Check for day range in script library

src/main/java/org/orecruncher/dsurround/lib/scripting/LibraryFunctions.java

@@ -2,17 +2,22 @@
 
 import org.jetbrains.annotations.Nullable;
 import org.orecruncher.dsurround.lib.Library;
+import org.orecruncher.dsurround.lib.di.ContainerManager;
 import org.orecruncher.dsurround.lib.platform.IPlatform;
+import org.orecruncher.dsurround.lib.system.ISystemClock;
 
+import java.time.*;
 import java.util.Objects;
 import java.util.regex.Pattern;
 
 /**
  * Library functions exposed via the JavaScript engine.  They are not directly used by code.
  */
+@SuppressWarnings("unused")
 public final class LibraryFunctions {
 
     private static final IPlatform PLATFORM = Library.PLATFORM;
+    private static final ISystemClock SYSTEM_CLOCK = ContainerManager.resolve(ISystemClock.class);
 
     public Object iif(final boolean flag, @Nullable final Object trueResult, @Nullable final Object falseResult) {
         return flag ? trueResult : falseResult;
@@ -40,4 +45,30 @@ public boolean isBetween(final double value, final double min, final double max)
     public boolean isModLoaded(final String mod) {
         return PLATFORM.isModLoaded(mod);
     }
+
+    public boolean isCurrentDateInRangeOf(int month, int day, int dayRange) {
+        try {
+            // Get the current Utc time. Assume the test date is the same year.
+            var theNow = LocalDate.ofInstant(SYSTEM_CLOCK.getUtcNow(), ZoneOffset.UTC);
+            var testDate = LocalDate.of(theNow.getYear(), month, day);
+
+            // If the test date is before the time window, it means the range is in the future
+            var begin = theNow.minusDays(dayRange);
+            if (begin.isAfter(testDate))
+                return false;
+
+            // So the test date is after the beginning of the window. See if it is before
+            // the end of the window. If so, it's in range.
+            var end = theNow.plusDays(dayRange);
+            if (!end.isBefore(testDate))
+                return true;
+
+            // So the range looks like it is in the past. It's possible that we are dealing with an end of year thing
+            // like new years. Handle that by adding one year to the test date and re-evaluate.
+            testDate = testDate.plusYears(1);
+            return !(begin.isAfter(testDate) || end.isBefore(testDate));
+        } catch (Throwable ignore) {
+        }
+        return false;
+    }
 }