Collision check before spawning

src/main/java/eu/m724/giants/GiantProcessor.java

@@ -151,13 +151,35 @@ public class GiantProcessor implements Listener {
         }
 
         configuration.effects.forEach(entity::addPotionEffect);
-        //trackedGiants.add((Giant) entity);
 
         logger.fine("Spawned a Giant at " + pos);
 
         return entity;
     }
 
+    /**
+     * The check is very approximate
+     *
+     * @param location the location
+     * @return whether a giant can be spawned here
+     */
+    public boolean isSpawnableAt(Location location) {
+        for (int y=0; y<=12; y++) {
+            if (!location.clone().add(0, y, 0).getBlock().isEmpty()) // isPassable also seems good
+                return false;
+        }
+
+        return true;
+    }
+
+    public LivingEntity spawnGiantIfPossible(Location location) {
+        if (isSpawnableAt(location)) {
+            return spawnGiant(location);
+        } else {
+            return null;
+        }
+    }
+
     @EventHandler
     public void onChunkLoad(ChunkLoadEvent event) {
         Entity[] entities = event.getChunk().getEntities();
@@ -194,10 +216,10 @@ public class GiantProcessor implements Listener {
 
         if (e.getEntityType() == EntityType.ZOMBIE) {
             if (configuration.chance > random.nextDouble()) {
-                e.setCancelled(true);
-                spawnGiant(e.getLocation());
-
                 logger.fine("Spawned a Giant by chance at " + e.getLocation());
+                if (spawnGiantIfPossible(e.getLocation()) != null) {
+                    e.setCancelled(true);
+                }
             }
         }
     }

src/main/java/eu/m724/giants/GiantsCommand.java

@@ -47,8 +47,11 @@ public class GiantsCommand implements CommandExecutor {
 
         if (action.equals("spawn")) {
             if (player != null) {
-                plugin.spawnGiant(player.getLocation());
+                if (plugin.spawnGiantIfPossible(player.getLocation()) == null) {
+                    sender.sendMessage("No space here for a Giant");
+                } else {
                     sender.sendMessage("Spawned a Giant");
+                }
             } else {
                 sender.sendMessage("Only players can use this command.");
             }

src/main/java/eu/m724/giants/GiantsPlugin.java

@@ -48,10 +48,11 @@ public class GiantsPlugin extends JavaPlugin implements CommandExecutor {
 			);
 		} catch (IOException e) {
 			getLogger().warning(e.getMessage());
-			getLogger().warning("Failed checking JAR signature. This is not important right now, but it usually indicates future problems.");
+			getLogger().warning("Failed checking JAR signature. This is not important right now, but it usually indicates future problems. If this persists, re-download the JAR from SpigotMC.");
 		} catch (JarVerifier.VerificationException e) {
 			getLogger().warning(e.getMessage());
-            getLogger().warning("Plugin JAR is of invalid signature. Please re-download the JAR.");
+            getLogger().warning("Plugin JAR is of invalid signature. If this persists, re-download the JAR from SpigotMC.");
+			getLogger().warning("Did you update from 2.0.7? If yes, you must re-download 2.0.9+ from SpigotMC, then delete plugins/.paper-remapped");
         }
 
 		/* bStats is optional. not anymore
@@ -79,4 +80,26 @@ public class GiantsPlugin extends JavaPlugin implements CommandExecutor {
 	public LivingEntity spawnGiant(Location location) {
 		return giantProcessor.spawnGiant(location);
 	}
+
+	/**
+	 * Checks if a giant can be spawned at a location<br>
+	 * The check is very approximate, but works for most scenarios
+	 *
+	 * @param location The location
+	 * @return Whether a giant can be spawned
+	 */
+	public boolean isSpawnableAt(Location location) {
+		return giantProcessor.isSpawnableAt(location);
+	}
+
+	/**
+	 * Checks if a giant can be spawned at a location and spawns it<br>
+	 * 	 * The check is very approximate, but works for most scenarios
+	 *
+	 * @param location The location
+	 * @return The spawned {@link Giant} or null if no room for it
+	 */
+	public LivingEntity spawnGiantIfPossible(Location location) {
+		return giantProcessor.spawnGiantIfPossible(location);
+	}
 }