add paging request

core/build.gradle.kts

@@ -13,7 +13,8 @@ repositories {
 
 dependencies {
     implementation(libs.kotlinx.serialization.json)
-    testImplementation(kotlin("test"))
+    implementation(libs.bundles.ktor.server)
+    implementation(libs.bundles.slf4j)
 }
 
 tasks.test {

core/src/main/kotlin/ai/neuon/utility/paging/PagingRequest.kt

@@ -0,0 +1,50 @@
+package ai.neuon.utility.paging
+
+import io.ktor.server.request.ApplicationRequest
+import kotlin.math.max
+
+sealed class PagingRequest {
+    companion object {
+        fun from(request: ApplicationRequest): PagingRequest {
+            val params = request.queryParameters
+            val pagingType = params["paging"]?.let {
+                Type.from(it)
+            } ?: Type.OFFSET
+
+            return when (pagingType) {
+                Type.NONE -> None
+                Type.OFFSET -> {
+                    val i = params["page"]?.toInt()
+                        ?.let { max(0, it) } ?: 0
+                    val limit = params["pageSize"]?.toInt()
+                        ?.let { max(1, it) } ?: 10
+                    Offset(index = i, limit = limit)
+                }
+            }
+        }
+    }
+
+    data object None : PagingRequest()
+
+    data class Offset(val index: Int, val limit: Int) : PagingRequest() {
+        val skip: Int
+            get() = index * limit
+    }
+
+    enum class Type(val key: String) {
+        NONE(key = "none"), OFFSET(key = "offset");
+
+        companion object {
+            /**
+             * @throws IllegalArgumentException
+             */
+            fun from(type: String): Type {
+                return when (type) {
+                    "none" -> NONE
+                    "offset" -> OFFSET
+                    else -> throw IllegalArgumentException("Unsupported pagination type, $type")
+                }
+            }
+        }
+    }
+}