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/*
 * Licensed to Metamarkets Group Inc. (Metamarkets) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. Metamarkets 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 io.druid.query.aggregation.histogram;

import io.druid.query.aggregation.BufferAggregator;
import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
import io.druid.segment.BaseFloatColumnValueSelector;

import java.nio.ByteBuffer;

public class ApproximateHistogramBufferAggregator implements BufferAggregator
{
  private final BaseFloatColumnValueSelector selector;
  private final int resolution;

  public ApproximateHistogramBufferAggregator(BaseFloatColumnValueSelector selector, int resolution)
  {
    this.selector = selector;
    this.resolution = resolution;
  }

  @Override
  public void init(ByteBuffer buf, int position)
  {
    ByteBuffer mutationBuffer = buf.duplicate();
    mutationBuffer.position(position);

    mutationBuffer.putInt(resolution);
    mutationBuffer.putInt(0); //initial binCount
    for (int i = 0; i < resolution; ++i) {
      mutationBuffer.putFloat(0f);
    }
    for (int i = 0; i < resolution; ++i) {
      mutationBuffer.putLong(0L);
    }

    // min
    mutationBuffer.putFloat(Float.POSITIVE_INFINITY);
    // max
    mutationBuffer.putFloat(Float.NEGATIVE_INFINITY);
  }

  @Override
  public void aggregate(ByteBuffer buf, int position)
  {
    ByteBuffer mutationBuffer = buf.duplicate();
    mutationBuffer.position(position);

    ApproximateHistogram h0 = ApproximateHistogram.fromBytesDense(mutationBuffer);
    h0.offer(selector.getFloat());

    mutationBuffer.position(position);
    h0.toBytesDense(mutationBuffer);
  }

  @Override
  public Object get(ByteBuffer buf, int position)
  {
    ByteBuffer mutationBuffer = buf.duplicate();
    mutationBuffer.position(position);
    return ApproximateHistogram.fromBytes(mutationBuffer);
  }

  @Override
  public float getFloat(ByteBuffer buf, int position)
  {
    throw new UnsupportedOperationException("ApproximateHistogramBufferAggregator does not support getFloat()");
  }


  @Override
  public long getLong(ByteBuffer buf, int position)
  {
    throw new UnsupportedOperationException("ApproximateHistogramBufferAggregator does not support getLong()");
  }

  @Override
  public double getDouble(ByteBuffer buf, int position)
  {
    throw new UnsupportedOperationException("ApproximateHistogramBufferAggregator does not support getDouble()");
  }

  @Override
  public void close()
  {
    // no resources to cleanup
  }

  @Override
  public void inspectRuntimeShape(RuntimeShapeInspector inspector)
  {
    inspector.visit("selector", selector);
  }
}