#include <lua.hpp>
#include <iostream>
#include <type_traits>
#include "luatb_typed_stack.h"


// TODO Make free functions work

// This class is only valid for function types. As a neat side-effect, having
// this specialization in the .ipp file, also hides all of the private members
// from the user (kind of).
template<typename ThisType, typename Ret, typename... Args>
class LuaTB<ThisType, Ret (ThisType::*)(Args...)>
{
public:
    template<Ret (ThisType::*func)(Args...)>
    static void registerFunction(ThisType *_this, lua_State *lua, std::string name)
    {
        // Store the 'this' pointer of the caller in the extraspace
        LuaTB<ThisType, Ret (ThisType::*)(Args...)>::stateToClassMap[lua] = _this;

        // Make a function visible to lua that will call 'func' with the correct
        // arguments
        lua_register(lua, name.c_str(), toLuaSignature<func>);
    }

private:
    static std::map<lua_State*, ThisType*> stateToClassMap;

    // Represents a function that can made visible to lua with the correct
    // signature. It will call the corresponding C++ function with the
    // correctly typed arguments
    template<Ret (ThisType::*func)(Args...)>
    static int toLuaSignature(lua_State *lua)
    {
        // The index of the topmost item on the stack equals the size of
        // the stack, which also equals the number of arguments
        int argc = lua_gettop(lua);

        // Check if the number of arguments match
        if(argc != sizeof...(Args))
        {
            std::cerr << "ERROR: LuaTB: Lua script called a function with wrong number of arguments (" << argc << " given, " << sizeof...(Args) << " expected)" << std::endl;
            return LUA_ERRSYNTAX;
        }

        // Call getArgument for every argument seperately to convert each argument
        // to the correct type and call the function afterwards
        ((*LuaTB<ThisType, Ret (ThisType::*)(Args...)>::stateToClassMap[lua]).*func)( (LuaTBTypedStack::getArgument<Args>(lua))... );

        return 0;
    }
};

// This needs to be here and not in a source file, because the compiler can't know
// the template types if it's in a separate module.
template<typename ThisType, typename Ret, typename... Args>
std::map<lua_State*, ThisType*> LuaTB<ThisType, Ret (ThisType::*)(Args...)>::stateToClassMap = std::map<lua_State*, ThisType*>();