path: root/src/scripting/lua.cpp

/*
 *  The Mana World Server
 *  Copyright 2007 The Mana World Development Team
 *
 *  This file is part of The Mana World.
 *
 *  The Mana World 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
 *  any later version.
 *
 *  The Mana World 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 The Mana World; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 *  $Id$
 */

#include <cassert>

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

#include "defines.h"
#include "game-server/accountconnection.hpp"
#include "game-server/buysell.hpp"
#include "game-server/character.hpp"
#include "game-server/collisiondetection.hpp"
#include "game-server/gamehandler.hpp"
#include "game-server/inventory.hpp"
#include "game-server/item.hpp"
#include "game-server/itemmanager.hpp"
#include "game-server/mapcomposite.hpp"
#include "game-server/mapmanager.hpp"
#include "game-server/monster.hpp"
#include "game-server/monstermanager.hpp"
#include "game-server/npc.hpp"
#include "game-server/quest.hpp"
#include "game-server/state.hpp"
#include "game-server/trigger.hpp"
#include "net/messageout.hpp"
#include "scripting/script.hpp"
#include "utils/logger.h"

/**
 * Implementation of the Script class for Lua.
 */
class LuaScript: public Script
{
    public:
        /**
         * Constructor.
         */
        LuaScript();

        /**
         * Destructor.
         */
        ~LuaScript();

        void load(char const *);

        void prepare(std::string const &);

        void push(int);

        void push(const std::string &);

        void push(Thing *);

        int execute();

        static void getQuestCallback(Character *, std::string const &,
                                     std::string const &, void *);

        void processDeathEvent(Being* thing);

    private:

        lua_State *mState;
        int nbArgs;
};

static char const registryKey = 0;


void raiseScriptError(lua_State *s, const char *format, ...)
{
    va_list args;
    va_start(args, format);
    char message[1024];
    vsprintf(message, format, args);
    va_end( args );

    LOG_WARN("Lua script error: "<<message);
    luaL_error(s, message);
}

/* Functions below are unsafe, as they assume the script has passed pointers
   to objects which have not yet been destroyed. If the script never keeps
   pointers around, there will be no problem. In order to be safe, the engine
   should replace pointers by local identifiers and store them in a map. By
   listening to the death of objects, it could keep track of pointers still
   valid in the map.
   TODO: do it. */

static NPC *getNPC(lua_State *s, int p)
{
    if (!lua_islightuserdata(s, p)) return NULL;
    Thing *t = static_cast<Thing *>(lua_touserdata(s, p));
    if (t->getType() != OBJECT_NPC) return NULL;
    return static_cast<NPC *>(t);
}

static Character *getCharacter(lua_State *s, int p)
{
    if (!lua_islightuserdata(s, p)) return NULL;
    Thing *t = static_cast<Thing *>(lua_touserdata(s, p));
    if (t->getType() != OBJECT_CHARACTER) return NULL;
    return static_cast<Character *>(t);
}

static Being *getBeing(lua_State *s, int p)
{
    if (!lua_islightuserdata(s, p)) return NULL;
    Thing *t = static_cast<Thing *>(lua_touserdata(s, p));
    return static_cast<Being *>(t);
}

/**
 * Callback for sending a NPC_MESSAGE.
 * tmw.npc_message(npc, character, string)
 */
static int LuaNpc_Message(lua_State *s)
{
    NPC *p = getNPC(s, 1);
    Character *q = getCharacter(s, 2);
    size_t l;
    char const *m = lua_tolstring(s, 3, &l);
    if (!p || !q || !m)
    {
        raiseScriptError(s, "npc_message called with incorrect parameters.");
        return 0;
    }
    MessageOut msg(GPMSG_NPC_MESSAGE);
    msg.writeShort(p->getPublicID());
    msg.writeString(std::string(m), l);
    gameHandler->sendTo(q, msg);
    return 0;
}

/**
 * Callback for sending a NPC_CHOICE.
 * tmw.npc_choice(npc, character, string...)
 */
static int LuaNpc_Choice(lua_State *s)
{
    NPC *p = getNPC(s, 1);
    Character *q = getCharacter(s, 2);
    if (!p || !q)
    {
        raiseScriptError(s, "npc_Choice called with incorrect parameters.");
        return 0;
    }
    MessageOut msg(GPMSG_NPC_CHOICE);
    msg.writeShort(p->getPublicID());
    for (int i = 3, i_end = lua_gettop(s); i <= i_end; ++i)
    {
        char const *m = lua_tostring(s, i);
        if (!m)
        {
            raiseScriptError(s, "npc_Choice called with incorrect parameters.");
            return 0;
        }
        msg.writeString(m);
    }
    gameHandler->sendTo(q, msg);
    return 0;
}

/**
 * Callback for creating a NPC on the current map with the current script.
 * tmw.npc_create(string name, int id, int x, int y): npc
 */
static int LuaNpc_Create(lua_State *s)
{
    if (!lua_isstring(s, 1) || !lua_isnumber(s, 2) || !lua_isnumber(s, 3) || !lua_isnumber(s, 4))
    {
        raiseScriptError(s, "npc_create called with incorrect parameters.");
        return 0;
    }
    lua_pushlightuserdata(s, (void *)&registryKey);
    lua_gettable(s, LUA_REGISTRYINDEX);
    Script *t = static_cast<Script *>(lua_touserdata(s, -1));
    NPC *q = new NPC(lua_tostring(s, 1), lua_tointeger(s, 2), t);
    MapComposite *m = t->getMap();
    if (!m)
    {
        raiseScriptError(s, "npc_create called outside a map.");
        return 0;
    }
    q->setMap(m);
    q->setPosition(Point(lua_tointeger(s, 3), lua_tointeger(s, 4)));
    bool b = GameState::insert(q);
    /* Do not try to deal with a failure there. There are some serious issues
       if an insertion failed on an almost empty map. */
    assert(b); (void)b;
    lua_pushlightuserdata(s, q);
    return 1;
}

/**
 * Callback for warping a player to another place.
 * tmw.chr_warp(character, nil/int map, int x, int y)
 */
static int LuaChr_Warp(lua_State *s)
{
    Character *q = getCharacter(s, 1);
    bool b = lua_isnil(s, 2);
    if (!q || !(b || lua_isnumber(s, 2)) ||
        !lua_isnumber(s, 3) || !lua_isnumber(s, 4))
    {
        raiseScriptError(s, "chr_warp called with incorrect parameters.");
        return 0;
    }
    MapComposite *m;
    if (b)
    {
        lua_pushlightuserdata(s, (void *)&registryKey);
        lua_gettable(s, LUA_REGISTRYINDEX);
        Script *t = static_cast<Script *>(lua_touserdata(s, -1));
        m = t->getMap();
    }
    else
    {
        m = MapManager::getMap(lua_tointeger(s, 2));
    }
    if (!m)
    {
        raiseScriptError(s, "chr_warp called with a non-existing map.");
        return 0;
    }
    GameState::enqueueWarp(q, m, lua_tointeger(s, 3), lua_tointeger(s, 4));
    return 0;
}

/**
 * Callback for inserting/removing items in inventory.
 * The function can be called several times in a row, but it is better to
 * perform all the changes at once, so as to reduce bandwidth. Removals
 * (negative amount) should be passed first, then insertions (positive amount).
 * If a removal fails, all the previous operations are canceled (except for
 * items dropped on the floor, hence why removals should be passed first), and
 * the function returns false. Otherwise the function will return true. When
 * the item identifier is zero, money is modified.
 * Note: If an insertion fails, extra items are dropped on the floor.
 * tmw.chr_inv_change(character, (int id, int nb)...): bool success
 */
static int LuaChr_InvChange(lua_State *s)
{
    Character *q = getCharacter(s, 1);
    if (!q)
    {
        raiseScriptError(s, "chr_inv_change called with incorrect parameters.");
        return 0;
    }
    int nb_items = (lua_gettop(s) - 1) / 2;
    Inventory inv(q, true);
    for (int i = 0; i < nb_items; ++i)
    {
        if (!lua_isnumber(s, i * 2 + 2) || !lua_isnumber(s, i * 2 + 3))
        {
            raiseScriptError(s, "chr_inv_change called with incorrect parameters.");
            return 0;
        }
        int id = lua_tointeger(s, i * 2 + 2);
        int nb = lua_tointeger(s, i * 2 + 3);

        if (id == 0)
        {
            if (!inv.changeMoney(nb))
            {
                inv.cancel();
                lua_pushboolean(s, 0);
                return 1;
            }
        }
        else if (nb < 0)
        {
            nb = inv.remove(id, -nb);
            if (nb)
            {
                inv.cancel();
                lua_pushboolean(s, 0);
                return 1;
            }
        }
        else
        {
            ItemClass *ic = ItemManager::getItem(id);
            if (!ic)
            {
                raiseScriptError(s, "chr_inv_change called with an unknown item.");
                continue;
            }
            nb = inv.insert(id, nb);
            if (nb)
            {
                Item *item = new Item(ic, nb);
                item->setMap(q->getMap());
                item->setPosition(q->getPosition());
                GameState::enqueueInsert(item);
            }
        }
    }
    lua_pushboolean(s, 1);
    return 1;
}

/**
 * Callback for counting items in inventory.
 * When an item identifier is zero, money is queried.
 * tmw.chr_inv_count(character, int id...): int count...
 */
static int LuaChr_InvCount(lua_State *s)
{
    Character *q = getCharacter(s, 1);
    if (!q)
    {
        raiseScriptError(s, "chr_inv_count called with incorrect parameters.");
        return 0;
    }
    int nb_items = lua_gettop(s) - 1;
    lua_checkstack(s, nb_items);
    Inventory inv(q);
    for (int i = 2; i <= nb_items + 1; ++i)
    {
        if (!lua_isnumber(s, i))
        {
            raiseScriptError(s, "chr_inv_count called with incorrect parameters.");
            return 0;
        }
        int id = lua_tointeger(s, i);
        int nb = id ? inv.count(id) : q->getPossessions().money;
        lua_pushinteger(s, nb);
    }
    return nb_items;
}

/**
 * Callback for trading between a player and an NPC.
 * tmw.npc_trade(npc, character, bool sell, table items)
 */
static int LuaNpc_Trade(lua_State *s)
{
    NPC *p = getNPC(s, 1);
    Character *q = getCharacter(s, 2);
    if (!p || !q || !lua_isboolean(s, 3) || !lua_istable(s, 4))
    {
        raiseScriptError(s, "npc_trade called with incorrect parameters.");
        return 0;
    }
    BuySell *t = new BuySell(q, lua_toboolean(s, 3));
    lua_pushnil(s);
    while (lua_next(s, 4))
    {
        if (!lua_istable(s, -1))
        {
            raiseScriptError(s, "npc_trade called with incorrect parameters.");
            t->cancel();
            return 0;
        }
        int v[3];
        for (int i = 0; i < 3; ++i)
        {
            lua_rawgeti(s, -1, i + 1);
            if (!lua_isnumber(s, -1))
            {
                raiseScriptError(s, "rpc_trade called with incorrect parameters.");
                t->cancel();
                return 0;
            }
            v[i] = lua_tointeger(s, -1);
            lua_pop(s, 1);
        }
        t->registerItem(v[0], v[1], v[2]);
        lua_pop(s, 1);
    }
    t->start(p);
    return 0;
}

/**
 * Function for making a being walk to a position
 * being_walk(Being *being, int x, int y, int speed)
 */
static int LuaBeing_Walk(lua_State *s)
{
    if (!lua_isnumber(s, 2) || !lua_isnumber(s, 3) || !lua_isnumber(s, 4))
    {
        raiseScriptError(s, "being_walk called with incorrect parameters.");
        return 0;
    }

    lua_pushlightuserdata(s, (void *)&registryKey);
    lua_gettable(s, LUA_REGISTRYINDEX);

    Being *being = getBeing(s, 1);
    Point destination(lua_tointeger(s, 2), lua_tointeger(s, 3));
    being->setDestination(destination);
    being->setSpeed(lua_tointeger(s, 4));

    return 0;
}

/**
 * Makes the being say something
 * tmw.being_say(source, message)
 */
static int LuaBeing_Say(lua_State *s)
{
    if (!lua_isuserdata(s, 1) || !lua_isstring(s, 2) )
    {
        raiseScriptError(s, "being_say called with incorrect parameters.");
        return 0;
    }

    Being *being = getBeing(s, 1);
    std::string message = lua_tostring(s, 2);

    if (being && message != "")
    {
        GameState::sayAround(being, message);
    } else {
        raiseScriptError(s, "being_say called with incorrect parameters.");
        return 0;
    }

    return 0;
}


/**
 * Applies combat damage to a being
 * tmw.being_damage(victim, value, delta, cth, type, element)
 */
static int LuaBeing_Damage(lua_State *s)
{
    Being *being = getBeing(s, 1);

    Damage damage;
    damage.base = lua_tointeger(s, 2);
    damage.delta = lua_tointeger(s, 3);
    damage.cth = lua_tointeger(s, 4);
    damage.type = lua_tointeger(s, 5);
    damage.element = lua_tointeger(s, 6);
    damage.usedSkill = 0;

    being->damage(NULL, damage);

    return 0;
}


/**
 * Function for getting the x-coordinate of the position of a being
 */
static int LuaPosX(lua_State *s)
{
    lua_pushlightuserdata(s, (void *)&registryKey);
    lua_gettable(s, LUA_REGISTRYINDEX);

    int x = getBeing(s, 1)->getPosition().x;
    lua_pushinteger(s, x);

    return 1;
}

/**
 * Function for getting the y-coordinate of the position of a being
 */
static int LuaPosY(lua_State *s)
{
    lua_pushlightuserdata(s, (void *)&registryKey);
    lua_gettable(s, LUA_REGISTRYINDEX);

    int y = getBeing(s, 1)->getPosition().y;
    lua_pushinteger(s, y);

    return 1;
}

/**
 * Callback for creating a monster on the current map.
 * tmw.monster_create(int type, int x, int y)
 */
static int LuaMonster_Create(lua_State *s)
{
    if (!lua_isnumber(s, 1) || !lua_isnumber(s, 2) || !lua_isnumber(s, 3))
    {
        raiseScriptError(s, "monster_create called with incorrect parameters.");
        return 0;
    }

    lua_pushlightuserdata(s, (void *)&registryKey);
    lua_gettable(s, LUA_REGISTRYINDEX);
    Script *t = static_cast<Script *>(lua_touserdata(s, -1));
    MapComposite *m = t->getMap();
    if (!m)
    {
        raiseScriptError(s, "monster_create called outside a map.");
        return 0;
    }

    int monsterId = lua_tointeger(s, 1);
    MonsterClass *spec = MonsterManager::getMonster(monsterId);
    if (!spec)
    {
        raiseScriptError(s, "monster_create called with invalid monster ID: %d", monsterId);
        //LOG_WARN("LuaMonster_Create invalid monster ID: " << monsterId);
        return 0;
    }

    Monster *q = new Monster(spec);
    q->setMap(m);
    q->setPosition(Point(lua_tointeger(s, 2), lua_tointeger(s, 3)));
    if (!GameState::insertSafe(q))
    {
        LOG_WARN("LuaMonster_Create failed to insert monster");
        return 0;
    }

    lua_pushlightuserdata(s, q);
    return 1;
}

/**
 * Called when the server has recovered the value of a quest variable.
 */
void LuaScript::getQuestCallback(Character *q, std::string const &name,
                                 std::string const &value, void *data)
{
    LuaScript *s = static_cast< LuaScript * >(data);
    assert(s->nbArgs == -1);
    lua_getglobal(s->mState, "quest_reply");
    lua_pushlightuserdata(s->mState, q);
    lua_pushstring(s->mState, name.c_str());
    lua_pushstring(s->mState, value.c_str());
    s->nbArgs = 3;
    s->execute();
}

/**
 * Callback for getting a quest variable. Starts a recovery and returns
 * immediatly, if the variable is not known yet.
 * tmw.chr_get_chest(character, string): nil or string
 */
static int LuaChr_GetQuest(lua_State *s)
{
    Character *q = getCharacter(s, 1);
    char const *m = lua_tostring(s, 2);
    if (!m || m[0] == 0)
    {
        raiseScriptError(s, "chr_get_quest called with incorrect parameters.");
        return 0;
    }
    std::string value, name = m;
    bool res = getQuestVar(q, name, value);
    if (res)
    {
        lua_pushstring(s, value.c_str());
        return 1;
    }
    lua_pushlightuserdata(s, (void *)&registryKey);
    lua_gettable(s, LUA_REGISTRYINDEX);
    Script *t = static_cast<Script *>(lua_touserdata(s, -1));
    QuestCallback f = { &LuaScript::getQuestCallback, t };
    recoverQuestVar(q, name, f);
    return 0;
}

/**
 * Callback for setting a quest variable.
 * tmw.chr_set_chest(character, string, string)
 */
static int LuaChr_SetQuest(lua_State *s)
{
    Character *q = getCharacter(s, 1);
    char const *m = lua_tostring(s, 2);
    char const *n = lua_tostring(s, 3);
    if (!m || !n || m[0] == 0)
    {
        raiseScriptError(s, "chr_set_quest called with incorrect parameters.");
        return 0;
    }
    setQuestVar(q, m, n);
    return 0;
}

/**
 * Creates a trigger area. Whenever an object enters this area
 * a Lua function is called.
 * tmw.trigger_create (x, y, width, height, function, id)
 */
static int LuaTrigger_Create(lua_State *s)
{
    //TODO: argument check
    if (!lua_isnumber(s, 1) ||
        !lua_isnumber(s, 2) ||
        !lua_isnumber(s, 3) ||
        !lua_isnumber(s, 4) ||
        !lua_isstring(s, 5) ||
        !lua_isnumber(s, 6) ||
        !lua_isboolean(s, 7))
    {
        raiseScriptError(s, "trigger_create called with incorrect parameters.");
        return 0;
    }

    lua_pushlightuserdata(s, (void *)&registryKey);
    lua_gettable(s, LUA_REGISTRYINDEX);
    Script *script = static_cast<Script *>(lua_touserdata(s, -1));
    int x = lua_tointeger(s, 1);
    int y = lua_tointeger(s, 2);
    int width = lua_tointeger(s, 3);
    int height = lua_tointeger(s, 4);
    std::string function = lua_tostring(s, 5);
    int id = lua_tointeger(s, 6);
    bool once = lua_toboolean(s, 7);

    LOG_INFO("Created script trigger at "<<x<<":"<<y<<" ("<<width<<"x"<<height<<") function: "<<function<<" ("<<id<<")");

    MapComposite *m = script->getMap();

    if (!m)
    {
        raiseScriptError(s, "trigger_create called for nonexistent a map.");
        return 0;
    }

    ScriptAction *action = new ScriptAction(script, function, id);
    Rectangle r = { x, y, width, height };
    TriggerArea *area = new TriggerArea(m, r, action, once);

    bool ret = GameState::insert(area);
    lua_pushboolean(s, ret);
    return 1;
}

/**
 * Creates a chat message in the users chatlog(s)
 * global message: tmw.chatmessage (message)
 * private massage: tmw.chatmessage (recipent, message)
 */
static int LuaChatmessage(lua_State *s)
{
    if (lua_gettop(s) == 2 && lua_isuserdata(s, 1) && lua_isstring(s, 2) )
    {
        Being *being = getBeing(s, 1);
        std::string message = lua_tostring(s, 2);

        if (being && message != "")
        {
            GameState::sayTo(being, NULL, message);
        }
    }
    else if(lua_gettop(s) == 1 && lua_isstring(s, 1))
    {
        // TODO: make chatserver send a global message
    }
    else
    {
        raiseScriptError(s, "being_say called with incorrect parameters.");
        return 0;
    }

    return 0;
}

/**
 * Gets a LUA table with the being IDs of all beings
 * inside of a circular area of the current map.
 * tmw.get_beings_in_circle (x, y, radius)
 */
static int LuaGetBeingsInCircle(lua_State *s)
{
    int x = lua_tointeger(s, 1);
    int y = lua_tointeger(s, 2);
    int r = lua_tointeger(s, 3);

    lua_pushlightuserdata(s, (void *)&registryKey);
    lua_gettable(s, LUA_REGISTRYINDEX);
    Script *t = static_cast<Script *>(lua_touserdata(s, -1));
    MapComposite *m = t->getMap();

    //create a lua table with the beings in the given area.
    lua_newtable(s);
    int tableStackPosition = lua_gettop(s);
    int tableIndex = 1;
    for (MovingObjectIterator i(m->getAroundPointIterator(Point(x, y), r)); i; ++i)
    {
        char t = (*i)->getType();
        if (t == OBJECT_NPC || t == OBJECT_CHARACTER || t == OBJECT_MONSTER)
        {
            Being *b = static_cast<Being *> (*i);
            if (Collision::CircleWithCircle(b->getPosition(), b->getSize(),
                                            Point(x, y), r))
            {
                lua_pushinteger(s, tableIndex);
                lua_pushlightuserdata (s, b);
                lua_settable (s, tableStackPosition);
                tableIndex++;
            }
        }
    }

    return 1;
}

/**
 * Gets the post for the character
 */
static int LuaGetPost(lua_State *s)
{
    if (lua_isuserdata(s, 1))
    {
        Character *c = getCharacter(s, 1);

        if (c)
        {
            accountHandler->getPost(c);
        }
    }

    return 0;
}

/**
 * Makes the server call the lua function deathEvent
 * with the being ID when the being dies.
 * tmw.note_on_death (being)
 */
static int LuaNoteOnDeath(lua_State *s)
{
    if (!lua_islightuserdata(s, 1) || lua_gettop(s) != 1)
    {
        raiseScriptError(s, "lua_noteOnDeath called with incorrect parameters.");
        return 0;
    }

    lua_pushlightuserdata(s, (void *)&registryKey);
    lua_gettable(s, LUA_REGISTRYINDEX);
    Script *t = static_cast<Script *>(lua_touserdata(s, -1));
    Being *being = getBeing(s, 1);
    if (!being)
    {
        raiseScriptError(s, "lua_noteOnDeath called for nonexistent being.");
        return 0;
    }

    being->addListener(t->getScriptDeathListener());
    return 0;
}

LuaScript::LuaScript():
    nbArgs(-1)
{
    mState = luaL_newstate();
    luaL_openlibs(mState);

    // Put some callback functions in the scripting environment.
    static luaL_reg const callbacks[] = {
        { "npc_create",             &LuaNpc_Create       },
        { "npc_message",            &LuaNpc_Message      },
        { "npc_choice",             &LuaNpc_Choice       },
        { "npc_trade",              &LuaNpc_Trade        },
        { "chr_warp",               &LuaChr_Warp         },
        { "chr_inv_change",         &LuaChr_InvChange    },
        { "chr_inv_count",          &LuaChr_InvCount     },
        { "chr_get_quest",          &LuaChr_GetQuest     },
        { "chr_set_quest",          &LuaChr_SetQuest     },
        { "monster_create",         &LuaMonster_Create   },
        { "being_walk",             &LuaBeing_Walk       },
        { "being_say",              &LuaBeing_Say        },
        { "being_damage",           &LuaBeing_Damage     },
        { "posX",                   &LuaPosX             },
        { "posY",                   &LuaPosY             },
        { "trigger_create",         &LuaTrigger_Create   },
        { "chatmessage",            &LuaChatmessage      },
        { "get_beings_in_circle",   &LuaGetBeingsInCircle},
        { "get_post",               &LuaGetPost          },
        { "note_on_death",          &LuaNoteOnDeath      },
        { NULL, NULL }
    };
    luaL_register(mState, "tmw", callbacks);

    // Make script object available to callback functions.
    lua_pushlightuserdata(mState, (void *)&registryKey);
    lua_pushlightuserdata(mState, this);
    lua_settable(mState, LUA_REGISTRYINDEX);

    lua_settop(mState, 0);
    loadFile("scripts/libs/libtmw.lua");
}

LuaScript::~LuaScript()
{
    lua_close(mState);
}

void LuaScript::prepare(std::string const &name)
{
    assert(nbArgs == -1);
    lua_getglobal(mState, name.c_str());
    nbArgs = 0;
}

void LuaScript::push(int v)
{
    assert(nbArgs >= 0);
    lua_pushinteger(mState, v);
    ++nbArgs;
}

void LuaScript::push(std::string const &v)
{
    assert(nbArgs >= 0);
    lua_pushstring(mState, v.c_str());
    ++nbArgs;
}


void LuaScript::push(Thing *v)
{
    assert(nbArgs >= 0);
    lua_pushlightuserdata(mState, v);
    ++nbArgs;
}

int LuaScript::execute()
{
    assert(nbArgs >= 0);
    int res = lua_pcall(mState, nbArgs, 1, 0);
    nbArgs = -1;
    if (res || !(lua_isnil(mState, 1) || lua_isnumber(mState, 1)))
    {
        char const *s = lua_tostring(mState, 1);
        LOG_WARN("Failure while calling Lua function: error=" << res
                 << ", type=" << lua_typename(mState, lua_type(mState, 1))
                 << ", message=" << (s ? s : ""));
        lua_pop(mState, 1);
        return 0;
    }
    res = lua_tointeger(mState, 1);
    lua_pop(mState, 1);
    return res;
}

void LuaScript::load(char const *prog)
{
    int res = luaL_loadstring(mState, prog);

    if (res == LUA_ERRSYNTAX)
    {
        LOG_ERROR("Syntax error while loading Lua script.");
        return;
    }

    // A Lua chunk is like a function, so "execute" it in order to initialize
    // it.
    res = lua_pcall(mState, 0, 0, 0);
    if (res)
    {
        LOG_ERROR("Failure while initializing Lua script: "
                  << lua_tostring(mState, -1));
        lua_settop(mState, 0);
        return;
    }
}

void LuaScript::processDeathEvent(Being *being)
{
    prepare("death_notification");
    push(being);
    //TODO: get and push a list of creatures who contributed to killing the
    //      being. This might be very interesting for scripting quests.
    execute();

    being->removeListener(getScriptDeathListener());
}

static Script *LuaFactory()
{
    return new LuaScript();
}

struct LuaRegister
{
    LuaRegister() { Script::registerEngine("lua", LuaFactory); }
};

static LuaRegister dummy;