Implement buying energy

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

@@ -0,0 +1,30 @@
+package emu.nebula.server.handlers;
+
+import emu.nebula.net.NetHandler;
+import emu.nebula.net.NetMsgId;
+import emu.nebula.proto.EnergyBuy.EnergyBuyResp;
+import emu.nebula.net.HandlerId;
+import emu.nebula.net.GameSession;
+
+@HandlerId(NetMsgId.energy_buy_req)
+public class HandlerEnergyBuyReq extends NetHandler {
+
+    @Override
+    public byte[] handle(GameSession session, byte[] message) throws Exception {
+        // Buy energy
+        var change = session.getPlayer().getInventory().buyEnergy();
+        
+        if (change == null) {
+            return session.encodeMsg(NetMsgId.energy_buy_failed_ack);
+        }
+        
+        // Build response
+        var rsp = EnergyBuyResp.newInstance()
+                .setChange(change.toProto())
+                .setCount(0); // TODO max energy buy count per day
+        
+        // Encode and send
+        return session.encodeMsg(NetMsgId.energy_buy_succeed_ack, rsp);
+    }
+
+}