#ifndef LLARP_UTIL_MEMFN
#define LLARP_UTIL_MEMFN

#include <memory>
#include <type_traits>
#include <utility>

namespace llarp::util
{
  // Wraps a member function and instance into a callable object that invokes
  // the method (non-const overload).
  template <
      typename Return,
      typename Class,
      typename Derived,
      typename... Arg,
      typename = std::enable_if_t<std::is_base_of<Class, Derived>::value>>
  auto
  memFn(Return (Class::*f)(Arg...), Derived* self)
  {
    return [f, self](Arg... args) -> Return { return (self->*f)(std::forward<Arg>(args)...); };
  }

  // Wraps a member function and instance into a lambda that invokes the
  // method (const overload).
  template <
      typename Return,
      typename Class,
      typename Derived,
      typename... Arg,
      typename = std::enable_if_t<std::is_base_of<Class, Derived>::value>>
  auto
  memFn(Return (Class::*f)(Arg...) const, const Derived* self)
  {
    return [f, self](Arg... args) -> Return { return (self->*f)(std::forward<Arg>(args)...); };
  }

  // Wraps a member function and shared pointer to an instance into a lambda
  // that invokes the method.
  template <
      typename Return,
      typename Class,
      typename Derived,
      typename... Arg,
      typename = std::enable_if_t<std::is_base_of<Class, Derived>::value>>
  auto
  memFn(Return (Class::*f)(Arg...), std::shared_ptr<Derived> self)
  {
    return [f, self = std::move(self)](Arg... args) -> Return {
      return (self.get()->*f)(std::forward<Arg>(args)...);
    };
  }

  // Wraps a member function and shared pointer to an instance into a lambda
  // that invokes the method (const method overload).
  template <
      typename Return,
      typename Class,
      typename Derived,
      typename... Arg,
      typename = std::enable_if_t<std::is_base_of<Class, Derived>::value>>
  auto
  memFn(Return (Class::*f)(Arg...) const, std::shared_ptr<Derived> self)
  {
    return [f, self = std::move(self)](Arg... args) -> Return {
      return (self.get()->*f)(std::forward<Arg>(args)...);
    };
  }

}  // namespace llarp::util

#endif