Calendar math fixes, clamp dates to supported range

Fixes for floor division of negative numbers.

We no longer throw an error with an out-of-range date is constructed.
Instead, if an epoch timestamp is used that is too small or large, we
clamp the range to our supported min/max.

codegen/src/suite/data.ts

@@ -11,16 +11,24 @@ export const LOCALES = [
 ];
 
 export const DATES: number[] = [
+  // Out of range negative date
+  -500000000000000,
+  // Minimum date -4712-01-01 00:00:00 UTC
+  -210866803200000,
   // Mon, February 6, 1956 4:54:57 PM
   -438678303000,
-  // Thursday, January 1, 1970 12:00:00 AM GMT
+  // Thursday, January 1, 1970 12:00:00 AM UTC
   0,
   // Wed, September 23, 1987 5:03:24 PM
   559415004000,
   // Sat, May 11, 1996 3:55:31 AM
   831786931000,
-  // Monday, January 27, 2020 12:34:56 PM GMT
+  // Monday, January 27, 2020 12:34:56 PM UTC
   1580128496000,
+  // Maximum date 8652-12-31 00:00:00 UTC
+  210895056000000,
+  // Out of range positive date
+  500000000000000,
 ];
 
 export const ZONES: string[] = [

src/main/java/com/squarespace/cldrengine/api/CalendarDate.java

@@ -816,7 +816,7 @@ protected String _toString(String type) {
     return String.format("%s %s%04d-%02d-%02d %02d:%02d:%02d.%03d %s",
         type,
         neg ? "-" : "",
-        year,
+        Math.abs(year),
         this.month(),
         this.dayOfMonth(),
         this.hourOfDay(),
@@ -931,8 +931,8 @@ protected long unixEpochFromJD (long jd, long msDay) {
    * is relative to these.
    */
   protected void computeBaseFields(long[] f) {
-    long jd = f[DateField.JULIAN_DAY];
-    checkJDRange(jd);
+    long jd = clamp(f[DateField.JULIAN_DAY], CalendarConstants.JD_MIN, CalendarConstants.JD_MAX);
+//    checkJDRange(jd);
 
     long msDay = f[DateField.MILLIS_IN_DAY];
     long ms = msDay + ((jd - CalendarConstants.JD_UNIX_EPOCH) * CalendarConstants.ONE_DAY_MS);
@@ -960,17 +960,21 @@ protected void computeBaseFields(long[] f) {
     f[DateField.DAY_OF_WEEK] = dow;
   }
 
-  protected long checkJDRange(long jd) {
-    // TODO: emit warning?
-
-//  throw new Error(
-//  `Julian day ${jd} is outside the supported range of this library: ` +
-//  `${ConstantsDesc.JD_MIN} to ${ConstantsDesc.JD_MAX}`);
-
-    if (jd < CalendarConstants.JD_MIN) {
-      return CalendarConstants.JD_MIN;
-    }
-    return jd > CalendarConstants.JD_MAX ? CalendarConstants.JD_MAX : jd;
+  private static long clamp(long n, long min, long max) {
+    return n < min ? min : (n > max ? max : n);
   }
 
+//  protected long checkJDRange(long jd) {
+//    // TODO: emit warning?
+//
+////  throw new Error(
+////  `Julian day ${jd} is outside the supported range of this library: ` +
+////  `${ConstantsDesc.JD_MIN} to ${ConstantsDesc.JD_MAX}`);
+//
+//    if (jd < CalendarConstants.JD_MIN) {
+//      return CalendarConstants.JD_MIN;
+//    }
+//    return jd > CalendarConstants.JD_MAX ? CalendarConstants.JD_MAX : jd;
+//  }
+
 }

src/main/java/com/squarespace/cldrengine/api/GregorianDate.java

@@ -1,5 +1,7 @@
 package com.squarespace.cldrengine.api;
 
+import static com.squarespace.cldrengine.internal.MathFix.floorDiv;
+
 import com.squarespace.cldrengine.internal.MathFix;
 import com.squarespace.cldrengine.utils.MathUtil;
 
@@ -135,7 +137,7 @@ protected void computeGregorianFields(long[] f) {
     if (doy >= mar1) {
       corr = isLeap ? 1 : 2;
     }
-    int month = (int)Math.floor((12 * (doy + corr) + 6) / 367);
+    int month = (int)MathFix.floorDiv(12 * (doy + corr) + 6, 367);
     long dom = doy - MONTH_COUNT[month][isLeap ? 3 : 2] + 1;
 
     f[DateField.EXTENDED_YEAR] = year;
@@ -152,8 +154,8 @@ protected void computeGregorianFields(long[] f) {
    */
   protected void computeJulianFields(long[] f) {
     long jed = f[DateField.JULIAN_DAY] - (CalendarConstants.JD_GREGORIAN_EPOCH - 2);
-    long eyear = (long)Math.floor((4 * jed + 1464) / 1461);
-    long jan1 = 365 * (eyear - 1) + (long)Math.floor((eyear - 1) / 4);
+    long eyear = floorDiv(4 * jed + 1464, 1461);
+    long jan1 = 365 * (eyear - 1) + floorDiv(eyear - 1, 4);
     long doy = jed - jan1;
     boolean isLeap = eyear % 4 == 0;
     long corr = 0;
@@ -162,7 +164,7 @@ protected void computeJulianFields(long[] f) {
       corr = isLeap ? 1 : 2;
     }
 
-    int month = (int)Math.floor((12 * (doy + corr) + 6) / 365);
+    int month = (int)(12 * (doy + corr) + 6) / 367;
     long dom = doy - MONTH_COUNT[month][isLeap ? 3 : 2] + 1;
 
     f[DateField.EXTENDED_YEAR] = eyear;
@@ -171,7 +173,7 @@ protected void computeJulianFields(long[] f) {
     f[DateField.DAY_OF_YEAR] = doy + 1;
     f[DateField.IS_LEAP] = isLeap ? 1 : 0;
   }
-
+  
   /**
    * Return true if the given year is a leap year in the Gregorian calendar; false otherwise.
    * Note that we switch to the Julian calendar at the Gregorian cutover year.
@@ -183,7 +185,7 @@ protected boolean leapGregorian(long year) {
     }
     return r;
   }
-
+  
   private static final int[][] MONTH_COUNT = new int[][] {
     new int[] { 31,  31,   0,   0 }, // Jan
     new int[] { 28,  29,  31,  31 }, // Feb

src/main/java/com/squarespace/cldrengine/api/PersianDate.java

@@ -1,5 +1,6 @@
 package com.squarespace.cldrengine.api;
 
+import com.squarespace.cldrengine.internal.MathFix;
 import com.squarespace.cldrengine.utils.MathUtil;
 
 /**
@@ -107,10 +108,10 @@ protected long monthStart(long eyear, double month, boolean useMonth) {
   private void computePersianFields(long[] f) {
     long jd = f[DateField.JULIAN_DAY];
     long days = jd - CalendarConstants.JD_PERSIAN_EPOCH;
-    long year = 1 + (long)Math.floor((33 * days + 3) / 12053);
-    long favardin1 = 365 * (year - 1) + (long)Math.floor((8 * year + 21) / 33);
+    long year = 1 + (long)MathFix.floorDiv((33 * days + 3), 12053);
+    long favardin1 = 365 * (year - 1) + (long)MathFix.floorDiv((8 * year + 21), 33);
     long doy = days - favardin1;
-    int month = (int)Math.floor(doy < 216 ? (doy / 31) : ((doy - 6) / 30));
+    int month = (int)(doy < 216 ? MathFix.floorDiv(doy, 31) : MathFix.floorDiv(doy - 6, 30));
     long dom = doy - MONTH_COUNT[month][2] + 1;
 
     f[DateField.ERA] = 0;

src/test/java/com/squarespace/cldrengine/api/GregorianDateTest.java

@@ -0,0 +1,49 @@
+package com.squarespace.cldrengine.api;
+
+import static org.testng.Assert.assertEquals;
+
+import org.testng.Assert;
+import org.testng.annotations.Test;
+
+import com.squarespace.cldrengine.CLDR;
+import com.squarespace.cldrengine.api.CalendarDate;
+import com.squarespace.cldrengine.api.GregorianDate;
+import com.squarespace.cldrengine.calendars.DayOfWeek;
+
+public class GregorianDateTest {
+
+	private static final CLDR EN = CLDR.get("en");
+	private static final String UTC = "Etc/UTC";
+	private static final String NEW_YORK = "America/New_York";
+
+	private static final long unixEpochFromJD(long jd, long msDay) {
+		long days = jd - CalendarConstants.JD_UNIX_EPOCH;
+		return days * CalendarConstants.ONE_DAY_MS + Math.round(msDay);
+	}
+
+	private static final CalendarDate make(long epoch, String zoneId) {
+		return GregorianDate.fromUnixEpoch(epoch, zoneId, DayOfWeek.SUNDAY, 1);
+	}
+
+	@Test
+	public void testMinMaxClamp() {
+		CalendarDate d;
+
+		long min = unixEpochFromJD(CalendarConstants.JD_MIN, 0);
+		long max = unixEpochFromJD(CalendarConstants.JD_MAX, 0);
+
+		d = make(min, "UTC");
+		assertEquals(d.toString(), "Gregorian -4712-01-01 00:00:00.000 Etc/UTC");
+
+		// Clamp to minimum date
+		d = make(min - CalendarConstants.ONE_DAY_MS, "UTC");
+		assertEquals(d.toString(), "Gregorian -4712-01-01 00:00:00.000 Etc/UTC");
+
+		d = make(max, "UTC");
+		assertEquals(d.toString(), "Gregorian 8652-12-31 00:00:00.000 Etc/UTC");
+
+		d = make(max + CalendarConstants.ONE_DAY_MS, "UTC");
+		assertEquals(d.toString(), "Gregorian 8652-12-31 00:00:00.000 Etc/UTC");
+	}
+
+}