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.service.paxos.uncommitted;
  
  import java.util.Comparator;
  import java.util.Iterator;
  import java.util.Objects;
  
  import com.google.common.base.Preconditions;
  import com.google.common.collect.Iterators;
  import com.google.common.collect.Lists;
  import com.google.common.primitives.Longs;
  
  import org.apache.cassandra.db.ConsistencyLevel;
  import org.apache.cassandra.db.DecoratedKey;
  import org.apache.cassandra.schema.TableId;
  import org.apache.cassandra.service.paxos.Ballot;
  import org.apache.cassandra.utils.CloseableIterator;
  import org.apache.cassandra.utils.MergeIterator;
  
  public class PaxosKeyState implements UncommittedPaxosKey
  {
      static final Comparator<PaxosKeyState> KEY_COMPARATOR = Comparator.comparing(o -> o.key);
      static final Comparator<PaxosKeyState> BALLOT_COMPARATOR = (o1, o2) -> Longs.compare(o1.ballot.uuidTimestamp(), o2.ballot.uuidTimestamp());
  
      final TableId tableId;
      final DecoratedKey key;
      final Ballot ballot;
      final boolean committed;
  
      public PaxosKeyState(TableId tableId, DecoratedKey key, Ballot ballot, boolean committed)
      {
          Preconditions.checkNotNull(tableId);
          Preconditions.checkNotNull(ballot);
          this.tableId = tableId;
          this.key = key;
          this.ballot = ballot;
          this.committed = committed;
      }
  
      public DecoratedKey getKey()
      {
          return key;
      }
  
      public ConsistencyLevel getConsistencyLevel()
      {
          switch (ballot.flag())
          {
              default: throw new IllegalStateException();
              case GLOBAL: return ConsistencyLevel.SERIAL;
              case LOCAL: return ConsistencyLevel.LOCAL_SERIAL;
              case NONE: return null;
          }
      }
  
      @Override
      public Ballot ballot()
      {
          return ballot;
      }
  
      public boolean equals(Object o)
      {
          if (this == o) return true;
          if (o == null || getClass() != o.getClass()) return false;
          PaxosKeyState that = (PaxosKeyState) o;
          return committed == that.committed &&
                 Objects.equals(key, that.key) &&
                 Objects.equals(ballot, that.ballot);
      }
  
      public int hashCode()
      {
          return Objects.hash(key, ballot, committed);
      }
  
      public String toString()
      {
          return "BallotState{" +
                 "tableId=" + tableId +
                 ", key=" + key +
                 ", ballot=" + ballot +
                 ", committed=" + committed +
                 '}';
      }
  
      static PaxosKeyState merge(PaxosKeyState left, PaxosKeyState right)
      {
          if (left == null)
              return right;
  
          if (right == null)
              return left;
  
          int cmp = BALLOT_COMPARATOR.compare(left, right);
  
          // prefer committed operations if the ballots are the same so they can be filtered out later
          if (cmp == 0)
              return left.committed ? left : right;
          else
              return cmp > 0 ? left : right;
      }
  
      static class Reducer extends MergeIterator.Reducer<PaxosKeyState, PaxosKeyState>
      {
          private PaxosKeyState mostRecent = null;
  
          public void reduce(int idx, PaxosKeyState current)
          {
              mostRecent = merge(mostRecent, current);
          }
  
          protected PaxosKeyState getReduced()
          {
              return mostRecent;
          }
  
          protected void onKeyChange()
          {
              super.onKeyChange();
              mostRecent = null;
          }
      }
  
      public static CloseableIterator<PaxosKeyState> mergeUncommitted(CloseableIterator<PaxosKeyState>... iterators)
      {
          return MergeIterator.get(Lists.newArrayList(iterators), PaxosKeyState.KEY_COMPARATOR, new Reducer());
      }
  
      public static CloseableIterator<UncommittedPaxosKey> toUncommittedInfo(CloseableIterator<PaxosKeyState> iter)
      {
          Iterator<PaxosKeyState> filtered = Iterators.filter(iter, k -> !k.committed);
          return new CloseableIterator<UncommittedPaxosKey>()
          {
              public void close()
              {
                  iter.close();
              }
  
              public boolean hasNext()
              {
                  return filtered.hasNext();
              }
  
              public UncommittedPaxosKey next()
              {
                  return filtered.next();
              }
          };
      }
  }
  