/*
 * 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.apex.translation.utils;

import static com.google.common.base.Preconditions.checkNotNull;

import com.datatorrent.api.Operator;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Arrays;
import java.util.List;
import java.util.Objects;
import org.apache.beam.runners.apex.ApexPipelineOptions;
import org.apache.beam.sdk.coders.Coder;
import org.apache.beam.sdk.coders.CoderException;
import org.apache.beam.sdk.coders.StructuredCoder;

/**
 * The common interface for all objects transmitted through streams.
 *
 * @param <T> The actual payload type.
 */
public interface ApexStreamTuple<T> {
  /**
   * Gets the value of the tuple.
   *
   * @return tuple
   */
  T getValue();

  /**
   * Data tuple class.
   *
   * @param <T> tuple type
   */
  class DataTuple<T> implements ApexStreamTuple<T> {
    private int unionTag;
    private T value;

    public static <T> DataTuple<T> of(T value) {
      return new DataTuple<>(value, 0);
    }

    private DataTuple(T value, int unionTag) {
      this.value = value;
      this.unionTag = unionTag;
    }

    @Override
    public T getValue() {
      return value;
    }

    public void setValue(T value) {
      this.value = value;
    }

    public int getUnionTag() {
      return unionTag;
    }

    public void setUnionTag(int unionTag) {
      this.unionTag = unionTag;
    }

    @Override
    public String toString() {
      return value.toString();
    }

  }

  /**
   * Tuple that includes a timestamp.
   *
   * @param <T> tuple type
   */
  class TimestampedTuple<T> extends DataTuple<T> {
    private long timestamp;

    public TimestampedTuple(long timestamp, T value) {
      super(value, 0);
      this.timestamp = timestamp;
    }

    public long getTimestamp() {
      return timestamp;
    }

    public void setTimestamp(long timestamp) {
      this.timestamp = timestamp;
    }

    @Override
    public int hashCode() {
      return Objects.hash(timestamp);
    }

    @Override
    public boolean equals(Object obj) {
      if (!(obj instanceof TimestampedTuple)) {
        return false;
      } else {
        TimestampedTuple<?> other = (TimestampedTuple<?>) obj;
        return (timestamp == other.timestamp) && Objects.equals(this.getValue(), other.getValue());
      }
    }

  }

  /**
   * Tuple that represents a watermark.
   *
   * @param <T> tuple type
   */
  class WatermarkTuple<T> extends TimestampedTuple<T> {
    public static <T> WatermarkTuple<T> of(long timestamp) {
      return new WatermarkTuple<>(timestamp);
    }

    protected WatermarkTuple(long timestamp) {
      super(timestamp, null);
    }

    @Override
    public String toString() {
      return "[Watermark " + getTimestamp() + "]";
    }
  }

  /**
   * Coder for {@link ApexStreamTuple}.
   */
  class ApexStreamTupleCoder<T> extends StructuredCoder<ApexStreamTuple<T>> {
    private static final long serialVersionUID = 1L;
    final Coder<T> valueCoder;

    public static <T> ApexStreamTupleCoder<T> of(Coder<T> valueCoder) {
      return new ApexStreamTupleCoder<>(valueCoder);
    }

    protected ApexStreamTupleCoder(Coder<T> valueCoder) {
      this.valueCoder = checkNotNull(valueCoder);
    }

    @Override
    public void encode(ApexStreamTuple<T> value, OutputStream outStream)
        throws CoderException, IOException {
      encode(value, outStream, Context.NESTED);
    }

    @Override
    public void encode(ApexStreamTuple<T> value, OutputStream outStream, Context context)
        throws CoderException, IOException {
      if (value instanceof WatermarkTuple) {
        outStream.write(1);
        new DataOutputStream(outStream).writeLong(((WatermarkTuple<?>) value).getTimestamp());
      } else {
        outStream.write(0);
        outStream.write(((DataTuple<?>) value).unionTag);
        valueCoder.encode(value.getValue(), outStream, context);
      }
    }

    @Override
    public ApexStreamTuple<T> decode(InputStream inStream) throws CoderException, IOException {
      return decode(inStream, Context.NESTED);
    }

    @Override
    public ApexStreamTuple<T> decode(InputStream inStream, Context context)
        throws CoderException, IOException {
      int b = inStream.read();
      if (b == 1) {
        return new WatermarkTuple<>(new DataInputStream(inStream).readLong());
      } else {
        int unionTag = inStream.read();
        return new DataTuple<>(valueCoder.decode(inStream, context), unionTag);
      }
    }

    @Override
    public List<? extends Coder<?>> getCoderArguments() {
      return Arrays.<Coder<?>>asList(valueCoder);
    }

    @Override
    public void verifyDeterministic() throws NonDeterministicException {
      verifyDeterministic(
          this,
          this.getClass().getSimpleName() + " requires a deterministic valueCoder",
          valueCoder);
    }

    /**
     * Returns the value coder.
     */
    public Coder<T> getValueCoder() {
      return valueCoder;
    }

  }

  /**
   * Central if data tuples received on and emitted from ports should be logged.
   * Should be called in setup and value cached in operator.
   */
  final class Logging {
    public static boolean isDebugEnabled(ApexPipelineOptions options, Operator operator) {
      return options.isTupleTracingEnabled();
    }
  }

}