Implement buying from mall shop

src/main/java/emu/nebula/server/handlers/HandlerMallShopOrderReq.java

@@ -0,0 +1,40 @@
+package emu.nebula.server.handlers;
+
+import emu.nebula.net.NetHandler;
+import emu.nebula.net.NetMsgId;
+import emu.nebula.proto.MallShopOrder.MallShopOrderReq;
+import emu.nebula.net.HandlerId;
+import emu.nebula.data.GameData;
+import emu.nebula.net.GameSession;
+
+@HandlerId(NetMsgId.mall_shop_order_req )
+public class HandlerMallShopOrderReq extends NetHandler {
+
+    @Override
+    public byte[] handle(GameSession session, byte[] message) throws Exception {
+        // Parse request
+        var req = MallShopOrderReq.parseFrom(message);
+        
+        // Get package data
+        var data = GameData.getMallPackageDataTable().get(req.getId().hashCode());
+        if (data == null) {
+            return session.encodeMsg(NetMsgId.mall_shop_order_failed_ack);
+        }
+        
+        // Buy items
+        var change = session.getPlayer().getInventory().buyItem(
+                data.getCurrencyItemId(),
+                data.getCurrencyItemQty(),
+                data.getProducts(),
+                req.getQty()
+        );
+        
+        if (change == null) {
+            return session.encodeMsg(NetMsgId.mall_shop_order_failed_ack);
+        }
+        
+        // Encode and send
+        return session.encodeMsg(NetMsgId.mall_shop_order_succeed_ack, change.toProto());
+    }
+
+}