Add safe-teleport detection to spawn points.

Towny/src/main/java/com/palmergames/bukkit/config/ConfigNodes.java

@@ -1277,6 +1277,12 @@ public enum ConfigNodes {
 			"# +------------------------------------------------------+ #",
 			"############################################################",
 			""),
+	SPAWNING_SAFE_TELEPORT(
+		"spawning.safe_teleport",
+		"false",
+		"# If enabled tries to find a safe location when teleporting to a town spawn/nation spawn/outpost",
+		"# can be used to prevent players from making kill boxes at those locations."
+	),
 	SPAWNING_COST_SPAWN_WARNINGS(
 			"spawning.spawn_cost_warnings",
 			"true",

Towny/src/main/java/com/palmergames/bukkit/towny/TownySettings.java

@@ -3663,6 +3663,10 @@ public static String getWebMapUrl() {
 		return getString(ConfigNodes.PLUGIN_WEB_MAP_URL);
 	}
 
+	public static boolean getSafetyTeleport() { 
+		return getBoolean(ConfigNodes.SPAWNING_SAFE_TELEPORT);
+	}
+
 	public static Map<Integer, TownLevel> getConfigTownLevel() {
 		return configTownLevel;
 	}

Towny/src/main/java/com/palmergames/bukkit/towny/utils/SpawnUtil.java

@@ -4,6 +4,7 @@
 import java.util.Locale;
 import java.util.Objects;
 import java.util.concurrent.CompletableFuture;
+
 import com.palmergames.bukkit.towny.event.NationSpawnEvent;
 import com.palmergames.bukkit.towny.event.SpawnEvent;
 import com.palmergames.bukkit.towny.event.TownSpawnEvent;
@@ -17,9 +18,13 @@
 import com.palmergames.bukkit.towny.object.spawnlevel.TownSpawnLevel;
 
 import com.palmergames.bukkit.towny.tasks.TeleportWarmupTimerTask;
+import com.palmergames.bukkit.util.ItemLists;
 import io.papermc.lib.PaperLib;
 import org.bukkit.Bukkit;
 import org.bukkit.Location;
+import org.bukkit.Material;
+import org.bukkit.World;
+import org.bukkit.block.Block;
 import org.bukkit.entity.Player;
 import org.bukkit.event.player.PlayerTeleportEvent.TeleportCause;
 
@@ -440,19 +445,88 @@ else if (town != null && town.hasSpawn())
 							return player.getWorld().getSpawnLocation();
 					});
 				} else if (town != null && town.hasSpawn())
-					yield CompletableFuture.completedFuture(town.getSpawnOrNull());
+					yield CompletableFuture.completedFuture(getSafeLocation(town.getSpawnOrNull()));
 				else
 					yield CompletableFuture.completedFuture(player.getWorld().getSpawnLocation());
 			case TOWN:
 				if (outpost)
-					yield CompletableFuture.completedFuture(getOutpostSpawnLocation(town, split));
+					yield CompletableFuture.completedFuture(getSafeLocation(getOutpostSpawnLocation(town, split)));
 				else
-					yield CompletableFuture.completedFuture(town.getSpawn());
+					yield CompletableFuture.completedFuture(getSafeLocation(town.getSpawn()));
 			case NATION:
-				yield CompletableFuture.completedFuture(nation.getSpawn());
+				yield CompletableFuture.completedFuture(getSafeLocation(nation.getSpawn()));
 		};
 	}
 
+	/**
+	 * Tries to find a safe location nearby to teleport the player to
+	 * if safety teleport is enabled, otherwise does nothing.
+	 * 
+	 * @param location Starting location
+	 * @return A safe location nearby, same location if already safe
+	 */
+	private static Location getSafeLocation(Location location) {
+		//if safety teleport isn't enabled do nothing
+		if (!TownySettings.getSafetyTeleport()) {
+			return location;
+		}
+
+		if (isSafeLocation(location)) {
+			return location;
+		}
+
+		Location up = location.clone();
+		Location down = location.clone();
+
+		// look for 20 blocks up and down for a safe location, 
+		// if you can't find it fail the teleport
+		// maybe add a translation key and add the player 
+		// as a parameter to print him an error message
+		for(int i = 0; i < 20; i++) {
+			up = up.add(0,1,0);
+			down = down.subtract(0, 1, 0);
+
+			if (isSafeLocation(up)) {
+				return up;
+			}
+
+			if (isSafeLocation(down)) {
+				return down;
+			}
+		}
+
+		return null;
+	}
+
+	private static boolean isSafeLocation(Location location) {
+		World world = location.getWorld();
+		if (world == null) return false;
+
+		// Check if location is in a block
+		Block block = world.getBlockAt(location);
+		Material type = block.getType();
+
+		if (!ItemLists.NOT_SOLID_BLOCKS.contains(type) || ItemLists.LIQUID_BLOCKS.contains(type)) {
+			return false;
+		}
+
+		// Check if block below is lava or water or nothing
+		Block belowBlock = world.getBlockAt(location.clone().subtract(0, 1, 0));
+		Material belowType = belowBlock.getType();
+		if (ItemLists.AIR_TYPES.contains(belowType) || ItemLists.LIQUID_BLOCKS.contains(type)) {
+			return false;
+		}
+
+		// Check if the location is directly above a solid block
+		Block aboveBlock = world.getBlockAt(location.clone().add(0, 1, 0));
+		Material aboveType = aboveBlock.getType();
+		if (!ItemLists.NOT_SOLID_BLOCKS.contains(aboveType) || ItemLists.LIQUID_BLOCKS.contains(aboveType)) {
+			return false;
+		}
+
+		return true;
+	}
+
 	/**
 	 * Complicated code that parses the given split to a named, numbered or
 	 * unnumbered outpost.

Towny/src/main/java/com/palmergames/bukkit/util/ItemLists.java

@@ -4,7 +4,6 @@
 import java.lang.reflect.Modifier;
 import java.util.Arrays;
 import java.util.Collection;
-import java.util.List;
 import java.util.Set;
 import java.util.stream.Collectors;
 
@@ -257,6 +256,11 @@ public Collection<String> getMaterialNameCollection() {
 	 */
 	public static final ItemLists CAULDRON_FILLABLE = newBuilder().add("WATER_BUCKET", "LAVA_BUCKET", "POWDER_SNOW_BUCKET").build();
 
+	/**
+	 * List of liquid blocks
+	 */
+	public static final ItemLists LIQUID_BLOCKS = newBuilder().add("WATER", "LAVA", "BUBBLE_COLUMN").build();
+
 	/**
 	 * List of hoes
 	 */
@@ -278,11 +282,49 @@ public Collection<String> getMaterialNameCollection() {
 			.includeList(PLANTABLES)
 			.add("TALL_GRASS","LARGE_FERN","VINE","TWISTING_VINES_PLANT","WEEPING_VINES_PLANT","NETHER_WART_BLOCK","CRIMSON_ROOTS","WARPED_ROOTS","NETHER_SPROUTS","BIG_DRIPLEAF","SMALL_DRIPLEAF").build();
 
+	/**
+	 * Minecraft uses 3 types of air
+	 */
+	public static final ItemLists AIR_TYPES = newBuilder()
+		.add("AIR")
+		.add("CAVE_AIR")
+		.add("VOID_AIR").build();
+
+	/**
+	 * List of all the banners
+	 */
+	public static final ItemLists BANNERS = newBuilder().endsWith("_BANNER").build();
+
+	/**
+	 * List of wall coral fans, players can fall through these
+	 */
+	public static final ItemLists CORAL_FANS = newBuilder()
+		.endsWith("_WALL_FAN")
+		.build();
+
+	/**
+	 * List of solid blocks
+	 */
+	public static final ItemLists NOT_SOLID_BLOCKS = newBuilder()
+			.add("TRIPWIRE", "TRIPWIRE_HOOK")
+			.add("REDSTONE_WIRE","COMPARATOR","REPEATER","LEVER")
+			.includeList(CORAL_FANS)
+			.includeList(AIR_TYPES)
+			.includeList(SIGNS)
+			.includeList(BUTTONS)
+			.includeList(PRESSURE_PLATES)
+			.includeList(FENCE_GATES) //if open they are basically air
+			.includeList(TRAPDOORS) //if open they are basically air
+			.includeList(DOORS) ////if open they are basically air
+			.includeList(TORCHES)
+			.includeList(BANNERS)
+			.includeList(PLANTS).build();
+
 	public static final ItemLists FALLING_BLOCKS = newBuilder()
 			.add("SAND", "RED_SAND", "GRAVEL", "SUSPICIOUS_SAND", "SUSPICIOUS_GRAVEL")
 			.endsWith("_CONCRETE_POWDER")
 			.build();
-
+	
 	/**
 	 * List of blocks which, when exploded, will not have their drops set to false, despite our asking.
 	 */