From f78e81d175d2b62f1456028f1508a027d3d75857 Mon Sep 17 00:00:00 2001
From: InsanusMokrassar <ovsyannikov.alexey95@gmail.com>
Date: Tue, 1 Dec 2020 15:34:12 +0600
Subject: [PATCH] PaginatedIterable

---
 CHANGELOG.md                                  |  3 ++
 .../pagination/utils/PaginatedIterable.kt     | 41 +++++++++++++++++++
 2 files changed, 44 insertions(+)
 create mode 100644 pagination/common/src/commonMain/kotlin/dev/inmo/micro_utils/pagination/utils/PaginatedIterable.kt

diff --git a/CHANGELOG.md b/CHANGELOG.md
index fbf9abe81b5..8e530261905 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,9 @@
 
 ## 0.4.8
 
+* `Pagination`
+    * Add `PaginatedIterable` and `PaginatedIterator`
+
 ## 0.4.7
 
 * `Ktor`
diff --git a/pagination/common/src/commonMain/kotlin/dev/inmo/micro_utils/pagination/utils/PaginatedIterable.kt b/pagination/common/src/commonMain/kotlin/dev/inmo/micro_utils/pagination/utils/PaginatedIterable.kt
new file mode 100644
index 00000000000..035dabbae10
--- /dev/null
+++ b/pagination/common/src/commonMain/kotlin/dev/inmo/micro_utils/pagination/utils/PaginatedIterable.kt
@@ -0,0 +1,41 @@
+package dev.inmo.micro_utils.pagination.utils
+
+import dev.inmo.micro_utils.pagination.*
+
+class PaginatedIterator<T>(
+    pageSize: Int,
+    private val countGetter: () -> Long,
+    private val paginationResultGetter: Pagination.() -> PaginationResult<T>
+) : Iterator<T> {
+    private var pagination = FirstPagePagination(pageSize)
+    private val currentStack = mutableListOf<T>()
+    override fun hasNext(): Boolean = currentStack.isNotEmpty() || (countGetter() < pagination.lastIndexExclusive)
+
+    override fun next(): T {
+        if (currentStack.isEmpty()) {
+            val resultPagination = paginationResultGetter.invoke(pagination)
+            pagination = resultPagination.nextPage()
+            currentStack.addAll(resultPagination.results)
+            require(currentStack.isNotEmpty()) { "There is no elements left" }
+        }
+        return currentStack.removeFirst()
+    }
+}
+
+class PaginatedIterable<T>(
+    private val pageSize: Int,
+    private val countGetter: () -> Long,
+    private val paginationResultGetter: Pagination.() -> PaginationResult<T>
+) : Iterable<T> {
+    override fun iterator(): Iterator<T> = PaginatedIterator(pageSize, countGetter, paginationResultGetter)
+}
+
+/**
+ * Will make iterable using incoming [countGetter] and [paginationResultGetter]
+ */
+@Suppress("NOTHING_TO_INLINE")
+inline fun <T> makeIterable(
+    noinline countGetter: () -> Long,
+    pageSize: Int = defaultMediumPageSize,
+    noinline paginationResultGetter: Pagination.() -> PaginationResult<T>
+): Iterable<T> = PaginatedIterable(pageSize, countGetter, paginationResultGetter)