add curse of panic

src/main/java/me/youhavetrouble/enchantio/Enchantio.java

@@ -26,6 +26,9 @@ public final class Enchantio extends JavaPlugin {
         if (EnchantioConfig.ENCHANTS.containsKey(SmeltingEnchant.KEY)) {
             getServer().getPluginManager().registerEvents(new SmeltingListener(), this);
         }
+        if (EnchantioConfig.ENCHANTS.containsKey(PanicEnchant.KEY)) {
+            getServer().getPluginManager().registerEvents(new PanicListener(), this);
+        }
     }
 
     @Override

src/main/java/me/youhavetrouble/enchantio/EnchantioConfig.java

@@ -228,6 +228,43 @@ public class EnchantioConfig {
             ENCHANTS.put(SmeltingEnchant.KEY, smeltingEnchant);
         }
 
+        ConfigurationSection cursesSection = configuration.getConfigurationSection("curses");
+        if (cursesSection == null) {
+            cursesSection = configuration.createSection("curses");
+        }
+
+        ConfigurationSection panicSection = cursesSection.getConfigurationSection("panic");
+        if (panicSection == null) {
+            panicSection = cursesSection.createSection("panic");
+        }
+
+        PanicEnchant panicEnchant = new PanicEnchant(
+                getInt(panicSection, "anvilCost", 1),
+                getInt(panicSection, "weight", 2),
+                EnchantmentRegistryEntry.EnchantmentCost.of(
+                        getInt(panicSection, "minimumCost.base", 0),
+                        getInt(panicSection, "minimumCost.additionalPerLevel", 3)
+                ),
+                EnchantmentRegistryEntry.EnchantmentCost.of(
+                        getInt(panicSection, "maximumCost.base", 20),
+                        getInt(panicSection, "maximumCost.additionalPerLevel", 1)
+                ),
+                getBoolean(panicSection, "canGetFromEnchantingTable", true),
+                getTagsFromList(getStringList(
+                        panicSection,
+                        "supportedItemTags",
+                        List.of(
+                                "#minecraft:enchantable/armor"
+                        )
+                )),
+                getInt(panicSection, "maxLevel", 1),
+                getDouble(panicSection, "panicChancePerLevel", 0.025)
+        );
+
+        if (getBoolean(panicSection, "enabled", true)) {
+            ENCHANTS.put(PanicEnchant.KEY, panicEnchant);
+        }
+
         configuration.save(configFile);
     }
 

src/main/java/me/youhavetrouble/enchantio/enchants/PanicEnchant.java

@@ -0,0 +1,106 @@
+package me.youhavetrouble.enchantio.enchants;
+
+import io.papermc.paper.registry.data.EnchantmentRegistryEntry;
+import io.papermc.paper.registry.keys.tags.EnchantmentTagKeys;
+import io.papermc.paper.registry.tag.TagKey;
+import io.papermc.paper.tag.TagEntry;
+import net.kyori.adventure.key.Key;
+import net.kyori.adventure.text.Component;
+import org.bukkit.enchantments.Enchantment;
+import org.bukkit.inventory.EquipmentSlotGroup;
+import org.bukkit.inventory.ItemType;
+
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.Set;
+
+@SuppressWarnings("UnstableApiUsage")
+public class PanicEnchant implements EnchantioEnchant {
+
+    public static final Key KEY = Key.key("enchantio:panic_curse");
+
+    private final int anvilCost, weight, maxLevel;
+    private final EnchantmentRegistryEntry.EnchantmentCost minimumCost;
+    private final EnchantmentRegistryEntry.EnchantmentCost maximumCost;
+    private final double panicChancePerLevel;
+    private final Set<TagEntry<ItemType>> supportedItemTags;
+    private final Set<TagKey<Enchantment>> enchantTagKeys = new HashSet<>();
+
+    public PanicEnchant(
+            int anvilCost,
+            int weight,
+            EnchantmentRegistryEntry.EnchantmentCost minimumCost,
+            EnchantmentRegistryEntry.EnchantmentCost maximumCost,
+            boolean canGetFromEnchantingTable,
+            Set<TagEntry<ItemType>> supportedItemTags,
+            int maxLevel,
+            double panicChancePerLevel
+    ) {
+        this.anvilCost = anvilCost;
+        this.weight = weight;
+        this.maxLevel = maxLevel;
+        this.minimumCost = minimumCost;
+        this.maximumCost = maximumCost;
+        this.supportedItemTags = supportedItemTags;
+        this.panicChancePerLevel = panicChancePerLevel;
+        if (canGetFromEnchantingTable) {
+            enchantTagKeys.add(EnchantmentTagKeys.IN_ENCHANTING_TABLE);
+        }
+        enchantTagKeys.add(EnchantmentTagKeys.CURSE);
+    }
+
+    @Override
+    public Key getKey() {
+        return KEY;
+    }
+
+    @Override
+    public Component getDescription() {
+        return Component.translatable("enchantio.enchant.panic_curse", "Curse of Panic");
+    }
+
+    @Override
+    public int getAnvilCost() {
+        return anvilCost;
+    }
+
+    @Override
+    public int getMaxLevel() {
+        return maxLevel;
+    }
+
+    @Override
+    public int getWeight() {
+        return weight;
+    }
+
+    @Override
+    public EnchantmentRegistryEntry.EnchantmentCost getMinimumCost() {
+        return minimumCost;
+    }
+
+    @Override
+    public EnchantmentRegistryEntry.EnchantmentCost getMaximumCost() {
+        return maximumCost;
+    }
+
+    @Override
+    public Iterable<EquipmentSlotGroup> getActiveSlots() {
+        return Set.of(EquipmentSlotGroup.ARMOR);
+    }
+
+    @Override
+    public Set<TagEntry<ItemType>> getSupportedItems() {
+        return supportedItemTags;
+    }
+
+    @Override
+    public Set<TagKey<Enchantment>> getEnchantTagKeys() {
+        return Collections.unmodifiableSet(enchantTagKeys);
+    }
+
+    public double getPanicChancePerLevel() {
+        return panicChancePerLevel;
+    }
+
+}

src/main/java/me/youhavetrouble/enchantio/events/PlayerPanicEvent.java

@@ -0,0 +1,68 @@
+package me.youhavetrouble.enchantio.events;
+
+import org.bukkit.entity.Player;
+import org.bukkit.event.Cancellable;
+import org.bukkit.event.HandlerList;
+import org.bukkit.event.player.PlayerEvent;
+import org.bukkit.inventory.ItemStack;
+import org.jetbrains.annotations.NotNull;
+
+import java.util.Collections;
+import java.util.List;
+
+/**
+ * Called when a player with the Panic enchantment takes damage and their hotbar is scrambled.
+ */
+public class PlayerPanicEvent extends PlayerEvent implements Cancellable {
+
+    private static final HandlerList HANDLERS = new HandlerList();
+
+    private boolean cancelled = false;
+    private final List<ItemStack> scrambledItems;
+
+    public PlayerPanicEvent(@NotNull Player player, @NotNull List<ItemStack> scrambledItems) {
+        super(player);
+        this.scrambledItems = scrambledItems;
+    }
+
+    /**
+     * Get the hotbar items that will be set for the player. List order will be preserved.
+     * @return The unmodifiable list of hotbar items
+     */
+    public List<ItemStack> getScrambledItems() {
+        return Collections.unmodifiableList(scrambledItems);
+    }
+
+    /**
+     * Set the new player hotbar items. List order will be preserved. List must have a size of 9.
+     * @param scrambledItems The new hotbar items
+     */
+    public void setScrambledItems(@NotNull List<ItemStack> scrambledItems) {
+        if (scrambledItems.size() != 9) {
+            throw new IllegalArgumentException("Scrambled items must have a size of 9");
+        }
+        this.scrambledItems.clear();
+        this.scrambledItems.addAll(scrambledItems);
+    }
+
+    @Override
+    public @NotNull HandlerList getHandlers() {
+        return HANDLERS;
+    }
+
+    @Override
+    public boolean isCancelled() {
+        return cancelled;
+    }
+
+    @Override
+    public void setCancelled(boolean cancel) {
+        this.cancelled = cancel;
+    }
+
+    @NotNull
+    public static HandlerList getHandlerList() {
+        return HANDLERS;
+    }
+
+}

src/main/java/me/youhavetrouble/enchantio/listeners/PanicListener.java

@@ -0,0 +1,76 @@
+package me.youhavetrouble.enchantio.listeners;
+
+import io.papermc.paper.registry.RegistryAccess;
+import io.papermc.paper.registry.RegistryKey;
+import me.youhavetrouble.enchantio.EnchantioConfig;
+import me.youhavetrouble.enchantio.enchants.BeheadingEnchant;
+import me.youhavetrouble.enchantio.enchants.EnchantioEnchant;
+import me.youhavetrouble.enchantio.enchants.PanicEnchant;
+import me.youhavetrouble.enchantio.events.PlayerPanicEvent;
+import org.bukkit.Bukkit;
+import org.bukkit.Registry;
+import org.bukkit.enchantments.Enchantment;
+import org.bukkit.entity.Player;
+import org.bukkit.event.EventHandler;
+import org.bukkit.event.EventPriority;
+import org.bukkit.event.Listener;
+import org.bukkit.event.entity.EntityDamageEvent;
+import org.bukkit.inventory.EquipmentSlot;
+import org.bukkit.inventory.EquipmentSlotGroup;
+import org.bukkit.inventory.ItemStack;
+import org.bukkit.inventory.PlayerInventory;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+import java.util.concurrent.ThreadLocalRandom;
+
+public class PanicListener implements Listener {
+
+    private final Registry<Enchantment> registry = RegistryAccess.registryAccess().getRegistry(RegistryKey.ENCHANTMENT);
+    private final Enchantment panic = registry.get(PanicEnchant.KEY);
+
+    @EventHandler(ignoreCancelled = true, priority = EventPriority.NORMAL)
+    public void onPlayerPanic(EntityDamageEvent event) {
+        if (panic == null) return;
+
+        if (!(event.getEntity() instanceof Player player)) return;
+
+        EnchantioEnchant enchant = EnchantioConfig.ENCHANTS.get(PanicEnchant.KEY);
+        if (!(enchant instanceof PanicEnchant panicEnchant)) return;
+
+        PlayerInventory inventory = player.getInventory();
+        ItemStack highestPanicEnchantItem = null;
+
+        for (ItemStack item : inventory.getArmorContents()) {
+            if (item == null) continue;
+            if (item.containsEnchantment(panic)) {
+                if (highestPanicEnchantItem == null) {
+                    highestPanicEnchantItem = item;
+                } else if (item.getEnchantmentLevel(panic) > highestPanicEnchantItem.getEnchantmentLevel(panic)) {
+                    highestPanicEnchantItem = item;
+                }
+            }
+        }
+
+        if (highestPanicEnchantItem == null) return;
+
+        double chance = highestPanicEnchantItem.getEnchantmentLevel(panic) * panicEnchant.getPanicChancePerLevel();
+
+        if (ThreadLocalRandom.current().nextDouble() > chance) return;
+
+        List<ItemStack> hotbarItems = new ArrayList<>(Arrays.stream(inventory.getContents()).toList().subList(0, 9));
+        Collections.shuffle(hotbarItems, ThreadLocalRandom.current());
+
+        PlayerPanicEvent playerPanicEvent = new PlayerPanicEvent(player, hotbarItems);
+        Bukkit.getPluginManager().callEvent(playerPanicEvent);
+        if (playerPanicEvent.isCancelled()) return;
+
+        for (int i = 0; i < 9; i++) {
+            inventory.setItem(i, playerPanicEvent.getScrambledItems().get(i));
+        }
+
+    }
+
+}