package de.blablubbabc.test2;

import org.bukkit.Location;
import org.bukkit.Material;
import org.bukkit.block.Block;
import org.bukkit.craftbukkit.v1_14_R1.entity.CraftVillager;
import org.bukkit.entity.Villager;
import org.bukkit.entity.Villager.Profession;
import org.bukkit.event.EventHandler;
import org.bukkit.event.Listener;
import org.bukkit.event.player.PlayerInteractEvent;
import org.bukkit.inventory.EquipmentSlot;
import org.bukkit.inventory.ItemStack;

public class NoAIVillagerTest implements Listener {

    @EventHandler
    public void onPlayerInteractEvent(PlayerInteractEvent event) {
        if (event.getHand() != EquipmentSlot.HAND) return;
        if (!event.hasBlock()) return;
        if (!event.hasItem()) return;
        ItemStack item = event.getItem();
        if (item.getType() != Material.CARROT) return;

        Block block = event.getClickedBlock();
        Location spawnLoc = block.getLocation().add(0.5D, 1.0D, 0.5D);
        block.getWorld().spawn(spawnLoc, Villager.class, (e) -> {
            e.setPersistent(false);
            e.setAI(false);
            e.setProfession(Profession.FARMER);

            // onGround is false initially.
            // Spigot's entity activation feature has a bypass for all falling entities (does not deactivate them while
            // they are falling, even if they are outside the activation range).
            // Since this entity has NoAi, it will never update its onGround flag.
            // -> Entity keeps getting ignored by the entity activation feature, and therefore keeps getting ticked even
            // outside the activation range. This results in even worse performance than compared to mob with AI that
            // does not bypass Spigot's entity activation feature.
            // See related ticket: https://hub.spigotmc.org/jira/browse/SPIGOT-3947

            // Workaround idea: Manually set the onGround flag to true
            // Possible alternative for reproducing this issue without relying on CB / NMS: Set the villager's NoAI flag
            // after a short delay (after the villager has set its onGround flag 'naturally' to true).
            ((CraftVillager) e).getHandle().onGround = true;

            // New problem now:
            // Spigot will occasionally skip ticking an supposedly active entity (every 4 ticks, see the entity
            // activation feature's checkIfActive function).
            // So instead of doing the entity's full tick, the entity's inactiveTick is called.
            // For villagers this will call the mob's 'mobTick' function, if Spigot's 'tick-inactive-villagers' setting
            // is enabled (it is by default). (This is supposed to retain some villager behavior: Found this
            // https://hub.spigotmc.org/jira/browse/SPIGOT-3846)
            // The problem with that however:
            // mobTick runs the villager's AI behaviors added in MC 1.14.
            // But in vanilla minecraft this function will not get called for NoAI mobs (see call hierarchy:
            // EntityLiving#tick -> EntityLiving#movementTick (checks NoAI flag) -> EntityInsentient#doTick ->
            // EntityVillager#mobTick).
            // But with Spigot this function will occasionally get run for NoAI mobs as well (with all its AI related
            // effects, such as working places getting searched, validated, professions updated, etc.).

            // Possible solution:
            // Check the mob's NoAI state before calling mobTick during the villager's inactive tick.
        });
    }
}