Create weekday.kt - port from haskell

weekday.kt

@@ -0,0 +1,57 @@
+import java.time.LocalDate
+import java.time.DayOfWeek
+import java.time.Month
+import java.time.format.DateTimeFormatter
+
+enum class Period {
+    Autumn,
+    Winter,
+    Spring
+}
+
+fun period(thisYear: (Month) -> LocalDate, today: LocalDate): Period {
+    return when {
+        today.isBefore(thisYear(Month.FEBRUARY).plusDays(9)) -> Period.Winter
+        today.isAfter(thisYear(Month.SEPTEMBER).minusDays(1)) -> Period.Autumn
+        else -> Period.Spring
+    }
+}
+
+fun week(p: Period, d: LocalDate): String {
+    return when (p) {
+        Period.Winter -> "Хороших праздников, удачной сессии!"
+        else -> {
+            if (d.dayOfWeek == DayOfWeek.SUNDAY) {
+                "Сегодня воскресенье, лучше иди домой"
+            } else {
+                val (y, x0) = toWeekDate(d)
+                val limit = if (p == Period.Spring) thisYear(Month.FEBRUARY).plusDays(9) else thisYear(Month.SEPTEMBER).plusDays(1)
+                val (_, x1) = toWeekDate(limit)
+                val limitIsSunday = limit.dayOfWeek == DayOfWeek.SUNDAY
+                val x = 1 + x0 - x1 - if (limitIsSunday) 1 else 0
+                "$x неделя"
+            }
+        }
+    }
+}
+
+fun toWeekDate(date: LocalDate): Pair<Int, Int> {
+    val weekOfYear = date.get(java.time.temporal.ChronoField.ALIGNED_WEEK_OF_YEAR)
+    val year = date.year
+    return Pair(year, weekOfYear.toInt())
+}
+
+fun thisYear(month: Month): LocalDate {
+    val now = LocalDate.now()
+    return LocalDate.of(now.year, month, 1)
+}
+
+fun main() {
+    val today = LocalDate.now()
+    val (year, _, _) = today.toGregorian()
+    println(week(period(::thisYear, today), today))
+}
+
+fun LocalDate.toGregorian(): Triple<Int, Int, Int> {
+    return Triple(this.year, this.monthValue, this.dayOfMonth)
+}