Bound item damage work and handle invalid metadata

AdvancedCore/src/main/java/com/bencodez/advancedcore/api/misc/PlayerManager.java

@@ -3,6 +3,7 @@
 import java.nio.charset.StandardCharsets;
 import java.util.UUID;
 import java.util.concurrent.ThreadLocalRandom;
+import java.util.random.RandomGenerator;
 import java.util.function.Consumer;
 
 import org.bukkit.Bukkit;
@@ -38,37 +39,79 @@ private PlayerManager() {
 	}
 
 	public boolean damageItemInHand(Player player, int damage) {
+		if (player == null || player.getInventory() == null) {
+			return false;
+		}
 		ItemStack itemInHand = player.getInventory().getItemInMainHand();
+		if (itemInHand == null || itemInHand.getType() == Material.AIR) {
+			return false;
+		}
 		ItemMeta meta = itemInHand.getItemMeta();
+		if (!(meta instanceof Damageable)) {
+			return false;
+		}
 		boolean isUnbreakable = false;
 		try {
 			isUnbreakable = meta.isUnbreakable();
 		} catch (NoSuchMethodError e) {
 			// Older versions don't have isUnbreakable(), ignore safely
 		}
-		if (meta instanceof Damageable && !isUnbreakable) {
+		if (!isUnbreakable) {
 			Damageable dMeta = (Damageable) meta;
-			int level = itemInHand.getEnchantmentLevel(MiscUtils.getInstance().getEnchant("UNBREAKING", "DURABILITY"));
-			int chance = (100 / (level + 1));
-			int addedDamage = 0;
-			for (int i = 0; i < damage; i++) {
-				if (chance == 100 || ThreadLocalRandom.current().nextInt(100) < chance) {
-					addedDamage++;
-				}
+			if (damage <= 0) {
+				return true;
 			}
+			int level = itemInHand.getEnchantmentLevel(MiscUtils.getInstance().getEnchant("UNBREAKING", "DURABILITY"));
+			int chance = (int) (100L / (Math.max(0, (long) level) + 1));
+			long currentDamage = Math.max(0L, dMeta.getDamage());
+			long hitsToBreak = Math.max(1L, (long) itemInHand.getType().getMaxDurability() - currentDamage);
+			int addedDamage = sampleDamage(damage, chance, hitsToBreak, ThreadLocalRandom.current());
 			if (addedDamage > 0) {
-				dMeta.setDamage(dMeta.getDamage() + addedDamage);
-				itemInHand.setItemMeta(dMeta);
-				if (dMeta.getDamage() > (itemInHand.getType().getMaxDurability())) {
+				if (addedDamage >= hitsToBreak) {
 					player.getInventory().setItemInMainHand(new ItemStack(Material.AIR));
 					return false;
 				}
+				dMeta.setDamage((int) (currentDamage + addedDamage));
+				itemInHand.setItemMeta(dMeta);
 			}
 			return true;
 		}
 		return false;
 	}
 
+	// The cap is the number of successful hits needed to remove the item.
+	static int sampleDamage(int attempts, int chance, long cap, RandomGenerator random) {
+		if (attempts <= 0 || chance <= 0) {
+			return 0;
+		}
+		int limit = (int) Math.min(cap, (long) attempts);
+		if (chance >= 100) {
+			return limit;
+		}
+		int hits = 0;
+		if (attempts <= 256) {
+			for (int i = 0; i < attempts && hits < limit; i++) {
+				if (random.nextInt(100) < chance) {
+					hits++;
+				}
+			}
+			return hits;
+		}
+		// Geometric gaps count failures before each success. Work is bounded by the
+		// item's remaining durability rather than the attacker supplied attempts.
+		double logFailure = Math.log1p(-chance / 100.0);
+		long remaining = attempts;
+		while (hits < limit && remaining > 0) {
+			long failures = (long) Math.floor(Math.log1p(-random.nextDouble()) / logFailure);
+			if (failures >= remaining) {
+				break;
+			}
+			remaining -= failures + 1;
+			hits++;
+		}
+		return hits;
+	}
+
 	/**
 	 * @deprecated Use {@link UuidLookup#getPlayerName(AdvancedCoreUser, String)}.
 	 */

AdvancedCore/src/test/java/com/bencodez/advancedcore/api/misc/PlayerManagerDamageItemTest.java

@@ -0,0 +1,133 @@
+package com.bencodez.advancedcore.api.misc;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTimeout;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.anyInt;
+import static org.mockito.ArgumentMatchers.argThat;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.mockStatic;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import java.time.Duration;
+import java.util.Random;
+
+import org.bukkit.Material;
+import org.bukkit.entity.Player;
+import org.bukkit.inventory.ItemStack;
+import org.bukkit.inventory.PlayerInventory;
+import org.bukkit.inventory.meta.Damageable;
+import org.junit.jupiter.api.Test;
+import org.mockito.MockedStatic;
+
+class PlayerManagerDamageItemTest {
+	private final PlayerManager manager = PlayerManager.getInstance();
+
+	@Test
+	void missingItemAndMetaAreSafe() {
+		assertFalse(manager.damageItemInHand(null, 1));
+		Player player = mock(Player.class);
+		PlayerInventory inventory = mock(PlayerInventory.class);
+		when(player.getInventory()).thenReturn(inventory);
+		assertFalse(manager.damageItemInHand(player, 1));
+		ItemStack item = mock(ItemStack.class);
+		when(inventory.getItemInMainHand()).thenReturn(item);
+		when(item.getType()).thenReturn(Material.AIR);
+		assertFalse(manager.damageItemInHand(player, 1));
+		when(item.getType()).thenReturn(Material.DIAMOND_SWORD);
+		assertFalse(manager.damageItemInHand(player, 1));
+	}
+
+	@Test
+	void nonPositiveDamageAndUnbreakableItemDoNotChangeDurability() {
+		Fixture fixture = new Fixture(3);
+		assertTrue(manager.damageItemInHand(fixture.player, 0));
+		assertTrue(manager.damageItemInHand(fixture.player, -100));
+		verify(fixture.meta, never()).setDamage(anyInt());
+		when(fixture.meta.isUnbreakable()).thenReturn(true);
+		assertFalse(manager.damageItemInHand(fixture.player, 100));
+		verify(fixture.item, never()).setItemMeta(any());
+	}
+
+	@Test
+	void removesItemWhenDamageReachesMaterialLimit() {
+		Fixture fixture = new Fixture(Material.LEGACY_WOOD_SWORD.getMaxDurability() - 1);
+		try (MockedStatic<MiscUtils> misc = mockStatic(MiscUtils.class)) {
+			misc.when(MiscUtils::getInstance).thenReturn(mock(MiscUtils.class));
+			when(fixture.item.getEnchantmentLevel(null)).thenReturn(0);
+			assertFalse(manager.damageItemInHand(fixture.player, 1));
+			verify(fixture.inventory).setItemInMainHand(argThat(item -> item.getType() == Material.AIR));
+			verify(fixture.meta, never()).setDamage(anyInt());
+		}
+	}
+
+	@Test
+	void appliesDamageAndRemovesItemPastMaximum() {
+		Fixture fixture = new Fixture(56);
+		try (MockedStatic<MiscUtils> misc = mockStatic(MiscUtils.class)) {
+			MiscUtils utils = mock(MiscUtils.class);
+			misc.when(MiscUtils::getInstance).thenReturn(utils);
+			when(fixture.item.getEnchantmentLevel(null)).thenReturn(0);
+			assertTrue(manager.damageItemInHand(fixture.player, 2));
+			verify(fixture.meta).setDamage(58);
+			verify(fixture.item).setItemMeta(fixture.meta);
+			Fixture breaking = new Fixture(59);
+			assertFalse(manager.damageItemInHand(breaking.player, 1));
+			verify(breaking.inventory).setItemInMainHand(any(ItemStack.class));
+			Fixture overflow = new Fixture(Integer.MAX_VALUE);
+			assertFalse(manager.damageItemInHand(overflow.player, Integer.MAX_VALUE));
+			verify(overflow.inventory).setItemInMainHand(any(ItemStack.class));
+		}
+	}
+
+	@Test
+	void extremeDamageFinishesPromptlyWithUnbreaking() {
+		Fixture fixture = new Fixture(0);
+		try (MockedStatic<MiscUtils> misc = mockStatic(MiscUtils.class)) {
+			MiscUtils utils = mock(MiscUtils.class);
+			misc.when(MiscUtils::getInstance).thenReturn(utils);
+			when(fixture.item.getEnchantmentLevel(null)).thenReturn(1);
+			assertTimeout(Duration.ofSeconds(2), () ->
+					assertFalse(manager.damageItemInHand(fixture.player, Integer.MAX_VALUE)));
+			verify(fixture.inventory).setItemInMainHand(any(ItemStack.class));
+		}
+	}
+
+	@Test
+	void boundedSamplerRetainsBinomialMoments() {
+		Random random = new Random(47291);
+		int count = 20_000;
+		double sum = 0;
+		double squared = 0;
+		for (int i = 0; i < count; i++) {
+			int hits = PlayerManager.sampleDamage(1_000, 50, 1_001, random);
+			sum += hits;
+			squared += (double) hits * hits;
+		}
+		double mean = sum / count;
+		double variance = squared / count - mean * mean;
+		assertEquals(500, mean, 1);
+		assertEquals(250, variance, 10);
+		assertEquals(0, PlayerManager.sampleDamage(100, 0, 10, random));
+		assertEquals(10, PlayerManager.sampleDamage(Integer.MAX_VALUE, 100, 10, random));
+	}
+
+	private static final class Fixture {
+		final Player player = mock(Player.class);
+		final PlayerInventory inventory = mock(PlayerInventory.class);
+		final ItemStack item = mock(ItemStack.class);
+		final Damageable meta = mock(Damageable.class);
+
+		Fixture(int currentDamage) {
+			when(player.getInventory()).thenReturn(inventory);
+			when(inventory.getItemInMainHand()).thenReturn(item);
+			when(item.getType()).thenReturn(Material.LEGACY_WOOD_SWORD);
+			when(item.getItemMeta()).thenReturn(meta);
+			when(meta.getDamage()).thenReturn(currentDamage);
+		}
+	}
+}