refactor(#18): Provide access to latest sender

This change adds a `sender` property to the `Context` interface to
provide processes access to the sender of the latest received message.

Please note that methods like `hold()` and `interrupt()` may change the value
of this property.

1 files changed, 8 insertions, 0 deletions

diff --git a/opendc-core/src/main/kotlin/com/atlarge/opendc/simulator/Context.kt b/opendc-core/src/main/kotlin/com/atlarge/opendc/simulator/Context.kt
index c89bdb59..13170256 100644
--- a/opendc-core/src/main/kotlin/com/atlarge/opendc/simulator/Context.kt
+++ b/opendc-core/src/main/kotlin/com/atlarge/opendc/simulator/Context.kt
@@ -51,6 +51,14 @@ interface Context<S, out M> {
     val delta: Duration
 
     /**
+     * The sender of the last received message or `null` in case the process has not received any messages yet.
+     *
+     * Note that this property is only guaranteed to be correct when accessing after a single suspending call. Methods
+     * like `hold()` and `interrupt()` may change the value of this property.
+     */
+    val sender: Entity<*, *>?
+
+    /**
      * The observable state of the entity bound to this scope.
      */
     var state: S