Brewery/src/com/dre/brewery/listeners/InventoryListener.java

package com.dre.brewery.listeners;

import org.bukkit.event.EventHandler;
import org.bukkit.event.EventPriority;
import org.bukkit.event.Listener;
import org.bukkit.event.inventory.BrewEvent;
import org.bukkit.inventory.BrewerInventory;
import org.bukkit.inventory.ItemStack;
import org.bukkit.Material;

import com.dre.brewery.Brew;

public class InventoryListener implements Listener {

	@EventHandler(priority = EventPriority.HIGH)
	public void onBrew(BrewEvent event) {
		int slot = 0;
		BrewerInventory inv = event.getContents();
		ItemStack item;
		boolean custom = false;
		Boolean[] contents = new Boolean[3];
		while (slot < 3) {
			item = inv.getItem(slot);
			contents[slot] = false;
			if (item != null) {
				if (item.getType() == Material.POTION) {
					if (item.hasItemMeta()) {
						int uid = Brew.getUID(item);
						if (Brew.potions.containsKey(uid)) {
							// has custom potion in "slot"
							if (Brew.get(uid).canDistill()) {
								// is further distillable
								contents[slot] = true;
								custom = true;
							}
						}
					}
				}
			}
			slot++;
		}
		if (custom) {
			event.setCancelled(true);
			Brew.distillAll(inv, contents);
		}

	}

}