Kryo codecs example

build.sbt

@@ -152,6 +152,10 @@ lazy val `codec-protobuf-js` = `codec-protobuf`.js
 lazy val `codec-examples` = project
   .in(file("examples"))
   .settings(
-    commons
+    commons,
+    libraryDependencies ++= Seq(
+      "io.monix" %%% "monix" % "3.0.0-RC1"
+    )
   )
   .dependsOn(`codec-core-jvm`)
+  .dependsOn(`codec-kryo`)

examples/src/main/scala/fluence/codec/examples/KryoCodecExample.scala

@@ -0,0 +1,65 @@
+package fluence.codec.examples
+
+import cats.Id
+import fluence.codec.kryo.KryoCodecs
+import fluence.codec.{CodecError, PureCodec}
+import monix.eval.Task
+import shapeless.{::, HNil}
+
+object KryoCodecExample {
+  case class Aircraft(manufacturer: String, model: String, tailNumber: String)
+  case class Fuel(amount: Double) extends AnyVal
+
+  case class UnknownClass(x: String)
+
+  def main(args: Array[String]): Unit = {
+    // This way we can define a typed collection of codecs using kryo for the underlying serialization.
+    //
+    // These codecs can be used only to transform the corresponding type: i.e. it won't be possible to
+    // use an aircraft codec to serialize fuel (which is essentially a typed wrapper over double value).
+    //
+    // It won't be possible to obtain from this collection a codec for previously not registered class.
+    // Type safety FTW!
+    //
+    // Note that different methods are used to register Aircraft and Fuel – that's because one is a reference,
+    // and another is a value type.
+    val codecs: KryoCodecs[Task, ::[Fuel, ::[Aircraft, ::[Array[Byte], ::[Long, ::[String, HNil]]]]]] = KryoCodecs()
+      .addCase(classOf[Aircraft])
+      .add[Fuel]
+      .build[Task]()
+
+    val skyhawk61942 = Aircraft("Cessna", "172S G1000", "N61942")
+    val tabsFuel = Fuel(53)
+
+    val aircraftCodec: PureCodec[Aircraft, Array[Byte]] = codecs.pureCodec[Aircraft]
+    val fuelCodec: PureCodec[Fuel, Array[Byte]] = codecs.pureCodec[Fuel]
+
+    // This will cause a compilation error, because the class was never registered with the codecs.
+    // "You requested an element of type (...).UnknownClass, but there is none in the HList"
+    //
+    // val unknownCodec = codecs.pureCodec[UnknownClass]
+
+
+    // Here all the standard machinery of codecs applies (for more examples, consider checking out PureCodecExample.
+    // We can serialize and deserialize the object – and unsurprisingly the original and restored values match.
+    //
+    // Let's serialize an aircraft instance.
+    {
+      val ser: Id[Either[CodecError, Array[Byte]]] = aircraftCodec.direct[Id](skyhawk61942).value
+      val deser: Id[Either[CodecError, Aircraft]] = aircraftCodec.inverse[Id](ser.right.get).value
+
+      println(ser.right.map(x => s"$skyhawk61942 => serialized size: ${x.length}"))
+      assert(deser == Right(skyhawk61942))
+    }
+
+
+    // Same thing for the fuel instance (which is AnyVal fwiw).
+    {
+      val ser: Id[Either[CodecError, Array[Byte]]] = fuelCodec.direct[Id](tabsFuel).value
+      val deser: Id[Either[CodecError, Fuel]] = fuelCodec.inverse[Id](ser.right.get).value
+
+      println(ser.right.map(x => s"$tabsFuel => serialized size: ${x.length}"))
+      assert(deser == Right(tabsFuel))
+    }
+  }
+}

kryo/src/main/scala/fluence/codec/kryo/KryoFactory.scala

@@ -21,8 +21,8 @@ import com.twitter.chill.{AllScalaRegistrar, KryoBase, KryoInstantiator}
 import org.objenesis.strategy.StdInstantiatorStrategy
 
 /**
- * This Instantiator enable compulsory class registration, registers all java and scala main classes.
- * This class required for [[com.twitter.chill.KryoPool]].
+ * This Instantiator enables compulsory class registration and registers all java and scala main classes.
+ * This class is required for [[com.twitter.chill.KryoPool]].
  * @param classesToReg additional classes for registration
  * @param registrationRequired if true, an exception is thrown when an unregistered class is encountered.
  */