Implement double-chest convenience functions

src/dev/w1zzrd/spigot/wizcompat/block/Chests.java

@@ -0,0 +1,34 @@
+package dev.w1zzrd.spigot.wizcompat.block;
+
+import org.bukkit.block.Block;
+import org.bukkit.block.Chest;
+import org.bukkit.block.DoubleChest;
+import org.bukkit.inventory.InventoryHolder;
+
+import java.util.Objects;
+
+public final class Chests {
+    private Chests() { throw new UnsupportedOperationException("Functional class"); }
+
+    public static InventoryHolder getChestInventoryHolder(final Chest chest) {
+        return Objects.requireNonNull(chest.getBlockInventory().getHolder()).getInventory().getHolder();
+    }
+
+    public static boolean isDoubleChest(final Block block) {
+        return block.getState() instanceof Chest && getChestInventoryHolder((Chest) block.getState()) instanceof DoubleChest;
+    }
+
+    public static Block getLeftChest(final Chest chest) {
+        if (isDoubleChest(chest.getBlock()))
+            return ((Chest) Objects.requireNonNull(((DoubleChest) getChestInventoryHolder(chest)).getLeftSide())).getBlock();
+        else
+            return chest.getBlock();
+    }
+
+    public static Block getRightChest(final Chest chest) {
+        if (isDoubleChest(chest.getBlock()))
+            return ((Chest) Objects.requireNonNull(((DoubleChest) getChestInventoryHolder(chest)).getRightSide())).getBlock();
+        else
+            return chest.getBlock();
+    }
+}