Custom payload fixes (#687)

* Fix remaining bytes issue of 1.7.10 custom payload

* Properly rewrite 1.7 books to 1.8 books

* Small code cleanup

Author: Beaness

common/src/main/java/com/viaversion/viarewind/protocol/v1_8to1_7_6_10/rewriter/PlayerPacketRewriter1_8.java

@@ -48,6 +48,7 @@
 import com.viaversion.viaversion.api.type.Types;
 import com.viaversion.viaversion.libs.gson.JsonElement;
 import com.viaversion.viaversion.libs.gson.JsonObject;
+import com.viaversion.viaversion.libs.gson.JsonPrimitive;
 import com.viaversion.viaversion.protocols.v1_8to1_9.packet.ClientboundPackets1_8;
 import com.viaversion.viaversion.protocols.v1_8to1_9.packet.ServerboundPackets1_8;
 import com.viaversion.viaversion.util.ComponentUtil;
@@ -788,6 +789,8 @@ public void register() {
             }
         });
 
+        // 1.7.10 custom payload constructor (String, ByteBuf) uses byteBuf.array(), so it sends the whole backing array capacity, not only the written bytes
+        // After reading the proper packet data we discard the remaining bytes
         protocol.registerServerbound(ServerboundPackets1_7_2_5.CUSTOM_PAYLOAD, new PacketHandlers() {
             @Override
             public void register() {
@@ -798,7 +801,27 @@ public void register() {
                     switch (channel) {
                         case "MC|TrSel": {
                             wrapper.passthrough(Types.INT);
-                            wrapper.read(Types.REMAINING_BYTES); // unused data ???
+                            wrapper.read(Types.REMAINING_BYTES); // Discard remaining bytes
+                            break;
+                        }
+                        case "MC|AdvCdm": {
+                            final byte commandBlockType = wrapper.passthrough(Types.BYTE);
+                            if (commandBlockType == 0) { // Block
+                                wrapper.passthrough(Types.INT); // X
+                                wrapper.passthrough(Types.INT); // Y
+                                wrapper.passthrough(Types.INT); // Z
+                            } else if (commandBlockType == 1) { // Minecart
+                                wrapper.passthrough(Types.INT); // Entity id
+                            }
+                            wrapper.passthrough(Types.STRING); // Command
+                            wrapper.write(Types.BOOLEAN, true); // Track output, added in 1.8, default to true
+                            wrapper.read(Types.REMAINING_BYTES); // Discard remaining bytes
+                            break;
+                        }
+                        case "MC|Beacon": {
+                            wrapper.passthrough(Types.INT); // Primary effect
+                            wrapper.passthrough(Types.INT); // Secondary effect
+                            wrapper.read(Types.REMAINING_BYTES); // Discard remaining bytes
                             break;
                         }
                         case "MC|ItemName": {
@@ -815,17 +838,28 @@ public void register() {
                         }
                         case "MC|BEdit":
                         case "MC|BSign": {
+                            final boolean signBook = channel.equals("MC|BSign");
                             final Item book = wrapper.read(RewindTypes.COMPRESSED_NBT_ITEM);
-                            CompoundTag tag = book.tag();
-                            if (tag != null && tag.contains("pages")) {
-                                ListTag<StringTag> pages = tag.getListTag("pages", StringTag.class);
-                                for (int i = 0; i < pages.size(); i++) {
-                                    StringTag page = pages.get(i);
-                                    String value = page.getValue();
-                                    value = ComponentUtil.legacyToJsonString(value);
-                                    page.setValue(value);
+                            wrapper.read(Types.REMAINING_BYTES); // Discard remaining bytes
+
+                            if (book == null) {
+                                wrapper.write(Types.ITEM1_8, null);
+                                break;
+                            }
+
+                            final CompoundTag tag = book.tag();
+                            if (signBook && tag != null && tag.contains("pages")) {
+                                final ListTag<StringTag> pages = tag.getListTag("pages", StringTag.class);
+                                if (pages != null) {
+                                    for (int i = 0; i < pages.size(); i++) {
+                                        final StringTag page = pages.get(i);
+                                        String value = page.getValue();
+                                        value = new JsonPrimitive(value).toString();
+                                        page.setValue(value);
+                                    }
                                 }
                             }
+                            protocol.getItemRewriter().handleItemToServer(wrapper.user(), book);
                             wrapper.write(Types.ITEM1_8, book);
                             break;
                         }