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.cql3.selection;
  
  import java.util.*;
  import java.util.stream.Collectors;
  
  import com.google.common.base.Objects;
  import com.google.common.collect.*;
  
  import org.apache.cassandra.schema.ColumnMetadata;
  import org.apache.cassandra.cql3.ColumnSpecification;
  
  /**
   * Separately maintains the ColumnSpecifications and their mappings to underlying
   * columns as we may receive null mappings. This occurs where a query result
   * includes a column specification which does not map to any particular real
   * column, e.g. COUNT queries or where no-arg functions like now() are used
   */
  public class SelectionColumnMapping implements SelectionColumns
  {
      private final List<ColumnSpecification> columnSpecifications;
      private final Multimap<ColumnSpecification, ColumnMetadata> columnMappings;
  
      private SelectionColumnMapping()
      {
          this.columnSpecifications = new ArrayList<>();
          this.columnMappings = HashMultimap.create();
      }
  
      protected static SelectionColumnMapping newMapping()
      {
          return new SelectionColumnMapping();
      }
  
      protected static SelectionColumnMapping simpleMapping(Iterable<ColumnMetadata> columnDefinitions)
      {
          SelectionColumnMapping mapping = new SelectionColumnMapping();
          for (ColumnMetadata def: columnDefinitions)
              mapping.addMapping(def, def);
          return mapping;
      }
  
      protected SelectionColumnMapping addMapping(ColumnSpecification colSpec, ColumnMetadata column)
      {
          columnSpecifications.add(colSpec);
          // functions without arguments do not map to any column, so don't
          // record any mapping in that case
          if (column != null)
              columnMappings.put(colSpec, column);
          return this;
      }
  
      protected SelectionColumnMapping addMapping(ColumnSpecification colSpec, Iterable<ColumnMetadata> columns)
      {
          columnSpecifications.add(colSpec);
          columnMappings.putAll(colSpec, columns);
          return this;
      }
  
      public List<ColumnSpecification> getColumnSpecifications()
      {
          // return a mutable copy as we may add extra columns
          // for ordering (CASSANDRA-4911 & CASSANDRA-8286)
          return Lists.newArrayList(columnSpecifications);
      }
  
      public Multimap<ColumnSpecification, ColumnMetadata> getMappings()
      {
          return Multimaps.unmodifiableMultimap(columnMappings);
      }
  
      public boolean equals(Object obj)
      {
          if (obj == null)
              return false;
  
          if (!(obj instanceof SelectionColumnMapping))
              return false;
  
          SelectionColumns other = (SelectionColumns)obj;
          return Objects.equal(columnMappings, other.getMappings())
              && Objects.equal(columnSpecifications, other.getColumnSpecifications());
      }
  
      public int hashCode()
      {
          return Objects.hashCode(columnMappings);
      }
  
      public String toString()
      {
          return columnMappings.asMap()
                               .entrySet()
                               .stream()
                               .map(entry ->
                                    entry.getValue()
                                         .stream()
                                         .map(colDef -> colDef.name.toString())
                                         .collect(Collectors.joining(", ", entry.getKey().name.toString() + ":[", "]")))
                               .collect(Collectors.joining(", ",
                                                           columnSpecifications.stream()
                                                                               .map(colSpec -> colSpec.name.toString())
                                                                               .collect(Collectors.joining(", ",
                                                                                                           "{ Columns:[",
                                                                                                           "], Mappings:{")),
                                                           "} }"));
      }
  }
  