From 2a5e795203ef50afec7a27984cb40f668b06d2f9 Mon Sep 17 00:00:00 2001
From: Edwin Jakobs <edwin@rndr.studio>
Date: Sun, 7 Nov 2021 15:31:35 +0100
Subject: [PATCH] [orx-olive] Add Once delegate

---
 orx-jvm/orx-olive/src/main/kotlin/OliveProgram.kt | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/orx-jvm/orx-olive/src/main/kotlin/OliveProgram.kt b/orx-jvm/orx-olive/src/main/kotlin/OliveProgram.kt
index 482a66ce..2146d2a4 100644
--- a/orx-jvm/orx-olive/src/main/kotlin/OliveProgram.kt
+++ b/orx-jvm/orx-olive/src/main/kotlin/OliveProgram.kt
@@ -5,8 +5,11 @@ import org.openrndr.Program
 import java.io.File
 import java.nio.file.Files
 import java.nio.file.Paths
+import kotlin.reflect.KProperty
 import kotlin.streams.toList
 
+
+
 open class OliveProgram(private val sourceLocation: String, private val scriptHost: OliveScriptHost, resources: Resources?) : Program() {
     val olive = extend(Olive<OliveProgram>(scriptMode = ScriptMode.OLIVE_PROGRAM, resources = resources)) {
         script = sourceLocation
@@ -14,6 +17,18 @@ open class OliveProgram(private val sourceLocation: String, private val scriptHo
     }
 }
 
+/**
+ * Delegate used to create instances exactly once. Instances survive a script reload.
+ */
+class Once<T:Any>(val build:() -> T) {
+    companion object {
+        private val values = mutableMapOf<String, Any>()
+    }
+    @Suppress("UNCHECKED_CAST")
+    operator fun getValue(thisRef:Any?, property:KProperty<*>) : T = values.getOrPut(property.name) { build() } as T
+}
+
+
 fun stackRootClassName(thread: Thread = Thread.currentThread(), sanitize: Boolean = true): String {
     val root = Thread.currentThread().stackTrace.last()
     val rootClass = root.className