DateFunc.java

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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

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   distributed under the License is distributed on an "AS IS" BASIS,
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   See the License for the specific language governing permissions and
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package org.apache.poi.ss.formula.functions;

import java.util.Calendar;
import java.util.GregorianCalendar;

import org.apache.poi.ss.formula.eval.ErrorEval;
import org.apache.poi.ss.formula.eval.EvaluationException;
import org.apache.poi.ss.formula.eval.NumberEval;
import org.apache.poi.ss.formula.eval.ValueEval;
import org.apache.poi.ss.usermodel.DateUtil;


/**
 * Implementation for the Excel function DATE
 *
 * @author Pavel Krupets (pkrupets at palmtreebusiness dot com)
 */
public final class DateFunc extends Fixed3ArgFunction {

	public static final Function instance = new DateFunc();

	private DateFunc() {
		// no fields to initialise
	}
	public ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg0, ValueEval arg1,
			ValueEval arg2) {
		double result;
		try {
			double d0 = NumericFunction.singleOperandEvaluate(arg0, srcRowIndex, srcColumnIndex);
			double d1 = NumericFunction.singleOperandEvaluate(arg1, srcRowIndex, srcColumnIndex);
			double d2 = NumericFunction.singleOperandEvaluate(arg2, srcRowIndex, srcColumnIndex);
			result = evaluate(getYear(d0), (int) (d1 - 1), (int) d2);
			NumericFunction.checkValue(result);
		} catch (EvaluationException e) {
			return e.getErrorEval();
		}
		return new NumberEval(result);
	}

	private static double evaluate(int year, int month, int pDay) throws EvaluationException {

		if (year < 0 || month < 0 || pDay < 0) {
			throw new EvaluationException(ErrorEval.VALUE_INVALID);
		}

		if (year == 1900 && month == Calendar.FEBRUARY && pDay == 29) {
			return 60.0;
		}

		int day = pDay;
		if (year == 1900) {
			if ((month == Calendar.JANUARY && day >= 60) ||
					(month == Calendar.FEBRUARY && day >= 30)) {
				day--;
			}
		}

		Calendar c = new GregorianCalendar();

		c.set(year, month, day, 0, 0, 0);
		c.set(Calendar.MILLISECOND, 0);

		return DateUtil.getExcelDate(c.getTime(), false); // TODO - fix 1900/1904 problem
	}

	private static int getYear(double d) {
		int year = (int)d;

		if (year < 0) {
			return -1;
		}

		return year < 1900 ? 1900 + year : year;
	}
}