Add default GameRule command. Fixes BUKKIT-2671

By: feildmaster <admin@feildmaster.com>

paper-api/src/main/java/org/bukkit/command/SimpleCommandMap.java

@@ -57,6 +57,7 @@ public class SimpleCommandMap implements CommandMap {
         fallbackCommands.add(new WeatherCommand());
         fallbackCommands.add(new SpawnpointCommand());
         fallbackCommands.add(new ClearCommand());
+        fallbackCommands.add(new GameRuleCommand());
     }
 
     public SimpleCommandMap(final Server server) {

paper-api/src/main/java/org/bukkit/command/defaults/GameRuleCommand.java

@@ -0,0 +1,90 @@
+package org.bukkit.command.defaults;
+
+import com.google.common.collect.ImmutableList;
+import org.apache.commons.lang.Validate;
+import org.bukkit.ChatColor;
+import org.bukkit.command.Command;
+import org.bukkit.command.CommandSender;
+import org.bukkit.util.StringUtil;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import org.bukkit.Bukkit;
+import org.bukkit.World;
+import org.bukkit.entity.HumanEntity;
+
+public class GameRuleCommand extends VanillaCommand {
+    private static final List<String> GAMERULE_STATES = ImmutableList.of("true", "false");
+
+    public GameRuleCommand() {
+        super("gamerule");
+        this.description = "Sets a server's game rules";
+        this.usageMessage = "/gamerule <rule name> <value> OR /gamerule <rule name>";
+        this.setPermission("bukkit.command.gamerule");
+    }
+
+    @Override
+    public boolean execute(CommandSender sender, String currentAlias, String[] args) {
+        if (!testPermission(sender)) return true;
+
+        if (args.length > 0) {
+            String rule = args[0];
+            World world = getGameWorld(sender);
+
+            if (world.isGameRule(rule)) {
+                if (args.length > 1) {
+                    String value = args[1];
+
+                    world.setGameRuleValue(rule, value);
+                    Command.broadcastCommandMessage(sender, "Game rule has been updated");
+                } else {
+                    String value = world.getGameRuleValue(rule);
+                    sender.sendMessage(rule + " = " + value);
+                }
+            } else {
+                sender.sendMessage(ChatColor.RED + "No game rule called " + rule + " is available");
+            }
+
+            return true;
+        } else {
+            sender.sendMessage(ChatColor.RED + "Usage: " + usageMessage);
+            sender.sendMessage("Rules: " + this.createString(getGameWorld(sender).getGameRules(), 0, ", "));
+
+            return true;
+        }
+    }
+
+    private World getGameWorld(CommandSender sender) {
+        if (sender instanceof HumanEntity) {
+            World world = ((HumanEntity) sender).getWorld();
+            if (world != null) {
+                return world;
+            }
+        }
+
+        return Bukkit.getWorlds().get(0);
+    }
+
+    @Override
+    public boolean matches(String input) {
+        return input.equalsIgnoreCase("gamerule");
+    }
+
+    @Override
+    public List<String> tabComplete(CommandSender sender, String alias, String[] args) throws IllegalArgumentException {
+        Validate.notNull(sender, "Sender cannot be null");
+        Validate.notNull(args, "Arguments cannot be null");
+        Validate.notNull(alias, "Alias cannot be null");
+
+        if (args.length == 1) {
+            return StringUtil.copyPartialMatches(args[0], Arrays.asList(getGameWorld(sender).getGameRules()), new ArrayList<String>());
+        }
+
+        if (args.length == 2) {
+            return StringUtil.copyPartialMatches(args[1], GAMERULE_STATES, new ArrayList<String>(GAMERULE_STATES.size()));
+        }
+
+        return ImmutableList.of();
+    }
+}

paper-api/src/main/java/org/bukkit/command/defaults/VanillaCommand.java

@@ -58,13 +58,17 @@ public abstract class VanillaCommand extends Command {
         return result;
     }
 
-    protected String createString(String[] args, int start) {
+    String createString(String[] args, int start) {
+        return createString(args, start, " ");
+    }
+
+    String createString(String[] args, int start, String glue) {
         StringBuilder string = new StringBuilder();
 
         for (int x = start; x < args.length; x++) {
             string.append(args[x]);
             if (x != args.length - 1) {
-                string.append(" ");
+                string.append(glue);
             }
         }