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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.
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package org.apache.poi.ss.formula.functions;

import org.apache.poi.ss.formula.OperationEvaluationContext;
import org.apache.poi.ss.formula.eval.*;

/**
 * Implementation for Excel HEX2DEC() function.
 * <p>
 * <b>Syntax</b>:<br> <b>HEX2DEC  </b>(<b>number</b>)<br>
 * <p>
 * Converts a hexadecimal number to decimal.
 * <p>
 * Number     is the hexadecimal number you want to convert. Number cannot contain more than 10 characters (40 bits).
 * The most significant bit of number is the sign bit.
 * The remaining 39 bits are magnitude bits. Negative numbers are represented using two's-complement notation.
 * Remark
 * If number is not a valid hexadecimal number, HEX2DEC returns the #NUM! error value.
 */
public class Hex2Dec extends Fixed1ArgFunction implements FreeRefFunction {

    public static final FreeRefFunction instance = new Hex2Dec();

    static final int HEXADECIMAL_BASE = 16;
    static final int MAX_NUMBER_OF_PLACES = 10;

    @Override
    public ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval numberVE) {
        final String hex;
        if (numberVE instanceof RefEval) {
            RefEval re = (RefEval) numberVE;
            hex = OperandResolver.coerceValueToString(re.getInnerValueEval(re.getFirstSheetIndex()));
        } else {
            hex = OperandResolver.coerceValueToString(numberVE);
        }
        try {
            return new NumberEval(BaseNumberUtils.convertToDecimal(hex, HEXADECIMAL_BASE, MAX_NUMBER_OF_PLACES));
        }  catch (IllegalArgumentException e) {
            return ErrorEval.NUM_ERROR;
        }
    }

    @Override
    public ValueEval evaluate(ValueEval[] args, OperationEvaluationContext ec) {
        if (args.length != 1) {
            return ErrorEval.VALUE_INVALID;
        }
        return evaluate(ec.getRowIndex(), ec.getColumnIndex(), args[0]);
    }
}
