Fix bug #48528 - support negative arguments to the DATE() function

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1331796 13f79535-47bb-0310-9956-ffa450edef68

src/documentation/content/xdocs/status.xml

@@ -34,6 +34,7 @@
 
     <changes>
         <release version="3.9-beta1" date="2012-??-??">
+          <action dev="poi-developers" type="fix">48528 - support negative arguments to the DATE() function</action>
           <action dev="poi-developers" type="fix">53092 - allow specifying of a TimeZone to DateUtil.getJavaDate(), for when it is known that a file comes from a different (known) timezone to the current machine</action>
           <action dev="poi-developers" type="fix">53043 - don't duplicate hyperlink relationships when saving XSSF file</action>
           <action dev="poi-developers" type="fix">53101 - fixed evaluation of SUM over cell range &gt; 255</action>

src/java/org/apache/poi/ss/formula/functions/DateFunc.java

@@ -54,16 +54,29 @@ public final class DateFunc extends Fixed3ArgFunction {
 		return new NumberEval(result);
 	}
 
+	/**
+	 * Note - works with Java Calendar months, not Excel months
+	 */
 	private static double evaluate(int year, int month, int pDay) throws EvaluationException {
-
+	   // We don't support negative years yet
-		if (year < 0 || month < 0 || pDay < 0) {
+		if (year < 0) {
 			throw new EvaluationException(ErrorEval.VALUE_INVALID);
 		}
+		// Negative months are fairly easy
+		while (month < 0) {
+		   year--;
+		   month += 12;
+		}
+		// Negative days are handled by the Java Calendar
 		
+		// Excel has bugs around leap years in 1900, handle them
+		// Special case for the non-existant 1900 leap year
 		if (year == 1900 && month == Calendar.FEBRUARY && pDay == 29) {
 			return 60.0;
 		}
 
+		// If they give a date in 1900 in Jan/Feb, with the days
+		//  putting it past the leap year, adjust
 		int day = pDay;
 		if (year == 1900) {
 			if ((month == Calendar.JANUARY && day >= 60) ||
@@ -72,12 +85,24 @@ public final class DateFunc extends Fixed3ArgFunction {
 			}
 		}
 
+		// Turn this into a Java date
 		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
+		// Handle negative days of the week, that pull us across
+		//  the 29th of Feb 1900
+		if (pDay < 0 && c.get(Calendar.YEAR) == 1900 &&
+		      month > Calendar.FEBRUARY && 
+		      c.get(Calendar.MONTH) < Calendar.MARCH) {
+		   c.add(Calendar.DATE, 1);
+		}
+
+		// TODO Identify if we're doing 1900 or 1904 date windowing
+		boolean use1904windowing = false;
+		
+		// Have this Java date turned back into an Excel one
+		return DateUtil.getExcelDate(c.getTime(), use1904windowing);
 	}
 
 	private static int getYear(double d) {

src/testcases/org/apache/poi/hssf/usermodel/TestFormulaEvaluatorBugs.java

@@ -293,6 +293,48 @@ public final class TestFormulaEvaluatorBugs extends TestCase {
 		}
 	}
 	
+	public void testDateWithNegativeParts_bug48528() {
+      HSSFWorkbook wb = new HSSFWorkbook();
+      HSSFSheet sheet = wb.createSheet("Sheet1");
+      HSSFRow row = sheet.createRow(1);
+      HSSFCell cell = row.createCell(0);
+      HSSFFormulaEvaluator fe = new HSSFFormulaEvaluator(wb);
+      
+      // 5th Feb 2012 = 40944
+      // 1st Feb 2012 = 40940
+      // 5th Jan 2012 = 40913
+      // 5th Dec 2011 = 40882
+      // 5th Feb 2011 = 40579
+      
+      cell.setCellFormula("DATE(2012,2,1)");
+      fe.notifyUpdateCell(cell);
+      assertEquals(40940.0, fe.evaluate(cell).getNumberValue());
+      
+      cell.setCellFormula("DATE(2012,2,1+4)");
+      fe.notifyUpdateCell(cell);
+      assertEquals(40944.0, fe.evaluate(cell).getNumberValue());
+      
+      cell.setCellFormula("DATE(2012,2-1,1+4)");
+      fe.notifyUpdateCell(cell);
+      assertEquals(40913.0, fe.evaluate(cell).getNumberValue());
+      
+      cell.setCellFormula("DATE(2012,2,1-27)");
+      fe.notifyUpdateCell(cell);
+      assertEquals(40913.0, fe.evaluate(cell).getNumberValue());
+      
+      cell.setCellFormula("DATE(2012,2-2,1+4)");
+      fe.notifyUpdateCell(cell);
+      assertEquals(40882.0, fe.evaluate(cell).getNumberValue());
+      
+      cell.setCellFormula("DATE(2012,2,1-58)");
+      fe.notifyUpdateCell(cell);
+      assertEquals(40882.0, fe.evaluate(cell).getNumberValue());
+      
+      cell.setCellFormula("DATE(2012,2-12,1+4)");
+      fe.notifyUpdateCell(cell);
+      assertEquals(40579.0, fe.evaluate(cell).getNumberValue());
+	}
+
 	private static final class EvalListener extends EvaluationListener {
 		private int _countCacheHits;
 		private int _countCacheMisses;