch (Throwable t) {
                  log.error("Analyze {} error", each, t);
              }
          }
      }
  
      private String formatMetricName(MetricRuleConfig rule, String meterRuleName) {
          StringJoiner metricName = new StringJoiner("_");
          metricName.add(rule.getMetricPrefix()).add(meterRuleName);
          return metricName.toString();
      }
  
      private void handleInitExp(String exp) {
          Expression e = DSL.parse(exp);
          final Result result = e.run(ImmutableMap.of());
          if (!result.isSuccess() && result.isThrowable()) {
              throw new ExpressionParsingException(
                  "failed to execute init expression: " + exp + ", error:" + result.getError());
          }
      }
  }
  