init with pagination

pagination/common/src/commonMain/kotlin/dev/inmo/micro_utils/pagination/Pagination.kt

@@ -0,0 +1,52 @@
+package dev.inmo.micro_utils.pagination
+
+import kotlin.math.ceil
+
+/**
+ * Base interface of pagination
+ *
+ * If you want to request something, you should use [SimplePagination]. If you need to return some result including
+ * pagination - [PaginationResult]
+ */
+interface Pagination {
+    /**
+     * Started with 0.
+     * Number of page inside of pagination. Offset can be calculated as [page] * [size]
+     */
+    val page: Int
+    /**
+     * Can be 0, but can't be < 0
+     * Size of current page. Offset can be calculated as [page] * [size]
+     */
+    val size: Int
+}
+
+/**
+ * First number in index of objects. It can be used as offset for databases or other data sources
+ */
+val Pagination.firstIndex: Int
+    get() = page * size
+
+/**
+ * Last number in index of objects. In fact, one [Pagination] object represent data in next range:
+ *
+ * [[firstIndex], [lastIndex]]; That means, that for [Pagination] with [Pagination.size] == 10 and [Pagination.page] == 1
+ * you will retrieve [Pagination.firstIndex] == 10 and [Pagination.lastIndex] == 19.
+ */
+val Pagination.lastIndex: Int
+    get() = firstIndex + size - 1
+
+/**
+ * Calculates pages count for given [datasetSize]
+ */
+fun calculatePagesNumber(datasetSize: Long, pageSize: Int): Int {
+    return ceil(datasetSize.toDouble() / pageSize).toInt()
+}
+/**
+ * Calculates pages count for given [datasetSize]
+ */
+fun calculatePagesNumber(datasetSize: Int, pageSize: Int): Int =
+    calculatePagesNumber(
+        datasetSize.toLong(),
+        pageSize
+    )

pagination/common/src/commonMain/kotlin/dev/inmo/micro_utils/pagination/PaginationResult.kt

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+package dev.inmo.micro_utils.pagination
+
+import kotlinx.serialization.Serializable
+
+@Serializable
+data class PaginationResult<T>(
+    override val page: Int,
+    val pagesNumber: Int,
+    val results: List<T>,
+    override val size: Int
+) : Pagination
+
+fun <T> List<T>.createPaginationResult(
+    pagination: Pagination,
+    commonObjectsNumber: Long
+) = PaginationResult(
+    pagination.page,
+    calculatePagesNumber(
+        commonObjectsNumber,
+        pagination.size
+    ),
+    this,
+    pagination.size
+)
+
+fun <T> Pair<Long, List<T>>.createPaginationResult(
+    pagination: Pagination
+) = second.createPaginationResult(pagination, first)

pagination/common/src/commonMain/kotlin/dev/inmo/micro_utils/pagination/SimplePagination.kt

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+package dev.inmo.micro_utils.pagination
+
+import kotlinx.serialization.Serializable
+
+const val defaultSmallPageSize = 2
+const val defaultMediumPageSize = 5
+const val defaultLargePageSize = 10
+const val defaultExtraLargePageSize = 15
+
+@Suppress("NOTHING_TO_INLINE", "FunctionName")
+inline fun FirstPagePagination(size: Int = defaultMediumPageSize) =
+    SimplePagination(
+        page = 0,
+        size = size
+    )
+
+@Suppress("NOTHING_TO_INLINE")
+inline fun Pagination.nextPage() =
+    SimplePagination(
+        page + 1,
+        size
+    )
+
+@Serializable
+data class SimplePagination(
+    override val page: Int,
+    override val size: Int
+) : Pagination
+
+fun Pagination(
+    page: Int,
+    size: Int
+) = SimplePagination(page, size)

pagination/common/src/commonMain/kotlin/dev/inmo/micro_utils/pagination/WalkPagination.kt

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+package dev.inmo.micro_utils.pagination
+
+inline fun doWithPagination(
+    startPagination: Pagination = FirstPagePagination(),
+    requestMaker: (pagination: Pagination) -> Pagination?
+) = requestMaker(startPagination).let {
+    var pagination = it
+    while (pagination != null) {
+        pagination = requestMaker(pagination)
+    }
+}
+
+@Suppress("NOTHING_TO_INLINE")
+inline fun PaginationResult<*>.nextPageIfNotEmpty() = if (results.isNotEmpty()) {
+    SimplePagination(
+        page + 1,
+        size
+    )
+} else {
+    null
+}
+
+@Suppress("NOTHING_TO_INLINE")
+inline fun PaginationResult<*>.thisPageIfNotEmpty(): Pagination? = if (results.isNotEmpty()) {
+    this
+} else {
+    null
+}