path: root/src/scriptapi.cpp

/*
Minetest-c55
Copyright (C) 2011 celeron55, Perttu Ahola <celeron55@gmail.com>

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License along
with this program; if not, write to the Free Software Foundation, Inc.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/

#include "scriptapi.h"

#include <iostream>
extern "C" {
#include <lua.h>
#include <lualib.h>
#include <lauxlib.h>
}

#include "log.h"
#include "server.h"
#include "porting.h"
#include "filesys.h"
#include "serverobject.h"
#include "script.h"
//#include "luna.h"
#include "luaentity_common.h"
#include "content_sao.h" // For LuaEntitySAO

/*
TODO:
- Node type definition
- Random node triggers
- Object visual client-side stuff
	- Blink effect
	- Spritesheets and animation
- Named node types and dynamic id allocation per MapBlock
- LuaNodeMetadata
	blockdef.has_metadata = true/false
	- Stores an inventory and stuff in a Settings object
	meta.inventory_add_list("main")
	blockdef.on_inventory_modified
	meta.set("owner", playername)
	meta.get("owner")
*/

static void stackDump(lua_State *L, std::ostream &o)
{
  int i;
  int top = lua_gettop(L);
  for (i = 1; i <= top; i++) {  /* repeat for each level */
	int t = lua_type(L, i);
	switch (t) {

	  case LUA_TSTRING:  /* strings */
	  	o<<"\""<<lua_tostring(L, i)<<"\"";
		break;

	  case LUA_TBOOLEAN:  /* booleans */
		o<<(lua_toboolean(L, i) ? "true" : "false");
		break;

	  case LUA_TNUMBER:  /* numbers */ {
	  	char buf[10];
		snprintf(buf, 10, "%g", lua_tonumber(L, i));
		o<<buf;
		break; }

	  default:  /* other values */
		o<<lua_typename(L, t);
		break;

	}
	o<<" ";
  }
  o<<std::endl;
}

static void realitycheck(lua_State *L)
{
	int top = lua_gettop(L);
	if(top >= 30){
		dstream<<"Stack is over 30:"<<std::endl;
		stackDump(L, dstream);
		script_error(L, "Stack is over 30 (reality check)");
	}
}

class StackUnroller
{
private:
	lua_State *m_lua;
	int m_original_top;
public:
	StackUnroller(lua_State *L):
		m_lua(L),
		m_original_top(-1)
	{
		m_original_top = lua_gettop(m_lua); // store stack height
	}
	~StackUnroller()
	{
		lua_settop(m_lua, m_original_top); // restore stack height
	}
};

v3f readFloatPos(lua_State *L, int index)
{
	v3f pos;
	lua_pushvalue(L, index); // Push pos
	luaL_checktype(L, -1, LUA_TTABLE);
	lua_getfield(L, -1, "x");
	pos.X = lua_tonumber(L, -1);
	lua_pop(L, 1);
	lua_getfield(L, -1, "y");
	pos.Y = lua_tonumber(L, -1);
	lua_pop(L, 1);
	lua_getfield(L, -1, "z");
	pos.Z = lua_tonumber(L, -1);
	lua_pop(L, 1);
	lua_pop(L, 1); // Pop pos
	pos *= BS; // Scale to internal format
	return pos;
}

/*
	Global functions
*/

// Register new object prototype
// register_entity(name, prototype)
static int l_register_entity(lua_State *L)
{
	const char *name = luaL_checkstring(L, 1);
	luaL_checktype(L, 2, LUA_TTABLE);
	infostream<<"register_entity: "<<name<<std::endl;

	// Get minetest.registered_entities
	lua_getglobal(L, "minetest");
	lua_getfield(L, -1, "registered_entities");
	luaL_checktype(L, -1, LUA_TTABLE);
	int registered_entities = lua_gettop(L);
	lua_pushvalue(L, 2); // Object = param 2 -> stack top
	// registered_entities[name] = object
	lua_setfield(L, registered_entities, name);
	
	// Get registered object to top of stack
	lua_pushvalue(L, 2);
	
	// Set __index to point to itself
	lua_pushvalue(L, -1);
	lua_setfield(L, -2, "__index");

	// Set metatable.__index = metatable
	luaL_getmetatable(L, "minetest.entity");
	lua_pushvalue(L, -1); // duplicate metatable
	lua_setfield(L, -2, "__index");
	// Set object metatable
	lua_setmetatable(L, -2);

	return 0; /* number of results */
}

// Register a global step function
// register_globalstep(function)
static int l_register_globalstep(lua_State *L)
{
	luaL_checktype(L, 1, LUA_TFUNCTION);
	infostream<<"register_globalstep"<<std::endl;

	lua_getglobal(L, "table");
	lua_getfield(L, -1, "insert");
	int table_insert = lua_gettop(L);
	// Get minetest.registered_globalsteps
	lua_getglobal(L, "minetest");
	lua_getfield(L, -1, "registered_globalsteps");
	luaL_checktype(L, -1, LUA_TTABLE);
	int registered_globalsteps = lua_gettop(L);
	// table.insert(registered_globalsteps, func)
	lua_pushvalue(L, table_insert);
	lua_pushvalue(L, registered_globalsteps);
	lua_pushvalue(L, 1); // push function from argument 1
	// Call insert
	if(lua_pcall(L, 2, 0, 0))
		script_error(L, "error: %s\n", lua_tostring(L, -1));

	return 0; /* number of results */
}

static const struct luaL_Reg minetest_f [] = {
	{"register_entity", l_register_entity},
	{"register_globalstep", l_register_globalstep},
	{NULL, NULL}
};

/*
	LuaEntity functions
*/

static const struct luaL_Reg minetest_entity_m [] = {
	{NULL, NULL}
};

/*
	Getters for stuff in main tables
*/

static void objectref_get(lua_State *L, u16 id)
{
	// Get minetest.object_refs[i]
	lua_getglobal(L, "minetest");
	lua_getfield(L, -1, "object_refs");
	luaL_checktype(L, -1, LUA_TTABLE);
	lua_pushnumber(L, id);
	lua_gettable(L, -2);
	lua_remove(L, -2); // object_refs
	lua_remove(L, -2); // minetest
}

static void luaentity_get(lua_State *L, u16 id)
{
	// Get minetest.luaentities[i]
	lua_getglobal(L, "minetest");
	lua_getfield(L, -1, "luaentities");
	luaL_checktype(L, -1, LUA_TTABLE);
	lua_pushnumber(L, id);
	lua_gettable(L, -2);
	lua_remove(L, -2); // luaentities
	lua_remove(L, -2); // minetest
}

/*
	Reference objects
*/
#define method(class, name) {#name, class::l_##name}

class EnvRef
{
private:
	ServerEnvironment *m_env;

	static const char className[];
	static const luaL_reg methods[];

	static EnvRef *checkobject(lua_State *L, int narg)
	{
		luaL_checktype(L, narg, LUA_TUSERDATA);
		void *ud = luaL_checkudata(L, narg, className);
		if(!ud) luaL_typerror(L, narg, className);
		return *(EnvRef**)ud;  // unbox pointer
	}
	
	// Exported functions

	// EnvRef:add_node(pos, content)
	// pos = {x=num, y=num, z=num}
	// content = number
	static int l_add_node(lua_State *L)
	{
		infostream<<"EnvRef::l_add_node()"<<std::endl;
		EnvRef *o = checkobject(L, 1);
		ServerEnvironment *env = o->m_env;
		if(env == NULL) return 0;
		// pos
		v3s16 pos;
		lua_pushvalue(L, 2); // Push pos
		luaL_checktype(L, -1, LUA_TTABLE);
		lua_getfield(L, -1, "x");
		pos.X = lua_tonumber(L, -1);
		lua_pop(L, 1);
		lua_getfield(L, -1, "y");
		pos.Y = lua_tonumber(L, -1);
		lua_pop(L, 1);
		lua_getfield(L, -1, "z");
		pos.Z = lua_tonumber(L, -1);
		lua_pop(L, 1);
		lua_pop(L, 1); // Pop pos
		// content
		u16 content = 0;
		lua_pushvalue(L, 3); // Push content
		content = lua_tonumber(L, -1);
		lua_pop(L, 1); // Pop content
		// Do it
		env->getMap().addNodeWithEvent(pos, MapNode(content));
		return 0;
	}

	static int gc_object(lua_State *L) {
		EnvRef *o = *(EnvRef **)(lua_touserdata(L, 1));
		delete o;
		return 0;
	}

public:
	EnvRef(ServerEnvironment *env):
		m_env(env)
	{
		infostream<<"EnvRef created"<<std::endl;
	}

	~EnvRef()
	{
		infostream<<"EnvRef destructing"<<std::endl;
	}

	// Creates an EnvRef and leaves it on top of stack
	// Not callable from Lua; all references are created on the C side.
	static void create(lua_State *L, ServerEnvironment *env)
	{
		EnvRef *o = new EnvRef(env);
		//infostream<<"EnvRef::create: o="<<o<<std::endl;
		*(void **)(lua_newuserdata(L, sizeof(void *))) = o;
		luaL_getmetatable(L, className);
		lua_setmetatable(L, -2);
	}

	static void set_null(lua_State *L)
	{
		EnvRef *o = checkobject(L, -1);
		o->m_env = NULL;
	}
	
	static void Register(lua_State *L)
	{
		lua_newtable(L);
		int methodtable = lua_gettop(L);
		luaL_newmetatable(L, className);
		int metatable = lua_gettop(L);

		lua_pushliteral(L, "__metatable");
		lua_pushvalue(L, methodtable);
		lua_settable(L, metatable);  // hide metatable from Lua getmetatable()

		lua_pushliteral(L, "__index");
		lua_pushvalue(L, methodtable);
		lua_settable(L, metatable);

		lua_pushliteral(L, "__gc");
		lua_pushcfunction(L, gc_object);
		lua_settable(L, metatable);

		lua_pop(L, 1);  // drop metatable

		luaL_openlib(L, 0, methods, 0);  // fill methodtable
		lua_pop(L, 1);  // drop methodtable

		// Cannot be created from Lua
		//lua_register(L, className, create_object);
	}
};
const char EnvRef::className[] = "EnvRef";
const luaL_reg EnvRef::methods[] = {
	method(EnvRef, add_node),
	{0,0}
};

class ObjectRef
{
private:
	ServerActiveObject *m_object;

	static const char className[];
	static const luaL_reg methods[];

	static ObjectRef *checkobject(lua_State *L, int narg)
	{
		luaL_checktype(L, narg, LUA_TUSERDATA);
		void *ud = luaL_checkudata(L, narg, className);
		if(!ud) luaL_typerror(L, narg, className);
		return *(ObjectRef**)ud;  // unbox pointer
	}
	
	static ServerActiveObject* getobject(ObjectRef *ref)
	{
		ServerActiveObject *co = ref->m_object;
		return co;
	}
	
	static LuaEntitySAO* getluaobject(ObjectRef *ref)
	{
		ServerActiveObject *obj = getobject(ref);
		if(obj == NULL)
			return NULL;
		if(obj->getType() != ACTIVEOBJECT_TYPE_LUAENTITY)
			return NULL;
		return (LuaEntitySAO*)obj;
	}
	
	// Exported functions
	
	// garbage collector
	static int gc_object(lua_State *L) {
		ObjectRef *o = *(ObjectRef **)(lua_touserdata(L, 1));
		//infostream<<"ObjectRef::gc_object: o="<<o<<std::endl;
		delete o;
		return 0;
	}

	// remove(self)
	static int l_remove(lua_State *L)
	{
		ObjectRef *ref = checkobject(L, 1);
		ServerActiveObject *co = getobject(ref);
		if(co == NULL) return 0;
		infostream<<"ObjectRef::l_remove(): id="<<co->getId()<<std::endl;
		co->m_removed = true;
		return 0;
	}
	
	// getpos(self)
	// returns: {x=num, y=num, z=num}
	static int l_getpos(lua_State *L)
	{
		ObjectRef *ref = checkobject(L, 1);
		ServerActiveObject *co = getobject(ref);
		if(co == NULL) return 0;
		v3f pos = co->getBasePosition() / BS;
		lua_newtable(L);
		lua_pushnumber(L, pos.X);
		lua_setfield(L, -2, "x");
		lua_pushnumber(L, pos.Y);
		lua_setfield(L, -2, "y");
		lua_pushnumber(L, pos.Z);
		lua_setfield(L, -2, "z");
		return 1;
	}
	
	// setpos(self, pos)
	static int l_setpos(lua_State *L)
	{
		ObjectRef *ref = checkobject(L, 1);
		//LuaEntitySAO *co = getluaobject(ref);
		ServerActiveObject *co = getobject(ref);
		if(co == NULL) return 0;
		// pos
		v3f pos = readFloatPos(L, 2);
		// Do it
		co->setPos(pos);
		return 0;
	}
	
	// moveto(self, pos, continuous=false)
	static int l_moveto(lua_State *L)
	{
		ObjectRef *ref = checkobject(L, 1);
		//LuaEntitySAO *co = getluaobject(ref);
		ServerActiveObject *co = getobject(ref);
		if(co == NULL) return 0;
		// pos
		v3f pos = readFloatPos(L, 2);
		// continuous
		bool continuous = lua_toboolean(L, 3);
		// Do it
		co->moveTo(pos, continuous);
		return 0;
	}

	// add_to_inventory(self, itemstring)
	// returns: true if item was added, false otherwise
	static int l_add_to_inventory(lua_State *L)
	{
		ObjectRef *ref = checkobject(L, 1);
		luaL_checkstring(L, 2);
		ServerActiveObject *co = getobject(ref);
		if(co == NULL) return 0;
		// itemstring
		const char *itemstring = lua_tostring(L, 2);
		infostream<<"ObjectRef::l_add_to_inventory(): id="<<co->getId()
				<<" itemstring=\""<<itemstring<<"\""<<std::endl;
		// Do it
		std::istringstream is(itemstring, std::ios::binary);
		ServerEnvironment *env = co->getEnv();
		assert(env);
		IGameDef *gamedef = env->getGameDef();
		InventoryItem *item = InventoryItem::deSerialize(is, gamedef);
		infostream<<"item="<<env<<std::endl;
		bool fits = co->addToInventory(item);
		// Return
		lua_pushboolean(L, fits);
		return 1;
	}

public:
	ObjectRef(ServerActiveObject *object):
		m_object(object)
	{
		//infostream<<"ObjectRef created for id="<<m_object->getId()<<std::endl;
	}

	~ObjectRef()
	{
		/*if(m_object)
			infostream<<"ObjectRef destructing for id="
					<<m_object->getId()<<std::endl;
		else
			infostream<<"ObjectRef destructing for id=unknown"<<std::endl;*/
	}

	// Creates an ObjectRef and leaves it on top of stack
	// Not callable from Lua; all references are created on the C side.
	static void create(lua_State *L, ServerActiveObject *object)
	{
		ObjectRef *o = new ObjectRef(object);
		//infostream<<"ObjectRef::create: o="<<o<<std::endl;
		*(void **)(lua_newuserdata(L, sizeof(void *))) = o;
		luaL_getmetatable(L, className);
		lua_setmetatable(L, -2);
	}

	static void set_null(lua_State *L)
	{
		ObjectRef *o = checkobject(L, -1);
		o->m_object = NULL;
	}
	
	static void Register(lua_State *L)
	{
		lua_newtable(L);
		int methodtable = lua_gettop(L);
		luaL_newmetatable(L, className);
		int metatable = lua_gettop(L);

		lua_pushliteral(L, "__metatable");
		lua_pushvalue(L, methodtable);
		lua_settable(L, metatable);  // hide metatable from Lua getmetatable()

		lua_pushliteral(L, "__index");
		lua_pushvalue(L, methodtable);
		lua_settable(L, metatable);

		lua_pushliteral(L, "__gc");
		lua_pushcfunction(L, gc_object);
		lua_settable(L, metatable);

		lua_pop(L, 1);  // drop metatable

		luaL_openlib(L, 0, methods, 0);  // fill methodtable
		lua_pop(L, 1);  // drop methodtable

		// Cannot be created from Lua
		//lua_register(L, className, create_object);
	}
};
const char ObjectRef::className[] = "ObjectRef";
const luaL_reg ObjectRef::methods[] = {
	method(ObjectRef, remove),
	method(ObjectRef, getpos),
	method(ObjectRef, setpos),
	method(ObjectRef, moveto),
	method(ObjectRef, add_to_inventory),
	{0,0}
};

// Creates a new anonymous reference if id=0
static void objectref_get_or_create(lua_State *L,
		ServerActiveObject *cobj)
{
	if(cobj->getId() == 0){
		ObjectRef::create(L, cobj);
	} else {
		objectref_get(L, cobj->getId());
	}
}

/*
	Main export function
*/

void scriptapi_export(lua_State *L, Server *server)
{
	realitycheck(L);
	assert(lua_checkstack(L, 20));
	infostream<<"scriptapi_export"<<std::endl;
	StackUnroller stack_unroller(L);
	
	// Register global functions in table minetest
	lua_newtable(L);
	luaL_register(L, NULL, minetest_f);
	lua_setglobal(L, "minetest");
	
	// Get the main minetest table
	lua_getglobal(L, "minetest");

	// Add tables to minetest
	
	/*lua_newtable(L);
	lua_setfield(L, -2, "registered_blocks");*/

	lua_newtable(L);
	lua_setfield(L, -2, "registered_entities");

	lua_newtable(L);
	lua_setfield(L, -2, "registered_globalsteps");

	lua_newtable(L);
	lua_setfield(L, -2, "object_refs");

	lua_newtable(L);
	lua_setfield(L, -2, "luaentities");

	// Create entity prototype
	luaL_newmetatable(L, "minetest.entity");
	// metatable.__index = metatable
	lua_pushvalue(L, -1); // Duplicate metatable
	lua_setfield(L, -2, "__index");
	// Put functions in metatable
	luaL_register(L, NULL, minetest_entity_m);
	// Put other stuff in metatable

	// Environment C reference
	EnvRef::Register(L);

	// Object C reference
	ObjectRef::Register(L);
}

void scriptapi_add_environment(lua_State *L, ServerEnvironment *env)
{
	realitycheck(L);
	assert(lua_checkstack(L, 20));
	infostream<<"scriptapi_add_environment"<<std::endl;
	StackUnroller stack_unroller(L);

	// Create EnvRef on stack
	EnvRef::create(L, env);
	int envref = lua_gettop(L);

	// minetest.env = envref
	lua_getglobal(L, "minetest");
	luaL_checktype(L, -1, LUA_TTABLE);
	lua_pushvalue(L, envref);
	lua_setfield(L, -2, "env");
}

#if 0
// Dump stack top with the dump2 function
static void dump2(lua_State *L, const char *name)
{
	// Dump object (debug)
	lua_getglobal(L, "dump2");
	luaL_checktype(L, -1, LUA_TFUNCTION);
	lua_pushvalue(L, -2); // Get previous stack top as first parameter
	lua_pushstring(L, name);
	if(lua_pcall(L, 2, 0, 0))
		script_error(L, "error: %s\n", lua_tostring(L, -1));
}
#endif

/*
	object_reference
*/

void scriptapi_add_object_reference(lua_State *L, ServerActiveObject *cobj)
{
	realitycheck(L);
	assert(lua_checkstack(L, 20));
	infostream<<"scriptapi_add_object_reference: id="<<cobj->getId()<<std::endl;
	StackUnroller stack_unroller(L);

	// Create object on stack
	ObjectRef::create(L, cobj); // Puts ObjectRef (as userdata) on stack
	int object = lua_gettop(L);

	// Get minetest.object_refs table
	lua_getglobal(L, "minetest");
	lua_getfield(L, -1, "object_refs");
	luaL_checktype(L, -1, LUA_TTABLE);
	int objectstable = lua_gettop(L);
	
	// object_refs[id] = object
	lua_pushnumber(L, cobj->getId()); // Push id
	lua_pushvalue(L, object); // Copy object to top of stack
	lua_settable(L, objectstable);
}

void scriptapi_rm_object_reference(lua_State *L, ServerActiveObject *cobj)
{
	realitycheck(L);
	assert(lua_checkstack(L, 20));
	infostream<<"scriptapi_rm_object_reference: id="<<cobj->getId()<<std::endl;
	StackUnroller stack_unroller(L);

	// Get minetest.object_refs table
	lua_getglobal(L, "minetest");
	lua_getfield(L, -1, "object_refs");
	luaL_checktype(L, -1, LUA_TTABLE);
	int objectstable = lua_gettop(L);
	
	// Get object_refs[id]
	lua_pushnumber(L, cobj->getId()); // Push id
	lua_gettable(L, objectstable);
	// Set object reference to NULL
	ObjectRef::set_null(L);
	lua_pop(L, 1); // pop object

	// Set object_refs[id] = nil
	lua_pushnumber(L, cobj->getId()); // Push id
	lua_pushnil(L);
	lua_settable(L, objectstable);
}

/*
	environment
*/

void scriptapi_environment_step(lua_State *L, float dtime)
{
	realitycheck(L);
	assert(lua_checkstack(L, 20));
	//infostream<<"scriptapi_luaentity_step: id="<<id<<std::endl;
	StackUnroller stack_unroller(L);

	// Get minetest.registered_globalsteps
	lua_getglobal(L, "minetest");
	lua_getfield(L, -1, "registered_globalsteps");
	luaL_checktype(L, -1, LUA_TTABLE);
	int table = lua_gettop(L);
	// Foreach
	lua_pushnil(L);
	while(lua_next(L, table) != 0){
		// key at index -2 and value at index -1
		luaL_checktype(L, -1, LUA_TFUNCTION);
		// Call function
		lua_pushnumber(L, dtime);
		if(lua_pcall(L, 1, 0, 0))
			script_error(L, "error: %s\n", lua_tostring(L, -1));
		// value removed, keep key for next iteration
	}
}

/*
	luaentity
*/

bool scriptapi_luaentity_add(lua_State *L, u16 id, const char *name,
		const char *init_state)
{
	realitycheck(L);
	assert(lua_checkstack(L, 20));
	infostream<<"scriptapi_luaentity_add: id="<<id<<" name=\""
			<<name<<"\""<<std::endl;
	StackUnroller stack_unroller(L);
	
	// Create object as a dummy string (TODO: Create properly)

	// Get minetest.registered_entities[name]
	lua_getglobal(L, "minetest");
	lua_getfield(L, -1, "registered_entities");
	luaL_checktype(L, -1, LUA_TTABLE);
	lua_pushstring(L, name);
	lua_gettable(L, -2);
	// Should be a table, which we will use as a prototype
	//luaL_checktype(L, -1, LUA_TTABLE);
	if(lua_type(L, -1) != LUA_TTABLE){
		errorstream<<"LuaEntity name \""<<name<<"\" not defined"<<std::endl;
		return false;
	}
	int prototype_table = lua_gettop(L);
	//dump2(L, "prototype_table");
	
	// Create entity object
	lua_newtable(L);
	int object = lua_gettop(L);

	// Set object metatable
	lua_pushvalue(L, prototype_table);
	lua_setmetatable(L, -2);
	
	// Add object reference
	// This should be userdata with metatable ObjectRef
	objectref_get(L, id);
	luaL_checktype(L, -1, LUA_TUSERDATA);
	if(!luaL_checkudata(L, -1, "ObjectRef"))
		luaL_typerror(L, -1, "ObjectRef");
	lua_setfield(L, -2, "object");

	// minetest.luaentities[id] = object
	lua_getglobal(L, "minetest");
	lua_getfield(L, -1, "luaentities");
	luaL_checktype(L, -1, LUA_TTABLE);
	lua_pushnumber(L, id); // Push id
	lua_pushvalue(L, object); // Copy object to top of stack
	lua_settable(L, -3);
	
	// This callback doesn't really make sense
	/*// Get on_activate function
	lua_pushvalue(L, object);
	lua_getfield(L, -1, "on_activate");
	luaL_checktype(L, -1, LUA_TFUNCTION);
	lua_pushvalue(L, object); // self
	// Call with 1 arguments, 0 results
	if(lua_pcall(L, 1, 0, 0))
		script_error(L, "error running function %s:on_activate: %s\n",
				name, lua_tostring(L, -1));*/

	return true;
}

void scriptapi_luaentity_rm(lua_State *L, u16 id)
{
	realitycheck(L);
	assert(lua_checkstack(L, 20));
	infostream<<"scriptapi_luaentity_rm: id="<<id<<std::endl;

	// Get minetest.luaentities table
	lua_getglobal(L, "minetest");
	lua_getfield(L, -1, "luaentities");
	luaL_checktype(L, -1, LUA_TTABLE);
	int objectstable = lua_gettop(L);
	
	// Set luaentities[id] = nil
	lua_pushnumber(L, id); // Push id
	lua_pushnil(L);
	lua_settable(L, objectstable);
	
	lua_pop(L, 2); // pop luaentities, minetest
}

std::string scriptapi_luaentity_get_state(lua_State *L, u16 id)
{
	realitycheck(L);
	assert(lua_checkstack(L, 20));
	infostream<<"scriptapi_luaentity_get_state: id="<<id<<std::endl;
	
	return "";
}

void scriptapi_luaentity_get_properties(lua_State *L, u16 id,
		LuaEntityProperties *prop)
{
	realitycheck(L);
	assert(lua_checkstack(L, 20));
	infostream<<"scriptapi_luaentity_get_properties: id="<<id<<std::endl;
	StackUnroller stack_unroller(L);

	// Get minetest.luaentities[id]
	luaentity_get(L, id);
	//int object = lua_gettop(L);

	lua_getfield(L, -1, "physical");
	if(lua_isboolean(L, -1))
		prop->physical = lua_toboolean(L, -1);
	lua_pop(L, 1);
	
	lua_getfield(L, -1, "weight");
	prop->weight = lua_tonumber(L, -1);
	lua_pop(L, 1);

	lua_getfield(L, -1, "collisionbox");
	if(lua_istable(L, -1)){
		lua_rawgeti(L, -1, 1);
		prop->collisionbox.MinEdge.X = lua_tonumber(L, -1);
		lua_pop(L, 1);
		lua_rawgeti(L, -1, 2);
		prop->collisionbox.MinEdge.Y = lua_tonumber(L, -1);
		lua_pop(L, 1);
		lua_rawgeti(L, -1, 3);
		prop->collisionbox.MinEdge.Z = lua_tonumber(L, -1);
		lua_pop(L, 1);
		lua_rawgeti(L, -1, 4);
		prop->collisionbox.MaxEdge.X = lua_tonumber(L, -1);
		lua_pop(L, 1);
		lua_rawgeti(L, -1, 5);
		prop->collisionbox.MaxEdge.Y = lua_tonumber(L, -1);
		lua_pop(L, 1);
		lua_rawgeti(L, -1, 6);
		prop->collisionbox.MaxEdge.Z = lua_tonumber(L, -1);
		lua_pop(L, 1);
	}
	lua_pop(L, 1);

	lua_getfield(L, -1, "visual");
	if(lua_isstring(L, -1))
		prop->visual = lua_tostring(L, -1);
	lua_pop(L, 1);
	
	lua_getfield(L, -1, "textures");
	if(lua_istable(L, -1)){
		prop->textures.clear();
		int table = lua_gettop(L);
		lua_pushnil(L);
		while(lua_next(L, table) != 0){
			// key at index -2 and value at index -1
			if(lua_isstring(L, -1))
				prop->textures.push_back(lua_tostring(L, -1));
			else
				prop->textures.push_back("");
			// removes value, keeps key for next iteration
			lua_pop(L, 1);
		}
	}
	lua_pop(L, 1);

}

void scriptapi_luaentity_step(lua_State *L, u16 id, float dtime)
{
	realitycheck(L);
	assert(lua_checkstack(L, 20));
	//infostream<<"scriptapi_luaentity_step: id="<<id<<std::endl;
	StackUnroller stack_unroller(L);

	// Get minetest.luaentities[id]
	luaentity_get(L, id);
	int object = lua_gettop(L);
	// State: object is at top of stack
	// Get step function
	lua_getfield(L, -1, "on_step");
	luaL_checktype(L, -1, LUA_TFUNCTION);
	lua_pushvalue(L, object); // self
	lua_pushnumber(L, dtime); // dtime
	// Call with 2 arguments, 0 results
	if(lua_pcall(L, 2, 0, 0))
		script_error(L, "error running function 'step': %s\n", lua_tostring(L, -1));
}

// Calls entity:on_punch(ObjectRef puncher)
void scriptapi_luaentity_punch(lua_State *L, u16 id,
		ServerActiveObject *puncher)
{
	realitycheck(L);
	assert(lua_checkstack(L, 20));
	//infostream<<"scriptapi_luaentity_step: id="<<id<<std::endl;
	StackUnroller stack_unroller(L);

	// Get minetest.luaentities[id]
	luaentity_get(L, id);
	int object = lua_gettop(L);
	// State: object is at top of stack
	// Get function
	lua_getfield(L, -1, "on_punch");
	luaL_checktype(L, -1, LUA_TFUNCTION);
	lua_pushvalue(L, object); // self
	objectref_get_or_create(L, puncher); // Clicker reference
	// Call with 2 arguments, 0 results
	if(lua_pcall(L, 2, 0, 0))
		script_error(L, "error running function 'on_punch': %s\n", lua_tostring(L, -1));
}

// Calls entity:on_rightclick(ObjectRef clicker)
void scriptapi_luaentity_rightclick(lua_State *L, u16 id,
		ServerActiveObject *clicker)
{
	realitycheck(L);
	assert(lua_checkstack(L, 20));
	//infostream<<"scriptapi_luaentity_step: id="<<id<<std::endl;
	StackUnroller stack_unroller(L);

	// Get minetest.luaentities[id]
	luaentity_get(L, id);
	int object = lua_gettop(L);
	// State: object is at top of stack
	// Get function
	lua_getfield(L, -1, "on_rightclick");
	luaL_checktype(L, -1, LUA_TFUNCTION);
	lua_pushvalue(L, object); // self
	objectref_get_or_create(L, clicker); // Clicker reference
	// Call with 2 arguments, 0 results
	if(lua_pcall(L, 2, 0, 0))
		script_error(L, "error running function 'on_rightclick': %s\n", lua_tostring(L, -1));
}