Adding Gamerule modification to scarpet (#610)

docs/scarpet/api/Auxiliary.md

@@ -487,6 +487,8 @@ Available options in the scarpet app space:
   * `world_path` - full path to the world saves folder
   * `world_folder` - name of the direct folder in the saves that holds world files
   * `world_carpet_rules` - returns all Carpet rules in a map form (`rule`->`value`). Note that the values are always returned as strings, so you can't do boolean comparisons directly. Includes rules from extensions with their namespace (`namespace:rule`->`value`). You can later listen to rule changes with the `on_carpet_rule_changes(rule, newValue)` event.
+  * `world_gamerules` - returns all gamerules in a map form (`rule`->`value`). Like carpet rules, values are returned as strings, so you can use appropriate value conversions using `bool()` or `number()` to convert them to other values. Gamerules are read-only to discourage app programmers to mess up with the settings intentionally applied by server admins. Isn't that just super annoying when a datapack messes up with your gamerule settings? It is still possible to change them though using `run('gamerule ...`.
+
 
  Relevant gameplay related properties
   * `game_difficulty` - current difficulty of the game: `'peacefu'`, `'easy'`, `'normal'`, or `'hard'`

src/main/java/carpet/script/api/Auxiliary.java

@@ -35,7 +35,6 @@ import carpet.script.value.ValueConversions;
 import carpet.utils.Messenger;
 import com.google.common.collect.ImmutableMap;
 import net.minecraft.block.BlockState;
-import net.minecraft.command.argument.EntityAnchorArgumentType;
 import net.minecraft.entity.Entity;
 import net.minecraft.entity.EntityType;
 import net.minecraft.entity.EquipmentSlot;
@@ -50,7 +49,6 @@ import net.minecraft.network.packet.s2c.play.TitleS2CPacket;
 import net.minecraft.network.packet.s2c.play.TitleS2CPacket.Action;
 import net.minecraft.particle.ParticleEffect;
 import net.minecraft.server.MinecraftServer;
-import net.minecraft.server.command.CommandOutput;
 import net.minecraft.server.command.ServerCommandSource;
 import net.minecraft.server.network.ServerPlayerEntity;
 import net.minecraft.server.world.ServerWorld;
@@ -64,7 +62,6 @@ import net.minecraft.util.InvalidIdentifierException;
 import net.minecraft.util.math.BlockPos;
 import net.minecraft.util.math.ChunkPos;
 import net.minecraft.util.math.EulerAngle;
-import net.minecraft.util.math.Vec2f;
 import net.minecraft.util.math.Vec3d;
 import net.minecraft.util.registry.DynamicRegistryManager;
 import net.minecraft.util.registry.Registry;

src/main/java/carpet/script/utils/SystemInfo.java

@@ -13,6 +13,7 @@ import carpet.settings.ParsedRule;
 import carpet.settings.SettingsManager;
 import com.sun.management.OperatingSystemMXBean;
 import net.minecraft.util.WorldSavePath;
+import net.minecraft.world.GameRules;
 
 import java.lang.management.ManagementFactory;
 import java.nio.file.Path;
@@ -124,6 +125,17 @@ public class SystemInfo {
             });
             return carpetRules;
         });
+        put("world_gamerules", c->{
+            Map<Value, Value> rules = new HashMap<>();
+            final GameRules gameRules = c.s.getWorld().getGameRules();
+            GameRules.accept(new GameRules.Visitor() {
+                @Override
+                public <T extends GameRules.Rule<T>> void visit(GameRules.Key<T> key, GameRules.Type<T> type) {
+                    rules.put(StringValue.of(key.getName()), StringValue.of(gameRules.get(key).toString()));
+                }
+            });
+            return MapValue.wrap(rules);
+        });
         put("scarpet_version", c -> StringValue.of(CarpetSettings.carpetVersion));
 
     }};