feat: add Service class to provide additional functionalities

src/main/kotlin/org/javafreedom/khol/KHolServices.kt

@@ -0,0 +1,23 @@
+package org.javafreedom.khol
+
+import kotlinx.datetime.DayOfWeek
+import kotlinx.datetime.LocalDate
+import org.javafreedom.khol.helper.rangeTo
+
+/**
+ * Provide some useful Service functions
+ */
+class KHolServices {
+
+    fun workdays(holidays: List<LocalDate>,
+                 start: LocalDate, end: LocalDate): List<LocalDate> =
+        (start..end)
+            .filter { isHoliday(holidays, it) }
+            .filter { !isWeekend(it) }
+            .toList()
+
+    fun isHoliday(holidays: List<LocalDate>, date: LocalDate) = holidays.contains(date)
+
+    fun isWeekend(date: LocalDate) =
+        date.dayOfWeek == DayOfWeek.SATURDAY || date.dayOfWeek == DayOfWeek.SUNDAY
+}

src/main/kotlin/org/javafreedom/khol/helper/LocalDateRangeHelper.kt

@@ -0,0 +1,44 @@
+package org.javafreedom.khol.helper
+
+import kotlinx.datetime.DateTimeUnit
+import kotlinx.datetime.LocalDate
+import kotlinx.datetime.plus
+
+/**
+ * This provides the iterator to be used in the progression. This can then used in range queries.
+ *
+ * Cloned by https://www.netguru.com/blog/traversing-through-dates-with-kotlin-range-expressions
+ */
+class DateIterator(val startDate: LocalDate,
+                   val endDateExclusive: LocalDate,
+                   val stepDays: Long): Iterator<LocalDate> {
+    private var currentDate = startDate
+
+    override fun hasNext() = currentDate < endDateExclusive
+
+    override fun next(): LocalDate {
+        val next = currentDate
+        currentDate = currentDate.plus(stepDays, DateTimeUnit.DAY)
+        return next
+    }
+
+}
+
+/**
+ * The progression used to loop through a range of localDates
+ */
+class DateProgression(override val start: LocalDate,
+                      override val endInclusive: LocalDate,
+                      val stepDays: Long = 1) :
+    Iterable<LocalDate>, ClosedRange<LocalDate> {
+
+    override fun iterator(): Iterator<LocalDate> =
+        DateIterator(start, endInclusive, stepDays)
+
+    infix fun step(days: Long) = DateProgression(start, endInclusive, days)
+}
+
+/**
+ * Extension Function to make the localdate range work
+ */
+operator fun LocalDate.rangeTo(other: LocalDate) = DateProgression(this, other)