#include <stdio.h>
#include <lua.h>

extern "c" {
    static int l_cppfunction(lua_State *L) {
        double arg = luaL_checknumber(L,1);
        lua_pushnumber(L, arg * 0.5);
        return 1;
    }
}


int main (int argc, char *argv[] ){
    printf("Test lua embedding");
    printf("init lua");
    lua_State *L;
    L = luaL_newState();
    printf("Load the (optional) standard libraries, to have to print function");
    luaL_openLibs(L);
    printf("Load chenk. without executing it.");
    if( luaL_loadfile(L, "hello.lua")){
        printf("Something went wrong loading the check (syntax error?)");
        printf(lua_tostring(L, -1));
        lua_pop(L,1);
    }

    printf("Make a insert a global var into lua from C++");
    lua_pushnumber(L, 1.1);
    lua_setglobal(L, "cppvar");

    printf("Execute the Lua chunk");
    if(lua_pcall(L, 0, LUA_MULTRET, 0)){
        printf("Something went wrong during execution");
        printf(lua_tostring(L, -1));
        lua_pop(L,1);
    }

    printf("read a global var from lua into C++");
    lua_getglobal(L, "luavar");
    double luavar = lua_tonumber(L, -1);
    lua_pop(L,1);
    printf("c++ can read the value set from lua luavar = %s", luavar );

    printf("execute a lua function from cpp");
    lua_getglobal(L, "myluafunction");
    lua_pushnumber(L, 5);
    lua_pcall(L,1,1,0);
    printf("the return value of the function was %s", lua_tostring(L, -1));
    lua_pop(L,1);

    printf("execute a cpp function from lua");
    printf("first register the function in lua");
    lua_pushcfunction(L , l_cppfunction);
    lua_setglobal(L, "cppfunction");

    printf("Call a lua function that uses the cpp function");
    lua_setglobal(L, "myFunction");
    lua_pushnumber(L, 5);
    lua_pcall(L,1,1,0);
    printf("the return value of the function was %s", lua_tonumber(L,-1));
    lua_pop(L,1);

    printf("Release the lua environment");
    lua_close(L);



}