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   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

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   distributed under the License is distributed on an "AS IS" BASIS,
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package org.apache.poi.hssf.record.formula.functions;

import org.apache.poi.hssf.record.formula.eval.EvaluationException;
import org.apache.poi.hssf.record.formula.eval.OperandResolver;
import org.apache.poi.hssf.record.formula.eval.ValueEval;
import org.apache.poi.hssf.record.formula.functions.LookupUtils.ValueVector;
import org.apache.poi.ss.formula.TwoDEval;

/**
 * Implementation of Excel function LOOKUP.<p/>
 *
 * LOOKUP finds an index  row in a lookup table by the first column value and returns the value from another column.
 *
 * <b>Syntax</b>:<br/>
 * <b>VLOOKUP</b>(<b>lookup_value</b>, <b>lookup_vector</b>, result_vector)<p/>
 *
 * <b>lookup_value</b>  The value to be found in the lookup vector.<br/>
 * <b>lookup_vector</> An area reference for the lookup data. <br/>
 * <b>result_vector</b> Single row or single column area reference from which the result value is chosen.<br/>
 *
 * @author Josh Micich
 */
public final class Lookup extends Var2or3ArgFunction {

	public ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg0, ValueEval arg1) {
		// complex rules to choose lookupVector and resultVector from the single area ref
		throw new RuntimeException("Two arg version of LOOKUP not supported yet");
	}

	public ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg0, ValueEval arg1,
			ValueEval arg2) {
		try {
			ValueEval lookupValue = OperandResolver.getSingleValue(arg0, srcRowIndex, srcColumnIndex);
			TwoDEval aeLookupVector = LookupUtils.resolveTableArrayArg(arg1);
			TwoDEval aeResultVector = LookupUtils.resolveTableArrayArg(arg2);

			ValueVector lookupVector = createVector(aeLookupVector);
			ValueVector resultVector = createVector(aeResultVector);
			if(lookupVector.getSize() > resultVector.getSize()) {
				// Excel seems to handle this by accessing past the end of the result vector.
				throw new RuntimeException("Lookup vector and result vector of differing sizes not supported yet");
			}
			int index = LookupUtils.lookupIndexOfValue(lookupValue, lookupVector, true);

			return resultVector.getItem(index);
		} catch (EvaluationException e) {
			return e.getErrorEval();
		}
	}

	private static ValueVector createVector(TwoDEval ae) {
		ValueVector result = LookupUtils.createVector(ae);
		if (result != null) {
			return result;
		}
		// extra complexity required to emulate the way LOOKUP can handles these abnormal cases.
		throw new RuntimeException("non-vector lookup or result areas not supported yet");
	}
}
