add prevent-block-place option

Prevents players from placing blocks outside the world border. Default
off.

This is for the PrisonPearl plugin, where if a player is imprisoned in a
chest placed far enough outside the world border it becomes impossible
to break the chest and free the player.

The BlockPlaceEvent listener is only registered if the option is
enabled.

src/main/java/com/wimbli/WorldBorder/BlockPlaceListener.java

@@ -0,0 +1,31 @@
+package com.wimbli.WorldBorder;
+
+import org.bukkit.Location;
+import org.bukkit.World;
+import org.bukkit.event.EventHandler;
+import org.bukkit.event.EventPriority;
+import org.bukkit.event.HandlerList;
+import org.bukkit.event.Listener;
+import org.bukkit.event.block.BlockPlaceEvent;
+
+public class BlockPlaceListener implements Listener {
+	@EventHandler(priority = EventPriority.LOWEST, ignoreCancelled = true)
+	public void onBlockPlace(BlockPlaceEvent event)
+	{
+		Location loc = event.getBlockPlaced().getLocation();
+		if (loc == null) return;
+	
+		World world = loc.getWorld();
+		if (world == null) return;
+		BorderData border = Config.Border(world.getName());
+		if (border == null) return;
+		
+		if (!border.insideBorder(loc.getX(), loc.getZ(), Config.ShapeRound())) {
+			event.setCancelled(true);
+		}
+	}
+
+	public void unregister() {
+		HandlerList.unregisterAll(this);
+	}
+}

src/main/java/com/wimbli/WorldBorder/Config.java

@@ -54,6 +54,7 @@ public class Config
 	private static boolean denyEnderpearl = false;
 	private static int fillAutosaveFrequency = 30;
 	private static int fillMemoryTolerance = 500;
+	private static boolean preventBlockPlace = false;
 
 	// for monitoring plugin efficiency
 //	public static long timeUsed = 0;
@@ -260,6 +261,18 @@ public class Config
 		world.playEffect(loc, Effect.GHAST_SHOOT, 0);
 	}
 	
+	public static void setPreventBlockPlace(boolean enable)
+	{
+		preventBlockPlace = enable;
+		log("prevent block place " + (enable ? "enabled" : "disabled") + ".");
+		save(true);
+	}
+	
+	public static boolean preventBlockPlace()
+	{
+		return preventBlockPlace;
+	}
+
 	public static boolean getIfPlayerKill()
 	{
 		return killPlayer;
@@ -566,6 +579,7 @@ public class Config
 		fillAutosaveFrequency = cfg.getInt("fill-autosave-frequency", 30);
 		importBypassStringList(cfg.getStringList("bypass-list-uuids"));
 		fillMemoryTolerance = cfg.getInt("fill-memory-tolerance", 500);
+		preventBlockPlace = cfg.getBoolean("prevent-block-place");
 
 		StartBorderTimer();
 
@@ -672,6 +686,7 @@ public class Config
 		cfg.set("fill-autosave-frequency", fillAutosaveFrequency);
 		cfg.set("bypass-list-uuids", exportBypassStringList());
 		cfg.set("fill-memory-tolerance", fillMemoryTolerance);
+		cfg.set("prevent-block-place", preventBlockPlace);
 
 		cfg.set("worlds", null);
 		for(Entry<String, BorderData> stringBorderDataEntry : borders.entrySet())

src/main/java/com/wimbli/WorldBorder/WBCommand.java

@@ -42,6 +42,7 @@ public class WBCommand implements CommandExecutor
 		addCmd(new CmdKnockback());		// 1
 		addCmd(new CmdWrap());			// 1
 		addCmd(new CmdWhoosh());		// 1
+		addCmd(new CmdPreventPlace());	// 1
 		addCmd(new CmdGetmsg());		// 1
 		addCmd(new CmdSetmsg());		// 1
 		addCmd(new CmdWshape());		// 3

src/main/java/com/wimbli/WorldBorder/WorldBorder.java

@@ -8,6 +8,7 @@ public class WorldBorder extends JavaPlugin
 {
 	public static volatile WorldBorder plugin = null;
 	public static volatile WBCommand wbCommand = null;
+	private BlockPlaceListener blockPlaceListener = null;
 
 	@Override
 	public void onEnable()
@@ -26,6 +27,10 @@ public class WorldBorder extends JavaPlugin
 		// keep an eye on teleports, to redirect them to a spot inside the border if necessary
 		getServer().getPluginManager().registerEvents(new WBListener(), this);
 		
+		if (Config.preventBlockPlace()) {
+			enableBlockPlaceListener(true);
+		}
+
 		// integrate with DynMap if it's available
 		DynMapFeatures.setup();
 
@@ -57,4 +62,13 @@ public class WorldBorder extends JavaPlugin
 	{
 		return getWorldBorder(worldName);
 	}
+
+	public void enableBlockPlaceListener(boolean enable) {
+		if (enable) {
+			getServer().getPluginManager().registerEvents(this.blockPlaceListener = new BlockPlaceListener(), this);
+		} else {
+			blockPlaceListener.unregister();
+		}
+		
+	}
 }

src/main/java/com/wimbli/WorldBorder/cmd/CmdPreventPlace.java

@@ -0,0 +1,47 @@
+package com.wimbli.WorldBorder.cmd;
+
+import java.util.List;
+
+import org.bukkit.command.CommandSender;
+import org.bukkit.entity.Player;
+import org.bukkit.event.HandlerList;
+
+import com.wimbli.WorldBorder.BlockPlaceListener;
+import com.wimbli.WorldBorder.Config;
+import com.wimbli.WorldBorder.WorldBorder;
+
+public class CmdPreventPlace extends WBCmd {
+
+	public CmdPreventPlace() {
+		name = permission = "preventblockplace";
+		minParams = 0;
+		maxParams = 1;
+
+		addCmdExample(nameEmphasized() + "<on|off> - turn prevent-block-place on or off.");
+		helpText = "Default value: off. This will prevent players from placing blocks outside the world's border.";
+	}
+	
+	@Override
+	public void cmdStatus(CommandSender sender)
+	{
+		sender.sendMessage(C_HEAD + "preventblockplace is " + enabledColored(Config.preventBlockPlace()) + C_HEAD + ".");
+	}
+
+	@Override
+	public void execute(CommandSender sender, Player player, List<String> params, String worldName)
+	{
+		if (params.size() == 1) {
+			boolean previousSetting = Config.preventBlockPlace();
+			Config.setPreventBlockPlace(strAsBool(params.get(0)));
+			if (previousSetting != Config.preventBlockPlace()) {
+				WorldBorder.plugin.enableBlockPlaceListener(Config.preventBlockPlace());
+			}
+		}
+
+		if (player != null)
+		{
+			Config.log((Config.preventBlockPlace() ? "Enabled" : "Disabled") + " preventblockplace at the command of player \"" + player.getName() + "\".");
+			cmdStatus(sender);
+		}
+	}
+}