X-Git-Url: https://git.pterodactylus.net/?p=Sone.git;a=blobdiff_plain;f=src%2Fmain%2Fkotlin%2Fnet%2Fpterodactylus%2Fsone%2Futils%2FPagination.kt;fp=src%2Fmain%2Fkotlin%2Fnet%2Fpterodactylus%2Fsone%2Futils%2FPagination.kt;h=130fe2e82c2bc9038ccc9124764822eb5f193e78;hp=0000000000000000000000000000000000000000;hb=ac6576e72155b3691ce6e5c56ee0c57eb9ac08c6;hpb=cc13ef909d3b9e265918e396466c320ce63235ae

diff --git a/src/main/kotlin/net/pterodactylus/sone/utils/Pagination.kt b/src/main/kotlin/net/pterodactylus/sone/utils/Pagination.kt
new file mode 100644
index 0000000..130fe2e
--- /dev/null
+++ b/src/main/kotlin/net/pterodactylus/sone/utils/Pagination.kt
@@ -0,0 +1,42 @@
+package net.pterodactylus.sone.utils
+
+/**
+ * Helper class for lists that need pagination. Setting the page or the page
+ * size will automatically recalculate all other parameters, and the next call
+ * to [Pagination.items] retrieves all items on the current page.
+ * <p>
+ * A pagination object can be used as an [Iterable]. When the [Iterator]
+ * from [Pagination.iterator] is requested, the iterator over
+ * [Pagination.items] is returned.
+ *
+ * @param <T>
+ *            The type of the list elements
+ */
+class Pagination<out T>(private val originalItems: List<T>, pageSize: Int): Iterable<T> {
+
+	var page: Int = 0
+		set(value) {
+			field = maxOf(0, minOf(value, lastPage))
+		}
+
+	var pageSize = pageSize
+		set(value) {
+			val oldFirstIndex = page * field
+			field = maxOf(1, value)
+			page = oldFirstIndex / field
+		}
+
+	val pageNumber get() = page + 1
+	val pageCount get() = maxOf((originalItems.size - 1) / pageSize + 1, 1)
+	val itemCount get() = minOf(originalItems.size - page * pageSize, pageSize)
+	val items get() = originalItems.subList(page * pageSize, minOf(originalItems.size, (page + 1) * pageSize))
+	val isFirst get() = page == 0
+	val isLast get() = page == lastPage
+	val isNecessary get() = pageCount > 1
+	val previousPage get() = page - 1
+	val nextPage get() = page + 1
+	val lastPage get() = pageCount - 1
+
+	override fun iterator() = items.iterator()
+
+}