implement simple drop system

data/Drop.json

+[
+  {
+    "monsterId": 20010201,
+    "dropDataList": [
+      {
+        "itemId": 223,
+        "minCount": 1,
+        "maxCount": 100,
+        "minWeight": 0,
+        "maxWeight": 10000
+      }
+    ]
+  }
+]
\ No newline at end of file

src/main/java/emu/grasscutter/game/drop/DropData.java

+package emu.grasscutter.game.drop;
+
+public class DropData {
+    private int minWeight;
+    private int maxWeight;
+    private int itemId;
+    private int minCount;
+    private int maxCount;
+    private boolean share = false;
+
+    public int getItemId() {
+        return itemId;
+    }
+
+    public void setItemId(int itemId) {
+        this.itemId = itemId;
+    }
+
+    public int getMinCount() {
+        return minCount;
+    }
+
+
+    public int getMaxCount() {
+        return maxCount;
+    }
+
+
+    public int getMinWeight() {
+        return minWeight;
+    }
+
+    public int getMaxWeight() {
+        return maxWeight;
+    }
+
+
+    public boolean isShare() {
+        return share;
+    }
+
+    public void setIsShare(boolean share) {
+        this.share = share;
+    }
+
+    public boolean isGive() {
+        return give;
+    }
+
+    private boolean give = false;
+
+    public boolean isExp() {
+        return exp;
+    }
+
+    private boolean exp = false;
+}

src/main/java/emu/grasscutter/game/drop/DropInfo.java

+package emu.grasscutter.game.drop;
+
+import java.util.List;
+
+public class DropInfo {
+    public int getMonsterId() {
+        return monsterId;
+    }
+
+    public List<DropData> getDropDataList() {
+        return dropDataList;
+    }
+
+    private int monsterId;
+    private List<DropData> dropDataList;
+}

src/main/java/emu/grasscutter/game/drop/DropManager.java

+package emu.grasscutter.game.drop;
+
+import com.google.gson.reflect.TypeToken;
+import emu.grasscutter.Grasscutter;
+import emu.grasscutter.data.GameData;
+import emu.grasscutter.data.def.ItemData;
+import emu.grasscutter.game.entity.EntityItem;
+import emu.grasscutter.game.entity.EntityMonster;
+import emu.grasscutter.game.player.Player;
+import emu.grasscutter.server.game.GameServer;
+import emu.grasscutter.utils.Position;
+import emu.grasscutter.utils.Utils;
+import it.unimi.dsi.fastutil.ints.Int2ObjectMap;
+import it.unimi.dsi.fastutil.ints.Int2ObjectOpenHashMap;
+
+import java.io.FileReader;
+import java.util.Collection;
+import java.util.List;
+
+public class DropManager {
+    public GameServer getGameServer() {
+        return gameServer;
+    }
+
+    private final GameServer gameServer;
+
+    public Int2ObjectMap<List<DropData>> getDropData() {
+        return dropData;
+    }
+
+    private final Int2ObjectMap<List<DropData>> dropData;
+
+    public DropManager(GameServer gameServer) {
+        this.gameServer = gameServer;
+        this.dropData = new Int2ObjectOpenHashMap<>();
+        this.load();
+    }
+
+    public synchronized void load() {
+        try (FileReader fileReader = new FileReader(Grasscutter.getConfig().DATA_FOLDER + "Drop.json")) {
+            getDropData().clear();
+            List<DropInfo> banners = Grasscutter.getGsonFactory().fromJson(fileReader, TypeToken.getParameterized(Collection.class, DropInfo.class).getType());
+            if(banners.size() > 0) {
+                for (DropInfo di : banners) {
+                    getDropData().put(di.getMonsterId(), di.getDropDataList());
+                }
+                Grasscutter.getLogger().info("Drop data successfully loaded.");
+            } else {
+                Grasscutter.getLogger().error("Unable to load drop data. Drop data size is 0.");
+            }
+        } catch (Exception e) {
+            // TODO Auto-generated catch block
+            e.printStackTrace();
+        }
+    }
+
+    private void processDrop(DropData dd, EntityMonster em, Player gp) {
+        int target = Utils.randomRange(1, 10000);
+        if (target >= dd.getMinWeight() && target < dd.getMaxWeight()) {
+            ItemData itemData = GameData.getItemDataMap().get(dd.getItemId());
+            int num = Utils.randomRange(dd.getMinCount(), dd.getMaxCount());
+            if (!dd.isGive()) {
+                if (itemData.isEquip()) {
+                    for (int i = 0; i < num; i++) {
+                        float range = (5f + (.1f * num));
+                        Position pos = em.getPosition().clone().addX((float) (Math.random() * range) - (range / 2)).addY(3f).addZ((float) (Math.random() * range) - (range / 2));
+                        EntityItem entity = new EntityItem(em.getScene(), gp, itemData, pos, num, dd.isShare());
+                        if (!dd.isShare())
+                            em.getScene().addEntityToSingleClient(gp, entity);
+                        else
+                            em.getScene().addEntity(entity);
+                    }
+                } else {
+                    Position pos = em.getPosition().clone().addY(3f);
+                    EntityItem entity = new EntityItem(em.getScene(), gp, itemData, pos, num, dd.isShare());
+                    if (!dd.isShare())
+                        em.getScene().addEntityToSingleClient(gp, entity);
+                    else
+                        em.getScene().addEntity(entity);
+                }
+            }
+        }
+    }
+
+    public void callDrop(EntityMonster em) {
+        int id = em.getMonsterData().getId();
+        if (getDropData().containsKey(id)) {
+            for (DropData dd : getDropData().get(id)) {
+                if (dd.isShare())
+                    processDrop(dd, em, null);
+                else {
+                    for (Player gp : em.getScene().getPlayers()) {
+                        processDrop(dd, em, gp);
+                    }
+                }
+            }
+        }
+    }
+}

src/main/java/emu/grasscutter/game/entity/EntityItem.java

@@ -6,7 +6,6 @@ import emu.grasscutter.game.player.Player;
 import emu.grasscutter.game.props.EntityIdType;
 import emu.grasscutter.game.props.PlayerProperty;
 import emu.grasscutter.game.world.Scene;
-import emu.grasscutter.game.world.World;
 import emu.grasscutter.net.proto.AbilitySyncStateInfoOuterClass.AbilitySyncStateInfo;
 import emu.grasscutter.net.proto.AnimatorParameterValueInfoPairOuterClass.AnimatorParameterValueInfoPair;
 import emu.grasscutter.net.proto.EntityAuthorityInfoOuterClass.EntityAuthorityInfo;
@@ -30,14 +29,30 @@ public class EntityItem extends EntityGadget {
 	
 	private final GameItem item;
 	private final long guid;
-	
+
+	private final boolean share;
+
 	public EntityItem(Scene scene, Player player, ItemData itemData, Position pos, int count) {
 		super(scene);
 		this.id = getScene().getWorld().getNextEntityId(EntityIdType.GADGET);
 		this.pos = new Position(pos);
 		this.rot = new Position();
-		this.guid = player.getNextGameGuid();
+		this.guid = player == null ? scene.getWorld().getHost().getNextGameGuid() : player.getNextGameGuid();
+		this.item = new GameItem(itemData, count);
+		this.share = true;
+	}
+
+	// In official game, some drop items are shared to all players, and some other items are independent to all players
+	// For example, if you killed a monster in MP mode, all players could get drops but rarity and number of them are different
+	// but if you broke regional mine, when someone picked up the drop then it disappeared
+	public EntityItem(Scene scene, Player player, ItemData itemData, Position pos, int count, boolean share) {
+		super(scene);
+		this.id = getScene().getWorld().getNextEntityId(EntityIdType.GADGET);
+		this.pos = new Position(pos);
+		this.rot = new Position();
+		this.guid = player == null ? scene.getWorld().getHost().getNextGameGuid() : player.getNextGameGuid();
 		this.item = new GameItem(itemData, count);
+		this.share = share;
 	}
 	
 	@Override
@@ -81,6 +96,10 @@ public class EntityItem extends EntityGadget {
 		return null;
 	}
 
+	public boolean isShare() {
+		return share;
+	}
+
 	@Override
 	public SceneEntityInfo toProto() {
 		EntityAuthorityInfo authority = EntityAuthorityInfo.newBuilder()

src/main/java/emu/grasscutter/game/player/Player.java

 package emu.grasscutter.game.player;
 
-import java.time.Instant;
-import java.util.*;
-
 import dev.morphia.annotations.*;
 import emu.grasscutter.GameConstants;
 import emu.grasscutter.Grasscutter;
-import emu.grasscutter.command.CommandHandler;
 import emu.grasscutter.data.GameData;
 import emu.grasscutter.data.def.PlayerLevelData;
 import emu.grasscutter.database.DatabaseHelper;
-import emu.grasscutter.game.avatar.AvatarProfileData;
-import emu.grasscutter.game.avatar.AvatarStorage;
 import emu.grasscutter.game.Account;
 import emu.grasscutter.game.CoopRequest;
 import emu.grasscutter.game.avatar.Avatar;
+import emu.grasscutter.game.avatar.AvatarProfileData;
+import emu.grasscutter.game.avatar.AvatarStorage;
 import emu.grasscutter.game.entity.EntityItem;
 import emu.grasscutter.game.entity.GameEntity;
 import emu.grasscutter.game.friends.FriendsList;
@@ -34,7 +30,6 @@ import emu.grasscutter.net.proto.HeadImageOuterClass.HeadImage;
 import emu.grasscutter.net.proto.InteractTypeOuterClass.InteractType;
 import emu.grasscutter.net.proto.MpSettingTypeOuterClass.MpSettingType;
 import emu.grasscutter.net.proto.OnlinePlayerInfoOuterClass.OnlinePlayerInfo;
-import emu.grasscutter.net.proto.PlayerApplyEnterMpReasonOuterClass.PlayerApplyEnterMpReason;
 import emu.grasscutter.net.proto.PlayerApplyEnterMpResultNotifyOuterClass;
 import emu.grasscutter.net.proto.PlayerLocationInfoOuterClass.PlayerLocationInfo;
 import emu.grasscutter.net.proto.PlayerWorldLocationInfoOuterClass;
@@ -42,11 +37,12 @@ import emu.grasscutter.net.proto.SocialDetailOuterClass.SocialDetail;
 import emu.grasscutter.server.game.GameServer;
 import emu.grasscutter.server.game.GameSession;
 import emu.grasscutter.server.packet.send.*;
-import emu.grasscutter.utils.Position;
 import emu.grasscutter.utils.DateHelper;
+import emu.grasscutter.utils.Position;
 import it.unimi.dsi.fastutil.ints.Int2ObjectMap;
 import it.unimi.dsi.fastutil.ints.Int2ObjectOpenHashMap;
 
+import java.time.Instant;
 import java.util.*;
 
 @Entity(value = "players", useDiscriminator = false)
@@ -714,19 +710,30 @@ public class Player {
 			return;
 		}
 
-		// Delete
-		entity.getScene().removeEntity(entity);
-
 		// Handle
 		if (entity instanceof EntityItem) {
 			// Pick item
 			EntityItem drop = (EntityItem) entity;
+			if (!drop.isShare()) // check drop owner to avoid someone picked up item in others' world
+			{
+				int dropOwner = (int)(drop.getGuid() >> 32);
+				if (dropOwner != getUid())
+					return;
+			}
+			entity.getScene().removeEntity(entity);
 			GameItem item = new GameItem(drop.getItemData(), drop.getCount());
 			// Add to inventory
 			boolean success = getInventory().addItem(item, ActionReason.SubfieldDrop);
 			if (success) {
-				this.sendPacket(new PacketGadgetInteractRsp(drop, InteractType.INTERACT_PICK_ITEM));
+
+				if (!drop.isShare()) // not shared drop
+					this.sendPacket(new PacketGadgetInteractRsp(drop, InteractType.INTERACT_PICK_ITEM));
+				else
+					this.getScene().broadcastPacket(new PacketGadgetInteractRsp(drop, InteractType.INTERACT_PICK_ITEM));
 			}
+		} else {
+			// Delete directly
+			entity.getScene().removeEntity(entity);
 		}
 
 		return;

src/main/java/emu/grasscutter/game/world/Scene.java

 package emu.grasscutter.game.world;
 
-import java.util.ArrayList;
-import java.util.Collection;
-import java.util.Collections;
-import java.util.HashSet;
-import java.util.Iterator;
-import java.util.LinkedList;
-import java.util.List;
-import java.util.Set;
-
-import org.danilopianini.util.SpatialIndex;
-
 import emu.grasscutter.Grasscutter;
 import emu.grasscutter.data.GameData;
 import emu.grasscutter.data.GameDepot;
-import emu.grasscutter.data.GameResource;
 import emu.grasscutter.data.def.MonsterData;
 import emu.grasscutter.data.def.SceneData;
 import emu.grasscutter.data.def.WorldLevelData;
-import emu.grasscutter.game.entity.EntityAvatar;
-import emu.grasscutter.game.entity.EntityClientGadget;
-import emu.grasscutter.game.entity.EntityGadget;
-import emu.grasscutter.game.entity.EntityMonster;
-import emu.grasscutter.game.entity.GameEntity;
+import emu.grasscutter.game.entity.*;
 import emu.grasscutter.game.player.Player;
 import emu.grasscutter.game.player.TeamInfo;
 import emu.grasscutter.game.props.ClimateType;
@@ -37,10 +21,12 @@ import emu.grasscutter.server.packet.send.PacketEntityFightPropUpdateNotify;
 import emu.grasscutter.server.packet.send.PacketLifeStateChangeNotify;
 import emu.grasscutter.server.packet.send.PacketSceneEntityAppearNotify;
 import emu.grasscutter.server.packet.send.PacketSceneEntityDisappearNotify;
-import emu.grasscutter.utils.Utils;
 import it.unimi.dsi.fastutil.ints.Int2ObjectMap;
 import it.unimi.dsi.fastutil.ints.Int2ObjectMaps;
 import it.unimi.dsi.fastutil.ints.Int2ObjectOpenHashMap;
+import org.danilopianini.util.SpatialIndex;
+
+import java.util.*;
 
 public class Scene {
 	private final World world;
@@ -228,6 +214,11 @@ public class Scene {
 		this.addEntityDirectly(entity);
 		this.broadcastPacket(new PacketSceneEntityAppearNotify(entity));
 	}
+
+	public synchronized void addEntityToSingleClient(Player player, GameEntity entity) {
+		this.addEntityDirectly(entity);
+		player.sendPacket(new PacketSceneEntityAppearNotify(entity));
+	}
 	
 	public synchronized void addEntities(Collection<GameEntity> entities) {
 		for (GameEntity entity : entities) {
@@ -310,6 +301,12 @@ public class Scene {
 	public void killEntity(GameEntity target, int attackerId) {
 		// Packet
 		this.broadcastPacket(new PacketLifeStateChangeNotify(attackerId, target, LifeState.LIFE_DEAD));
+
+		// Reward drop
+		if (target instanceof EntityMonster) {
+			Grasscutter.getGameServer().getDropManager().callDrop((EntityMonster) target);
+		}
+
 		this.removeEntity(target);
 		
 		// Death event

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

 package emu.grasscutter.server.game;
 
-import java.net.InetSocketAddress;
-import java.time.OffsetDateTime;
-import java.util.*;
-import java.util.concurrent.ConcurrentHashMap;
-
 import emu.grasscutter.GameConstants;
 import emu.grasscutter.Grasscutter;
 import emu.grasscutter.command.CommandMap;
 import emu.grasscutter.database.DatabaseHelper;
 import emu.grasscutter.game.Account;
+import emu.grasscutter.game.drop.DropManager;
 import emu.grasscutter.game.dungeons.DungeonManager;
 import emu.grasscutter.game.gacha.GachaManager;
 import emu.grasscutter.game.managers.ChatManager;
@@ -27,6 +23,11 @@ import emu.grasscutter.server.event.internal.ServerStartEvent;
 import emu.grasscutter.server.event.internal.ServerStopEvent;
 import emu.grasscutter.task.TaskMap;
 
+import java.net.InetSocketAddress;
+import java.time.OffsetDateTime;
+import java.util.*;
+import java.util.concurrent.ConcurrentHashMap;
+
 public final class GameServer extends KcpServer {
 	private final InetSocketAddress address;
 	private final GameServerPacketHandler packetHandler;
@@ -42,6 +43,7 @@ public final class GameServer extends KcpServer {
 	private final DungeonManager dungeonManager;
 	private final CommandMap commandMap;
 	private final TaskMap taskMap;
+	private final DropManager dropManager;
 	
 	public GameServer(InetSocketAddress address) {
 		super(address);
@@ -60,6 +62,7 @@ public final class GameServer extends KcpServer {
 		this.dungeonManager = new DungeonManager(this);
 		this.commandMap = new CommandMap(true);
 		this.taskMap = new TaskMap(true);
+		this.dropManager = new DropManager(this);
 		
 		// Schedule game loop.
 		Timer gameLoop = new Timer();
@@ -109,6 +112,10 @@ public final class GameServer extends KcpServer {
 	public MultiplayerManager getMultiplayerManager() {
 		return multiplayerManager;
 	}
+
+	public DropManager getDropManager() {
+		return dropManager;
+	}
 	
 	public DungeonManager getDungeonManager() {
 		return dungeonManager;