Add event cancellation watcher

1 files changed, 47 insertions, 0 deletions

diff --git a/src/main/java/moe/nea/kowalski/init/EventClassTransformer.java b/src/main/java/moe/nea/kowalski/init/EventClassTransformer.java
new file mode 100644
index 0000000..a80a5b5
--- /dev/null
+++ b/src/main/java/moe/nea/kowalski/init/EventClassTransformer.java
@@ -0,0 +1,47 @@
+package moe.nea.kowalski.init;
+
+import net.minecraft.launchwrapper.IClassTransformer;
+import org.objectweb.asm.ClassReader;
+import org.objectweb.asm.ClassWriter;
+import org.objectweb.asm.Opcodes;
+import org.objectweb.asm.tree.*;
+
+import java.util.ListIterator;
+
+public class EventClassTransformer implements IClassTransformer {
+    @Override
+    public byte[] transform(String name, String transformedName, byte[] basicClass) {
+        if (!"net.minecraftforge.fml.common.eventhandler.Event".equals(name))
+            return basicClass;
+        ClassNode classNode = new ClassNode();
+        ClassReader classReader = new ClassReader(basicClass);
+        classReader.accept(classNode, 0);
+        for (MethodNode method : classNode.methods) {
+            if (method.name.equals("setCanceled")) {
+                transformCancelMethod(method);
+            }
+        }
+        ClassWriter writer = new ClassWriter(0);
+        classNode.accept(writer);
+        return writer.toByteArray();
+    }
+
+    private void transformCancelMethod(MethodNode method) {
+        ListIterator<AbstractInsnNode> iterator =
+                method.instructions.iterator();
+        while (iterator.hasNext()) {
+            AbstractInsnNode insn = iterator.next();
+            if (insn.getOpcode() != Opcodes.PUTFIELD) {
+                continue;
+            }
+            method.instructions.insert(insn, buildCallKowalski());
+        }
+    }
+
+    private InsnList buildCallKowalski() {
+        InsnList insnList = new InsnList();
+        insnList.add(new VarInsnNode(Opcodes.ALOAD, 0));
+        insnList.add(new MethodInsnNode(Opcodes.INVOKESTATIC, "moe/nea/kowalski/Kowalski", "eventIsBeingCancelled", "(Lnet/minecraftforge/fml/common/eventhandler/Event;)V", false));
+        return insnList;
+    }
+}