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.cassandra.db.virtual.walker;
  
  import java.util.function.Supplier;
  
  import org.apache.cassandra.db.virtual.model.Column;
  
  /**
   * Utility class for quick iteration over row attributes and row values.
   * Walk order is defined by {@link Column} annotations and is the same as
   * in CQL (partition key columns first, then clustering columns, then regular columns).
   */
  public interface RowWalker<R>
  {
      /**
       * Returns the number of columns of the given type in the row.
       *
       * @param type the type of column
       * @return the number of columns of the given type in the row.
       */
      int count(Column.Type type);
  
      /**
       * Visit the metadata of the row.
       *
       * @param visitor the visitor to accept the metadata
       */
      void visitMeta(MetadataVisitor visitor);
  
      /**
       * Visit the row.
       *
       * @param row     the row to visit
       * @param visitor the visitor to accept the row
       */
      void visitRow(R row, RowMetadataVisitor visitor);
  
      /**
       * Visitor for metadata of the row.
       */
      interface MetadataVisitor
      {
          /**
           * Process the metadata.
           *
           * @param type  the type of column
           * @param name  the name of the column
           * @param clazz the class of the column
           * @param <T>   the type of the column
           */
          <T> void accept(Column.Type type, String name, Class<T> clazz);
      }
  
      /**
       * Visitor for a row value and its metadata.
       */
      interface RowMetadataVisitor
      {
          /**
           * Process the row metadata.
           *
           * @param type  the type of column
           * @param name  the name of the column
           * @param clazz the class of the column
           * @param value the value of the column
           * @param <T>   the type of the column
           */
          <T> void accept(Column.Type type, String name, Class<T> clazz, Supplier<T> value);
      }
  }
  