dbg.h

/*****************************************************************************

                                dbg(...) macro

License (MIT):

  Copyright (c) 2019 David Peter <mail@david-peter.de>

  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files (the "Software"), to
  deal in the Software without restriction, including without limitation the
  rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
  sell copies of the Software, and to permit persons to whom the Software is
  furnished to do so, subject to the following conditions:

  The above copyright notice and this permission notice shall be included in
  all copies or substantial portions of the Software.

  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  SOFTWARE.

*****************************************************************************/

#ifndef DBG_MACRO_DBG_H
#define DBG_MACRO_DBG_H

#if defined(__unix__) || (defined(__APPLE__) && defined(__MACH__))
#define DBG_MACRO_UNIX
#elif defined(_MSC_VER)
#define DBG_MACRO_WINDOWS
#endif

#ifndef DBG_MACRO_NO_WARNING
#pragma message("WARNING: the 'dbg.h' header is included in your code base")
#endif  // DBG_MACRO_NO_WARNING

#include <algorithm>
#include <chrono>
#include <ctime>
#include <iomanip>
#include <ios>
#include <iostream>
#include <memory>
#include <queue>
#include <sstream>
#include <stack>
#include <string>
#include <tuple>
#include <type_traits>
#include <vector>

#ifdef DBG_MACRO_UNIX
#include <unistd.h>
#endif

#if __cplusplus >= 201703L
#define DBG_MACRO_CXX_STANDARD 17
#elif __cplusplus >= 201402L
#define DBG_MACRO_CXX_STANDARD 14
#else
#define DBG_MACRO_CXX_STANDARD 11
#endif

#if DBG_MACRO_CXX_STANDARD >= 17
#include <optional>
#include <variant>
#endif

namespace dbg {

inline bool isColorizedOutputEnabled() {
#if defined(DBG_MACRO_FORCE_COLOR)
  return true;
#elif defined(DBG_MACRO_UNIX)
  return isatty(fileno(stderr));
#else
  return true;
#endif
}

struct time {};

namespace pretty_function {

// Compiler-agnostic version of __PRETTY_FUNCTION__ and constants to
// extract the template argument in `type_name_impl`

#if defined(__clang__)
#define DBG_MACRO_PRETTY_FUNCTION __PRETTY_FUNCTION__
static constexpr size_t PREFIX_LENGTH =
    sizeof("const char *dbg::type_name_impl() [T = ") - 1;
static constexpr size_t SUFFIX_LENGTH = sizeof("]") - 1;
#elif defined(__GNUC__) && !defined(__clang__)
#define DBG_MACRO_PRETTY_FUNCTION __PRETTY_FUNCTION__
static constexpr size_t PREFIX_LENGTH =
    sizeof("const char* dbg::type_name_impl() [with T = ") - 1;
static constexpr size_t SUFFIX_LENGTH = sizeof("]") - 1;
#elif defined(_MSC_VER)
#define DBG_MACRO_PRETTY_FUNCTION __FUNCSIG__
static constexpr size_t PREFIX_LENGTH =
    sizeof("const char *__cdecl dbg::type_name_impl<") - 1;
static constexpr size_t SUFFIX_LENGTH = sizeof(">(void)") - 1;
#else
#error "This compiler is currently not supported by dbg_macro."
#endif

}  // namespace pretty_function

// Formatting helpers

template <typename T>
struct print_formatted {
  static_assert(std::is_integral<T>::value,
                "Only integral types are supported.");

  print_formatted(T value, int numeric_base)
      : inner(value), base(numeric_base) {}

  operator T() const { return inner; }

  const char* prefix() const {
    switch (base) {
      case 8:
        return "0o";
      case 16:
        return "0x";
      case 2:
        return "0b";
      default:
        return "";
    }
  }

  T inner;
  int base;
};

template <typename T>
print_formatted<T> hex(T value) {
  return print_formatted<T>{value, 16};
}

template <typename T>
print_formatted<T> oct(T value) {
  return print_formatted<T>{value, 8};
}

template <typename T>
print_formatted<T> bin(T value) {
  return print_formatted<T>{value, 2};
}

// Implementation of 'type_name<T>()'

template <typename T>
const char* type_name_impl() {
  return DBG_MACRO_PRETTY_FUNCTION;
}

template <typename T>
struct type_tag {};

template <int&... ExplicitArgumentBarrier, typename T>
typename std::enable_if<(std::rank<T>::value == 0), std::string>::type
get_type_name(type_tag<T>) {
  namespace pf = pretty_function;

  std::string type = type_name_impl<T>();
  return type.substr(pf::PREFIX_LENGTH,
                     type.size() - pf::PREFIX_LENGTH - pf::SUFFIX_LENGTH);
}

template <typename T>
std::string type_name() {
  if (std::is_volatile<T>::value) {
    if (std::is_pointer<T>::value) {
      return type_name<typename std::remove_volatile<T>::type>() + " volatile";
    } else {
      return "volatile " + type_name<typename std::remove_volatile<T>::type>();
    }
  }
  if (std::is_const<T>::value) {
    if (std::is_pointer<T>::value) {
      return type_name<typename std::remove_const<T>::type>() + " const";
    } else {
      return "const " + type_name<typename std::remove_const<T>::type>();
    }
  }
  if (std::is_pointer<T>::value) {
    return type_name<typename std::remove_pointer<T>::type>() + "*";
  }
  if (std::is_lvalue_reference<T>::value) {
    return type_name<typename std::remove_reference<T>::type>() + "&";
  }
  if (std::is_rvalue_reference<T>::value) {
    return type_name<typename std::remove_reference<T>::type>() + "&&";
  }
  return get_type_name(type_tag<T>{});
}

// Prefer bitsize variant over standard integral types
#define DBG_MACRO_REGISTER_TYPE_ASSOC(t_std, t_bit)             \
  inline constexpr const char* get_type_name(type_tag<t_std>) { \
    return std::is_same<t_std, t_bit>::value ? #t_bit : #t_std; \
  }

DBG_MACRO_REGISTER_TYPE_ASSOC(unsigned char, uint8_t)
DBG_MACRO_REGISTER_TYPE_ASSOC(unsigned short, uint16_t)
DBG_MACRO_REGISTER_TYPE_ASSOC(unsigned int, uint32_t)
DBG_MACRO_REGISTER_TYPE_ASSOC(unsigned long, uint64_t)
DBG_MACRO_REGISTER_TYPE_ASSOC(signed char, int8_t)
DBG_MACRO_REGISTER_TYPE_ASSOC(short, int16_t)
DBG_MACRO_REGISTER_TYPE_ASSOC(int, int32_t)
DBG_MACRO_REGISTER_TYPE_ASSOC(long, int64_t)

inline std::string get_type_name(type_tag<std::string>) {
  return "std::string";
}

template <typename T>
typename std::enable_if<(std::rank<T>::value == 1), std::string>::type
get_array_dim() {
  return "[" + std::to_string(std::extent<T>::value) + "]";
}

template <typename T>
typename std::enable_if<(std::rank<T>::value > 1), std::string>::type
get_array_dim() {
  return "[" + std::to_string(std::extent<T>::value) + "]" +
         get_array_dim<typename std::remove_extent<T>::type>();
}

template <typename T>
typename std::enable_if<(std::rank<T>::value > 0), std::string>::type
get_type_name(type_tag<T>) {
  return type_name<typename std::remove_all_extents<T>::type>() + get_array_dim<T>();
}

template <typename T, size_t N>
std::string get_type_name(type_tag<std::array<T, N>>) {
  return "std::array<" + type_name<T>() + ", " + std::to_string(N) + ">";
}

template <typename T>
std::string get_type_name(type_tag<std::vector<T, std::allocator<T>>>) {
  return "std::vector<" + type_name<T>() + ">";
}

template <typename T1, typename T2>
std::string get_type_name(type_tag<std::pair<T1, T2>>) {
  return "std::pair<" + type_name<T1>() + ", " + type_name<T2>() + ">";
}

template <typename... T>
std::string type_list_to_string() {
  std::string result;
  auto unused = {(result += type_name<T>() + ", ", 0)..., 0};
  static_cast<void>(unused);

#if DBG_MACRO_CXX_STANDARD >= 17
  if constexpr (sizeof...(T) > 0) {
#else
  if (sizeof...(T) > 0) {
#endif
    result.pop_back();
    result.pop_back();
  }
  return result;
}

template <typename... T>
std::string get_type_name(type_tag<std::tuple<T...>>) {
  return "std::tuple<" + type_list_to_string<T...>() + ">";
}

template <typename T>
inline std::string get_type_name(type_tag<print_formatted<T>>) {
  return type_name<T>();
}

// Implementation of 'is_detected' to specialize for container-like types

namespace detail_detector {

struct nonesuch {
  nonesuch() = delete;
  ~nonesuch() = delete;
  nonesuch(nonesuch const&) = delete;
  void operator=(nonesuch const&) = delete;
};

template <typename...>
using void_t = void;

template <class Default,
          class AlwaysVoid,
          template <class...>
          class Op,
          class... Args>
struct detector {
  using value_t = std::false_type;
  using type = Default;
};

template <class Default, template <class...> class Op, class... Args>
struct detector<Default, void_t<Op<Args...>>, Op, Args...> {
  using value_t = std::true_type;
  using type = Op<Args...>;
};

}  // namespace detail_detector

template <template <class...> class Op, class... Args>
using is_detected = typename detail_detector::
    detector<detail_detector::nonesuch, void, Op, Args...>::value_t;

namespace detail {

namespace {
using std::begin;
using std::end;
#if DBG_MACRO_CXX_STANDARD < 17
template <typename T>
constexpr auto size(const T& c) -> decltype(c.size()) {
  return c.size();
}
template <typename T, std::size_t N>
constexpr std::size_t size(const T (&)[N]) {
  return N;
}
#else
using std::size;
#endif
}  // namespace

// Specializations for container adapters

template <class T, class C>
T pop(std::stack<T, C>& adapter) {
  T value = std::move(adapter.top());
  adapter.pop();
  return value;
}

template <class T, class C>
T pop(std::queue<T, C>& adapter) {
  T value = std::move(adapter.front());
  adapter.pop();
  return value;
}

template <class T, class C, class Cmp>
T pop(std::priority_queue<T, C, Cmp>& adapter) {
  T value = std::move(adapter.top());
  adapter.pop();
  return value;
}

template <typename T>
struct remove_cvref {
  typedef typename std::remove_cv<typename std::remove_reference<T>::type>::type
      type;
};

template <typename T>
using remove_cvref_t = typename remove_cvref<T>::type;

template <typename T>
using detect_begin_t = decltype(detail::begin(std::declval<T>()));

template <typename T>
using detect_end_t = decltype(detail::end(std::declval<T>()));

template <typename T>
using detect_size_t = decltype(detail::size(std::declval<T>()));

template <typename T>
struct is_container {
  static constexpr bool value =
      is_detected<detect_begin_t, T>::value &&
      is_detected<detect_end_t, T>::value &&
      is_detected<detect_size_t, T>::value &&
      !std::is_same<std::string, remove_cvref_t<T>>::value;
};

template <typename T>
using detect_underlying_container_t =
    typename remove_cvref_t<T>::container_type;

template <typename T>
struct is_container_adapter {
  static constexpr bool value =
      is_detected<detect_underlying_container_t, T>::value;
};

template <typename T>
using ostream_operator_t =
    decltype(std::declval<std::ostream&>() << std::declval<T>());

template <typename T>
struct has_ostream_operator : is_detected<ostream_operator_t, T> {};

}  // namespace detail

// Helper to dbg(…)-print types
template <typename T>
struct print_type {};

template <typename T>
print_type<T> type() {
  return print_type<T>{};
}

// Forward declarations of "pretty_print"

template <typename T>
inline void pretty_print(std::ostream& stream, const T& value, std::true_type);

template <typename T>
inline void pretty_print(std::ostream&, const T&, std::false_type);

template <typename T>
inline typename std::enable_if<
    !detail::is_container<const T&>::value &&
        !detail::is_container_adapter<const T&>::value &&
        !std::is_enum<T>::value,
    bool>::type
pretty_print(std::ostream& stream, const T& value);

inline bool pretty_print(std::ostream& stream, const bool& value);

inline bool pretty_print(std::ostream& stream, const char& value);

template <typename P>
inline bool pretty_print(std::ostream& stream, P* const& value);

template <typename T, typename Deleter>
inline bool pretty_print(std::ostream& stream,
                         std::unique_ptr<T, Deleter>& value);

template <typename T>
inline bool pretty_print(std::ostream& stream, std::shared_ptr<T>& value);

template <size_t N>
inline bool pretty_print(std::ostream& stream, const char (&value)[N]);

template <>
inline bool pretty_print(std::ostream& stream, const char* const& value);

template <typename... Ts>
inline bool pretty_print(std::ostream& stream, const std::tuple<Ts...>& value);

template <>
inline bool pretty_print(std::ostream& stream, const std::tuple<>&);

template <>
inline bool pretty_print(std::ostream& stream, const time&);

template <typename T>
inline bool pretty_print(std::ostream& stream, const print_formatted<T>& value);

template <typename T>
inline bool pretty_print(std::ostream& stream, const print_type<T>&);

template <typename Enum>
inline typename std::enable_if<std::is_enum<Enum>::value, bool>::type
pretty_print(std::ostream& stream, Enum const& value);

inline bool pretty_print(std::ostream& stream, const std::string& value);

#if DBG_MACRO_CXX_STANDARD >= 17

inline bool pretty_print(std::ostream& stream, const std::string_view& value);

#endif

template <typename T1, typename T2>
inline bool pretty_print(std::ostream& stream, const std::pair<T1, T2>& value);

#if DBG_MACRO_CXX_STANDARD >= 17

template <typename T>
inline bool pretty_print(std::ostream& stream, const std::optional<T>& value);

template <typename... Ts>
inline bool pretty_print(std::ostream& stream,
                         const std::variant<Ts...>& value);

#endif

template <typename Container>
inline typename std::enable_if<detail::is_container<const Container&>::value,
                               bool>::type
pretty_print(std::ostream& stream, const Container& value);

template <typename ContainerAdapter>
inline typename std::enable_if<
    detail::is_container_adapter<const ContainerAdapter&>::value,
    bool>::type
pretty_print(std::ostream& stream, ContainerAdapter value);

// Specializations of "pretty_print"

template <typename T>
inline void pretty_print(std::ostream& stream, const T& value, std::true_type) {
  stream << value;
}

template <typename T>
inline void pretty_print(std::ostream&, const T&, std::false_type) {
  static_assert(detail::has_ostream_operator<const T&>::value,
                "Type does not support the << ostream operator");
}

template <typename T>
inline typename std::enable_if<
    !detail::is_container<const T&>::value &&
        !detail::is_container_adapter<const T&>::value &&
        !std::is_enum<T>::value,
    bool>::type
pretty_print(std::ostream& stream, const T& value) {
  pretty_print(stream, value,
               typename detail::has_ostream_operator<const T&>::type{});
  return true;
}

inline bool pretty_print(std::ostream& stream, const bool& value) {
  stream << std::boolalpha << value;
  return true;
}

inline bool pretty_print(std::ostream& stream, const char& value) {
  const bool printable = value >= 0x20 && value <= 0x7E;

  if (printable) {
    stream << "'" << value << "'";
  } else {
    stream << "'\\x" << std::setw(2) << std::setfill('0') << std::hex
           << std::uppercase << (0xFF & value) << "'";
  }
  return true;
}

template <typename P>
inline bool pretty_print(std::ostream& stream, P* const& value) {
  if (value == nullptr) {
    stream << "nullptr";
  } else {
    stream << value;
  }
  return true;
}

template <typename T, typename Deleter>
inline bool pretty_print(std::ostream& stream,
                         std::unique_ptr<T, Deleter>& value) {
  pretty_print(stream, value.get());
  return true;
}

template <typename T>
inline bool pretty_print(std::ostream& stream, std::shared_ptr<T>& value) {
  pretty_print(stream, value.get());
  stream << " (use_count = " << value.use_count() << ")";

  return true;
}

template <size_t N>
inline bool pretty_print(std::ostream& stream, const char (&value)[N]) {
  stream << value;
  return false;
}

template <>
inline bool pretty_print(std::ostream& stream, const char* const& value) {
  stream << '"' << value << '"';
  return true;
}

template <size_t Idx>
struct pretty_print_tuple {
  template <typename... Ts>
  static void print(std::ostream& stream, const std::tuple<Ts...>& tuple) {
    pretty_print_tuple<Idx - 1>::print(stream, tuple);
    stream << ", ";
    pretty_print(stream, std::get<Idx>(tuple));
  }
};

template <>
struct pretty_print_tuple<0> {
  template <typename... Ts>
  static void print(std::ostream& stream, const std::tuple<Ts...>& tuple) {
    pretty_print(stream, std::get<0>(tuple));
  }
};

template <typename... Ts>
inline bool pretty_print(std::ostream& stream, const std::tuple<Ts...>& value) {
  stream << "{";
  pretty_print_tuple<sizeof...(Ts) - 1>::print(stream, value);
  stream << "}";

  return true;
}

template <>
inline bool pretty_print(std::ostream& stream, const std::tuple<>&) {
  stream << "{}";

  return true;
}

template <>
inline bool pretty_print(std::ostream& stream, const time&) {
  using namespace std::chrono;

  const auto now = system_clock::now();
  const auto us =
      duration_cast<microseconds>(now.time_since_epoch()).count() % 1000000;
  const auto hms = system_clock::to_time_t(now);
#if defined(_MSC_VER) && _MSC_VER >= 1600
  struct tm t;
  localtime_s(&t, &hms);
  const std::tm* tm = &t;
#else
  const std::tm* tm = std::localtime(&hms);
#endif
  stream << "current time = " << std::put_time(tm, "%H:%M:%S") << '.'
         << std::setw(6) << std::setfill('0') << us;
  return false;
}

// Converts decimal integer to binary string
template <typename T>
std::string decimalToBinary(T n) {
  const size_t length = 8 * sizeof(T);
  std::string toRet;
  toRet.resize(length);

  for (size_t i = 0; i < length; ++i) {
    const auto bit_at_index_i = static_cast<char>((n >> i) & 1);
    toRet[length - 1 - i] = bit_at_index_i + '0';
  }

  return toRet;
}

template <typename T>
inline bool pretty_print(std::ostream& stream,
                         const print_formatted<T>& value) {
  if (value.inner < 0) {
    stream << "-";
  }
  stream << value.prefix();

  // Print using setbase
  if (value.base != 2) {
    stream << std::setw(sizeof(T)) << std::setfill('0')
           << std::setbase(value.base) << std::uppercase;

    if (value.inner >= 0) {
      // The '+' sign makes sure that a uint_8 is printed as a number
      stream << +value.inner;
    } else {
      using unsigned_type = typename std::make_unsigned<T>::type;
      stream << +(static_cast<unsigned_type>(-(value.inner + 1)) + 1);
    }
  } else {
    // Print for binary
    if (value.inner >= 0) {
      stream << decimalToBinary(value.inner);
    } else {
      using unsigned_type = typename std::make_unsigned<T>::type;
      stream << decimalToBinary<unsigned_type>(
          static_cast<unsigned_type>(-(value.inner + 1)) + 1);
    }
  }

  return true;
}

template <typename T>
inline bool pretty_print(std::ostream& stream, const print_type<T>&) {
  stream << type_name<T>();

  stream << " [sizeof: " << sizeof(T) << " byte, ";

  stream << "trivial: ";
  if (std::is_trivial<T>::value) {
    stream << "yes";
  } else {
    stream << "no";
  }

  stream << ", standard layout: ";
  if (std::is_standard_layout<T>::value) {
    stream << "yes";
  } else {
    stream << "no";
  }
  stream << "]";

  return false;
}

template <typename Enum>
inline typename std::enable_if<std::is_enum<Enum>::value, bool>::type
pretty_print(std::ostream& stream, Enum const& value) {
  using UnderlyingType = typename std::underlying_type<Enum>::type;
  stream << static_cast<UnderlyingType>(value);

  return true;
}

inline bool pretty_print(std::ostream& stream, const std::string& value) {
  stream << '"' << value << '"';
  return true;
}

#if DBG_MACRO_CXX_STANDARD >= 17

inline bool pretty_print(std::ostream& stream, const std::string_view& value) {
  stream << '"' << std::string(value) << '"';
  return true;
}

#endif

template <typename T1, typename T2>
inline bool pretty_print(std::ostream& stream, const std::pair<T1, T2>& value) {
  stream << "{";
  pretty_print(stream, value.first);
  stream << ", ";
  pretty_print(stream, value.second);
  stream << "}";
  return true;
}

#if DBG_MACRO_CXX_STANDARD >= 17

template <typename T>
inline bool pretty_print(std::ostream& stream, const std::optional<T>& value) {
  if (value) {
    stream << '{';
    pretty_print(stream, *value);
    stream << '}';
  } else {
    stream << "nullopt";
  }

  return true;
}

template <typename... Ts>
inline bool pretty_print(std::ostream& stream,
                         const std::variant<Ts...>& value) {
  stream << "{";
  std::visit([&stream](auto&& arg) { pretty_print(stream, arg); }, value);
  stream << "}";

  return true;
}

#endif

template <typename Container>
inline typename std::enable_if<detail::is_container<const Container&>::value,
                               bool>::type
pretty_print(std::ostream& stream, const Container& value) {
  stream << "{";
  const size_t size = detail::size(value);
  const size_t n = std::min(size_t{10}, size);
  size_t i = 0;
  using std::begin;
  using std::end;
  for (auto it = begin(value); it != end(value) && i < n; ++it, ++i) {
    pretty_print(stream, *it);
    if (i != n - 1) {
      stream << ", ";
    }
  }

  if (size > n) {
    stream << ", ...";
    stream << " size:" << size;
  }

  stream << "}";
  return true;
}

template <typename ContainerAdapter>
inline typename std::enable_if<
    detail::is_container_adapter<const ContainerAdapter&>::value,
    bool>::type
pretty_print(std::ostream& stream, ContainerAdapter value) {
  stream << "{";
  const size_t size = detail::size(value);
  const size_t n = std::min(size_t{10}, size);

  std::vector<typename ContainerAdapter::value_type> elements;
  elements.reserve(n);
  for (size_t i = 0; i < n; ++i) {
    elements.push_back(detail::pop(value));
  }
  std::reverse(elements.begin(), elements.end());

  if (size > n) {
    stream << "..., ";
  }
  for (size_t i = 0; i < n; ++i) {
    pretty_print(stream, elements[i]);
    if (i != n - 1) {
      stream << ", ";
    }
  }
  if (size > n) {
    stream << " (size:" << size << ")";
  }

  stream << "}";
  return true;
}

template <typename T, typename... U>
struct last {
  using type = typename last<U...>::type;
};

template <typename T>
struct last<T> {
  using type = T;
};

template <typename... T>
using last_t = typename last<T...>::type;

class DebugOutput {
 public:
  // Helper alias to avoid obscure type `const char* const*` in signature.
  using expr_t = const char*;

  DebugOutput(const char* filepath, int line, const char* function_name)
      : m_use_colorized_output(isColorizedOutputEnabled()) {
    std::string path = filepath;
    const std::size_t path_length = path.length();
    if (path_length > MAX_PATH_LENGTH) {
      path = ".." + path.substr(path_length - MAX_PATH_LENGTH, MAX_PATH_LENGTH);
    }
    std::stringstream ss;
    ss << ansi(ANSI_DEBUG) << "[" << path << ":" << line << " ("
       << function_name << ")] " << ansi(ANSI_RESET);
    m_location = ss.str();
  }

  template <typename... T>
  auto print(std::initializer_list<expr_t> exprs,
             std::initializer_list<std::string> types,
             T&&... values) -> last_t<T...> {
    if (exprs.size() != sizeof...(values)) {
      std::cerr
          << m_location << ansi(ANSI_WARN)
          << "The number of arguments mismatch, please check unprotected comma"
          << ansi(ANSI_RESET) << std::endl;
    }
    return print_impl_loop(true, exprs.begin(), types.begin(), std::forward<T>(values)...);
  }

 private:
  template <typename T>
  T&& print_impl(bool opens_line, bool close_line, const expr_t* expr, const std::string* type, T&& value) {
    const T& ref = value;
    std::stringstream stream_value;
    const bool print_expr_and_type = pretty_print(stream_value, ref);

    std::stringstream output;
    if (opens_line) {
      output << m_location;
    }
    if (print_expr_and_type) {
      output << ansi(ANSI_EXPRESSION) << *expr << ansi(ANSI_RESET) << " = ";
    }
    output << ansi(ANSI_VALUE) << stream_value.str() << ansi(ANSI_RESET);
    if (print_expr_and_type) {
      output << " (" << ansi(ANSI_TYPE) << *type << ansi(ANSI_RESET) << ")";
    }
    if (close_line) {
      output << std::endl;
    } else {
      output << ", ";
    }
    std::cerr << output.str() << std::flush;

    return std::forward<T>(value);
  }

  template <typename T>
  T&& print_impl_loop(bool opens_line, const expr_t* expr, const std::string* type, T&& value) {
    return print_impl(opens_line, true, expr, type, std::forward<T>(value));
  }

  template <typename T, typename... U>
  auto print_impl_loop(bool opens_line,
                  const expr_t* exprs,
                  const std::string* types,
                  T&& value,
                  U&&... rest) -> last_t<T, U...> {
#ifdef DBG_MACRO_SINGLE_LINE
    bool close_line = false;
#else
    bool close_line = true;
#endif
    print_impl(opens_line, close_line, exprs, types, std::forward<T>(value));
#ifdef DBG_MACRO_SINGLE_LINE
    opens_line = false;
#endif
    return print_impl_loop(opens_line, exprs + 1, types + 1, std::forward<U>(rest)...);
  }

  const char* ansi(const char* code) const {
    if (m_use_colorized_output) {
      return code;
    } else {
      return ANSI_EMPTY;
    }
  }

  const bool m_use_colorized_output;

  std::string m_location;

  static constexpr std::size_t MAX_PATH_LENGTH = 20;

  static constexpr const char* const ANSI_EMPTY = "";
  static constexpr const char* const ANSI_DEBUG = "\x1b[02m";
  static constexpr const char* const ANSI_WARN = "\x1b[33m";
  static constexpr const char* const ANSI_EXPRESSION = "\x1b[36m";
  static constexpr const char* const ANSI_VALUE = "\x1b[01m";
  static constexpr const char* const ANSI_TYPE = "\x1b[32m";
  static constexpr const char* const ANSI_RESET = "\x1b[0m";
};

// Identity function to suppress "-Wunused-value" warnings in DBG_MACRO_DISABLE
// mode
template <typename T>
T&& identity(T&& t) {
  return std::forward<T>(t);
}

template <typename T, typename... U>
auto identity(T&&, U&&... u) -> last_t<U...> {
  return identity(std::forward<U>(u)...);
}

}  // namespace dbg

#ifndef DBG_MACRO_DISABLE

// Force expanding argument with commas for MSVC, ref:
// https://stackoverflow.com/questions/35210637/macro-expansion-argument-with-commas
// Note that "args" should be a tuple with parentheses, such as "(e1, e2, ...)".
#define DBG_IDENTITY(x) x
#define DBG_CALL(fn, args) DBG_IDENTITY(fn args)

#define DBG_CAT_IMPL(_1, _2) _1##_2
#define DBG_CAT(_1, _2) DBG_CAT_IMPL(_1, _2)

#define DBG_16TH_IMPL(_1, _2, _3, _4, _5, _6, _7, _8, _9, _10, _11, _12, _13, \
                      _14, _15, _16, ...)                                     \
  _16
#define DBG_16TH(args) DBG_CALL(DBG_16TH_IMPL, args)
#define DBG_NARG(...) \
  DBG_16TH((__VA_ARGS__, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0))

// DBG_VARIADIC_CALL(fn, data, e1, e2, ...) => fn_N(data, (e1, e2, ...))
#define DBG_VARIADIC_CALL(fn, data, ...) \
  DBG_CAT(fn##_, DBG_NARG(__VA_ARGS__))(data, (__VA_ARGS__))

// (e1, e2, e3, ...) => e1
#define DBG_HEAD_IMPL(_1, ...) _1
#define DBG_HEAD(args) DBG_CALL(DBG_HEAD_IMPL, args)

// (e1, e2, e3, ...) => (e2, e3, ...)
#define DBG_TAIL_IMPL(_1, ...) (__VA_ARGS__)
#define DBG_TAIL(args) DBG_CALL(DBG_TAIL_IMPL, args)

#define DBG_MAP_1(fn, args) DBG_CALL(fn, args)
#define DBG_MAP_2(fn, args) fn(DBG_HEAD(args)), DBG_MAP_1(fn, DBG_TAIL(args))
#define DBG_MAP_3(fn, args) fn(DBG_HEAD(args)), DBG_MAP_2(fn, DBG_TAIL(args))
#define DBG_MAP_4(fn, args) fn(DBG_HEAD(args)), DBG_MAP_3(fn, DBG_TAIL(args))
#define DBG_MAP_5(fn, args) fn(DBG_HEAD(args)), DBG_MAP_4(fn, DBG_TAIL(args))
#define DBG_MAP_6(fn, args) fn(DBG_HEAD(args)), DBG_MAP_5(fn, DBG_TAIL(args))
#define DBG_MAP_7(fn, args) fn(DBG_HEAD(args)), DBG_MAP_6(fn, DBG_TAIL(args))
#define DBG_MAP_8(fn, args) fn(DBG_HEAD(args)), DBG_MAP_7(fn, DBG_TAIL(args))
#define DBG_MAP_9(fn, args) fn(DBG_HEAD(args)), DBG_MAP_8(fn, DBG_TAIL(args))
#define DBG_MAP_10(fn, args) fn(DBG_HEAD(args)), DBG_MAP_9(fn, DBG_TAIL(args))
#define DBG_MAP_11(fn, args) fn(DBG_HEAD(args)), DBG_MAP_10(fn, DBG_TAIL(args))
#define DBG_MAP_12(fn, args) fn(DBG_HEAD(args)), DBG_MAP_11(fn, DBG_TAIL(args))
#define DBG_MAP_13(fn, args) fn(DBG_HEAD(args)), DBG_MAP_12(fn, DBG_TAIL(args))
#define DBG_MAP_14(fn, args) fn(DBG_HEAD(args)), DBG_MAP_13(fn, DBG_TAIL(args))
#define DBG_MAP_15(fn, args) fn(DBG_HEAD(args)), DBG_MAP_14(fn, DBG_TAIL(args))
#define DBG_MAP_16(fn, args) fn(DBG_HEAD(args)), DBG_MAP_15(fn, DBG_TAIL(args))

// DBG_MAP(fn, e1, e2, e3, ...) => fn(e1), fn(e2), fn(e3), ...
#define DBG_MAP(fn, ...) DBG_VARIADIC_CALL(DBG_MAP, fn, __VA_ARGS__)

#define DBG_STRINGIFY_IMPL(x) #x
#define DBG_STRINGIFY(x) DBG_STRINGIFY_IMPL(x)

#define DBG_TYPE_NAME(x) dbg::type_name<decltype(x)>()

#define dbg(...)                                    \
  dbg::DebugOutput(__FILE__, __LINE__, __func__)    \
      .print({DBG_MAP(DBG_STRINGIFY, __VA_ARGS__)}, \
             {DBG_MAP(DBG_TYPE_NAME, __VA_ARGS__)}, __VA_ARGS__)
#else
#define dbg(...) dbg::identity(__VA_ARGS__)
#endif  // DBG_MACRO_DISABLE

#endif  // DBG_MACRO_DBG_H