custom events backend, and entity attribute query.

docs/scarpet/api/Entities.md

@@ -519,6 +519,12 @@ Regardless of the options selected, the result could be:
  - block value if block is in reach, or
  - a coordinate triple if `'exact'` option was used and hit was successful.
 
+### `query(e, 'attribute')` `query(e, 'attribute', name)`
+
+returns the value of an attribute of the living entity. If the name is not provided, 
+returns a map of all attributes and values of this entity. If an attribute doesn't apply to the entity,
+or the entity is not a living entity, `null` is returned.
+
 ### `query(e, 'brain', memory)`
 
 Retrieves brain memory for entity. Possible memory units highly depend on the game version. Brain is availalble

src/main/java/carpet/script/CarpetEventServer.java

@@ -1048,6 +1048,37 @@ public class CarpetEventServer
         public void onWorldEvent(ServerWorld world, BlockPos pos) { }
         public void onWorldEventFlag(ServerWorld world, BlockPos pos, int flag) { }
         public void onCarpetRuleChanges(ParsedRule<?> rule, ServerCommandSource source) { }
+        public void onCustomPlayerEvent(ServerPlayerEntity player, Object ... args)
+        {
+            if (handler.reqArgs != (args.length+1))
+                throw new InternalExpressionException("Expected "+handler.reqArgs+" arguments for "+name+", got "+(args.length+1));
+            handler.call(
+                    () -> {
+                        List<Value> valArgs = new ArrayList<>();
+                        valArgs.add(EntityValue.of(player));
+                        for (Object o: args)
+                        {
+                            valArgs.add(ValueConversions.guess(player.getServerWorld(), o));
+                        }
+                        return valArgs;
+                    }, player::getCommandSource
+            );
+        }
+        public void onCustomWorldEvent(ServerWorld world, Object ... args)
+        {
+            if (handler.reqArgs != args.length)
+                throw new InternalExpressionException("Expected "+handler.reqArgs+" arguments for "+name+", got "+args.length);
+            handler.call(
+                    () -> {
+                        List<Value> valArgs = new ArrayList<>();
+                        for (Object o: args)
+                        {
+                            valArgs.add(ValueConversions.guess(world, o));
+                        }
+                        return valArgs;
+                    }, () -> CarpetServer.minecraft_server.getCommandSource().withWorld(world)
+            );
+        }
     }
 
 

src/main/java/carpet/script/value/EntityValue.java

@@ -25,6 +25,8 @@ import net.minecraft.entity.ai.brain.Memory;
 import net.minecraft.entity.EntityGroup;
 import net.minecraft.entity.ai.brain.MemoryModuleType;
 import net.minecraft.entity.ai.pathing.Path;
+import net.minecraft.entity.attribute.AttributeContainer;
+import net.minecraft.entity.attribute.EntityAttribute;
 import net.minecraft.entity.projectile.ProjectileEntity;
 import net.minecraft.entity.vehicle.AbstractMinecartEntity;
 import net.minecraft.nbt.StringTag;
@@ -832,6 +834,22 @@ public class EntityValue extends Value
             return Value.NULL;
         });
 
+        put("attribute", (e, a) ->{
+            if (!(e instanceof LivingEntity)) return Value.NULL;
+            LivingEntity el = (LivingEntity)e;
+            if (a == null)
+            {
+                AttributeContainer container = el.getAttributes();
+                return MapValue.wrap(Registry.ATTRIBUTE.stream().filter(container::hasAttribute).collect(Collectors.toMap(aa -> ValueConversions.of(Registry.ATTRIBUTE.getId(aa)), aa -> NumericValue.of(container.getValue(aa)))));
+            }
+            Identifier id =  new Identifier(a.getString());
+            EntityAttribute attrib = Registry.ATTRIBUTE.getOrEmpty(id).orElseThrow(
+                    () -> new InternalExpressionException("Unknown attribute: "+a.getString())
+            );
+            if (!el.getAttributes().hasAttribute(attrib)) return Value.NULL;
+            return NumericValue.of(el.getAttributeValue(attrib));
+        });
+
         put("nbt",(e, a) -> {
             CompoundTag nbttagcompound = e.toTag((new CompoundTag()));
             if (a==null)

src/main/java/carpet/script/value/ValueConversions.java

@@ -34,6 +34,7 @@ import net.minecraft.util.math.BlockBox;
 import net.minecraft.util.math.BlockPos;
 import net.minecraft.util.math.ColumnPos;
 import net.minecraft.util.math.Vec3d;
+import net.minecraft.util.math.Vec3i;
 import net.minecraft.util.registry.Registry;
 import net.minecraft.util.registry.RegistryKey;
 import net.minecraft.world.World;
@@ -396,4 +397,26 @@ public class ValueConversions
                 predicateData.getCMDataTag() == null?Value.NULL:new NBTSerializableValue(predicateData.getCMDataTag())
         );
     }
+
+    public static Value guess(ServerWorld serverWorld, Object o) {
+        if (o instanceof List)
+            return ListValue.wrap(((List<?>) o).stream().map(oo -> guess(serverWorld, oo)).collect(Collectors.toList()));
+        if (o instanceof BlockPos)
+            return new BlockValue(null, serverWorld, (BlockPos)o);
+        if (o instanceof Entity)
+            return EntityValue.of((Entity) o);
+        if (o instanceof Vec3d)
+            return of((Vec3d)o);
+        if (o instanceof Vec3i)
+            return of(new BlockPos((Vec3i)o));
+        if (o instanceof ItemStack)
+            return of((ItemStack)o);
+        if (o instanceof Boolean)
+            return BooleanValue.of((Boolean) o);
+        if (o instanceof Number)
+            return NumericValue.of((Number) o);
+        if (o instanceof Identifier)
+            return of((Identifier)o);
+        return StringValue.of(o.toString());
+    }
 }