add helpers to run sum calculations in an async fashion

Author: rhappe

build.gradle.kts

@@ -7,6 +7,7 @@ group = Publishing.GroupId
 version = Publishing.Version
 
 dependencies {
+    implementation(libs.kotlin.coroutines)
     implementation(libs.kotlin.stdlib)
     implementation(libs.soberg.aoc.api)
 

src/main/kotlin/com/soberg/aoc/utlities/extensions/AsyncSum.kt

@@ -0,0 +1,45 @@
+package com.soberg.aoc.utlities.extensions
+
+import kotlinx.coroutines.CoroutineDispatcher
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.runBlocking
+import java.util.concurrent.atomic.AtomicInteger
+import java.util.concurrent.atomic.AtomicLong
+import kotlin.experimental.ExperimentalTypeInference
+
+@OptIn(ExperimentalTypeInference::class)
+@OverloadResolutionByLambdaReturnType
+@JvmName("asyncSumOfInt")
+inline fun <T> Iterable<T>.asyncSumOf(
+    dispatcher: CoroutineDispatcher = Dispatchers.Default,
+    crossinline selector: (T) -> Int,
+): Int {
+    val sum = AtomicInteger()
+    runBlocking(dispatcher) {
+        forEach {
+            launch {
+                sum.getAndAdd(selector(it))
+            }
+        }
+    }
+    return sum.get()
+}
+
+@OptIn(ExperimentalTypeInference::class)
+@OverloadResolutionByLambdaReturnType
+@JvmName("asyncSumOfLong")
+inline fun <T> Iterable<T>.asyncSumOf(
+    dispatcher: CoroutineDispatcher = Dispatchers.Default,
+    crossinline selector: (T) -> Long,
+): Long {
+    val sum = AtomicLong()
+    runBlocking(dispatcher) {
+        forEach {
+            launch {
+                sum.getAndAdd(selector(it))
+            }
+        }
+    }
+    return sum.get()
+}

src/test/kotlin/com/soberg/aoc/utlities/extensions/AsyncSumTest.kt

@@ -0,0 +1,27 @@
+package com.soberg.aoc.utlities.extensions
+
+import assertk.assertThat
+import assertk.assertions.isEqualTo
+import org.junit.jupiter.api.Test
+
+class AsyncSumTest {
+    private val testData = "The quick brown fox jumped over the lazy dog".split(" ")
+
+    @Test
+    fun `return sum of integers`() {
+        val letterCount = testData.asyncSumOf {
+            it.length
+        }
+
+        assertThat(letterCount).isEqualTo(36)
+    }
+
+    @Test
+    fun `return sum of longs`() {
+        val letterCount = testData.asyncSumOf {
+            it.length.toLong()
+        }
+
+        assertThat(letterCount).isEqualTo(36)
+    }
+}