Fix to handle kelp and bamboo spread.

Addresses #2053. This is actually due to a server bug
https://hub.spigotmc.org/jira/browse/SPIGOT-5312. This change uses the
BlockSpreadEvent to trap kelp and bamboo and bamboo sapling.

src/main/java/world/bentobox/bentobox/listeners/flags/worldsettings/OfflineGrowthListener.java

@@ -3,9 +3,11 @@ package world.bentobox.bentobox.listeners.flags.worldsettings;
 import java.util.UUID;
 
 import org.bukkit.Bukkit;
+import org.bukkit.Material;
 import org.bukkit.event.EventHandler;
 import org.bukkit.event.EventPriority;
 import org.bukkit.event.block.BlockGrowEvent;
+import org.bukkit.event.block.BlockSpreadEvent;
 
 import world.bentobox.bentobox.api.flags.FlagListener;
 import world.bentobox.bentobox.lists.Flags;
@@ -34,4 +36,26 @@ public class OfflineGrowthListener extends FlagListener {
             e.setCancelled(true);
         });
     }
+
+    @EventHandler(priority = EventPriority.LOW, ignoreCancelled = true)
+    public void onSpread(BlockSpreadEvent e) {
+        if (!getIWM().inWorld(e.getBlock().getWorld()) || Flags.OFFLINE_GROWTH.isSetForWorld(e.getBlock().getWorld())) {
+            // We do not want to run any check if this is not the right world or if it is allowed.
+            return;
+        }
+        // Check what is spreading - disallow Bamboo and Kelp growth
+        Material m = e.getBlock().getType();
+        if (!m.equals(Material.KELP) && !m.equals(Material.BAMBOO) && !m.equals(Material.BAMBOO_SAPLING)) {
+            return;
+        }
+        // Check if island exists and members are online
+        getIslands().getProtectedIslandAt(e.getBlock().getLocation()).ifPresent(i -> {
+            for (UUID uuid : i.getMemberSet(RanksManager.COOP_RANK)) {
+                if (Bukkit.getPlayer(uuid) != null) {
+                    return;
+                }
+            }
+            e.setCancelled(true);
+        });
+    }
 }

src/test/java/world/bentobox/bentobox/listeners/flags/worldsettings/OfflineGrowthListenerTest.java

@@ -14,11 +14,13 @@ import java.util.UUID;
 
 import org.bukkit.Bukkit;
 import org.bukkit.Location;
+import org.bukkit.Material;
 import org.bukkit.World;
 import org.bukkit.block.Block;
 import org.bukkit.block.BlockState;
 import org.bukkit.entity.Player;
 import org.bukkit.event.block.BlockGrowEvent;
+import org.bukkit.event.block.BlockSpreadEvent;
 import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
@@ -88,6 +90,7 @@ public class OfflineGrowthListenerTest {
         // Blocks
         when(block.getWorld()).thenReturn(world);
         when(block.getLocation()).thenReturn(inside);
+        when(block.getType()).thenReturn(Material.KELP);
 
         PowerMockito.mockStatic(Util.class);
         when(Util.getWorld(any())).thenReturn(world);
@@ -191,4 +194,113 @@ public class OfflineGrowthListenerTest {
         assertFalse(e.isCancelled());
     }
 
+    /**
+     * Test method for {@link OfflineGrowthListener#onSpread(BlockSpreadEvent}.
+     */
+    @Test
+    public void testOnSpreadDoNothing() {
+        // Make an event to give some current to block
+        BlockSpreadEvent e = new BlockSpreadEvent(block, block, blockState);
+        OfflineGrowthListener orl = new OfflineGrowthListener();
+        Flags.OFFLINE_GROWTH.setSetting(world, true);
+        orl.onSpread(e);
+        // Allow growth
+        assertFalse(e.isCancelled());
+    }
+
+    /**
+     * Test method for {@link OfflineGrowthListener#onSpread(BlockSpreadEvent}.
+     */
+    @Test
+    public void testOnSpreadMembersOnline() {
+        // Make an event to give some current to block
+        BlockSpreadEvent e = new BlockSpreadEvent(block, block, blockState);
+        OfflineGrowthListener orl = new OfflineGrowthListener();
+        // Offline Growth not allowed
+        Flags.OFFLINE_GROWTH.setSetting(world, false);
+        // Members are online
+        when(Bukkit.getPlayer(any(UUID.class))).thenReturn(mock(Player.class));
+
+        orl.onSpread(e);
+        // Allow growth
+        assertFalse(e.isCancelled());
+    }
+
+    /**
+     * Test method for {@link OfflineGrowthListener#onSpread(BlockSpreadEvent}.
+     */
+    @Test
+    public void testOnSpreadMembersOffline() {
+        // Make an event to give some current to block
+        BlockSpreadEvent e = new BlockSpreadEvent(block, block, blockState);
+        OfflineGrowthListener orl = new OfflineGrowthListener();
+        // Offline Growth not allowed
+        Flags.OFFLINE_GROWTH.setSetting(world, false);
+        // Members are online
+        when(Bukkit.getPlayer(any(UUID.class))).thenReturn(null);
+
+        orl.onCropGrow(e);
+        // Block growth
+        assertTrue(e.isCancelled());
+
+        when(block.getType()).thenReturn(Material.BAMBOO);
+        orl.onSpread(e);
+        // Block growth
+        assertTrue(e.isCancelled());
+
+        when(block.getType()).thenReturn(Material.BAMBOO_SAPLING);
+        orl.onSpread(e);
+        // Block growth
+        assertTrue(e.isCancelled());
+    }
+
+    /**
+     * Test method for {@link OfflineGrowthListener#onSpread(BlockSpreadEvent}.
+     */
+    @Test
+    public void testOnSpreadMembersOfflineTree() {
+        when(block.getType()).thenReturn(Material.SPRUCE_LOG);
+        // Make an event to give some current to block
+        BlockSpreadEvent e = new BlockSpreadEvent(block, block, blockState);
+        OfflineGrowthListener orl = new OfflineGrowthListener();
+        // Offline Growth not allowed
+        Flags.OFFLINE_GROWTH.setSetting(world, false);
+        // Members are online
+        when(Bukkit.getPlayer(any(UUID.class))).thenReturn(null);
+
+        orl.onSpread(e);
+        // Do not block growth
+        assertFalse(e.isCancelled());
+    }
+
+    /**
+     * Test method for {@link OfflineGrowthListener#onSpread(BlockSpreadEvent}.
+     */
+    @Test
+    public void testOnSpreadNonIsland() {
+        // Make an event to give some current to block
+        BlockSpreadEvent e = new BlockSpreadEvent(block, block, blockState);
+        OfflineGrowthListener orl = new OfflineGrowthListener();
+        Flags.OFFLINE_GROWTH.setSetting(world, false);
+        when(im.getProtectedIslandAt(eq(inside))).thenReturn(Optional.empty());
+        orl.onSpread(e);
+        // Allow growth
+        assertFalse(e.isCancelled());
+    }
+
+    /**
+     * Test method for {@link OfflineGrowthListener#onSpread(BlockSpreadEvent}.
+     */
+    @Test
+    public void testOnSpreadNonBentoBoxWorldIsland() {
+        when(iwm.inWorld(any(World.class))).thenReturn(false);
+        // Make an event to give some current to block
+        BlockSpreadEvent e = new BlockSpreadEvent(block, block, blockState);
+        OfflineGrowthListener orl = new OfflineGrowthListener();
+        Flags.OFFLINE_GROWTH.setSetting(world, false);
+        when(im.getProtectedIslandAt(eq(inside))).thenReturn(Optional.empty());
+        orl.onSpread(e);
+        // Allow growth
+        assertFalse(e.isCancelled());
+    }
 }