Add reliquary decomposition (aka strongbox).

src/main/java/emu/grasscutter/game/combine/CombineManger.java

 package emu.grasscutter.game.combine;
 
+import emu.grasscutter.Grasscutter;
+import emu.grasscutter.data.DataLoader;
 import emu.grasscutter.data.GameData;
 import emu.grasscutter.data.common.ItemParamData;
 import emu.grasscutter.data.excels.CombineData;
 import emu.grasscutter.game.inventory.GameItem;
+import emu.grasscutter.game.inventory.Inventory;
 import emu.grasscutter.game.inventory.ItemType;
 import emu.grasscutter.game.player.Player;
 import emu.grasscutter.game.props.ActionReason;
 import emu.grasscutter.net.proto.RetcodeOuterClass;
+import emu.grasscutter.net.proto.RetcodeOuterClass.Retcode;
 import emu.grasscutter.server.game.GameServer;
 import emu.grasscutter.server.packet.send.PacketCombineFormulaDataNotify;
 import emu.grasscutter.server.packet.send.PacketCombineRsp;
+import emu.grasscutter.server.packet.send.PacketReliquaryDecomposeRsp;
+import emu.grasscutter.utils.Utils;
 import it.unimi.dsi.fastutil.Pair;
+import it.unimi.dsi.fastutil.ints.Int2ObjectMap;
+import it.unimi.dsi.fastutil.ints.Int2ObjectOpenHashMap;
 
+import java.io.InputStreamReader;
+import java.io.Reader;
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.List;
 
+import com.google.gson.reflect.TypeToken;
+
 public class CombineManger {
     private final GameServer gameServer;
+	private final static Int2ObjectMap<List<Integer>> reliquaryDecomposeData = new Int2ObjectOpenHashMap<>();
 
     public GameServer getGameServer() {
         return gameServer;
@@ -27,6 +41,22 @@ public class CombineManger {
         this.gameServer = gameServer;
     }
 
+    public static void initialize() {
+		// Read the data we need for strongbox.
+		try (Reader fileReader = new InputStreamReader(DataLoader.load("ReliquaryDecompose.json"))) {
+			List<ReliquaryDecomposeEntry> decomposeEntries = Grasscutter.getGsonFactory().fromJson(fileReader, TypeToken.getParameterized(Collection.class, ReliquaryDecomposeEntry.class).getType());
+
+			for (ReliquaryDecomposeEntry entry : decomposeEntries) {
+				reliquaryDecomposeData.put(entry.getConfigId(), entry.getItems());
+			}
+
+			Grasscutter.getLogger().debug("Loaded {} reliquary decompose entries.", reliquaryDecomposeData.size());
+		}
+		catch (Exception ex) {
+			Grasscutter.getLogger().error("Unable to load reliquary decompose data.", ex);
+		}
+	}
+
     public boolean unlockCombineDiagram(Player player, GameItem diagramItem) {
 		// Make sure this is actually a diagram.
 		if (!diagramItem.getItemData().getItemUse().get(0).getUseOp().equals("ITEM_USE_UNLOCK_COMBINE")) {
@@ -87,4 +117,44 @@ public class CombineManger {
         return result;
     }
 
+    public synchronized void decomposeReliquaries(Player player, int configId, int count, List<Long> input) {
+        // Check if the configId is legal.
+        List<Integer> possibleDrops = reliquaryDecomposeData.get(configId);
+        if (possibleDrops == null) {
+            player.sendPacket(new PacketReliquaryDecomposeRsp(Retcode.RET_RELIQUARY_DECOMPOSE_PARAM_ERROR));
+            return;
+        }
+        
+        // Check if the number of input items matches the output count.
+        if (input.size() != count * 3) {
+            player.sendPacket(new PacketReliquaryDecomposeRsp(Retcode.RET_RELIQUARY_DECOMPOSE_PARAM_ERROR));
+            return;
+        }
+
+        // Check if all the input reliquaries actually are in the player's inventory.
+        for (long guid : input) {
+            if (player.getInventory().getItemByGuid(guid) == null) {
+                player.sendPacket(new PacketReliquaryDecomposeRsp(Retcode.RET_RELIQUARY_DECOMPOSE_PARAM_ERROR));
+                return;
+            }
+        }
+
+        // Delete the input reliquaries.
+        for (long guid : input) {
+            player.getInventory().removeItem(guid);
+        }
+
+        // Generate outoput reliquaries.
+        List<Long> resultItems = new ArrayList<>();
+        for (int i = 0; i < count; i++) {
+            int itemId = Utils.drawRandomListElement(possibleDrops);
+			GameItem newReliquary = new GameItem(itemId, 1);
+
+            player.getInventory().addItem(newReliquary);
+            resultItems.add(newReliquary.getGuid());
+        }
+
+        // Send packet.
+        player.sendPacket(new PacketReliquaryDecomposeRsp(resultItems));
+    }
 }

src/main/java/emu/grasscutter/game/combine/ReliquaryDecomposeEntry.java

+package emu.grasscutter.game.combine;
+
+import java.util.List;
+
+public class ReliquaryDecomposeEntry {
+    private int configId;
+    private List<Integer> items;
+
+    public int getConfigId() {
+        return configId;
+    }
+    public void setConfigId(int configId) {
+        this.configId = configId;
+    }
+
+    public List<Integer> getItems() {
+        return items;
+    }
+    public void setItems(List<Integer> items) {
+        this.items = items;
+    } 
+}

src/main/java/emu/grasscutter/server/game/GameServer.java

@@ -92,6 +92,7 @@ public final class GameServer extends KcpServer {
 		EnergyManager.initialize();
 		StaminaManager.initialize();
 		CookingManager.initialize();
+		CombineManger.initialize();
 
 		this.address = address;
 		this.packetHandler = new GameServerPacketHandler(PacketHandler.class);

src/main/java/emu/grasscutter/server/packet/recv/HandlerReliquaryDecomposeReq.java

+package emu.grasscutter.server.packet.recv;
+
+import emu.grasscutter.net.packet.Opcodes;
+import emu.grasscutter.net.packet.PacketOpcodes;
+import emu.grasscutter.net.proto.ReliquaryDecomposeReqOuterClass.ReliquaryDecomposeReq;
+import emu.grasscutter.net.packet.PacketHandler;
+import emu.grasscutter.server.game.GameSession;
+
+@Opcodes(PacketOpcodes.ReliquaryDecomposeReq)
+public class HandlerReliquaryDecomposeReq extends PacketHandler {
+	@Override
+	public void handle(GameSession session, byte[] header, byte[] payload) throws Exception {
+		ReliquaryDecomposeReq req = ReliquaryDecomposeReq.parseFrom(payload);
+		session.getServer().getCombineManger().decomposeReliquaries(session.getPlayer(), req.getConfigId(), req.getTargetCount(), req.getGuidListList());
+	}
+}

src/main/java/emu/grasscutter/server/packet/send/PacketReliquaryDecomposeRsp.java

+package emu.grasscutter.server.packet.send;
+
+import java.util.List;
+
+import emu.grasscutter.net.packet.BasePacket;
+import emu.grasscutter.net.packet.PacketOpcodes;
+import emu.grasscutter.net.proto.ReliquaryDecomposeRspOuterClass.ReliquaryDecomposeRsp;
+import emu.grasscutter.net.proto.RetcodeOuterClass.Retcode;
+
+public class PacketReliquaryDecomposeRsp extends BasePacket {
+	public PacketReliquaryDecomposeRsp(Retcode retcode) {
+		super(PacketOpcodes.ReliquaryDecomposeRsp);
+
+		ReliquaryDecomposeRsp proto = ReliquaryDecomposeRsp.newBuilder()
+				.setRetcode(retcode.getNumber())
+				.build();
+		
+		this.setData(proto);
+	}
+
+	public PacketReliquaryDecomposeRsp(List<Long> output) {
+		super(PacketOpcodes.ReliquaryDecomposeRsp);
+
+		ReliquaryDecomposeRsp proto = ReliquaryDecomposeRsp.newBuilder()
+				.addAllGuidList(output)
+				.build();
+		
+		this.setData(proto);
+	}
+}

src/main/java/emu/grasscutter/utils/Utils.java

@@ -399,4 +399,13 @@ public final class Utils {
 		// Should never happen.
 		return list.get(0);
 	}
+
+	/***
+	 * Draws a random element from the given list, following a uniform probability distribution.
+	 * @param list The list from which to draw the element.
+	 * @return A randomly drawn element from the given list.
+	 */
+	public static <T> T drawRandomListElement(List<T> list) {
+		return drawRandomListElement(list, null);
+	}
 }

src/main/resources/defaults/data/ReliquaryDecompose.json

+[
+    {
+        "configId": 1,
+        "comment": "Gladiator",
+        "items": [75513, 75514, 75523, 75524, 75533, 75534, 75543, 75544, 75553, 75554]
+    },
+    {
+        "configId": 2,
+        "comment": "Wanderer's Troupe",
+        "items": [77513, 77514, 77523, 77524, 77533, 77534, 77543, 77544, 77553, 77554]
+    },
+    {
+        "configId": 3,
+        "comment": "Bloodstained",
+        "items": [82513, 82514, 82523, 82524, 82533, 82534, 82543, 82544, 82553, 82554]
+    },
+    {
+        "configId": 4,
+        "comment": "Noblesse",
+        "items": [81513, 81514, 81523, 81524, 81533, 81534, 81543, 81544, 81553, 81554]
+    }
+]
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