Destructuring a Date into Years, Months, Weeks, Days, Hours, Minutes and Seconds in Kotlin

TimeAgo.kt

object TimeAgo {
  fun toRelative(millis: Long, spans: List<Span>): Map<Span, Long> {
    var millisMutable = millis
    return spans.sortedBy(Span::order).associateWith { span ->
      val timeDelta: Long = millisMutable / span.millis
      if (timeDelta.isGreaterThanZero()) millisMutable -= span.millis * timeDelta
      timeDelta
    }
  }

  enum class Span(val order: Int, val millis: Long) {
    YEARS(0, TimeUnit.DAYS.toMillis(365)),
    MONTHS(1, TimeUnit.DAYS.toMillis(30)),
    WEEKS(2, TimeUnit.DAYS.toMillis(7)),
    DAYS(3, TimeUnit.DAYS.toMillis(1)),
    HOURS(4, TimeUnit.HOURS.toMillis(1)),
    MINUTES(5, TimeUnit.MINUTES.toMillis(1)),
    SECONDS(6, TimeUnit.SECONDS.toMillis(1))
  }
}

fun Map<Span, Long>.getYears(): Long = this[YEARS] ?: 0L
fun Map<Span, Long>.getMonths(): Long = this[MONTHS] ?: 0L
fun Map<Span, Long>.getWeeks(): Long = this[WEEKS] ?: 0L
fun Map<Span, Long>.getDays(): Long = this[DAYS] ?: 0L
fun Map<Span, Long>.getHours(): Long = this[HOURS] ?: 0L
fun Map<Span, Long>.getMinutes(): Long = this[MINUTES] ?: 0L
fun Map<Span, Long>.getSeconds(): Long = this[SECONDS] ?: 0L

TimeAgoTest.kt

class TimeAgoTest {
  @Test
  fun timeAgoTest() {
    TimeAgo.toRelative(ONE_YEAR, listOf(YEARS)).getYears().shouldBe(1)
    TimeAgo.toRelative(ONE_MONTH, listOf(MONTHS)).getMonths().shouldBe(1)
    TimeAgo.toRelative(ONE_WEEK, listOf(WEEKS)).getWeeks().shouldBe(1)
    TimeAgo.toRelative(ONE_DAY, listOf(DAYS)).getDays().shouldBe(1)
    TimeAgo.toRelative(ONE_HOUR, listOf(HOURS)).getHours().shouldBe(1)
    TimeAgo.toRelative(ONE_MINUTE, listOf(MINUTES)).getMinutes().shouldBe(1)
    TimeAgo.toRelative(ONE_SECOND, listOf(SECONDS)).getSeconds().shouldBe(1)

    TimeAgo.toRelative(ONE_MONTH, listOf(WEEKS, DAYS, HOURS)).run {
      getWeeks().shouldBe(4)
      getDays().shouldBe(2)
      getHours().shouldBe(0)
    }
  }
}