content: /*
   * 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.calcite.adapter.druid;
  
  import com.fasterxml.jackson.core.JsonGenerator;
  
  import java.io.IOException;
  import java.util.Locale;
  
  import static org.apache.calcite.adapter.druid.DruidQuery.writeFieldIf;
  
  import static java.util.Objects.requireNonNull;
  
  /**
   * Druid Json Expression based Virtual Column.
   * Virtual columns is used as "projection" concept throughout Druid using expression.
   */
  public class VirtualColumn implements DruidJson {
    private final String name;
  
    private final String expression;
  
    private final DruidType outputType;
  
    public VirtualColumn(String name, String expression, DruidType outputType) {
      this.name = requireNonNull(name, "name");
      this.expression = requireNonNull(expression, "expression");
      this.outputType = outputType == null ? DruidType.FLOAT : outputType;
    }
  
    @Override public void write(JsonGenerator generator) throws IOException {
      generator.writeStartObject();
      generator.writeStringField("type", "expression");
      generator.writeStringField("name", name);
      generator.writeStringField("expression", expression);
      writeFieldIf(generator, "outputType", getOutputType().toString().toUpperCase(Locale.ENGLISH));
      generator.writeEndObject();
    }
  
    public String getName() {
      return name;
    }
  
    public String getExpression() {
      return expression;
    }
  
    public DruidType getOutputType() {
      return outputType;
    }
  
    /**
     * Virtual Column builder.
     */
    public static class Builder {
      private String name;
  
      private String expression;
  
      private DruidType type;
  
      public Builder withName(String name) {
        this.name = name;
        return this;
      }
  
      public Builder withExpression(String expression) {
        this.expression = expression;
        return this;
      }
  
      public Builder withType(DruidType type) {
        this.type = type;
        return this;
      }
  
      public VirtualColumn build() {
        return new VirtualColumn(name, expression, type);
      }
    }
  
    public static Builder builder() {
      return new Builder();
    }
  }
  