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.sdk.coders;
  
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.OutputStream;
  import java.util.Arrays;
  import java.util.List;
  import org.apache.beam.sdk.util.common.ElementByteSizeObserver;
  import org.apache.beam.sdk.values.KV;
  import org.apache.beam.sdk.values.TypeDescriptor;
  import org.apache.beam.sdk.values.TypeParameter;
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  /**
   * A {@code KvCoder} encodes {@link KV}s.
   *
   * @param <K> the type of the keys of the KVs being transcoded
   * @param <V> the type of the values of the KVs being transcoded
   */
  public class KvCoder<K extends @Nullable Object, V extends @Nullable Object>
      extends StructuredCoder<KV<K, V>> {
    public static <K, V> KvCoder<K, V> of(Coder<K> keyCoder, Coder<V> valueCoder) {
      return new KvCoder<>(keyCoder, valueCoder);
    }
  
    public Coder<K> getKeyCoder() {
      return keyCoder;
    }
  
    public Coder<V> getValueCoder() {
      return valueCoder;
    }
  
    /////////////////////////////////////////////////////////////////////////////
  
    private final Coder<K> keyCoder;
    private final Coder<V> valueCoder;
  
    private KvCoder(Coder<K> keyCoder, Coder<V> valueCoder) {
      this.keyCoder = keyCoder;
      this.valueCoder = valueCoder;
    }
  
    @Override
    public void encode(KV<K, V> kv, OutputStream outStream) throws IOException, CoderException {
      encode(kv, outStream, Context.NESTED);
    }
  
    @Override
    public void encode(KV<K, V> kv, OutputStream outStream, Context context)
        throws IOException, CoderException {
      if (kv == null) {
        throw new CoderException("cannot encode a null KV");
      }
      keyCoder.encode(kv.getKey(), outStream);
      valueCoder.encode(kv.getValue(), outStream, context);
    }
  
    @Override
    public KV<K, V> decode(InputStream inStream) throws IOException, CoderException {
      return decode(inStream, Context.NESTED);
    }
  
    @Override
    public KV<K, V> decode(InputStream inStream, Context context) throws IOException, CoderException {
      K key = keyCoder.decode(inStream);
      V value = valueCoder.decode(inStream, context);
      return KV.of(key, value);
    }
  
    @Override
    public List<? extends Coder<?>> getCoderArguments() {
      return Arrays.asList(keyCoder, valueCoder);
    }
  
    @Override
    public void verifyDeterministic() throws NonDeterministicException {
      verifyDeterministic(this, "Key coder must be deterministic", getKeyCoder());
      verifyDeterministic(this, "Value coder must be deterministic", getValueCoder());
    }
  
    @Override
    public boolean consistentWithEquals() {
      return keyCoder.consistentWithEquals() && valueCoder.consistentWithEquals();
    }
  
    @Override
    public Object structuralValue(KV<K, V> kv) {
      if (consistentWithEquals()) {
        return kv;
      } else {
        return KV.of(
            getKeyCoder().structuralValue(kv.getKey()),
            getValueCoder().structuralValue(kv.getValue()));
      }
    }
  
    /** Returns whether both keyCoder and valueCoder are considered not expensive. */
    @Override
    public boolean isRegisterByteSizeObserverCheap(KV<K, V> kv) {
      return keyCoder.isRegisterByteSizeObserverCheap(kv.getKey())
          && valueCoder.isRegisterByteSizeObserverCheap(kv.getValue());
    }
  
    /** Notifies ElementByteSizeObserver about the byte size of the encoded value using this coder. */
    @Override
    public void registerByteSizeObserver(KV<K, V> kv, ElementByteSizeObserver observer)
        throws Exception {
      if (kv == null) {
        throw new CoderException("cannot encode a null KV");
      }
      keyCoder.registerByteSizeObserver(kv.getKey(), observer);
      valueCoder.registerByteSizeObserver(kv.getValue(), observer);
    }
  
    @Override
    public TypeDescriptor<KV<K, V>> getEncodedTypeDescriptor() {
      return new TypeDescriptor<KV<K, V>>() {}.where(
              new TypeParameter<K>() {}, keyCoder.getEncodedTypeDescriptor())
          .where(new TypeParameter<V>() {}, valueCoder.getEncodedTypeDescriptor());
    }
  }
  