Merge pull request #299 from Elyahu41/fix/spa-nan-zenith-hang

SPACalculator: return NaN instead of running for hours when the target zenith is NaN
Thanks @ Elyahu41

Author: KosherJava

src/main/java/com/kosherjava/zmanim/util/SPACalculator.java

@@ -311,6 +311,11 @@ private double getUTCSunRiseSet(LocalDate localDate, GeoLocation geoLocation, do
 			}
 		}
 		double adjustedZenith = adjustZenith(zenith, elevation, localDate);
+		if (!Double.isFinite(adjustedZenith)) {
+			// A NaN or infinite zenith (or a NaN / infinite refraction, solar radius or earth radius, which make the adjusted
+			// zenith NaN) has no crossing, and the bracketing search can't rule out any interval of a NaN function.
+			return Double.NaN;
+		}
 		double riseSet = solveRiseSet(localDate, geoLocation, adjustedZenith, solarEvent);
 		if (Double.isNaN(riseSet)) {
 			return Double.NaN;
@@ -654,6 +659,11 @@ private static final class CrossingSearch {
 		 * @return the crossing time, or NaN if the interval holds none
 		 */
 		double find(double start, double end, double a, double b) {
+			if (Double.isNaN(a) || Double.isNaN(b)) {
+				// No interval of a NaN function can be discarded, so without this the search would split all the way down to
+				// TIME_TOLERANCE in every branch (about 2^27 evaluations).
+				return Double.NaN;
+			}
 			double width = end - start;
 			double slope = (b - a) / width;
 			double slopeError = curvature * width / 2.0 + 2.0 * ROUNDING_ERROR / width;

src/test/java/com/kosherjava/zmanim/util/SPACalculatorTest.java

@@ -322,4 +322,28 @@ public void defaultsAndSetters() {
 	public void getCalculatorName() {
 		assertEquals("NREL Solar Position Algorithm", calculator().getCalculatorName());
 	}
+
+	/**
+	 * A NaN target zenith (from a NaN / infinite zenith, refraction or solar radius, or a negative / NaN earth radius) used to
+	 * make the bracketing rise / set search run for hours. It must return NaN like the other calculators.
+	 */
+	@Test(timeout = 10_000)
+	public void nonFiniteZenithReturnsNaNPromptly() {
+		GeoLocation location = new GeoLocation("Lakewood, NJ", 40.0721087, -74.2400243, 5017, ZoneId.of("America/New_York"));
+		LocalDate date = LocalDate.of(2026, 1, 1);
+		assertTrue(Double.isNaN(calculator().getUTCSunrise(date, location, Double.POSITIVE_INFINITY, false)));
+		assertTrue(Double.isNaN(calculator().getUTCSunset(date, location, Double.NaN, false)));
+
+		SPACalculator negativeEarthRadius = calculator();
+		negativeEarthRadius.setEarthRadius(-6371);
+		assertTrue(Double.isNaN(negativeEarthRadius.getUTCSunrise(date, location, 90.0, true)));
+
+		SPACalculator nanRefraction = calculator();
+		nanRefraction.setRefraction(Double.NaN);
+		assertTrue(Double.isNaN(nanRefraction.getUTCSunset(date, location, 90.0, false)));
+
+		SPACalculator infiniteSolarRadius = calculator();
+		infiniteSolarRadius.setSolarRadius(Double.POSITIVE_INFINITY);
+		assertTrue(Double.isNaN(infiniteSolarRadius.getUTCSunrise(date, location, 90.0, false)));
+	}
 }