/* Example of Outcome used with error code enums
(C) 2017-2020 Niall Douglas <http://www.nedproductions.biz/> (3 commits)


Boost Software License - Version 1.0 - August 17th, 2003

Permission is hereby granted, free of charge, to any person or organization
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*/

#include "../../../include/boost/outcome.hpp"

#include <iostream>

//! [declaration]
struct udt
{
  int a{0};
  explicit udt(int _a)
      : a(_a)
  {
  }
  udt() = default;
  int operator*() const { return a; }
};
enum class err
{
  success,
  failure1,
  failure2
};

// Tell the standard library that enum err is an error code enum
// by specialising the is_error_code_enum trait. See
// http://en.cppreference.com/w/cpp/error/error_code/is_error_code_enum
namespace std
{
  template <> struct is_error_code_enum<err> : std::true_type
  {
  };
}

// We also must declare a free function make_error_code. This is
// discovered via ADL by the standard library. See
// http://en.cppreference.com/w/cpp/error/errc/make_error_code
inline std::error_code make_error_code(err c)
{
  // We need to inherit from std::error_category to define
  // an error code domain with the standard library for
  // our strongly typed enum. See
  // http://en.cppreference.com/w/cpp/error/error_category
  static struct err_category : std::error_category
  {
    virtual const char *name() const noexcept override final { return "err_category"; };
    virtual std::string message(int c) const override final
    {
      switch(static_cast<err>(c))
      {
      case err::success:
        return "err::success";
      case err::failure1:
        return "err::failure1";
      case err::failure2:
        return "err::failure2";
      }
      return "unknown";
    }
  } category;
  return std::error_code(static_cast<int>(c), category);
}
//! [declaration]

using namespace BOOST_OUTCOME_V2_NAMESPACE;

int main()
{
  //! [usage]
  result<udt, err> res(err::failure1);

  // What happens here? What exception type is thrown?
  try
  {
    std::cout << *res.value() << std::endl;
  }
  catch(const std::exception &e)
  {
    std::cerr << "Exception thrown was " << e.what() << std::endl;
  }
  //! [usage]
  return 0;
}

void test()
{
  //! [usage2]
  result<udt /*, std::error_code */> res(err::failure1);

  // What happens here? What exception type is thrown?
  try
  {
    std::cout << *res.value() << std::endl;
  }
  catch(const std::exception &e)
  {
    // Prints "Exception thrown was failure1", exactly the same as before
    std::cerr << "Exception thrown was " << e.what() << std::endl;
  }
  //! [usage2]
}

//! [usage3]
result<udt> boo()
{
  return err::failure1;
}
result<udt> foo()
{
  BOOST_OUTCOME_TRY(v, (boo()));
  return udt{5};  // emplace construct udt with 5
}
//! [usage3]