refactor: Rework monitor interfaces

2 files changed, 23 insertions, 16 deletions

diff --git a/opendc/opendc-core/src/main/kotlin/com/atlarge/opendc/core/services/ServiceRegistry.kt b/opendc/opendc-core/src/main/kotlin/com/atlarge/opendc/core/services/ServiceRegistry.kt
index a036a705..75aa778f 100644
--- a/opendc/opendc-core/src/main/kotlin/com/atlarge/opendc/core/services/ServiceRegistry.kt
+++ b/opendc/opendc-core/src/main/kotlin/com/atlarge/opendc/core/services/ServiceRegistry.kt
@@ -25,10 +25,15 @@
 package com.atlarge.opendc.core.services
 
 /**
- * A service registry for a datacenter zone.
+ * An immutable service registry interface.
  */
 public interface ServiceRegistry {
     /**
+     * The keys in this registry.
+     */
+    public val keys: Collection<ServiceKey<*>>
+
+    /**
      * Determine if this map contains the service with the specified [ServiceKey].
      *
      * @param key The key of the service to check for.
@@ -41,12 +46,18 @@ public interface ServiceRegistry {
      *
      * @param key The key of the service to obtain.
      * @return The references to the service.
-     * @throws IllegalArgumentException if the key does not exists in the map.
+     * @throws IllegalArgumentException if the key does not exist in the map.
      */
     public operator fun <T : Any> get(key: ServiceKey<T>): T
 
     /**
-     * Register the specified [ServiceKey] in this registry.
+     * Return the result of associating the specified [service] with the given [key] in this registry.
      */
-    public operator fun <T : Any> set(key: ServiceKey<T>, service: T): ServiceRegistry
+    public fun <T : Any> put(key: ServiceKey<T>, service: T): ServiceRegistry
 }
+
+/**
+ * Construct an empty [ServiceRegistry].
+ */
+@Suppress("FunctionName")
+public fun ServiceRegistry(): ServiceRegistry = ServiceRegistryImpl(emptyMap())
diff --git a/opendc/opendc-core/src/main/kotlin/com/atlarge/opendc/core/services/ServiceRegistryImpl.kt b/opendc/opendc-core/src/main/kotlin/com/atlarge/opendc/core/services/ServiceRegistryImpl.kt
index e3fa171d..0686ebaf 100644
--- a/opendc/opendc-core/src/main/kotlin/com/atlarge/opendc/core/services/ServiceRegistryImpl.kt
+++ b/opendc/opendc-core/src/main/kotlin/com/atlarge/opendc/core/services/ServiceRegistryImpl.kt
@@ -27,22 +27,18 @@ package com.atlarge.opendc.core.services
 /**
  * Default implementation of the [ServiceRegistry] interface.
  */
-public class ServiceRegistryImpl : ServiceRegistry {
-    /**
-     * The map containing the registered services.
-     */
-    private val services: MutableMap<ServiceKey<*>, Any> = mutableMapOf()
+internal class ServiceRegistryImpl(private val map: Map<ServiceKey<*>, Any>) : ServiceRegistry {
+    override val keys: Collection<ServiceKey<*>>
+        get() = map.keys
 
-    override fun <T : Any> set(key: ServiceKey<T>, service: T) {
-        services[key] = service
-    }
-
-    override fun contains(key: ServiceKey<*>): Boolean = key in services
+    override fun contains(key: ServiceKey<*>): Boolean = key in map
 
     override fun <T : Any> get(key: ServiceKey<T>): T {
         @Suppress("UNCHECKED_CAST")
-        return services[key] as T
+        return map[key] as T
     }
 
-    override fun toString(): String = services.toString()
+    override fun <T : Any> put(key: ServiceKey<T>, service: T): ServiceRegistry = ServiceRegistryImpl(map.plus(key to service))
+
+    override fun toString(): String = map.toString()
 }