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.beam.sdk.extensions.sql.impl.cep;
  
  import org.apache.beam.vendor.calcite.v1_40_0.org.apache.calcite.rex.RexPatternFieldRef;
  
  /**
   * A {@code CEPFieldRef} instance represents a node that points to a specified field in a {@code
   * Row}. It has similar functionality as Calcite's {@code RexPatternFieldRef}.
   */
  public class CEPFieldRef extends CEPOperation {
  
    private final String alpha;
    private final int fieldIndex;
  
    CEPFieldRef(String alpha, int fieldIndex) {
      this.alpha = alpha;
      this.fieldIndex = fieldIndex;
    }
  
    public static CEPFieldRef of(RexPatternFieldRef rexFieldRef) {
      return new CEPFieldRef(rexFieldRef.getAlpha(), rexFieldRef.getIndex());
    }
  
    public String getAlpha() {
      return alpha;
    }
  
    public int getIndex() {
      return fieldIndex;
    }
  
    @Override
    public String toString() {
      return String.format("%s.$%d", alpha, fieldIndex);
    }
  }
  