implement simple drop system

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

@@ -0,0 +1,57 @@
+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

@@ -0,0 +1,16 @@
+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

@@ -0,0 +1,99 @@
+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);
+                    }
+                }
+            }
+        }
+    }
+}