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.query.graphql.resolver;
  
  import graphql.kickstart.tools.GraphQLQueryResolver;
  import graphql.org.antlr.v4.runtime.misc.ParseCancellationException;
  import java.text.DecimalFormat;
  import org.antlr.v4.runtime.CharStreams;
  import org.antlr.v4.runtime.CommonTokenStream;
  import org.antlr.v4.runtime.tree.ParseTree;
  import org.apache.skywalking.oap.query.graphql.mqe.rt.MQEVisitor;
  import org.apache.skywalking.oap.query.graphql.mqe.rt.exception.ParseErrorListener;
  import org.apache.skywalking.oap.query.graphql.type.mql.ExpressionResult;
  import org.apache.skywalking.oap.query.graphql.type.mql.ExpressionResultType;
  import org.apache.skywalking.oap.server.core.query.input.Entity;
  import org.apache.skywalking.oap.server.core.query.input.Duration;
  import org.apache.skywalking.oap.server.library.module.ModuleManager;
  import org.apache.skywalking.mqe.rt.grammar.MQELexer;
  import org.apache.skywalking.mqe.rt.grammar.MQEParser;
  
  public class MetricsExpressionQuery implements GraphQLQueryResolver {
      private final MetricsQuery metricsQuery;
      private final RecordsQuery recordsQuery;
      private final DecimalFormat valueFormat = new DecimalFormat();
  
      public MetricsExpressionQuery(ModuleManager moduleManager) {
          this.metricsQuery = new MetricsQuery(moduleManager);
          this.recordsQuery = new RecordsQuery(moduleManager);
          this.valueFormat.setGroupingUsed(false);
      }
  
      public ExpressionResult execExpression(String expression, Entity entity, Duration duration) {
          MQELexer lexer = new MQELexer(
              CharStreams.fromString(expression));
          lexer.addErrorListener(new ParseErrorListener());
          MQEParser parser = new MQEParser(new CommonTokenStream(lexer));
          parser.addErrorListener(new ParseErrorListener());
          ParseTree tree;
          try {
              tree = parser.expression();
          } catch (ParseCancellationException e) {
              ExpressionResult errorResult = new ExpressionResult();
              errorResult.setType(ExpressionResultType.UNKNOWN);
              errorResult.setError(e.getMessage());
              return errorResult;
          }
          MQEVisitor visitor = new MQEVisitor(metricsQuery, recordsQuery, entity, duration);
          ExpressionResult parseResult = visitor.visit(tree);
  
          parseResult.getResults().forEach(mqeValues -> {
              mqeValues.getValues().forEach(mqeValue -> {
                  if (!mqeValue.isEmptyValue()) {
                      mqeValue.setValue(valueFormat.format(mqeValue.getDoubleValue()));
                  }
              });
          });
  
          return parseResult;
      }
  }
  