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.beam.runners.dataflow.worker.windmill.state;
  
  import java.io.Closeable;
  import java.io.IOException;
  import java.util.concurrent.ExecutionException;
  import java.util.concurrent.Future;
  import org.apache.beam.runners.core.StateNamespace;
  import org.apache.beam.runners.core.StateTag;
  import org.apache.beam.runners.dataflow.worker.windmill.Windmill;
  import org.apache.beam.sdk.coders.Coder;
  import org.apache.beam.sdk.state.ValueState;
  import org.apache.beam.sdk.util.ByteStringOutputStream;
  import org.apache.beam.vendor.grpc.v1p69p0.com.google.protobuf.ByteString;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.util.concurrent.Futures;
  
  @SuppressWarnings({
    "nullness" // TODO(https://github.com/apache/beam/issues/20497)
  })
  public class WindmillValue<T> extends SimpleWindmillState implements ValueState<T> {
    private final StateNamespace namespace;
    private final StateTag<ValueState<T>> address;
    private final ByteString stateKey;
    private final String stateFamily;
    private final Coder<T> coder;
  
    /** Whether we've modified the value since creation of this state. */
    private boolean modified = false;
    /** Whether the in memory value is the true value. */
    private boolean valueIsKnown = false;
    /** The size of the encoded value */
    private long cachedSize = -1;
  
    private T value;
  
    WindmillValue(
        StateNamespace namespace,
        StateTag<ValueState<T>> address,
        String stateFamily,
        Coder<T> coder,
        boolean isNewKey,
        WindmillStateTagUtil windmillStateTagUtil) {
      this.namespace = namespace;
      this.address = address;
      this.stateKey = windmillStateTagUtil.encodeKey(namespace, address);
      this.stateFamily = stateFamily;
      this.coder = coder;
      if (isNewKey) {
        this.valueIsKnown = true;
        this.value = null;
      }
    }
  
    @Override
    public void clear() {
      modified = true;
      valueIsKnown = true;
      value = null;
    }
  
    @Override
    @SuppressWarnings("FutureReturnValueIgnored")
    public WindmillValue<T> readLater() {
      getFuture();
      return this;
    }
  
    @Override
    public T read() {
      try (Closeable scope = scopedReadState()) {
        if (!valueIsKnown) {
          cachedSize = -1;
        }
        value = getFuture().get();
        valueIsKnown = true;
        return value;
      } catch (InterruptedException | ExecutionException | IOException e) {
        if (e instanceof InterruptedException) {
          Thread.currentThread().interrupt();
        }
        throw new RuntimeException("Unable to read value from state", e);
      }
    }
  
    @Override
    public void write(T value) {
      modified = true;
      valueIsKnown = true;
      cachedSize = -1;
      this.value = value;
    }
  
    @Override
    protected Windmill.WorkItemCommitRequest persistDirectly(WindmillStateCache.ForKeyAndFamily cache)
        throws IOException {
      if (!valueIsKnown) {
        // The value was never read, written or cleared.
        // Thus nothing to update in Windmill.
        // And no need to add to global cache.
        return Windmill.WorkItemCommitRequest.newBuilder().buildPartial();
      }
  
      ByteString encoded = null;
      if (cachedSize == -1 || modified) {
        ByteStringOutputStream stream = new ByteStringOutputStream();
        if (value != null) {
          coder.encode(value, stream, Coder.Context.OUTER);
        }
        encoded = stream.toByteString();
        cachedSize = (long) encoded.size() + stateKey.size();
      }
  
      // Place in cache to avoid a future read.
      cache.put(namespace, address, this, cachedSize);
  
      if (!modified) {
        // The value was read, but never written or cleared.
        // But nothing to update in Windmill.
        return Windmill.WorkItemCommitRequest.newBuilder().buildPartial();
      }
  
      // The value was written or cleared. Commit that change to Windmill.
      modified = false;
      Windmill.WorkItemCommitRequest.Builder commitBuilder =
          Windmill.WorkItemCommitRequest.newBuilder();
      commitBuilder
          .addValueUpdatesBuilder()
          .setTag(stateKey)
          .setStateFamily(stateFamily)
          .getValueBuilder()
          .setData(encoded)
          .setTimestamp(Long.MAX_VALUE);
      return commitBuilder.buildPartial();
    }
  
    private Future<T> getFuture() {
      // WindmillStateReader guarantees that we can ask for a future for a particular tag multiple
      // times and it will efficiently be reused.
      return valueIsKnown
          ? Futures.immediateFuture(value)
          : reader.valueFuture(stateKey, stateFamily, coder);
    }
  }
  