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.tcm;
  
  import java.io.IOException;
  import java.nio.ByteBuffer;
  import java.util.Collections;
  import java.util.List;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import org.apache.cassandra.db.SystemKeyspace;
  import org.apache.cassandra.io.util.DataInputBuffer;
  import org.apache.cassandra.io.util.DataOutputBuffer;
  import org.apache.cassandra.tcm.serialization.VerboseMetadataSerializer;
  import org.apache.cassandra.tcm.serialization.Version;
  
  public interface MetadataSnapshots
  {
      Logger logger = LoggerFactory.getLogger(MetadataSnapshots.class);
  
      ClusterMetadata getSnapshot(Epoch epoch);
      ClusterMetadata getSnapshotBefore(Epoch epoch);
      ClusterMetadata getLatestSnapshot();
      List<Epoch> listSnapshotsSince(Epoch epoch);
      void storeSnapshot(ClusterMetadata metadata);
  
      static ByteBuffer toBytes(ClusterMetadata metadata) throws IOException
      {
          Version serializationVersion = Version.minCommonSerializationVersion();
          long serializedSize = VerboseMetadataSerializer.serializedSize(ClusterMetadata.serializer, metadata, serializationVersion);
          ByteBuffer bytes = ByteBuffer.allocate((int) serializedSize);
          try (DataOutputBuffer dob = new DataOutputBuffer(bytes))
          {
              VerboseMetadataSerializer.serialize(ClusterMetadata.serializer, metadata, dob, serializationVersion);
          }
          bytes.flip().rewind();
          return bytes;
      }
  
      @SuppressWarnings("resource")
      static ClusterMetadata fromBytes(ByteBuffer serialized) throws IOException
      {
          if (serialized == null)
              return null;
  
          return VerboseMetadataSerializer.deserialize(ClusterMetadata.serializer,
                                                       new DataInputBuffer(serialized, false));
      }
  
      MetadataSnapshots NO_OP = new NoOp();
  
      class NoOp implements MetadataSnapshots
      {
          @Override
          public ClusterMetadata getSnapshot(Epoch epoch)
          {
              return null;
          }
  
          @Override
          public ClusterMetadata getSnapshotBefore(Epoch epoch) {return null;}
  
          @Override
          public ClusterMetadata getLatestSnapshot() {return null;}
  
          @Override
          public List<Epoch> listSnapshotsSince(Epoch epoch)
          {
              return Collections.emptyList();
          }
  
          @Override
          public void storeSnapshot(ClusterMetadata metadata) {}
      }
  
      class SystemKeyspaceMetadataSnapshots implements MetadataSnapshots
      {
          @Override
          public ClusterMetadata getSnapshot(Epoch epoch)
          {
              try
              {
                  return fromBytes(SystemKeyspace.getSnapshot(epoch));
              }
              catch (IOException e)
              {
                  logger.error("Could not load snapshot", e);
                  return null;
              }
          }
  
          @Override
          public ClusterMetadata getSnapshotBefore(Epoch epoch)
          {
              try
              {
                  return fromBytes(SystemKeyspace.findSnapshotBefore(epoch));
              }
              catch (IOException e)
              {
                  logger.error("Could not load snapshot before " + epoch, e);
                  return null;
              }
          }
  
          @Override
          public ClusterMetadata getLatestSnapshot()
          {
              try
              {
                  ByteBuffer snapshot = SystemKeyspace.findLastSnapshot();
                  if (snapshot != null)
                      return fromBytes(snapshot);
              }
              catch (IOException e)
              {
                  logger.error("Could not find latest snapshot");
              }
              return null;
          }
  
          @Override
          public List<Epoch> listSnapshotsSince(Epoch epoch)
          {
              return SystemKeyspace.listSnapshotsSince(epoch);
          }
  
          @Override
          public void storeSnapshot(ClusterMetadata metadata)
          {
              try
              {
                  SystemKeyspace.storeSnapshot(metadata.epoch, toBytes(metadata));
              }
              catch (IOException e)
              {
                  throw new RuntimeException(e);
              }
          }
      }
  }
  