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 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
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 * 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
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 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
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package org.apache.hadoop.hive.ql.udf.generic;

import com.facebook.presto.hive.$internal.org.slf4j.Logger;
import com.facebook.presto.hive.$internal.org.slf4j.LoggerFactory;
import org.apache.hadoop.hive.ql.exec.Description;
import org.apache.hadoop.hive.ql.exec.UDFArgumentTypeException;
import org.apache.hadoop.hive.ql.exec.WindowFunctionDescription;
import org.apache.hadoop.hive.ql.metadata.HiveException;
import org.apache.hadoop.hive.ql.parse.SemanticException;
import org.apache.hadoop.hive.ql.parse.WindowingSpec.BoundarySpec;
import org.apache.hadoop.hive.ql.plan.ptf.BoundaryDef;
import org.apache.hadoop.hive.ql.plan.ptf.WindowFrameDef;
import org.apache.hadoop.hive.ql.udf.generic.GenericUDAFEvaluator.AggregationBuffer;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspector;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspectorUtils;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspectorUtils.ObjectInspectorCopyOption;
import org.apache.hadoop.hive.serde2.objectinspector.primitive.PrimitiveObjectInspectorFactory;
import org.apache.hadoop.hive.serde2.objectinspector.primitive.PrimitiveObjectInspectorUtils;
import org.apache.hadoop.hive.serde2.typeinfo.TypeInfo;
import org.apache.hadoop.hive.serde2.typeinfo.TypeInfoFactory;

@WindowFunctionDescription(description = @Description(name = "last_value", value = "_FUNC_(x)"),
  supportsWindow = true, pivotResult = false, impliesOrder = true)
public class GenericUDAFLastValue extends AbstractGenericUDAFResolver {

  static final Logger LOG = LoggerFactory.getLogger(GenericUDAFLastValue.class.getName());

  @Override
  public GenericUDAFEvaluator getEvaluator(TypeInfo[] parameters) throws SemanticException {
    if (parameters.length > 2) {
      throw new UDFArgumentTypeException(2, "At most 2 arguments expected");
    }
    if (parameters.length > 1 && !parameters[1].equals(TypeInfoFactory.booleanTypeInfo)) {
      throw new UDFArgumentTypeException(1, "second argument must be a boolean expression");
    }
    return createEvaluator();
  }

  protected GenericUDAFLastValueEvaluator createEvaluator() {
    return new GenericUDAFLastValueEvaluator();
  }

  static class LastValueBuffer implements AggregationBuffer {

    Object val;
    boolean firstRow;
    boolean skipNulls;

    LastValueBuffer() {
      init();
    }

    void init() {
      val = null;
      firstRow = true;
      skipNulls = false;
    }

  }

  public static class GenericUDAFLastValueEvaluator extends GenericUDAFEvaluator {

    ObjectInspector inputOI;
    ObjectInspector outputOI;

    @Override
    public ObjectInspector init(Mode m, ObjectInspector[] parameters) throws HiveException {
      super.init(m, parameters);
      if (m != Mode.COMPLETE) {
        throw new HiveException("Only COMPLETE mode supported for Rank function");
      }
      inputOI = parameters[0];
      outputOI = ObjectInspectorUtils.getStandardObjectInspector(inputOI,
        ObjectInspectorCopyOption.WRITABLE);
      return outputOI;
    }

    @Override
    public AggregationBuffer getNewAggregationBuffer() throws HiveException {
      return new LastValueBuffer();
    }

    @Override
    public void reset(AggregationBuffer agg) throws HiveException {
      ((LastValueBuffer) agg).init();
    }

    @Override
    public void iterate(AggregationBuffer agg, Object[] parameters) throws HiveException {
      LastValueBuffer lb = (LastValueBuffer) agg;
      if (lb.firstRow) {
        lb.firstRow = false;
        if (parameters.length == 2) {
          lb.skipNulls = PrimitiveObjectInspectorUtils.getBoolean(parameters[1],
            PrimitiveObjectInspectorFactory.writableBooleanObjectInspector);
        }
      }

      Object o = ObjectInspectorUtils.copyToStandardObject(parameters[0], inputOI,
        ObjectInspectorCopyOption.WRITABLE);

      if (!lb.skipNulls || o != null) {
        lb.val = o;
      }
    }

    @Override
    public Object terminatePartial(AggregationBuffer agg) throws HiveException {
      throw new HiveException("terminatePartial not supported");
    }

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

    @Override
    public Object terminate(AggregationBuffer agg) throws HiveException {
      LastValueBuffer lb = (LastValueBuffer) agg;
      return lb.val;

    }

    @Override
    public GenericUDAFEvaluator getWindowingEvaluator(WindowFrameDef wFrmDef) {
      return new LastValStreamingFixedWindow(this, wFrmDef);
    }
  }

  static class LastValStreamingFixedWindow extends GenericUDAFStreamingEvaluator