/*
 * 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.DataInputStream;
import java.io.DataOutputStream;
import java.io.EOFException;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.UTFDataFormatException;
import org.apache.beam.sdk.values.TypeDescriptor;

/**
 * A {@link DoubleCoder} encodes {@link Double} values in 8 bytes using Java serialization.
 */
public class DoubleCoder extends AtomicCoder<Double> {

  public static DoubleCoder of() {
    return INSTANCE;
  }

  /////////////////////////////////////////////////////////////////////////////

  private static final DoubleCoder INSTANCE = new DoubleCoder();
  private static final TypeDescriptor<Double> TYPE_DESCRIPTOR = new TypeDescriptor<Double>() {};

  private DoubleCoder() {}

  @Override
  public void encode(Double value, OutputStream outStream)
      throws IOException, CoderException {
    if (value == null) {
      throw new CoderException("cannot encode a null Double");
    }
    new DataOutputStream(outStream).writeDouble(value);
  }

  @Override
  public Double decode(InputStream inStream)
      throws IOException, CoderException {
    try {
      return new DataInputStream(inStream).readDouble();
    } catch (EOFException | UTFDataFormatException exn) {
      // These exceptions correspond to decoding problems, so change
      // what kind of exception they're branded as.
      throw new CoderException(exn);
    }
  }

  /**
   * {@inheritDoc}
   *
   * @throws NonDeterministicException always.
   *         Floating-point operations are not guaranteed to be deterministic, even
   *         if the storage format might be, so floating point representations are not
   *         recommended for use in operations that require deterministic inputs.
   */
  @Override
  public void verifyDeterministic() throws NonDeterministicException {
    throw new NonDeterministicException(this,
        "Floating point encodings are not guaranteed to be deterministic.");
  }

  /**
   * {@inheritDoc}
   *
   * @return {@code true}. This coder is injective.
   */
  @Override
  public boolean consistentWithEquals() {
    return true;
  }

  /**
   * {@inheritDoc}
   *
   * @return {@code true}. {@link DoubleCoder#getEncodedElementByteSize} returns a constant.
   */
  @Override
  public boolean isRegisterByteSizeObserverCheap(Double value) {
    return true;
  }

  @Override
  public TypeDescriptor<Double> getEncodedTypeDescriptor() {
    return TYPE_DESCRIPTOR;
  }

  /**
   * {@inheritDoc}
   *
   * @return {@code 8}, the byte size of a {@link Double} encoded using Java serialization.
   */
  @Override
  protected long getEncodedElementByteSize(Double value)
      throws Exception {
    if (value == null) {
      throw new CoderException("cannot encode a null Double");
    }
    return 8;
  }
}