#include <experimental/meta>
#include <string>
#include <iostream>
#include <utility>

struct Witness {
  int nodiscard;
  int maybe_unused;
  int deprecated;
};

struct [[nodiscard, maybe_unused]] Foo;

consteval auto member_named(std::string_view name) {
  for (std::meta::info field : nonstatic_data_members_of(^^Witness)) {
    if (has_identifier(field) && identifier_of(field) == name)
      return field;
  }
  std::unreachable();
}

consteval bool testIsAttribute() {
  constexpr auto attr = ^^[[nodiscard]];
  return std::meta::is_attribute(attr);
}

consteval bool testIdentifierOf() {
  constexpr auto attr = ^^[[deprecated]];
  Witness s{0, 0, 0};
  s.[: member_named(std::meta::identifier_of(attr)) :]++;
  return s.deprecated == 1;
}

consteval bool testAttributesOfAttr() {
  constexpr auto attr = ^^[[nodiscard]];

  return std::meta::identifier_of(std::meta::attributes_of(attr)[0]) == "nodiscard"
    && std::meta::attributes_of(attr).size() == 1;
}

consteval bool testAttributesOfType() {
    Witness s{0, 0, 0};
    s.[: member_named(std::meta::identifier_of(std::meta::attributes_of(^^Foo)[0])) :]++;
    s.[: member_named(std::meta::identifier_of(std::meta::attributes_of(^^Foo)[1])) :]++;
    return s.nodiscard == 1 && s.maybe_unused == 1;
}

consteval bool testSplicingAttr() {
  constexpr auto r = ^^[[deprecated]];
  struct [[ [: r :] ]] {} iAmDeprecated = {};
  return std::meta::identifier_of(std::meta::attributes_of(^^iAmDeprecated)[0]) == "deprecated";
}

consteval bool testSplicingType() {
  constexpr auto r = ^^Foo;
  struct [[ [: r :] ]] Bar;
  return std::meta::identifier_of(std::meta::attributes_of(^^Bar)[0]) == "nodiscard"
    &&  std::meta::identifier_of(std::meta::attributes_of(^^Bar)[1]) == "maybe_unused";
}

int main(int, char**) {

  static_assert(testIsAttribute(), "Fail ^^[[ ]]");

  static_assert(testIdentifierOf(), "Fail std::meta::identifiers_of");

  static_assert(testAttributesOfAttr(), "Fail std::meta::attributes_of(^^[[ ]])");
  static_assert(testAttributesOfType(), "Fail std::meta::attributes_of(^^MyType)");

  static_assert(testSplicingAttr(), "Fail [[ [: ^^attr :] ]]");
  static_assert(testSplicingType(), "Fail [[ [: ^^type :] ]]");

  return 0;
}