Handle book edit change

common/src/main/java/us/myles/ViaVersion/protocols/protocol1_16_4to1_16_3/Protocol1_16_4To1_16_3.java

@@ -1,13 +1,29 @@
 package us.myles.ViaVersion.protocols.protocol1_16_4to1_16_3;
 
 import us.myles.ViaVersion.api.protocol.Protocol;
+import us.myles.ViaVersion.api.remapper.PacketRemapper;
+import us.myles.ViaVersion.api.type.Type;
 import us.myles.ViaVersion.protocols.protocol1_16_2to1_16_1.ClientboundPackets1_16_2;
 import us.myles.ViaVersion.protocols.protocol1_16_2to1_16_1.ServerboundPackets1_16_2;
 
 public class Protocol1_16_4To1_16_3 extends Protocol<ClientboundPackets1_16_2, ClientboundPackets1_16_2, ServerboundPackets1_16_2, ServerboundPackets1_16_2> {
 
+    public Protocol1_16_4To1_16_3() {
+        super(ClientboundPackets1_16_2.class, ClientboundPackets1_16_2.class, ServerboundPackets1_16_2.class, ServerboundPackets1_16_2.class);
+    }
+
     @Override
     protected void registerPackets() {
-
+        registerIncoming(ServerboundPackets1_16_2.EDIT_BOOK, new PacketRemapper() {
+            @Override
+            public void registerMap() {
+                map(Type.FLAT_VAR_INT_ITEM);
+                map(Type.BOOLEAN);
+                handler(wrapper -> {
+                    int slot = wrapper.read(Type.VAR_INT);
+                    wrapper.write(Type.VAR_INT, slot == 40 ? 1 : 0); // 40 = offhand, everything else assumed as mainhand
+                });
+            }
+        });
     }
 }