merge: Increase minimum Java version to 17 (#115)

This pull request increases the minimum version of Java required by OpenDC to 17.
This new version of Java introduces several new features compared to our old minimum 
version (11), which we attempt to apply in this conversion.

## Implementation Notes :hammer_and_pick:

* Increase minimum Java version to Java 17 
* Use RandomGenerator as randomness source 
* Add common dispatcher interface 
* Add compatibility with Kotlin coroutines
* Use InstantSource as time source
* Re-implement SimulationScheduler as Dispatcher 
* Replace use of CoroutineContext by Dispatcher 

## External Dependencies :four_leaf_clover:

* Java 17

## Breaking API Changes :warning:

* The use of `CoroutineContext` and `Clock` as parameters of classes has been replaced 
  by the `Dispatcher` interface.
* The use of `Clock` has been replaced by `InstantSource` which does not carry time
   zone info.
* The use of `Random` and `SplittableRandom` as parameter type has been replaced 
   by `RandomGenerator`

5 files changed, 51 insertions, 31 deletions

diff --git a/buildSrc/src/main/kotlin/Libs.kt b/buildSrc/src/main/kotlin/Libs.kt
index 6a73e1b9..09432b06 100644
--- a/buildSrc/src/main/kotlin/Libs.kt
+++ b/buildSrc/src/main/kotlin/Libs.kt
@@ -24,32 +24,27 @@
 
 import org.gradle.api.JavaVersion
 import org.gradle.api.Project
+import org.gradle.api.artifacts.VersionCatalog
 import org.gradle.api.artifacts.VersionCatalogsExtension
 import org.gradle.kotlin.dsl.getByType
 
 /**
- * This class makes the version catalog accessible for the build scripts until Gradle adds support for it.
- *
- * See https://github.com/gradle/gradle/issues/15383
+ * Obtain the default [VersionCatalog] of the project.
  */
-public class Libs(project: Project) {
-    /**
-     * The version catalog of the project.
-     */
-    private val versionCatalog = project.extensions.getByType(VersionCatalogsExtension::class).named("libs")
+public val Project.defaultVersionCatalog: VersionCatalog
+    get() = project.extensions.getByType(VersionCatalogsExtension::class).named("libs")
 
-    /**
-     * Obtain the version for the specified [dependency][name].
-     */
-    operator fun get(name: String): String {
-        val dep = versionCatalog.findLibrary(name).get().get()
-        return "${dep.module.group}:${dep.module.name}:${dep.versionConstraint.displayName}"
-    }
+/**
+ * Obtain the dependency string for the specified [name].
+ */
+public operator fun VersionCatalog.get(name: String): String {
+    val dep = findLibrary(name).get().get()
+    return "${dep.module.group}:${dep.module.name}:${dep.versionConstraint.displayName}"
+}
 
-    companion object {
-        /**
-         * The JVM version to target.
-         */
-        val jvmTarget = JavaVersion.VERSION_11
-    }
+/**
+ * Obtain the string representation of the version with the given [name].
+ */
+public fun VersionCatalog.getVersion(name: String): String {
+    return findVersion(name).get().displayName
 }
diff --git a/buildSrc/src/main/kotlin/benchmark-conventions.gradle.kts b/buildSrc/src/main/kotlin/benchmark-conventions.gradle.kts
index 554d2279..e16733a4 100644
--- a/buildSrc/src/main/kotlin/benchmark-conventions.gradle.kts
+++ b/buildSrc/src/main/kotlin/benchmark-conventions.gradle.kts
@@ -50,7 +50,7 @@ tasks.named("jmh", JMHTask::class) {
 
 dependencies {
     constraints {
-        val libs = Libs(project)
-        jmh(libs["commons.math3"]) // XXX Force JMH to use the same commons-math3 version as OpenDC
+        val versionCatalog = project.defaultVersionCatalog
+        jmh(versionCatalog["commons.math3"]) // XXX Force JMH to use the same commons-math3 version as OpenDC
     }
 }
diff --git a/buildSrc/src/main/kotlin/java-conventions.gradle.kts b/buildSrc/src/main/kotlin/java-conventions.gradle.kts
index 8857d4ab..875ae2a7 100644
--- a/buildSrc/src/main/kotlin/java-conventions.gradle.kts
+++ b/buildSrc/src/main/kotlin/java-conventions.gradle.kts
@@ -31,8 +31,10 @@ repositories {
 }
 
 java {
-    sourceCompatibility = Libs.jvmTarget
-    targetCompatibility = Libs.jvmTarget
+    toolchain {
+        val javaVersion = project.defaultVersionCatalog.getVersion("java")
+        languageVersion.set(JavaLanguageVersion.of(javaVersion))
+    }
 }
 
 tasks.withType<JavaCompile> {
diff --git a/buildSrc/src/main/kotlin/kotlin-conventions.gradle.kts b/buildSrc/src/main/kotlin/kotlin-conventions.gradle.kts
index 5ccc06a4..79afdf7c 100644
--- a/buildSrc/src/main/kotlin/kotlin-conventions.gradle.kts
+++ b/buildSrc/src/main/kotlin/kotlin-conventions.gradle.kts
@@ -29,8 +29,15 @@ plugins {
 }
 
 /* Project configuration */
+
+kotlin {
+    jvmToolchain {
+        val javaVersion = project.defaultVersionCatalog.getVersion("java")
+        languageVersion.set(JavaLanguageVersion.of(javaVersion))
+    }
+}
+
 tasks.withType<KotlinCompile>().configureEach {
-    kotlinOptions.jvmTarget = Libs.jvmTarget.toString()
     kotlinOptions.freeCompilerArgs += "-opt-in=kotlin.RequiresOptIn"
     kotlinOptions.freeCompilerArgs += "-Xjvm-default=all"
 }
diff --git a/buildSrc/src/main/kotlin/testing-conventions.gradle.kts b/buildSrc/src/main/kotlin/testing-conventions.gradle.kts
index ebeb58a4..a7fa9da9 100644
--- a/buildSrc/src/main/kotlin/testing-conventions.gradle.kts
+++ b/buildSrc/src/main/kotlin/testing-conventions.gradle.kts
@@ -34,10 +34,26 @@ tasks.test {
 }
 
 dependencies {
-    val libs = Libs(project)
+    val versionCatalog = project.defaultVersionCatalog
 
-    testImplementation(libs["junit.jupiter.api"])
-    testImplementation(libs["junit.jupiter.params"])
-    testImplementation(libs["mockk"])
-    testRuntimeOnly(libs["junit.jupiter.engine"])
+    testImplementation(versionCatalog["junit.jupiter.api"])
+    testImplementation(versionCatalog["junit.jupiter.params"])
+    testImplementation(versionCatalog["mockk"])
+    testRuntimeOnly(versionCatalog["junit.jupiter.engine"])
+}
+
+tasks.register<Test>("testsOn18") {
+    javaLauncher.set(javaToolchains.launcherFor {
+        languageVersion.set(JavaLanguageVersion.of(18))
+    })
+
+    useJUnitPlatform()
+}
+
+tasks.register<Test>("testsOn19") {
+    javaLauncher.set(javaToolchains.launcherFor {
+        languageVersion.set(JavaLanguageVersion.of(19))
+    })
+
+    useJUnitPlatform()
 }