more ASM work...

src/main/java/com/falsepattern/lib/asm/ASMUtil.java

@@ -1,5 +1,8 @@
 package com.falsepattern.lib.asm;
 
+import com.falsepattern.lib.asm.exceptions.AsmClassNotFoundException;
+import com.falsepattern.lib.asm.exceptions.AsmFieldNotFoundException;
+import com.falsepattern.lib.asm.exceptions.AsmMethodNotFoundException;
 import com.falsepattern.lib.internal.CoreLoadingPlugin;
 import com.falsepattern.lib.mapping.MappingManager;
 import com.falsepattern.lib.mapping.types.MappingType;
@@ -9,9 +12,15 @@ import com.falsepattern.lib.mapping.types.UniversalField;
 import com.falsepattern.lib.mapping.types.UniversalMethod;
 import lombok.SneakyThrows;
 import lombok.val;
+import org.apache.logging.log4j.Logger;
+import org.objectweb.asm.ClassReader;
+import org.objectweb.asm.ClassVisitor;
+import org.objectweb.asm.ClassWriter;
+import org.objectweb.asm.Opcodes;
 import org.objectweb.asm.tree.ClassNode;
 import org.objectweb.asm.tree.FieldNode;
 import org.objectweb.asm.tree.MethodNode;
+import org.objectweb.asm.util.CheckClassAdapter;
 
 import java.util.Arrays;
 import java.util.Objects;
@@ -133,6 +142,18 @@ public class ASMUtil {
         }
     }
 
+    public static ClassNode parseClass(byte[] bytes, int readerFlags) {
+        val cn = new ClassNode(Opcodes.ASM5);
+        val reader = new ClassReader(bytes);
+        reader.accept(cn, readerFlags);
+        return cn;
+    }
+
+    public static byte[] serializeClass(ClassNode cn, int writerFlags) {
+        val writer = new ClassWriter(writerFlags);
+        return writer.toByteArray();
+    }
+
     public static boolean anyEquals(String str, String... options) {
         for (val option: options) {
             if (Objects.equals(str, option)) {

src/main/java/com/falsepattern/lib/asm/IClassNodeTransformer.java

@@ -0,0 +1,13 @@
+package com.falsepattern.lib.asm;
+
+import org.objectweb.asm.tree.ClassNode;
+
+public interface IClassNodeTransformer {
+    String getName();
+    boolean shouldTransform(ClassNode cn, String transformedName, boolean obfuscated);
+    default int internalSortingOrder() {
+        return 0;
+    }
+
+    void transform(ClassNode cn, String transformedName, boolean obfuscated);
+}

src/main/java/com/falsepattern/lib/asm/SmartTransformer.java

@@ -0,0 +1,55 @@
+package com.falsepattern.lib.asm;
+
+import com.falsepattern.lib.asm.exceptions.AsmTransformException;
+import com.falsepattern.lib.internal.CoreLoadingPlugin;
+import lombok.val;
+import org.apache.logging.log4j.Logger;
+import org.objectweb.asm.ClassReader;
+import org.objectweb.asm.ClassWriter;
+
+import net.minecraft.launchwrapper.IClassTransformer;
+
+import java.util.ArrayList;
+import java.util.Comparator;
+import java.util.List;
+
+/**
+ * An ASM transformation dispatcher utility, inspired by mixins.
+ */
+public interface SmartTransformer extends IClassTransformer {
+    Logger logger();
+    List<IClassNodeTransformer> transformers();
+    @Override
+    default byte[] transform(String name, String transformedName, byte[] bytes) {
+        if (bytes == null) {
+            return null;
+        }
+        val transformers = new ArrayList<IClassNodeTransformer>();
+        val cn = ASMUtil.parseClass(bytes, ClassReader.EXPAND_FRAMES);
+        for (val transformer: transformers()) {
+            if (transformer.shouldTransform(cn, transformedName, CoreLoadingPlugin.isObfuscated())) {
+                transformers.add(transformer);
+            }
+        }
+        if (transformers.isEmpty()) {
+            return bytes;
+        }
+        transformers.sort(Comparator.comparingInt(IClassNodeTransformer::internalSortingOrder));
+        val log = logger();
+        for (val transformer: transformers) {
+            log.debug("Patching {} with {}...", transformedName, transformer.getName());
+            try {
+                transformer.transform(cn, transformedName, CoreLoadingPlugin.isObfuscated());
+            } catch (RuntimeException | Error t) {
+                log.error("Error transforming {} with {}: {}", transformedName, transformer.getName(), t.getMessage());
+                throw t;
+            } catch (Throwable t) {
+                log.error("Error transforming {} with {}: {}", transformedName, transformer.getName(), t.getMessage());
+                throw new RuntimeException(t);
+            }
+        }
+        val result = ASMUtil.serializeClass(cn, ClassWriter.COMPUTE_FRAMES);
+        log.debug("Patched {} successfully.", transformedName);
+        return result;
+    }
+}

src/main/java/com/falsepattern/lib/asm/exceptions/AsmClassNotFoundException.java

@@ -1,4 +1,4 @@
-package com.falsepattern.lib.asm;
+package com.falsepattern.lib.asm.exceptions;
 
 public class AsmClassNotFoundException extends AsmTransformException {
     public AsmClassNotFoundException(final String clazz) {

src/main/java/com/falsepattern/lib/asm/exceptions/AsmFieldNotFoundException.java

@@ -1,4 +1,4 @@
-package com.falsepattern.lib.asm;
+package com.falsepattern.lib.asm.exceptions;
 
 public class AsmFieldNotFoundException extends AsmTransformException {
     public AsmFieldNotFoundException(final String field) {

src/main/java/com/falsepattern/lib/asm/exceptions/AsmMethodNotFoundException.java

@@ -1,4 +1,4 @@
-package com.falsepattern.lib.asm;
+package com.falsepattern.lib.asm.exceptions;
 
 public class AsmMethodNotFoundException extends AsmTransformException {
     public AsmMethodNotFoundException(final String method) {

src/main/java/com/falsepattern/lib/asm/exceptions/AsmTransformException.java

@@ -1,4 +1,4 @@
-package com.falsepattern.lib.asm;
+package com.falsepattern.lib.asm.exceptions;
 
 public class AsmTransformException extends RuntimeException {
     public AsmTransformException(final String message) {