add VoxelStructure lua usertype

src/logic/scripting/lua/libgeneration.cpp

@@ -5,6 +5,8 @@
 #include "coders/binary_json.hpp"
 #include "world/Level.hpp"
 #include "world/generator/VoxelStructure.hpp"
+#include "engine.hpp"
+#include "lua_custom_types.hpp"
 
 using namespace scripting;
 
@@ -25,6 +27,21 @@ static int l_save_structure(lua::State* L) {
     return 0;
 }
 
+static int l_load_structure(lua::State* L) {
+    auto paths = engine->getPaths();
+    auto filename = lua::require_string(L, 1);
+    auto path = paths->resolve(filename);
+    if (!std::filesystem::exists(path)) {
+        throw std::runtime_error("file "+path.u8string()+" does not exist");
+    }
+    auto map = files::read_binary_json(path);
+
+    auto structure = std::make_shared<VoxelStructure>();
+    structure->deserialize(map);
+    return lua::newuserdata<lua::LuaVoxelStructure>(L, std::move(structure));
+}
+
 const luaL_Reg generationlib[] = {
     {"save_structure", lua::wrap<l_save_structure>},
+    {"load_structure", lua::wrap<l_load_structure>},
     {NULL, NULL}};