YetAnotherRayCaster/LuaScript.h at master · VladDoc/YetAnotherRayCaster · GitHub

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#ifndef LUASCRIPT_H
#define LUASCRIPT_H

#include <string>
#include <vector>
#include <iostream>

// Lua is written in C, so compiler needs to know how to link its libraries
extern "C" {
# include "lua.h"
# include "lauxlib.h"
# include "lualib.h"
}

class LuaScript {
public:
    LuaScript(const std::string& filename)
    {
        L = luaL_newstate();
        if (luaL_loadfile(L, filename.c_str()) || lua_pcall(L, 0, 0, 0))
        {
            std::cout<<"Error: script not loaded ("<<filename<<")"<<std::endl;
            L = 0;
        }
    }

    ~LuaScript()
    {
        if(L) lua_close(L);
    }

    operator bool() const noexcept {
        return (bool)L;
    }
        // Generic default get
    template<typename T>
    T lua_getdefault(const std::string& variableName) {
      return T{};
    }

    void printError(const std::string& variableName, const std::string& reason)
    {
        std::cout<<"Error: can't get ["<<variableName<<"]. "<<reason<<std::endl;
    }

    template<typename T>
    T lua_get(const std::string& variableName) {
       return T{};
    }

    bool lua_gettostack(const std::string& variableName) {
        level = 0;
        std::string var = "";
        for(unsigned int i = 0; i < variableName.size(); i++)
        {
            if(variableName.at(i) == '.')
            {
                if(level == 0)
                {
                    lua_getglobal(L, var.c_str());
                }
                else
                {
                    lua_getfield(L, -1, var.c_str());
                }

                if(lua_isnil(L, -1))
                {
                    printError(variableName, var + " is not defined");
                    return false;
                }
                else
                {
                    var = "";
                    level++;
                }
            }
            else
            {
                var += variableName.at(i);
            }
        }
        if(level == 0)
        {
            lua_getglobal(L, var.c_str());
        }
        else {
            lua_getfield(L, -1, var.c_str());
        }
        if(lua_isnil(L, -1))
        {
            printError(variableName, var + " is not defined");
            return false;
        }

        return true;
    }

    template<typename T>
    T get(const std::string& variableName) {
        if(!L)
        {
            printError(variableName, "Script is not loaded");
            return T{};
        }

        T result;
        if(lua_gettostack(variableName))   // variable succesfully on top of stack
        {
            result = lua_get<T>(variableName);
        }
        else {
            result = T{};
        }

        lua_pop(L, level + 1); // pop all existing elements from stack
        return result;
    }

private:
    lua_State* L;
    int level;
};


template <>
inline bool LuaScript::lua_get(const std::string& variableName) {
    return (bool)lua_toboolean(L, -1);
}

template <>
inline float LuaScript::lua_get(const std::string& variableName) {
    if(!lua_isnumber(L, -1)) {
      printError(variableName, "Not a number");
    }
    return (float)lua_tonumber(L, -1);
}

template <>
inline int LuaScript::lua_get(const std::string& variableName) {
    if(!lua_isnumber(L, -1)) {
      printError(variableName, "Not a number");
    }
    return (int)lua_tonumber(L, -1);
}

template <>
inline std::string LuaScript::lua_get(const std::string& variableName) {
    std::string s;
    if(lua_isstring(L, -1)) {
      s = std::string(lua_tostring(L, -1));
    } else {
      printError(variableName, "Not a string");
    }
    return s;
}

#endif