Merge pull request #803 from focus-shift/improve-relative-to-weekday-in-month-parser-code

Improve relative to weekday in month parser code

Author: derTobsch

jollyday-core/src/main/java/de/focus_shift/jollyday/core/parser/impl/RelativeToWeekdayInMonthParser.java

@@ -6,33 +6,52 @@
 import de.focus_shift.jollyday.core.parser.functions.FindWeekDayInMonth;
 import de.focus_shift.jollyday.core.parser.predicates.ValidLimitation;
 import de.focus_shift.jollyday.core.spi.Holidays;
-import de.focus_shift.jollyday.core.spi.Relation;
+import de.focus_shift.jollyday.core.spi.RelativeToWeekdayInMonth;
 
 import java.time.LocalDate;
 import java.time.Year;
 import java.util.List;
 
+import static de.focus_shift.jollyday.core.spi.Relation.BEFORE;
 import static java.util.stream.Collectors.toList;
 
 /**
- * <p>
  * RelativeToWeekdayInMonthParser class.
- * </p>
+ * <p>
+ * Resolves the holiday date for a given relative-to-weekday-in-month configuration.
+ * <p>
+ * This method works as follows:
+ * <ul>
+ *   <li>Finds the base date in the month using the weekdayInMonth configuration.</li>
+ *   <li>Calculates the difference in days to the target weekday, considering the direction (BEFORE or AFTER).</li>
+ *   <li>Returns a Holiday for the resulting date.</li>
+ * </ul>
  */
 public class RelativeToWeekdayInMonthParser implements HolidayParser {
 
   @Override
   public List<Holiday> parse(final Year year, final Holidays holidays) {
     return holidays.relativeToWeekdayInMonth().stream()
       .filter(new ValidLimitation(year))
-      .map(rwm -> {
-        LocalDate date = new FindWeekDayInMonth(year).apply(rwm.weekdayInMonth()).plusDays(1);
-        int direction = rwm.when() == Relation.BEFORE ? -1 : 1;
-        while (date.getDayOfWeek() != rwm.weekday()) {
-          date = date.plusDays(direction);
-        }
-        return new CreateHoliday(date).apply(rwm);
-      })
+      .map(relativeToWeekdayInMonth -> resolveHolidayForRelativeToWeekdayInMonth(year, relativeToWeekdayInMonth))
       .collect(toList());
   }
+
+  private Holiday resolveHolidayForRelativeToWeekdayInMonth(final Year year, final RelativeToWeekdayInMonth rwm) {
+    final LocalDate baseDate = new FindWeekDayInMonth(year).apply(rwm.weekdayInMonth());
+
+    final int currentDayValue = baseDate.getDayOfWeek().getValue();
+    final int targetDayValue = rwm.weekday().getValue();
+    final int direction = (rwm.when() == BEFORE ? -1 : 1);
+
+    int daysDifference = targetDayValue - currentDayValue;
+    if (direction < 0 && daysDifference >= 0) {
+      daysDifference -= 7;
+    } else if (direction > 0 && daysDifference <= 0) {
+      daysDifference += 7;
+    }
+
+    final LocalDate resultDate = baseDate.plusDays(daysDifference);
+    return new CreateHoliday(resultDate).apply(rwm);
+  }
 }

jollyday-core/src/test/java/de/focus_shift/jollyday/core/parser/impl/RelativeToWeekdayInMonthParserTest.java

@@ -24,6 +24,7 @@
 
 import static de.focus_shift.jollyday.core.HolidayType.PUBLIC_HOLIDAY;
 import static de.focus_shift.jollyday.core.spi.Limited.YearCycle.EVERY_YEAR;
+import static de.focus_shift.jollyday.core.spi.Occurrence.FIRST;
 import static de.focus_shift.jollyday.core.spi.Occurrence.LAST;
 import static java.time.DayOfWeek.MONDAY;
 import static java.time.DayOfWeek.TUESDAY;
@@ -53,6 +54,21 @@ void ensureThatRelativeToWeekdayInMonthWithRelationBeforeIsValid(final Relation
     assertThat(calculatedHoliday.get(0).getDate()).isEqualTo(expectedLocalDate);
   }
 
+  @ParameterizedTest
+  @CsvSource({"BEFORE,2025-03-31", "AFTER,2025-04-14"})
+  void ensureThatRelativeToWeekdayInMonthWithRelationBeforeIsValidAndIsOnSameWeekday(final Relation relation, final LocalDate expectedLocalDate) {
+
+    final Year year = Year.of(2025);
+    final FixedWeekdayInMonth fixedWeekdayInMonth = getFixedWeekdayInMonth(APRIL, MONDAY, FIRST);
+    final RelativeToWeekdayInMonth relativeToWeekdayInMonth = getRelativeToWeekdayInMonth(MONDAY, relation, fixedWeekdayInMonth, year, year);
+
+    final RelativeToWeekdayInMonthParser sut = new RelativeToWeekdayInMonthParser();
+    when(holidays.relativeToWeekdayInMonth()).thenReturn(List.of(relativeToWeekdayInMonth));
+
+    final List<Holiday> calculatedHoliday = sut.parse(year, holidays);
+    assertThat(calculatedHoliday.get(0).getDate()).isEqualTo(expectedLocalDate);
+  }
+
   @Nested
   class LimitedTests {