package de.blablubbabc.test2;

import org.bukkit.Bukkit;
import org.bukkit.Material;
import org.bukkit.inventory.ItemStack;
import org.bukkit.inventory.PlayerInventory;
import org.bukkit.plugin.Plugin;

/*
 * Some dummy reason for periodically modifying the player's inventory: The
 * plugin slowly replenishes arrow stacks. It runs very frequently to increase
 * the chance of running into this issue.
 * Essential here: It uses PlayerInventory.get/setStorageContents() to apply
 * inventory changes. setStorageContents copies the items (see
 * CraftInventory.setItem and CraftItemStack.asNMSCopy).
 *
 * The player might currently charge a trident item while the active trident
 * item is replaced with a new ItemStack instance. Minecraft remembers the
 * itemstack that was used at the beginning of the charge (see
 * EntityHuman.activeItem). When checking if the player is still holding the
 * currently charging item, minecraft compares the active item's material with
 * the currently held item. Since the material is still the same after the
 * inventory got updated, minecraft will not abort the charging.
 * However, once the trident is thrown minecraft tries to remove it from the
 * player's inventory by searching for the exact ItemStack instance. This
 * fails, since the ItemStack is no longer the same instance.
 * The consequence is that the trident is thrown (and can then be picked up by
 * the player again), while no trident item is removed from the player's
 * inventory. The result is that the player is able to duplicate the trident
 * item this way.
 */
public class TridentDuplicationBug {

    public void onEnable(Plugin plugin) {
        Bukkit.getScheduler().runTaskTimer(plugin, () -> {
            Bukkit.getOnlinePlayers().forEach(player -> {
                PlayerInventory playerInventory = player.getInventory();
                ItemStack[] newPlayerContents = playerInventory.getStorageContents();
                int size = newPlayerContents.length;
                for (int slot = 0; slot < size; ++slot) {
                    ItemStack slotItem = newPlayerContents[slot];
                    if (slotItem != null && slotItem.getType() == Material.ARROW
                            && slotItem.getAmount() < slotItem.getMaxStackSize()) {
                        slotItem.setAmount(slotItem.getMaxStackSize());
                    }
                }
                // apply inventory changes:
                playerInventory.setStorageContents(newPlayerContents);
                player.sendMessage("Arrows replenished!");
            });
        }, 20L, 5L);
    }
}