1 files changed, 89 insertions, 0 deletions
diff --git a/src/main/kotlin/util/asm/AsmAnnotationUtil.kt b/src/main/kotlin/util/asm/AsmAnnotationUtil.kt
new file mode 100644
index 0000000..fb0e92c
--- /dev/null
+++ b/src/main/kotlin/util/asm/AsmAnnotationUtil.kt
@@ -0,0 +1,89 @@
+package moe.nea.firmament.util.asm
+
+import com.google.common.base.Defaults
+import java.lang.reflect.InvocationHandler
+import java.lang.reflect.Method
+import java.lang.reflect.Proxy
+import org.objectweb.asm.Type
+import org.objectweb.asm.tree.AnnotationNode
+
+object AsmAnnotationUtil {
+	class AnnotationProxy(
+		val originalType: Class<out Annotation>,
+		val annotationNode: AnnotationNode,
+	) : InvocationHandler {
+		val offsets = annotationNode.values.withIndex()
+			.chunked(2)
+			.map { it.first() }
+			.associate { (idx, value) -> value as String to idx + 1 }
+
+		fun nestArrayType(depth: Int, comp: Class<*>): Class<*> =
+			if (depth == 0) comp
+			else java.lang.reflect.Array.newInstance(nestArrayType(depth - 1, comp), 0).javaClass
+
+		fun unmap(
+			value: Any?,
+			comp: Class<*>,
+			depth: Int,
+		): Any? {
+			value ?: return null
+			if (depth > 0)
+				return ((value as List<Any>)
+					.map { unmap(it, comp, depth - 1) } as java.util.List<Any>)
+					.toArray(java.lang.reflect.Array.newInstance(nestArrayType(depth - 1, comp), 0) as Array<*>)
+			if (comp.isEnum) {
+				comp as Class<out Enum<*>>
+				when (value) {
+					is String -> return java.lang.Enum.valueOf(comp, value)
+					is List<*> -> return java.lang.Enum.valueOf(comp, value[1] as String)
+					else -> error("Unknown enum variant $value for $comp")
+				}
+			}
+			when (value) {
+				is Type -> return Class.forName(value.className)
+				is AnnotationNode -> return createProxy(comp as Class<out Annotation>, value)
+				is String, is Boolean, is Byte, is Double, is Int, is Float, is Long, is Short, is Char -> return value
+			}
+			error("Unknown enum variant $value for $comp")
+		}
+
+		fun defaultFor(fullType: Class<*>): Any? {
+			if (fullType.isArray) return java.lang.reflect.Array.newInstance(fullType.componentType, 0)
+			if (fullType.isPrimitive) {
+				return Defaults.defaultValue(fullType)
+			}
+			if (fullType == String::class.java)
+				return ""
+			return null
+		}
+
+		override fun invoke(
+			proxy: Any,
+			method: Method,
+			args: Array<out Any?>?
+		): Any? {
+			val name = method.name
+			val ret = method.returnType
+			val retU = generateSequence(ret) { if (it.isArray) it.componentType else null }
+				.toList()
+			val arrayDepth = retU.size - 1
+			val componentType = retU.last()
+
+			val off = offsets[name]
+			if (off == null) {
+				return defaultFor(ret)
+			}
+			return unmap(annotationNode.values[off], componentType, arrayDepth)
+		}
+	}
+
+	fun <T : Annotation> createProxy(
+		annotationClass: Class<T>,
+		annotationNode: AnnotationNode
+	): T {
+		require(Type.getType(annotationClass) == Type.getType(annotationNode.desc))
+		return Proxy.newProxyInstance(javaClass.classLoader,
+		                              arrayOf(annotationClass),
+		                              AnnotationProxy(annotationClass, annotationNode)) as T
+	}
+}