1 package net.pterodactylus.sone.utils
4 * Helper class for lists that need pagination. Setting the page or the page
5 * size will automatically recalculate all other parameters, and the next call
6 * to [Pagination.items] retrieves all items on the current page.
8 * A pagination object can be used as an [Iterable]. When the [Iterator]
9 * from [Pagination.iterator] is requested, the iterator over
10 * [Pagination.items] is returned.
13 * The type of the list elements
15 class Pagination<out T>(private val originalItems: List<T>, pageSize: Int): Iterable<T> {
19 field = maxOf(0, minOf(value, lastPage))
22 var pageSize = pageSize
24 val oldFirstIndex = page * field
25 field = maxOf(1, value)
26 page = oldFirstIndex / field
29 val pageNumber get() = page + 1
30 val pageCount get() = maxOf((originalItems.size - 1) / pageSize + 1, 1)
31 val itemCount get() = minOf(originalItems.size - page * pageSize, pageSize)
32 val items get() = originalItems.subList(page * pageSize, minOf(originalItems.size, (page + 1) * pageSize))
33 val isFirst get() = page == 0
34 val isLast get() = page == lastPage
35 val isNecessary get() = pageCount > 1
36 val previousPage get() = page - 1
37 val nextPage get() = page + 1
38 val lastPage get() = pageCount - 1
40 override fun iterator() = items.iterator()
42 fun turnTo(page: Int) = apply { this.page = page }
46 fun <T> Iterable<T>.paginate(pageSize: Int) = Pagination<T>(toList(), pageSize)