Instanced Utils (#632)

* Instanced Utils

* Use default equals and toString

1 files changed, 104 insertions, 0 deletions

diff --git a/src/main/java/de/hysky/skyblocker/utils/InstancedUtils.java b/src/main/java/de/hysky/skyblocker/utils/InstancedUtils.java
new file mode 100644
index 00000000..1da4fa11
--- /dev/null
+++ b/src/main/java/de/hysky/skyblocker/utils/InstancedUtils.java
@@ -0,0 +1,104 @@
+package de.hysky.skyblocker.utils;
+
+import java.lang.invoke.MethodHandle;
+import java.lang.invoke.MethodHandles;
+import java.lang.reflect.Field;
+import java.lang.runtime.ObjectMethods;
+import java.util.Arrays;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.stream.Stream;
+
+import org.slf4j.Logger;
+
+import com.mojang.logging.LogUtils;
+
+import it.unimi.dsi.fastutil.objects.ObjectOpenHashSet;
+
+/**
+ * @implNote If implementing any of these onto a class, ensure that all subclasses have an implementation of the methods too.
+ */
+public class InstancedUtils {
+	private static final Logger LOGGER = LogUtils.getLogger();
+	private static final Map<Class<?>, MethodHandle> EQUALS_CACHE = new ConcurrentHashMap<>();
+	private static final Map<Class<?>, MethodHandle> HASH_CODE_CACHE = new ConcurrentHashMap<>();
+	private static final Map<Class<?>, MethodHandle> TO_STRING_CACHE = new ConcurrentHashMap<>();
+
+	public static MethodHandle equals(Class<?> type) {
+		if (EQUALS_CACHE.containsKey(type)) return EQUALS_CACHE.get(type);
+
+		try {
+			Field[] fields = getClassFields(type);
+			MethodHandle[] getters = getFieldGetters(fields);
+
+			//The field names param can be anything as equals and hashCode don't care about it.
+			MethodHandle equalsHandle = (MethodHandle) ObjectMethods.bootstrap(MethodHandles.lookup(), "equals", MethodHandle.class, type, "", getters);
+
+			EQUALS_CACHE.put(type, equalsHandle);
+
+			return equalsHandle;
+		} catch (Throwable t) {
+			LOGGER.error("[Skyblocked Instanced Utils] Failed to create an equals method handle.", t);
+
+			throw new RuntimeException();
+		}
+	}
+
+	public static MethodHandle hashCode(Class<?> type) {
+		if (HASH_CODE_CACHE.containsKey(type)) return HASH_CODE_CACHE.get(type);
+
+		try {
+			Field[] fields = getClassFields(type);
+			MethodHandle[] getters = getFieldGetters(fields);
+
+			//The field names param can be anything as equals and hashCode don't care about it.
+			MethodHandle hashCodeHandle = (MethodHandle) ObjectMethods.bootstrap(MethodHandles.lookup(), "hashCode", MethodHandle.class, type, "", getters);
+
+			HASH_CODE_CACHE.put(type, hashCodeHandle);
+
+			return hashCodeHandle;
+		} catch (Throwable t) {
+			LOGGER.error("[Skyblocked Instanced Utils] Failed to create a hashCode method handle.", t);
+
+			throw new RuntimeException();
+		}
+	}
+
+	public static MethodHandle toString(Class<?> type) {
+		if (TO_STRING_CACHE.containsKey(type)) return TO_STRING_CACHE.get(type);
+
+		try {
+			Field[] fields = getClassFields(type);
+			MethodHandle[] getters = getFieldGetters(fields);
+			String fieldNames = String.join(";", Arrays.stream(fields).map(Field::getName).toArray(String[]::new));
+
+			MethodHandle toStringHandle = (MethodHandle) ObjectMethods.bootstrap(MethodHandles.lookup(), "toString", MethodHandle.class, type, fieldNames, getters);
+
+			TO_STRING_CACHE.put(type, toStringHandle);
+
+			return toStringHandle;
+		} catch (Throwable t) {
+			LOGGER.error("[Skyblocked Instanced Utils] Failed to create a toString method handle.", t);
+
+			throw new RuntimeException();
+		}
+	}
+
+	private static Field[] getClassFields(Class<?> type) {
+		return Stream.concat(Arrays.stream(type.getDeclaredFields()), Arrays.stream(type.getFields())).distinct().toArray(Field[]::new);
+	}
+
+	private static MethodHandle[] getFieldGetters(Field[] fields) throws Throwable {
+		ObjectOpenHashSet<MethodHandle> handles = new ObjectOpenHashSet<>();
+
+		for (Field field : fields) {
+			field.setAccessible(true);				
+
+			MethodHandle getter = MethodHandles.lookup().unreflectGetter(field);
+
+			handles.add(getter);
+		}
+
+		return handles.toArray(MethodHandle[]::new);
+	}
+}