Add basics of GUI

ic_plugin_core/src/main/java/nl/interestingcorner/core/gui/ChestGUI.java

@@ -0,0 +1,29 @@
+package nl.interestingcorner.core.gui;
+
+import java.util.List;
+
+import org.bukkit.Bukkit;
+import org.bukkit.entity.Player;
+import org.bukkit.inventory.Inventory;
+import org.bukkit.inventory.ItemStack;
+
+/**
+ * Generalized chest GUI for use in plugins.
+ */
+public class ChestGUI {
+    public static void open(Player player, String title, List<ItemStack> items) {
+        int itemsAmount = items.size();
+        int size;
+        if (itemsAmount <= 9) {
+            size = 9;
+        } else {
+            // TODO: handle pagination for >54 items
+            size = ((itemsAmount / 9) + 1) * 9;
+        }
+        Inventory gui = Bukkit.createInventory(null, size, title);
+        for (ItemStack item : items) {
+            gui.addItem(item);
+        }
+        player.openInventory(gui);
+    }
+}

ic_plugin_core/src/main/java/nl/interestingcorner/core/gui/ChestGUIListener.java

@@ -0,0 +1,27 @@
+package nl.interestingcorner.core.gui;
+
+import org.bukkit.entity.Player;
+import org.bukkit.event.EventHandler;
+import org.bukkit.event.Listener;
+import org.bukkit.event.inventory.InventoryClickEvent;
+
+/**
+ * Generalized listener for chest GUIs. Extend or register with custom logic.
+ */
+public class ChestGUIListener implements Listener {
+    private final String guiTitle;
+
+    public ChestGUIListener(String guiTitle) {
+        this.guiTitle = guiTitle;
+    }
+
+    @EventHandler
+    public void onInventoryClick(InventoryClickEvent event) {
+        if (event.getView().getTitle().equals(guiTitle)) {
+            event.setCancelled(true);
+            if (event.getCurrentItem() == null) return;
+            Player player = (Player) event.getWhoClicked();
+            // Extend this class and override this method for custom slot handling
+        }
+    }
+}

ic_plugin_core/src/main/java/nl/interestingcorner/core/gui/GUI.java

@@ -1,19 +1,81 @@
 package nl.interestingcorner.core.gui;
 
+import java.util.ArrayList;
+import java.util.List;
+
+import org.bukkit.Bukkit;
+import org.bukkit.entity.Player;
 import org.bukkit.inventory.Inventory;
 import org.bukkit.inventory.InventoryHolder;
+import org.bukkit.inventory.ItemStack;
 
 public class GUI implements InventoryHolder {
     public static final int MAX_INVENTORY_SIZE = 54; // max size of inventory before pages are needed
-    public static final int MAX_PAGE_INVENTORY_SIZE = 45; // max amount of items on a page
+    public static final int DEFAULT_PAGE_SIZE = 45; // default items per page (excluding navigation row)
 
     private Inventory inventory;
+    private List<ItemStack> items;
     private int currentPage;
+    private String title;
+    private int pageSize;
+
+    public GUI(String title, int pageSize) {
+        this.title = title;
+        this.pageSize = Math.min(pageSize, MAX_INVENTORY_SIZE);
+        this.items = new ArrayList<>();
+        this.currentPage = 0;
+        this.inventory = null;
+    }
+
+    public void setItems(List<ItemStack> items) {
+        this.items = new ArrayList<>(items);
+        this.currentPage = 0;
+        updateInventory();
+    }
+
+    public void addItem(ItemStack item) {
+        this.items.add(item);
+        updateInventory();
+    }
+
+    public void show(Player player) {
+        updateInventory();
+        player.openInventory(this.inventory);
+    }
+
+    public void nextPage() {
+        if ((currentPage + 1) * pageSize < items.size()) {
+            currentPage++;
+            updateInventory();
+        }
+    }
+
+    public void previousPage() {
+        if (currentPage > 0) {
+            currentPage--;
+            updateInventory();
+        }
+    }
+
+    public int getPagesAmount() {
+        return (int) Math.ceil((double) items.size() / pageSize);
+    }
+
+    private void updateInventory() {
+        // Create inventory for the current page
+        int size = Math.min(pageSize, MAX_INVENTORY_SIZE);
+        this.inventory = Bukkit.createInventory(this, size, title);
+        int start = currentPage * pageSize;
+        int end = Math.min(start + pageSize, items.size());
+        List<ItemStack> pageItems = items.subList(start, end);
+        for (int i = 0; i < pageItems.size(); i++) {
+            this.inventory.setItem(i, pageItems.get(i));
+        }
+        // TODO: Add navigation items if needed
+    }
 
     @Override
     public Inventory getInventory() {
-        // TODO Auto-generated method stub
-        throw new UnsupportedOperationException("Unimplemented method 'getInventory'");
+        return this.inventory;
     }
-    
 }

ic_plugin_core/src/main/java/nl/interestingcorner/core/gui/GUIBuilder.java

@@ -4,7 +4,6 @@ import java.util.List;
 
 import org.bukkit.Bukkit;
 import org.bukkit.inventory.Inventory;
-import org.bukkit.inventory.InventoryHolder;
 import org.bukkit.inventory.ItemStack;
 
 public class GUIBuilder {
@@ -22,7 +21,7 @@ public class GUIBuilder {
         int itemsAmount = items.size();
         int pagesAmount = getPagesAmount(itemsAmount);
 
-        Inventory gui = Bukkit.createInventory(null, MAX_INVENTORY_SIZE, "Coordinates Menu");
+        Inventory gui = Bukkit.createInventory(null, GUI.MAX_INVENTORY_SIZE, "Coordinates Menu");
 
         for (ItemStack item : items) {
             gui.addItem(item);
@@ -32,8 +31,8 @@ public class GUIBuilder {
     }
 
     private static int getPagesAmount(int itemsAmount) {
-        if (itemsAmount > MAX_INVENTORY_SIZE) {
-            return ((itemsAmount / MAX_PAGE_INVENTORY_SIZE) + 1);
+        if (itemsAmount > GUI.MAX_INVENTORY_SIZE) {
+            return ((itemsAmount / GUI.DEFAULT_PAGE_SIZE) + 1);
         }
         return 1;
     }