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/**
 * 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.hadoop.hive.ql.udf.generic;

import java.util.ArrayList;
import java.util.List;

import org.apache.hadoop.hive.ql.metadata.HiveException;
import org.apache.hadoop.hive.ql.parse.WindowingSpec.BoundarySpec;
import org.apache.hadoop.hive.ql.udf.generic.GenericUDAFEvaluator.AggregationBuffer;
import org.apache.hadoop.hive.ql.util.JavaDataModel;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspector;

@SuppressWarnings({ "deprecation", "unchecked" })
public abstract class GenericUDAFStreamingEvaluator extends
    GenericUDAFEvaluator implements ISupportStreamingModeForWindowing {

  protected final GenericUDAFEvaluator wrappedEval;
  protected final int numPreceding;
  protected final int numFollowing;

  public GenericUDAFStreamingEvaluator(GenericUDAFEvaluator wrappedEval,
      int numPreceding, int numFollowing) {
    this.wrappedEval = wrappedEval;
    this.numPreceding = numPreceding;
    this.numFollowing = numFollowing;
    this.mode = wrappedEval.mode;
  }

  class StreamingState extends AbstractAggregationBuffer {
    final AggregationBuffer wrappedBuf;
    final int numPreceding;
    final int numFollowing;
    final List results;
    int numRows;

    StreamingState(int numPreceding, int numFollowing, AggregationBuffer buf) {
      this.wrappedBuf = buf;
      this.numPreceding = numPreceding;
      this.numFollowing = numFollowing;
      results = new ArrayList();
      numRows = 0;
    }

    protected void reset() {
      results.clear();
      numRows = 0;
    }
  }

  @Override
  public ObjectInspector init(Mode m, ObjectInspector[] parameters)
      throws HiveException {
    return wrappedEval.init(m, parameters);
  }

  @Override
  public void reset(AggregationBuffer agg) throws HiveException {
    StreamingState ss = (StreamingState) agg;
    wrappedEval.reset(ss.wrappedBuf);
    ss.reset();
  }

  @Override
  public Object terminatePartial(AggregationBuffer agg) throws HiveException {
    throw new HiveException(getClass().getSimpleName()
        + ": terminatePartial not supported");
  }

  @Override
  public void merge(AggregationBuffer agg, Object partial) throws HiveException {
    throw new HiveException(getClass().getSimpleName()
        + ": merge not supported");
  }

  @Override
  public Object getNextResult(AggregationBuffer agg) throws HiveException {
    StreamingState ss = (StreamingState) agg;
    if (!ss.results.isEmpty()) {
      T1 res = ss.results.remove(0);
      if (res == null) {
        return ISupportStreamingModeForWindowing.NULL_RESULT;
      }
      return res;
    }
    return null;
  }

  public static abstract class SumAvgEnhancer extends
      GenericUDAFStreamingEvaluator {

    public SumAvgEnhancer(GenericUDAFEvaluator wrappedEval, int numPreceding,
        int numFollowing) {
      super(wrappedEval, numPreceding, numFollowing);
    }

    class SumAvgStreamingState extends StreamingState {

      final List intermediateVals;

      SumAvgStreamingState(int numPreceding, int numFollowing,
          AggregationBuffer buf) {
        super(numPreceding, numFollowing, buf);
        intermediateVals = new ArrayList();
      }

      @Override
      public int estimate() {
        if (!(wrappedBuf instanceof AbstractAggregationBuffer)) {
          return -1;
        }
        int underlying = ((AbstractAggregationBuffer) wrappedBuf).estimate();
        if (underlying == -1) {
          return -1;
        }
        if (numPreceding == BoundarySpec.UNBOUNDED_AMOUNT) {
          return -1;
        }
        /*
         * sz Estimate = sz needed by underlying AggBuffer + sz for results + sz
         * for intermediates + 3 * JavaDataModel.PRIMITIVES1 sz of results = sz
         * of underlying * wdwSz sz of intermediates = sz of underlying * wdwSz
         */

        int wdwSz = numPreceding + numFollowing + 1;
        return underlying + (underlying * wdwSz) + (underlying * wdwSz)
            + (3 * JavaDataModel.PRIMITIVES1);
      }

      protected void reset() {
        intermediateVals.clear();
        super.reset();
      }
    }

    @Override
    public AggregationBuffer getNewAggregationBuffer() throws HiveException {
      AggregationBuffer underlying = wrappedEval.getNewAggregationBuffer();
      return new SumAvgStreamingState(numPreceding, numFollowing, underlying);
    }

    @Override
    public void iterate(AggregationBuffer agg, Object[] parameters)
        throws HiveException {
      SumAvgStreamingState ss = (SumAvgStreamingState) agg;

      wrappedEval.iterate(ss.wrappedBuf, parameters);

      if (ss.numRows >= ss.numFollowing) {
        ss.results.add(getNextResult(ss));
      }
      if (ss.numPreceding != BoundarySpec.UNBOUNDED_AMOUNT) {
        ss.intermediateVals.add(getCurrentIntermediateResult(ss));
      }

      ss.numRows++;
    }

    @Override
    public Object terminate(AggregationBuffer agg) throws HiveException {
      SumAvgStreamingState ss = (SumAvgStreamingState) agg;
      Object o = wrappedEval.terminate(ss.wrappedBuf);

      for (int i = 0; i < ss.numFollowing; i++) {
        ss.results.add(getNextResult(ss));
        ss.numRows++;
      }
      return o;
    }

    @Override
    public int getRowsRemainingAfterTerminate() throws HiveException {
      throw new UnsupportedOperationException();
    }

    protected abstract T1 getNextResult(SumAvgStreamingState ss)
        throws HiveException;

    protected abstract T2 getCurrentIntermediateResult(SumAvgStreamingState ss)
        throws HiveException;

  }
}