Prevent growth as mentioned in design doc for most plants

src/main/java/de/doggoat/growableRebalance/GrowableRebalance.java

@@ -1,6 +1,9 @@
 package de.doggoat.growableRebalance;
 
+import de.doggoat.growableRebalance.listeners.BlockGrowEventListener;
+import de.doggoat.growableRebalance.listeners.BlockSpreadEventListener;
 import de.doggoat.growableRebalance.listeners.GrowthEventListener;
+import org.bukkit.plugin.PluginManager;
 import org.bukkit.plugin.java.JavaPlugin;
 
 public final class GrowableRebalance extends JavaPlugin {
@@ -8,7 +11,10 @@ public final class GrowableRebalance extends JavaPlugin {
     @Override
     public void onEnable() {
         // Plugin startup logic
-        getServer().getPluginManager().registerEvents(new GrowthEventListener(), this);
+        PluginManager pluginManager = getServer().getPluginManager();
+        pluginManager.registerEvents(new GrowthEventListener(this), this);
+        pluginManager.registerEvents(new BlockGrowEventListener(this), this);
+        pluginManager.registerEvents(new BlockSpreadEventListener(this), this);
     }
 
     @Override

src/main/java/de/doggoat/growableRebalance/PlantUtils.java

@@ -0,0 +1,19 @@
+package de.doggoat.growableRebalance;
+
+import org.bukkit.Location;
+import org.bukkit.Material;
+
+public class PlantUtils {
+    public static Location getVerticalPlantGround(Location plantStart) {
+        Material plantMaterial = plantStart.getBlock().getType();
+        Location plantGround = plantStart;
+        while (plantStart.getBlock().getType() == plantMaterial) {
+            plantGround = plantGround.add(0, -1, 0);
+        }
+        return plantGround;
+    }
+
+    public static Location getSingleBlockGround(Location plantStart) {
+        return plantStart.add(0, -1, 0);
+    }
+}

src/main/java/de/doggoat/growableRebalance/listeners/BlockGrowEventListener.java

@@ -0,0 +1,70 @@
+package de.doggoat.growableRebalance.listeners;
+
+import de.doggoat.growableRebalance.PlantUtils;
+import org.bukkit.Location;
+import org.bukkit.Material;
+import org.bukkit.event.EventHandler;
+import org.bukkit.event.Listener;
+import org.bukkit.event.block.BlockGrowEvent;
+import org.bukkit.plugin.java.JavaPlugin;
+import java.util.logging.Logger;
+import java.util.Arrays;
+import java.util.List;
+
+public class BlockGrowEventListener implements Listener {
+
+    List<Material> forbiddenGrowthBlocks = Arrays.asList(
+            Material.MOSS_BLOCK, Material.MUD,
+            Material.MUDDY_MANGROVE_ROOTS, Material.SUSPICIOUS_GRAVEL,
+            Material.SUSPICIOUS_SAND
+    );
+    List<Material> allowedGourdGrowthBlocks = Arrays.asList(Material.GRASS_BLOCK, Material.DIRT, Material.FARMLAND);
+    JavaPlugin plugin;
+    Logger log;
+
+    public BlockGrowEventListener(JavaPlugin plugin) {
+        this.plugin = plugin;
+        this.log = plugin.getLogger();
+    }
+
+    @EventHandler
+    public void onBlockGrow(BlockGrowEvent e) {
+        switch (e.getNewState().getType()) {
+            case SWEET_BERRY_BUSH:
+                this.onGroundBelow(e);
+                break;
+            case SUGAR_CANE:
+            case CACTUS:
+                this.onStackableGrow(e);
+                break;
+            case MELON:
+            case PUMPKIN:
+                this.onGourdGrow(e);
+                break;
+        }
+
+    }
+
+    public void onGourdGrow(BlockGrowEvent e) {
+        Location ground = PlantUtils.getSingleBlockGround(e.getBlock().getLocation());
+        if (!allowedGourdGrowthBlocks.contains(ground.getBlock().getType())) {
+            e.setCancelled(true);
+        }
+    }
+
+    public void onGroundBelow(BlockGrowEvent e) {
+        Location ground = PlantUtils.getVerticalPlantGround(e.getBlock().getLocation());
+        if (forbiddenGrowthBlocks.contains(ground.getBlock().getType())) {
+            e.setCancelled(true);
+        }
+    }
+
+    public void onStackableGrow(BlockGrowEvent e) {
+        Location plantStart = e.getBlock().getLocation().add(0, -1, 0);
+        Location ground = PlantUtils.getVerticalPlantGround(plantStart);
+        if (forbiddenGrowthBlocks.contains(ground.getBlock().getType())) {
+            e.setCancelled(true);
+        }
+    }
+
+}

src/main/java/de/doggoat/growableRebalance/listeners/BlockSpreadEventListener.java

@@ -0,0 +1,62 @@
+package de.doggoat.growableRebalance.listeners;
+
+import de.doggoat.growableRebalance.PlantUtils;
+import org.bukkit.Location;
+import org.bukkit.Material;
+import org.bukkit.event.Listener;
+import org.bukkit.event.EventHandler;
+import org.bukkit.event.block.BlockSpreadEvent;
+import org.bukkit.plugin.java.JavaPlugin;
+import java.util.logging.Logger;
+import java.util.Arrays;
+import java.util.List;
+
+public class BlockSpreadEventListener implements Listener {
+
+    JavaPlugin plugin;
+    Logger log;
+    List<Material> allowedKelpGrowthBlocks = Arrays.asList(
+            Material.DIRT, Material.SAND, Material.RED_SAND
+    );
+    List<Material> forbiddenBambooGrowthBlocks = Arrays.asList(
+            Material.MOSS_BLOCK, Material.MUD, Material.MUDDY_MANGROVE_ROOTS,
+            Material.GRAVEL, Material.SUSPICIOUS_GRAVEL,
+            Material.SAND, Material.SUSPICIOUS_SAND
+    );
+
+    public BlockSpreadEventListener(JavaPlugin plugin) {
+        this.plugin = plugin;
+        this.log = plugin.getLogger();
+    }
+
+    @EventHandler
+    public void onBlockSpread(BlockSpreadEvent e) {
+        switch (e.getSource().getType()) {
+            case Material.KELP:
+                this.onKelpSpread(e);
+                break;
+            case Material.BAMBOO:
+                this.onBambooSpread(e);
+                break;
+            default:
+                log.info("BlockSpreadEvent: Source " + e.getSource().getType());
+                break;
+        }
+    }
+
+    public void onKelpSpread(BlockSpreadEvent e) {
+        Location plantStart = e.getSource().getLocation();
+        Location plantGround = PlantUtils.getVerticalPlantGround(plantStart);
+        if (!allowedKelpGrowthBlocks.contains(plantGround.getBlock().getType())) {
+            e.setCancelled(true);
+        }
+    }
+
+    public void onBambooSpread(BlockSpreadEvent e) {
+        Location plantStart = e.getBlock().getLocation().add(0, -1, 0);
+        Location plantGround = PlantUtils.getVerticalPlantGround(plantStart);
+        if (forbiddenBambooGrowthBlocks.contains(plantGround.getBlock().getType())) {
+            e.setCancelled(true);
+        }
+    }
+}

src/main/java/de/doggoat/growableRebalance/listeners/GrowthEventListener.java

@@ -5,7 +5,8 @@ import org.bukkit.entity.Player;
 import org.bukkit.event.EventHandler;
 import org.bukkit.event.Listener;
 import org.bukkit.event.world.StructureGrowEvent;
-
+import org.bukkit.plugin.java.JavaPlugin;
+import java.util.logging.Logger;
 import java.util.Arrays;
 import java.util.List;
 
@@ -13,12 +14,19 @@ public class GrowthEventListener implements Listener {
 
     List<Material> dirtBlocks = Arrays.asList(Material.ROOTED_DIRT, Material.PODZOL);
     List<Material> unreplaceableBlocks = Arrays.asList(Material.MOSS_BLOCK, Material.MUD, Material.MUDDY_MANGROVE_ROOTS);
+    JavaPlugin plugin;
+    Logger log;
+
+    public GrowthEventListener(JavaPlugin plugin) {
+        this.plugin = plugin;
+        log = plugin.getLogger();
+    }
 
     @EventHandler
     public void onStructureGrow(StructureGrowEvent e) {
         Player p = e.getPlayer();
         List<BlockState> forbiddenBlocks = e.getBlocks().stream()
-                .filter(blockState-> unreplaceableBlocks.contains(blockState.getBlock().getType()))
+                .filter(blockState -> unreplaceableBlocks.contains(blockState.getBlock().getType()))
                 .filter(blockState -> dirtBlocks.contains(blockState.getType()))
                 .toList();