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;
  
  import java.util.Iterator;
  import java.util.NavigableMap;
  import java.util.function.Supplier;
  
  import com.google.common.collect.AbstractIterator;
  
  import org.apache.cassandra.db.DataRange;
  import org.apache.cassandra.db.DecoratedKey;
  import org.apache.cassandra.db.EmptyIterators;
  import org.apache.cassandra.db.PartitionPosition;
  import org.apache.cassandra.db.filter.ClusteringIndexFilter;
  import org.apache.cassandra.db.filter.ColumnFilter;
  import org.apache.cassandra.db.filter.RowFilter;
  import org.apache.cassandra.db.partitions.AbstractUnfilteredPartitionIterator;
  import org.apache.cassandra.db.partitions.PartitionUpdate;
  import org.apache.cassandra.db.partitions.SingletonUnfilteredPartitionIterator;
  import org.apache.cassandra.db.partitions.UnfilteredPartitionIterator;
  import org.apache.cassandra.db.rows.UnfilteredRowIterator;
  import org.apache.cassandra.dht.AbstractBounds;
  import org.apache.cassandra.exceptions.InvalidRequestException;
  import org.apache.cassandra.schema.TableMetadata;
  
  import static org.apache.cassandra.utils.Clock.Global.currentTimeMillis;
  
  /**
   * An abstract virtual table implementation that builds the resultset on demand.
   */
  public abstract class AbstractVirtualTable implements VirtualTable
  {
      protected final TableMetadata metadata;
  
      protected AbstractVirtualTable(TableMetadata metadata)
      {
          if (!metadata.isVirtual())
              throw new IllegalArgumentException("Cannot instantiate a non-virtual table");
  
          this.metadata = metadata;
      }
  
      public TableMetadata metadata()
      {
          return metadata;
      }
  
      /**
       * Provide a {@link DataSet} that is contains all of the virtual table's data.
       */
      public abstract DataSet data();
  
      /**
       * Provide a {@link DataSet} that is potentially restricted to the provided partition - but is allowed to contain
       * other partitions.
       */
      public DataSet data(DecoratedKey partitionKey)
      {
          return data();
      }
  
      @Override
      public UnfilteredPartitionIterator select(DecoratedKey partitionKey, ClusteringIndexFilter clusteringIndexFilter, ColumnFilter columnFilter, RowFilter rowFilter)
      {
          Partition partition = data(partitionKey).getPartition(partitionKey);
  
          if (null == partition)
              return EmptyIterators.unfilteredPartition(metadata);
  
          long now = currentTimeMillis();
          UnfilteredRowIterator rowIterator = partition.toRowIterator(metadata(), clusteringIndexFilter, columnFilter, now);
          return new SingletonUnfilteredPartitionIterator(rowIterator);
      }
  
      @Override
      public final UnfilteredPartitionIterator select(DataRange dataRange, ColumnFilter columnFilter, RowFilter rowFilter)
      {
          DataSet data = data();
  
          if (data.isEmpty())
              return EmptyIterators.unfilteredPartition(metadata);
  
          Iterator<Partition> iterator = data.getPartitions(dataRange);
  
          long now = currentTimeMillis();
  
          return new AbstractUnfilteredPartitionIterator()
          {
              @Override
              public UnfilteredRowIterator next()
              {
                  Partition partition = iterator.next();
                  return partition.toRowIterator(metadata, dataRange.clusteringIndexFilter(partition.key()), columnFilter, now);
              }
  
              @Override
              public boolean hasNext()
              {
                  return iterator.hasNext();
              }
  
              @Override
              public TableMetadata metadata()
              {
                  return metadata;
              }
          };
      }
  
      @Override
      public void apply(PartitionUpdate update)
      {
          throw new InvalidRequestException("Modification is not supported by table " + metadata);
      }
  
      @Override
      public void truncate()
      {
          throw new InvalidRequestException("Truncation is not supported by table " + metadata);
      }
  
      @Override
      public String toString()
      {
          return metadata().toString();
      }
  
      public interface DataSet
      {
          boolean isEmpty();
          Partition getPartition(DecoratedKey partitionKey);
          Iterator<Partition> getPartitions(DataRange range);
      }
  
      public interface Partition
      {
          DecoratedKey key();
          UnfilteredRowIterator toRowIterator(TableMetadata metadata, ClusteringIndexFilter clusteringIndexFilter, ColumnFilter columnFilter, long now);
      }
  
      /**
       * An abstract, map-backed DataSet implementation. Can be backed by any {@link NavigableMap}, then either maintained
       * persistently, or built on demand and thrown away after use, depending on the implementing class.
       */
      public static abstract class AbstractDataSet implements DataSet
      {
          protected final NavigableMap<DecoratedKey, Partition> partitions;
  
          protected AbstractDataSet(NavigableMap<DecoratedKey, Partition> partitions)
          {
              this.partitions = partitions;
          }
  
          public boolean isEmpty()
          {
              return partitions.isEmpty();
          }
  
          public Partition getPartition(DecoratedKey key)
          {
              return partitions.get(key);
          }
  
          public Iterator<Partition> getPartitions(DataRange dataRange)
          {
              AbstractBounds<PartitionPosition> keyRange = dataRange.keyRange();
              PartitionPosition startKey = keyRange.left;
              PartitionPosition endKey = keyRange.right;
  
              NavigableMap<DecoratedKey, Partition> selection = partitions;
  
              if (startKey.isMinimum() && endKey.isMinimum())
                  return selection.values().iterator();
  
              if (startKey.isMinimum() && endKey instanceof DecoratedKey)
                  return selection.headMap((DecoratedKey) endKey, keyRange.isEndInclusive()).values().iterator();
  
              if (startKey instanceof DecoratedKey && endKey instanceof DecoratedKey)
              {
                  return selection.subMap((DecoratedKey) startKey, keyRange.isStartInclusive(), (DecoratedKey) endKey, keyRange.isEndInclusive())
                                  .values()
                                  .iterator();
              }
  
              if (startKey instanceof DecoratedKey)
                  selection = selection.tailMap((DecoratedKey) startKey, keyRange.isStartInclusive());
  
              if (endKey instanceof DecoratedKey)
                  selection = selection.headMap((DecoratedKey) endKey, keyRange.isEndInclusive());
  
              // If we have reach this point it means that one of the PartitionPosition is a KeyBound and we have
              // to use filtering for eliminating the unwanted partitions.
              Iterator<Partition> iterator = selection.values().iterator();
  
              return new AbstractIterator<Partition>()
              {
                  private boolean encounteredPartitionsWithinRange;
  
                  @Override
                  protected Partition computeNext()
                  {
                      while (iterator.hasNext())
                      {
                          Partition partition = iterator.next();
                          if (dataRange.contains(partition.key()))
                          {
                              encounteredPartitionsWithinRange = true;
                              return partition;
                          }
  
                          // we encountered some partitions within the range, but the last one is outside of the range: we are done
                          if (encounteredPartitionsWithinRange)
                              return endOfData();
                      }
  
                      return endOfData();
                  }
              };
          }
      }
  
      public static class SimpleTable extends AbstractVirtualTable
      {
          private final Supplier<? extends AbstractVirtualTable.DataSet> supplier;
          public SimpleTable(TableMetadata metadata, Supplier<AbstractVirtualTable.DataSet> supplier)
          {
              super(metadata);
              this.supplier = supplier;
          }
  
          public AbstractVirtualTable.DataSet data()
          {
              return supplier.get();
          }
      }
  }
  