Introduce MessageHandler interface

Author: theUniC

.java-version

@@ -1 +1 @@
-21
+23

gradle.properties

@@ -3,4 +3,4 @@ org.gradle.caching=true
 kotlin.code.style=official
 
 groupId=io.github.theunic
-version=0.3.0
+version=0.4.0

kcommand-core/src/main/kotlin/io/github/theunic/kcommand/core/AbstractMessageBus.kt

@@ -6,11 +6,11 @@ import kotlin.reflect.KClass
 abstract class AbstractMessageBus<M : Any, R : Any>(
     private val middlewares: List<Middleware<M, R>> = listOf(),
 ) : MessageBus<M, R> {
-    private val subscriptions: MutableMap<KClass<out M>, suspend (M) -> R> = mutableMapOf()
+    private val subscriptions: MutableMap<KClass<out M>, MessageHandler<M, R>> = mutableMapOf()
 
     override fun subscribe(
         messageType: KClass<out M>,
-        messageHandler: suspend (M) -> R,
+        messageHandler: MessageHandler<M, R>,
     ) {
         synchronized(subscriptions) {
             subscriptions[messageType] = messageHandler
@@ -39,9 +39,9 @@ abstract class AbstractMessageBus<M : Any, R : Any>(
         chain(command)
     }
 
-    private suspend fun handleCommand(command: M): R = getCommandHandler(command::class)(command)
+    private suspend fun handleCommand(command: M): R = getCommandHandler(command::class).handle(command)
 
-    private fun getCommandHandler(commandClass: KClass<out M>): suspend (M) -> R {
+    private fun getCommandHandler(commandClass: KClass<out M>): MessageHandler<M, R> {
         synchronized(subscriptions) {
             return subscriptions[commandClass]
                 ?: throw IllegalArgumentException("No handler found for command: $commandClass")

kcommand-core/src/main/kotlin/io/github/theunic/kcommand/core/MessageBus.kt

@@ -8,6 +8,6 @@ interface MessageBus<M : Any, R> {
 
     fun subscribe(
         messageType: KClass<out M>,
-        messageHandler: suspend (M) -> R,
+        messageHandler: MessageHandler<M, R>,
     )
 }

kcommand-core/src/main/kotlin/io/github/theunic/kcommand/core/MessageHandler.kt

@@ -0,0 +1,5 @@
+package io.github.theunic.kcommand.core
+
+interface MessageHandler<M, R> {
+    suspend fun handle(message: M): R
+}

kcommand-core/src/test/kotlin/io/github/theunic/kcommand/core/DefaultMessageBusTest.kt

@@ -26,7 +26,10 @@ class DefaultMessageBusTest :
         }
 
         given("A message bus with a subscription") {
-            val messageHandler: suspend (String) -> Int = { it.length }
+            val messageHandler =
+                object : MessageHandler<String, Int> {
+                    override suspend fun handle(message: String) = message.length
+                }
             messageBus.subscribe(String::class, messageHandler)
 
             `when`("a message sent to the message bus") {
@@ -51,7 +54,10 @@ class DefaultMessageBusTest :
                 }
 
             val newMessageBus = DefaultMessageBus(listOf(modifyingMiddleware))
-            val messageHandler = { command: String -> command }
+            val messageHandler =
+                object : MessageHandler<String, String> {
+                    override suspend fun handle(message: String) = message
+                }
             newMessageBus.subscribe(String::class, messageHandler)
 
             `when`("A message goes through middleware") {

kcommand-core/src/test/kotlin/io/github/theunic/kcommand/core/SimpleMessageBusTest.kt

@@ -8,7 +8,12 @@ class SimpleMessageBusTest :
         given("A Simple Message Bus") {
             val messageBus = SimpleMessageBus<String, Int>()
             `when`("A subscription is done") {
-                messageBus.subscribe(String::class) { it.length }
+                messageBus.subscribe(
+                    String::class,
+                    object : MessageHandler<String, Int> {
+                        override suspend fun handle(message: String) = message.length
+                    },
+                )
                 and("A message is sent to the bus") {
                     val message = "Hello, world!"
                     val result = messageBus.handle(message).await()