Final Changes & Fixes | v0.1 IS OUT

src/main/java/ir/wy/wycore/WyCore.java

@@ -1,5 +1,6 @@
 package ir.wy.wycore;
 
+import ir.wy.wycore.gui.*;
 import ir.wy.wycore.Heart;
 import io.papermc.lib.*;
 import lombok.Getter;

src/main/java/ir/wy/wycore/gui/GUI.java

@@ -0,0 +1,10 @@
+package ir.wy.wycore.gui;
+
+import org.bukkit.event.inventory.InventoryClickEvent;
+import org.bukkit.inventory.Inventory;
+import org.bukkit.inventory.InventoryHolder;
+
+public interface GUI extends InventoryHolder {
+    void onInventoryClick(InventoryClickEvent event);
+    void addContent(Inventory inventory);
+}

src/main/java/ir/wy/wycore/gui/PagedGUI.java

@@ -0,0 +1,48 @@
+package ir.wy.wycore.gui;
+
+import ir.wy.wycore.Design;
+import ir.wy.wycore.Item;
+import ir.wy.wycore.utils.InventoryUtils;
+import ir.wy.wycore.utils.ItemStackUtils;
+
+
+import lombok.AllArgsConstructor;
+import org.bukkit.inventory.Inventory;
+import org.bukkit.inventory.ItemStack;
+
+import java.util.Collection;
+import java.util.List;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.stream.Collectors;
+
+@AllArgsConstructor
+public abstract class PagedGUI<T> implements GUI {
+
+
+    private final int page;
+    private final Design design;
+    private final Item previousPage;
+    private final Item nextPage;
+
+    @Override
+    public void addContent(Inventory inventory) {
+        InventoryUtils.fillInventory(inventory, design);
+
+        inventory.setItem(inventory.getSize() - 3, ItemStackUtils.makeItem(nextPage));
+        inventory.setItem(inventory.getSize() - 7, ItemStackUtils.makeItem(previousPage));
+
+        int elementsPerPage = inventory.getSize() - 9;
+        List<T> objects = getPageObjects().stream()
+                .skip((long) (page - 1) * elementsPerPage)
+                .limit(elementsPerPage)
+                .collect(Collectors.toList());
+        AtomicInteger slot = new AtomicInteger(0);
+        for (T t : objects) {
+            inventory.setItem(slot.getAndIncrement(), getItemStack(t));
+        }
+    }
+
+    public abstract Collection<T> getPageObjects();
+
+    public abstract ItemStack getItemStack(T t);
+}