Collecting events with overlapping dates

eventsoverlapping.kt

import java.time.LocalDate

data class Event(val id: Int, val startDate: LocalDate, val endDate: LocalDate, val name: String)


fun LocalDate(string: String): LocalDate = LocalDate.parse(string)

fun Event.overlap(another: Event): Boolean {

    //    this:------(start)----------------(end)---------------------->
    // another:-------------------(start)--------------------(end)----->
    if (another.startDate >= startDate && another.endDate>= endDate) {
        return true
    }


    //    this:------(start)----------------(end)---------------------->
    // another:-(start)--------------------------------------(end)----->
    if (another.startDate < startDate && another.endDate >= endDate) {
        return true
    }

    //    this:------(start)----------------(end)---------------------->
    // another:----------(start)----------(end)------------------------>
    if (another.startDate >= startDate && another.endDate <= startDate) {
        return true
    }

    return false
}


fun main(args: Array<String>) {

    val events = listOf(
        Event(1, LocalDate("2022-04-20"), LocalDate("2022-04-21"), "event-1"),
        Event(2, LocalDate("2022-04-21"), LocalDate("2022-04-21"), "event-2"),
        Event(3, LocalDate("2022-05-01"), LocalDate("2022-05-01"), "event-3"),
        Event(4, LocalDate("2022-05-06"), LocalDate("2022-05-10"), "event-4"),
        Event(5, LocalDate("2022-05-09"), LocalDate("2022-05-12"), "event-5")
    ).sortedBy(Event::startDate)

    val overlappingEvents =
        events.fold(mutableListOf<MutableList<Event>>()) { collected, event ->
            if (collected.isEmpty()) {
                collected += mutableListOf(event)
            } else if (event.overlap(collected.last().last())) {
                collected.last().add(event)
            } else {
                collected.add(mutableListOf(event))
            }
            collected
        }

    overlappingEvents.forEachIndexed { index, list ->
        println("[${index + 1}] --------------------------------------------------")
        list.forEach(::println)
    }
}