Merge pull request #345 from CivMC/anti-derailment

A partial fix for minecart derailment

plugins/simpleadminhacks-paper/src/main/java/com/programmerdan/minecraft/simpleadminhacks/hacks/basic/AntiDerailment.java

@@ -0,0 +1,99 @@
+package com.programmerdan.minecraft.simpleadminhacks.hacks.basic;
+
+import com.destroystokyo.paper.event.entity.EntityRemoveFromWorldEvent;
+import com.programmerdan.minecraft.simpleadminhacks.SimpleAdminHacks;
+import com.programmerdan.minecraft.simpleadminhacks.framework.BasicHack;
+import com.programmerdan.minecraft.simpleadminhacks.framework.BasicHackConfig;
+import net.minecraft.world.entity.vehicle.AbstractMinecart;
+import org.bukkit.Tag;
+import org.bukkit.block.Block;
+import org.bukkit.craftbukkit.v1_18_R2.entity.CraftEntity;
+import org.bukkit.craftbukkit.v1_18_R2.entity.CraftMinecart;
+import org.bukkit.entity.Entity;
+import org.bukkit.entity.Minecart;
+import org.bukkit.entity.Player;
+import org.bukkit.event.EventHandler;
+import org.bukkit.event.vehicle.VehicleMoveEvent;
+import org.bukkit.util.Vector;
+
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * Prevents minecarts from derailing by forcibly slowing them down to 8m/s when they would otherwise derail
+ */
+public class AntiDerailment extends BasicHack {
+
+	private Map<Minecart, Vector> previousTickMinecartVelocity;
+
+	public AntiDerailment(SimpleAdminHacks plugin, BasicHackConfig config) {
+		super(plugin, config);
+	}
+
+	@Override
+	public void onEnable() {
+		super.onEnable();
+		previousTickMinecartVelocity = new HashMap<>();
+	}
+
+	@Override
+	public void onDisable() {
+		super.onDisable();
+		previousTickMinecartVelocity.clear();
+	}
+
+	@EventHandler
+	public void on(EntityRemoveFromWorldEvent e) {
+		if (e.getEntity() instanceof Minecart minecart) {
+			previousTickMinecartVelocity.remove(minecart);
+		}
+	}
+
+	@EventHandler
+	public void onDerailment(VehicleMoveEvent e) {
+		// This method is EXTREMELY fucked but basically if it detects a super fast minecart is going to derail, it will
+		// undo one tick of movement and redo it at 8m/s (the default minecart speed)
+		// To do this it also needs to store the velocity from the previous tick to recreate the movement properly
+
+		if (!(e.getVehicle() instanceof Minecart minecart)) {
+			return;
+		}
+
+		List<Entity> passengers = minecart.getPassengers();
+		if (passengers.size() != 1 || !(passengers.get(0) instanceof Player)) {
+			previousTickMinecartVelocity.put(minecart, minecart.getVelocity());
+			return;
+		}
+
+		if (minecart.getMaxSpeed() == 0.4D || !previousTickMinecartVelocity.containsKey(minecart)) {
+			previousTickMinecartVelocity.put(minecart, minecart.getVelocity());
+			return;
+		}
+
+		Block fromBlock = e.getFrom().getBlock();
+		if (!Tag.RAILS.isTagged(fromBlock.getType())) {
+			previousTickMinecartVelocity.put(minecart, minecart.getVelocity());
+			return;
+		}
+
+		Block block = e.getTo().getBlock();
+		if (Tag.RAILS.isTagged(block.getType())) {
+			previousTickMinecartVelocity.put(minecart, minecart.getVelocity());
+
+			if (e.getTo().getY() < e.getFrom().getY()) {
+				return;
+			}
+			return;
+		}
+
+		AbstractMinecart handle = ((CraftMinecart) minecart).getHandle();
+		handle.setPos(e.getFrom().getX(), e.getFrom().getY(), e.getFrom().getZ());
+		minecart.setVelocity(previousTickMinecartVelocity.get(minecart));
+		double maxSpeed = minecart.getMaxSpeed();
+		minecart.setMaxSpeed(0.4D); // 8m/s, default minecart speed
+		handle.tick();
+		minecart.setMaxSpeed(maxSpeed);
+		previousTickMinecartVelocity.put(minecart, minecart.getVelocity());
+	}
+}

plugins/simpleadminhacks-paper/src/main/resources/config.yml

@@ -545,3 +545,5 @@ hacks:
     enabled: true
     minSpeed: 0.1125
     maxSpeed: 0.438827582278 # 18.5m/s
+  AntiDerailment:
+    enabled: true