Chron.scala

chron.scala

// A simply port of Google Task's recurring task scheduler to Scala 3 ADT:	
// https://tasks.google.com/embed/?origin=https://calendar.google.com&fullWidth=1

import java.time._

enum Cadence:
  case Daily
  case Weekly(on: Set[DayOfWeek] = Set(DayOfWeek.SUNDAY))
  case Monthly(on: Set[DayOfMonth] = Set(DayOfMonth.Day(1)))
  case Yearly(on: Set[MonthDay] = Set(MonthDay.of(1, 1)))

enum DayOfMonth:
  case Day(day: Int)
  case LastDay(daysFromEnd: Int = 0)
  case First(day: DayOfWeek)
  case Second(day: DayOfWeek)
  case Third(day: DayOfWeek)
  case Fourth(day: DayOfWeek)
  case Last(day: DayOfWeek)

enum End:
  case Never
  case On(date: LocalDate)
  case After(occurences: Int)

case class Schedule(
  every: Int,
  cadence: Cadence,
  at: LocalTime = LocalTime.MIDNIGHT,
  starts: LocalDate = LocalDate.now(),
  ends: End = End.Never
)

// Example usage to schedule every 2 months on the 2nd day of month and the last Friday
Schedule(
  every = 2,
  cadence = Cadence.Monthly(
    on = Set(
      DayOfMonth.Day(2), 
      DayOfMonth.Last(DayOfWeek.FRIDAY)
    )
  )
)