SecretRoomPiece

public class SecretRoomPiece
{

    private static final ResourceLocation SECRET_ROOM = new ResourceLocation(Necromod.MODID, "secret_room");

    private static final Map<ResourceLocation, BlockPos> OFFSET = ImmutableMap.of(SECRET_ROOM, new BlockPos(0, 1, 0));

    public static void start(TemplateManager manager, BlockPos pos, Rotation rot, List<StructurePiece> pieces, Random rand) {
        BlockPos rotationOffset = new BlockPos(0, 0, 0).rotate(rot);
        BlockPos blockPos = rotationOffset.offset(pos);
        pieces.add(new SecretRoomPiece.Piece(manager, SECRET_ROOM, blockPos, rot));
    }

    public static class Piece extends TemplateStructurePiece {
        private final ResourceLocation resourceLocation;
        private final Rotation rotation;


        public Piece(TemplateManager templateManagerIn, ResourceLocation resourceLocationIn, BlockPos pos, Rotation rotationIn) {
            super(NecromodStructures.Secret_Room_Piece, 0);
            this.resourceLocation = resourceLocationIn;
            this.templatePosition = pos;
            this.rotation = rotationIn;
            this.loadTemplate(templateManagerIn);
        }


        public Piece(TemplateManager templateManagerIn, CompoundNBT tagCompound) {
            super(NecromodStructures.Secret_Room_Piece, tagCompound);
            this.resourceLocation = new ResourceLocation(tagCompound.getString("Template"));
            this.rotation = Rotation.valueOf(tagCompound.getString("Rot"));
            this.loadTemplate(templateManagerIn);
        }


        private void loadTemplate(TemplateManager templateManager) {
            Template template = templateManager.getOrCreate(this.resourceLocation);
            PlacementSettings placementsettings = (new PlacementSettings()).setRotation(this.rotation).setMirror(Mirror.NONE);
            this.setup(template, this.templatePosition, placementsettings);
        }


        /**
         * (abstract) Helper method to read subclass data from NBT
         */
        @Override
        protected void addAdditionalSaveData(CompoundNBT tagCompound) {
            super.addAdditionalSaveData(tagCompound);
            tagCompound.putString("Template", this.resourceLocation.toString());
            tagCompound.putString("Rot", this.rotation.name());
        }

        @Override
        protected void handleDataMarker(String function, BlockPos pos, IServerWorld worldIn, Random rand, MutableBoundingBox sbb)
        {
            if ("chest".equals(function))
            {
                worldIn.setBlock(pos, Blocks.AIR.defaultBlockState(), 3);
                TileEntity tileentity = worldIn.getBlockEntity(pos.below());
                if (tileentity instanceof ChestTileEntity)
                {
                   ((ChestTileEntity)tileentity).setLootTable(NecromodLootTable.SECRET_ROOM_CHEST, rand.nextLong());
                }

             }

        }

        @Override
        public boolean postProcess(ISeedReader p_230383_1_, StructureManager p_230383_2_, ChunkGenerator p_230383_3_, Random p_230383_4_, MutableBoundingBox p_230383_5_, ChunkPos p_230383_6_, BlockPos p_230383_7_)
        {
            this.placeSettings.setRotation(this.rotation).setMirror(Mirror.NONE).setIgnoreEntities(true);
            BlockPos blockpos = SecretRoomPiece.OFFSET.get(this.resourceLocation);
            this.templatePosition.offset(Template.calculateRelativePosition(placeSettings, new BlockPos(0 - blockpos.getX(), blockpos.getY(), 0 - blockpos.getZ())));

            return super.postProcess(p_230383_1_, p_230383_2_, p_230383_3_, p_230383_4_, p_230383_5_, p_230383_6_, p_230383_7_);
        }
    }
}