DisableFogSpider.java

package com.Joedobo27.disablefogspider;


import javassist.CannotCompileException;
import javassist.ClassPool;
import javassist.NotFoundException;
import javassist.expr.ExprEditor;
import javassist.expr.MethodCall;
import org.gotti.wurmunlimited.modloader.classhooks.HookManager;
import org.gotti.wurmunlimited.modloader.interfaces.Initable;
import org.gotti.wurmunlimited.modloader.interfaces.ServerStartedListener;
import org.gotti.wurmunlimited.modloader.interfaces.WurmServerMod;

import java.util.Objects;
import java.util.logging.Level;
import java.util.logging.Logger;

public class DisableFogSpider implements WurmServerMod, Initable, ServerStartedListener {

    private static ClassPool classPool;
    private static Logger logger;

    @Override
    public void init() {
        try {
            boolean fogSpiderDisabled = disableFogSpiderInPoll();

            if (fogSpiderDisabled){
                logger.log(Level.INFO, "Fog Spider creation disabled SUCCESSFUL.");
            }
            else {
                logger.log(Level.INFO, "Fog Spider creation disabled FAILURE.");
            }
        }catch (NotFoundException | CannotCompileException e) {
            logger.log(Level.WARNING, e.getMessage(), e);
        }
    }

    @Override
    public void onServerStarted() {
        JAssistClassData.voidClazz();
    }

    /**
     * Change Zone.poll() to disable the creation of Fog spiders.
     * Use ExprEditor to change getFog() so it always returns Float.MIN_VALUE and thus disables creation.
     * was--
     *      if (this.isOnSurface()) {
     *          if (Server.getWeather().getFog() > 0.5f && Zone.fogSpiders.size() < Zones.worldTileSizeX / 10) {
     *
     * Edit was on bytecode index 322 which goes with line number 534.
     *
     * @return boolean type. Was the change successful?
     * @throws NotFoundException JA related, forwarded.
     * @throws CannotCompileException JA related, forwarded.
     */
    private boolean disableFogSpiderInPoll() throws NotFoundException, CannotCompileException {
        final boolean[] toReturn = new boolean[]{false};
        JAssistClassData forage = new JAssistClassData("com.wurmonline.server.zones.Zone", classPool);
        JAssistMethodData poll =  new JAssistMethodData(forage, "(I)V", "poll");

        poll.getCtMethod().instrument(new ExprEditor() {
            @Override
            public void edit(MethodCall methodCall) throws CannotCompileException {
                if (Objects.equals("getFog", methodCall.getMethodName()) && methodCall.getLineNumber() == 534){
                    logger.log(Level.FINE, "Zone.class, poll(), installed hook at line: " + methodCall.getLineNumber());
                    methodCall.replace("$_ = Float.MIN_VALUE;");
                    toReturn[0] = true;
                }
            }
        });
        return toReturn[0];
    }

    static {
       classPool = HookManager.getInstance().getClassPool();
       logger = Logger.getLogger(DisableFogSpider.class.getName());
    }

}