Create SelectEntityGUI that allows to select an entity from all living creatures.

It displays mobs in two ways: as Mob eggs or as Mob Heads.

src/main/java/world/bentobox/challenges/panel/util/SelectEntityGUI.java

@@ -0,0 +1,275 @@
+package world.bentobox.challenges.panel.util;
+
+
+import org.apache.commons.lang.WordUtils;
+import org.bukkit.Material;
+import org.bukkit.entity.EntityType;
+import org.bukkit.inventory.ItemStack;
+import java.util.*;
+import java.util.function.BiConsumer;
+
+import world.bentobox.bentobox.api.panels.PanelItem;
+import world.bentobox.bentobox.api.panels.builders.PanelBuilder;
+import world.bentobox.bentobox.api.panels.builders.PanelItemBuilder;
+import world.bentobox.bentobox.api.user.User;
+import world.bentobox.challenges.utils.HeadLib;
+
+
+/**
+ * This GUI allows to select single entity and return it via Consumer.
+ */
+public class SelectEntityGUI
+{
+	public SelectEntityGUI(User user, BiConsumer<Boolean, EntityType> consumer)
+	{
+		this(user, Collections.emptySet(), true, consumer);
+	}
+
+
+	public SelectEntityGUI(User user, Set<EntityType> excludedEntities, boolean asEggs, BiConsumer<Boolean, EntityType> consumer)
+	{
+		this.consumer = consumer;
+		this.user = user;
+		this.asEggs = asEggs;
+
+		this.entities = new ArrayList<>(EntityType.values().length);
+
+		for (EntityType entityType : EntityType.values())
+		{
+			if (entityType.isAlive() && !excludedEntities.contains(entityType))
+			{
+				this.entities.add(entityType);
+			}
+		}
+
+		// Sort mobs by their name for easier search.
+		this.entities.sort(Comparator.comparing(Enum::name));
+
+		this.build(0);
+	}
+
+
+// ---------------------------------------------------------------------
+// Section: Methods
+// ---------------------------------------------------------------------
+
+
+	/**
+	 * This method builds
+	 */
+	private void build(int pageIndex)
+	{
+		PanelBuilder panelBuilder = new PanelBuilder().user(this.user).name(this.user.getTranslation("challenges.gui.choose-entity-title"));
+
+		// Maximal elements in page.
+		final int MAX_ELEMENTS = 36;
+
+		final int correctPage;
+
+		if (pageIndex < 0)
+		{
+			correctPage = this.entities.size() / MAX_ELEMENTS;
+		}
+		else if (pageIndex > (this.entities.size() / MAX_ELEMENTS))
+		{
+			correctPage = 0;
+		}
+		else
+		{
+			correctPage = pageIndex;
+		}
+
+		// Navigation buttons
+
+		panelBuilder.item(3,
+			new PanelItemBuilder().
+				icon(Material.SIGN).
+				name(this.user.getTranslation("challenges.gui.buttons.previous")).
+				clickHandler( (panel, user1, clickType, slot) -> {
+					this.build(correctPage - 1);
+					return true;
+				}).build());
+
+		panelBuilder.item(4,
+			new PanelItemBuilder().
+				icon(Material.OAK_DOOR).
+				name(this.user.getTranslation("challenges.gui.buttons.return")).
+				clickHandler( (panel, user1, clickType, slot) -> {
+					this.consumer.accept(false, null);
+					return true;
+				}).build());
+
+		panelBuilder.item(5,
+			new PanelItemBuilder().
+				icon(Material.SIGN).
+				name(this.user.getTranslation("challenges.gui.buttons.next")).
+				clickHandler( (panel, user1, clickType, slot) -> {
+					this.build(correctPage + 1);
+					return true;
+				}).build());
+
+		int entitiesIndex = MAX_ELEMENTS * correctPage;
+
+		// I want first row to be only for navigation and return button.
+		int index = 9;
+
+		while (entitiesIndex < ((correctPage + 1) * MAX_ELEMENTS) &&
+			entitiesIndex < this.entities.size())
+		{
+			panelBuilder.item(index++, this.createEntityButton(this.entities.get(entitiesIndex++)));
+		}
+
+		panelBuilder.build();
+
+		panelBuilder.build();
+	}
+
+
+	/**
+	 * This method builds PanelItem for given entity.
+	 * @param entity Entity which PanelItem must be created.
+	 * @return new PanelItem for given Entity.
+	 */
+	private PanelItem createEntityButton(EntityType entity)
+	{
+		return new PanelItemBuilder().
+			name(WordUtils.capitalize(entity.name().toLowerCase().replace("_", " "))).
+			icon(this.asEggs ? this.getEntityEgg(entity) : this.getEntityHead(entity)).
+			clickHandler((panel, user1, clickType, slot) -> {
+				this.consumer.accept(true, entity);
+				return true;
+			}).build();
+	}
+
+
+	/**
+	 * This method transforms entity into egg or block that corresponds given entity. If entity egg is not
+	 * found, then it is replaced by block that represents entity or barrier block.
+	 * @param entity Entity which egg must be returned.
+	 * @return ItemStack that may be egg for given entity.
+	 */
+	private ItemStack getEntityEgg(EntityType entity)
+	{
+		ItemStack itemStack;
+
+		switch (entity)
+		{
+			case PIG_ZOMBIE:
+				itemStack = new ItemStack(Material.ZOMBIE_PIGMAN_SPAWN_EGG);
+				break;
+			case ENDER_DRAGON:
+				itemStack = new ItemStack(Material.DRAGON_EGG);
+				break;
+			case WITHER:
+				itemStack = new ItemStack(Material.SOUL_SAND);
+				break;
+			case PLAYER:
+				itemStack = new ItemStack(Material.PLAYER_HEAD);
+				break;
+			case MUSHROOM_COW:
+				itemStack = new ItemStack(Material.MOOSHROOM_SPAWN_EGG);
+				break;
+			case SNOWMAN:
+				itemStack = new ItemStack(Material.CARVED_PUMPKIN);
+				break;
+			case IRON_GOLEM:
+				itemStack = new ItemStack(Material.IRON_BLOCK);
+				break;
+			case ARMOR_STAND:
+				itemStack = new ItemStack(Material.ARMOR_STAND);
+				break;
+			default:
+				Material material = Material.getMaterial(entity.name() + "_SPAWN_EGG");
+
+				if (material == null)
+				{
+					itemStack = new ItemStack(Material.BARRIER);
+				}
+				else
+				{
+					itemStack = new ItemStack(material);
+				}
+
+				break;
+		}
+
+		return itemStack;
+	}
+
+
+	/**
+	 * This method transforms entity into player head with skin that corresponds given entity. If entity head
+	 * is not found, then it is replaced by barrier block.
+	 * @param entity Entity which head must be returned.
+	 * @return ItemStack that may be head for given entity.
+	 */
+	private ItemStack getEntityHead(EntityType entity)
+	{
+		ItemStack itemStack;
+
+		switch (entity)
+		{
+			case PLAYER:
+				itemStack = new ItemStack(Material.PLAYER_HEAD);
+				break;
+			case WITHER_SKELETON:
+				itemStack = new ItemStack(Material.WITHER_SKELETON_SKULL);
+				break;
+			case ARMOR_STAND:
+				itemStack = new ItemStack(Material.ARMOR_STAND);
+				break;
+			case SKELETON:
+				itemStack = new ItemStack(Material.SKELETON_SKULL);
+				break;
+			case GIANT:
+			case ZOMBIE:
+				itemStack = new ItemStack(Material.ZOMBIE_HEAD);
+				break;
+			case CREEPER:
+				itemStack = new ItemStack(Material.CREEPER_HEAD);
+				break;
+			case ENDER_DRAGON:
+				itemStack = new ItemStack(Material.DRAGON_HEAD);
+				break;
+			default:
+				HeadLib head = HeadLib.getHead(entity.name());
+
+				if (head == null)
+				{
+					itemStack = new ItemStack(Material.BARRIER);
+				}
+				else
+				{
+					itemStack = head.toItemStack();
+				}
+				break;
+		}
+
+		return itemStack;
+	}
+
+
+// ---------------------------------------------------------------------
+// Section: Variables
+// ---------------------------------------------------------------------
+
+	/**
+	 * This variable stores consumer.
+	 */
+	private BiConsumer<Boolean, EntityType> consumer;
+
+	/**
+	 * User who runs GUI.
+	 */
+	private User user;
+
+	/**
+	 * This variable stores if mobs must be displayed as Eggs "true" or Heads "false".
+	 */
+	private boolean asEggs;
+
+	/**
+	 * Entities that must be in list.
+	 */
+	private List<EntityType> entities;
+}