include/fmt/compile.h

// Formatting library for C++ - experimental format string compilation
//
// Copyright (c) 2012 - present, Victor Zverovich and fmt contributors
// All rights reserved.
//
// For the license information refer to format.h.

#ifndef FMT_COMPILE_H_
#define FMT_COMPILE_H_

#include "format.h"

FMT_BEGIN_NAMESPACE
namespace detail {

// An output iterator that counts the number of objects written to it and
// discards them.
class counting_iterator {
 private:
  size_t count_;

 public:
  using iterator_category = std::output_iterator_tag;
  using difference_type = std::ptrdiff_t;
  using pointer = void;
  using reference = void;
  using _Unchecked_type = counting_iterator;  // Mark iterator as checked.

  struct value_type {
    template <typename T> void operator=(const T&) {}
  };

  counting_iterator() : count_(0) {}

  size_t count() const { return count_; }

  counting_iterator& operator++() {
    ++count_;
    return *this;
  }
  counting_iterator operator++(int) {
    auto it = *this;
    ++*this;
    return it;
  }

  friend counting_iterator operator+(counting_iterator it, difference_type n) {
    it.count_ += static_cast<size_t>(n);
    return it;
  }

  value_type operator*() const { return {}; }
};

template <typename Char, typename InputIt>
inline counting_iterator copy_str(InputIt begin, InputIt end,
                                  counting_iterator it) {
  return it + (end - begin);
}

template <typename OutputIt> class truncating_iterator_base {
 protected:
  OutputIt out_;
  size_t limit_;
  size_t count_ = 0;

  truncating_iterator_base() : out_(), limit_(0) {}

  truncating_iterator_base(OutputIt out, size_t limit)
      : out_(out), limit_(limit) {}

 public:
  using iterator_category = std::output_iterator_tag;
  using value_type = typename std::iterator_traits<OutputIt>::value_type;
  using difference_type = std::ptrdiff_t;
  using pointer = void;
  using reference = void;
  using _Unchecked_type =
      truncating_iterator_base;  // Mark iterator as checked.

  OutputIt base() const { return out_; }
  size_t count() const { return count_; }
};

// An output iterator that truncates the output and counts the number of objects
// written to it.
template <typename OutputIt,
          typename Enable = typename std::is_void<
              typename std::iterator_traits<OutputIt>::value_type>::type>
class truncating_iterator;

template <typename OutputIt>
class truncating_iterator<OutputIt, std::false_type>
    : public truncating_iterator_base<OutputIt> {
  mutable typename truncating_iterator_base<OutputIt>::value_type blackhole_;

 public:
  using value_type = typename truncating_iterator_base<OutputIt>::value_type;

  truncating_iterator() = default;

  truncating_iterator(OutputIt out, size_t limit)
      : truncating_iterator_base<OutputIt>(out, limit) {}

  truncating_iterator& operator++() {
    if (this->count_++ < this->limit_) ++this->out_;
    return *this;
  }

  truncating_iterator operator++(int) {
    auto it = *this;
    ++*this;
    return it;
  }

  value_type& operator*() const {
    return this->count_ < this->limit_ ? *this->out_ : blackhole_;
  }
};

template <typename OutputIt>
class truncating_iterator<OutputIt, std::true_type>
    : public truncating_iterator_base<OutputIt> {
 public:
  truncating_iterator() = default;

  truncating_iterator(OutputIt out, size_t limit)
      : truncating_iterator_base<OutputIt>(out, limit) {}

  template <typename T> truncating_iterator& operator=(T val) {
    if (this->count_++ < this->limit_) *this->out_++ = val;
    return *this;
  }

  truncating_iterator& operator++() { return *this; }
  truncating_iterator& operator++(int) { return *this; }
  truncating_iterator& operator*() { return *this; }
};

// A compile-time string which is compiled into fast formatting code.
class compiled_string {};

template <typename S>
struct is_compiled_string : std::is_base_of<compiled_string, S> {};

/**
  \rst
  Converts a string literal *s* into a format string that will be parsed at
  compile time and converted into efficient formatting code. Requires C++17
  ``constexpr if`` compiler support.

  **Example**::

    // Converts 42 into std::string using the most efficient method and no
    // runtime format string processing.
    std::string s = fmt::format(FMT_COMPILE("{}"), 42);
  \endrst
 */
#ifdef __cpp_if_constexpr
#  define FMT_COMPILE(s) \
    FMT_STRING_IMPL(s, fmt::detail::compiled_string, explicit)
#else
#  define FMT_COMPILE(s) FMT_STRING(s)
#endif

#if FMT_USE_NONTYPE_TEMPLATE_PARAMETERS
template <typename Char, size_t N, fixed_string<Char, N> Str>
struct udl_compiled_string : compiled_string {
  using char_type = Char;
  constexpr operator basic_string_view<char_type>() const {
    return {Str.data, N - 1};
  }
};
#endif

template <typename T, typename... Tail>
const T& first(const T& value, const Tail&...) {
  return value;
}

#ifdef __cpp_if_constexpr
template <typename... Args> struct type_list {};

// Returns a reference to the argument at index N from [first, rest...].
template <int N, typename T, typename... Args>
constexpr const auto& get([[maybe_unused]] const T& first,
                          [[maybe_unused]] const Args&... rest) {
  static_assert(N < 1 + sizeof...(Args), "index is out of bounds");
  if constexpr (N == 0)
    return first;
  else
    return get<N - 1>(rest...);
}

template <typename Char, typename... Args>
constexpr int get_arg_index_by_name(basic_string_view<Char> name,
                                    type_list<Args...>) {
  return get_arg_index_by_name<Args...>(name);
}

template <int N, typename> struct get_type_impl;

template <int N, typename... Args> struct get_type_impl<N, type_list<Args...>> {
  using type = remove_cvref_t<decltype(get<N>(std::declval<Args>()...))>;
};

template <int N, typename T>
using get_type = typename get_type_impl<N, T>::type;

template <typename T> struct is_compiled_format : std::false_type {};

template <typename Char> struct text {
  basic_string_view<Char> data;
  using char_type = Char;

  template <typename OutputIt, typename... Args>
  constexpr OutputIt format(OutputIt out, const Args&...) const {
    return write<Char>(out, data);
  }
};

template <typename Char>
struct is_compiled_format<text<Char>> : std::true_type {};

template <typename Char>
constexpr text<Char> make_text(basic_string_view<Char> s, size_t pos,
                               size_t size) {
  return {{&s[pos], size}};
}

template <typename Char> struct code_unit {
  Char value;
  using char_type = Char;

  template <typename OutputIt, typename... Args>
  constexpr OutputIt format(OutputIt out, const Args&...) const {
    return write<Char>(out, value);
  }
};

// This ensures that the argument type is convertible to `const T&`.
template <typename T, int N, typename... Args>
constexpr const T& get_arg_checked(const Args&... args) {
  const auto& arg = get<N>(args...);
  if constexpr (detail::is_named_arg<remove_cvref_t<decltype(arg)>>()) {
    return arg.value;
  } else {
    return arg;
  }
}

template <typename Char>
struct is_compiled_format<code_unit<Char>> : std::true_type {};

// A replacement field that refers to argument N.
template <typename Char, typename T, int N> struct field {
  using char_type = Char;

  template <typename OutputIt, typename... Args>
  constexpr OutputIt format(OutputIt out, const Args&... args) const {
    return write<Char>(out, get_arg_checked<T, N>(args...));
  }
};

template <typename Char, typename T, int N>
struct is_compiled_format<field<Char, T, N>> : std::true_type {};

// A replacement field that refers to argument with name.
template <typename Char> struct runtime_named_field {
  using char_type = Char;
  basic_string_view<Char> name;

  template <typename OutputIt, typename T>
  constexpr static bool try_format_argument(
      OutputIt& out,
      // [[maybe_unused]] due to unused-but-set-parameter warning in GCC 7,8,9
      [[maybe_unused]] basic_string_view<Char> arg_name, const T& arg) {
    if constexpr (is_named_arg<typename std::remove_cv<T>::type>::value) {
      if (arg_name == arg.name) {
        out = write<Char>(out, arg.value);
        return true;
      }
    }
    return false;
  }

  template <typename OutputIt, typename... Args>
  constexpr OutputIt format(OutputIt out, const Args&... args) const {
    bool found = (try_format_argument(out, name, args) || ...);
    if (!found) {
      throw format_error("argument with specified name is not found");
    }
    return out;
  }
};

template <typename Char>
struct is_compiled_format<runtime_named_field<Char>> : std::true_type {};

// A replacement field that refers to argument N and has format specifiers.
template <typename Char, typename T, int N> struct spec_field {
  using char_type = Char;
  formatter<T, Char> fmt;

  template <typename OutputIt, typename... Args>
  constexpr FMT_INLINE OutputIt format(OutputIt out,
                                       const Args&... args) const {
    const auto& vargs =
        fmt::make_format_args<basic_format_context<OutputIt, Char>>(args...);
    basic_format_context<OutputIt, Char> ctx(out, vargs);
    return fmt.format(get_arg_checked<T, N>(args...), ctx);
  }
};

template <typename Char, typename T, int N>
struct is_compiled_format<spec_field<Char, T, N>> : std::true_type {};

template <typename L, typename R> struct concat {
  L lhs;
  R rhs;
  using char_type = typename L::char_type;

  template <typename OutputIt, typename... Args>
  constexpr OutputIt format(OutputIt out, const Args&... args) const {
    out = lhs.format(out, args...);
    return rhs.format(out, args...);
  }
};

template <typename L, typename R>
struct is_compiled_format<concat<L, R>> : std::true_type {};

template <typename L, typename R>
constexpr concat<L, R> make_concat(L lhs, R rhs) {
  return {lhs, rhs};
}

struct unknown_format {};

template <typename Char>
constexpr size_t parse_text(basic_string_view<Char> str, size_t pos) {
  for (size_t size = str.size(); pos != size; ++pos) {
    if (str[pos] == '{' || str[pos] == '}') break;
  }
  return pos;
}

template <typename Args, size_t POS, int ID, typename S>
constexpr auto compile_format_string(S format_str);

template <typename Args, size_t POS, int ID, typename T, typename S>
constexpr auto parse_tail(T head, S format_str) {
  if constexpr (POS !=
                basic_string_view<typename S::char_type>(format_str).size()) {
    constexpr auto tail = compile_format_string<Args, POS, ID>(format_str);
    if constexpr (std::is_same<remove_cvref_t<decltype(tail)>,
                               unknown_format>())
      return tail;
    else
      return make_concat(head, tail);
  } else {
    return head;
  }
}

template <typename T, typename Char> struct parse_specs_result {
  formatter<T, Char> fmt;
  size_t end;
  int next_arg_id;
};

constexpr int manual_indexing_id = -1;

template <typename T, typename Char>
constexpr parse_specs_result<T, Char> parse_specs(basic_string_view<Char> str,
                                                  size_t pos, int next_arg_id) {
  str.remove_prefix(pos);
  auto ctx = basic_format_parse_context<Char>(str, {}, next_arg_id);
  auto f = formatter<T, Char>();
  auto end = f.parse(ctx);
  return {f, pos + fmt::detail::to_unsigned(end - str.data()) + 1,
          next_arg_id == 0 ? manual_indexing_id : ctx.next_arg_id()};
}

template <typename Char> struct arg_id_handler {
  arg_ref<Char> arg_id;

  constexpr int operator()() {
    FMT_ASSERT(false, "handler cannot be used with automatic indexing");
    return 0;
  }
  constexpr int operator()(int id) {
    arg_id = arg_ref<Char>(id);
    return 0;
  }
  constexpr int operator()(basic_string_view<Char> id) {
    arg_id = arg_ref<Char>(id);
    return 0;
  }

  constexpr void on_error(const char* message) { throw format_error(message); }
};

template <typename Char> struct parse_arg_id_result {
  arg_ref<Char> arg_id;
  const Char* arg_id_end;
};

template <int ID, typename Char>
constexpr auto parse_arg_id(const Char* begin, const Char* end) {
  auto handler = arg_id_handler<Char>{arg_ref<Char>{}};
  auto arg_id_end = parse_arg_id(begin, end, handler);
  return parse_arg_id_result<Char>{handler.arg_id, arg_id_end};
}

template <typename T, typename Enable = void> struct field_type {
  using type = remove_cvref_t<T>;
};

template <typename T>
struct field_type<T, enable_if_t<detail::is_named_arg<T>::value>> {
  using type = remove_cvref_t<decltype(T::value)>;
};

template <typename T, typename Args, size_t END_POS, int ARG_INDEX, int NEXT_ID,
          typename S>
constexpr auto parse_replacement_field_then_tail(S format_str) {
  using char_type = typename S::char_type;
  constexpr auto str = basic_string_view<char_type>(format_str);
  constexpr char_type c = END_POS != str.size() ? str[END_POS] : char_type();
  if constexpr (c == '}') {
    return parse_tail<Args, END_POS + 1, NEXT_ID>(
        field<char_type, typename field_type<T>::type, ARG_INDEX>(),
        format_str);
  } else if constexpr (c == ':') {
    constexpr auto result = parse_specs<typename field_type<T>::type>(
        str, END_POS + 1, NEXT_ID == manual_indexing_id ? 0 : NEXT_ID);
    return parse_tail<Args, result.end, result.next_arg_id>(
        spec_field<char_type, typename field_type<T>::type, ARG_INDEX>{
            result.fmt},
        format_str);
  }
}

// Compiles a non-empty format string and returns the compiled representation
// or unknown_format() on unrecognized input.
template <typename Args, size_t POS, int ID, typename S>
constexpr auto compile_format_string(S format_str) {
  using char_type = typename S::char_type;
  constexpr auto str = basic_string_view<char_type>(format_str);
  if constexpr (str[POS] == '{') {
    if constexpr (POS + 1 == str.size())
      throw format_error("unmatched '{' in format string");
    if constexpr (str[POS + 1] == '{') {
      return parse_tail<Args, POS + 2, ID>(make_text(str, POS, 1), format_str);
    } else if constexpr (str[POS + 1] == '}' || str[POS + 1] == ':') {
      static_assert(ID != manual_indexing_id,
                    "cannot switch from manual to automatic argument indexing");
      constexpr auto next_id =
          ID != manual_indexing_id ? ID + 1 : manual_indexing_id;
      return parse_replacement_field_then_tail<get_type<ID, Args>, Args,
                                               POS + 1, ID, next_id>(
          format_str);
    } else {
      constexpr auto arg_id_result =
          parse_arg_id<ID>(str.data() + POS + 1, str.data() + str.size());
      constexpr auto arg_id_end_pos = arg_id_result.arg_id_end - str.data();
      constexpr char_type c =
          arg_id_end_pos != str.size() ? str[arg_id_end_pos] : char_type();
      static_assert(c == '}' || c == ':', "missing '}' in format string");
      if constexpr (arg_id_result.arg_id.kind == arg_id_kind::index) {
        static_assert(
            ID == manual_indexing_id || ID == 0,
            "cannot switch from automatic to manual argument indexing");
        constexpr auto arg_index = arg_id_result.arg_id.val.index;
        return parse_replacement_field_then_tail<get_type<arg_index, Args>,
                                                 Args, arg_id_end_pos,
                                                 arg_index, manual_indexing_id>(
            format_str);
      } else if constexpr (arg_id_result.arg_id.kind == arg_id_kind::name) {
        constexpr auto arg_index =
            get_arg_index_by_name(arg_id_result.arg_id.val.name, Args{});
        if constexpr (arg_index != invalid_arg_index) {
          constexpr auto next_id =
              ID != manual_indexing_id ? ID + 1 : manual_indexing_id;
          return parse_replacement_field_then_tail<
              decltype(get_type<arg_index, Args>::value), Args, arg_id_end_pos,
              arg_index, next_id>(format_str);
        } else {
          if constexpr (c == '}') {
            return parse_tail<Args, arg_id_end_pos + 1, ID>(
                runtime_named_field<char_type>{arg_id_result.arg_id.val.name},
                format_str);
          } else if constexpr (c == ':') {
            return unknown_format();  // no type info for specs parsing
          }
        }
      }
    }
  } else if constexpr (str[POS] == '}') {
    if constexpr (POS + 1 == str.size())
      throw format_error("unmatched '}' in format string");
    return parse_tail<Args, POS + 2, ID>(make_text(str, POS, 1), format_str);
  } else {
    constexpr auto end = parse_text(str, POS + 1);
    if constexpr (end - POS > 1) {
      return parse_tail<Args, end, ID>(make_text(str, POS, end - POS),
                                       format_str);
    } else {
      return parse_tail<Args, end, ID>(code_unit<char_type>{str[POS]},
                                       format_str);
    }
  }
}

template <typename... Args, typename S,
          FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
constexpr auto compile(S format_str) {
  constexpr auto str = basic_string_view<typename S::char_type>(format_str);
  if constexpr (str.size() == 0) {
    return detail::make_text(str, 0, 0);
  } else {
    constexpr auto result =
        detail::compile_format_string<detail::type_list<Args...>, 0, 0>(
            format_str);
    return result;
  }
}
#endif  // __cpp_if_constexpr
}  // namespace detail

FMT_MODULE_EXPORT_BEGIN

#ifdef __cpp_if_constexpr

template <typename CompiledFormat, typename... Args,
          typename Char = typename CompiledFormat::char_type,
          FMT_ENABLE_IF(detail::is_compiled_format<CompiledFormat>::value)>
FMT_INLINE std::basic_string<Char> format(const CompiledFormat& cf,
                                          const Args&... args) {
  auto s = std::basic_string<Char>();
  cf.format(std::back_inserter(s), args...);
  return s;
}

template <typename OutputIt, typename CompiledFormat, typename... Args,
          FMT_ENABLE_IF(detail::is_compiled_format<CompiledFormat>::value)>
constexpr FMT_INLINE OutputIt format_to(OutputIt out, const CompiledFormat& cf,
                                        const Args&... args) {
  return cf.format(out, args...);
}

template <typename S, typename... Args,
          FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
FMT_INLINE std::basic_string<typename S::char_type> format(const S&,
                                                           Args&&... args) {
  if constexpr (std::is_same<typename S::char_type, char>::value) {
    constexpr auto str = basic_string_view<typename S::char_type>(S());
    if constexpr (str.size() == 2 && str[0] == '{' && str[1] == '}') {
      const auto& first = detail::first(args...);
      if constexpr (detail::is_named_arg<
                        remove_cvref_t<decltype(first)>>::value) {
        return fmt::to_string(first.value);
      } else {
        return fmt::to_string(first);
      }
    }
  }
  constexpr auto compiled = detail::compile<Args...>(S());
  if constexpr (std::is_same<remove_cvref_t<decltype(compiled)>,
                             detail::unknown_format>()) {
    return format(static_cast<basic_string_view<typename S::char_type>>(S()),
                  std::forward<Args>(args)...);
  } else {
    return format(compiled, std::forward<Args>(args)...);
  }
}

template <typename OutputIt, typename S, typename... Args,
          FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
FMT_CONSTEXPR OutputIt format_to(OutputIt out, const S&, Args&&... args) {
  constexpr auto compiled = detail::compile<Args...>(S());
  if constexpr (std::is_same<remove_cvref_t<decltype(compiled)>,
                             detail::unknown_format>()) {
    return format_to(out,
                     static_cast<basic_string_view<typename S::char_type>>(S()),
                     std::forward<Args>(args)...);
  } else {
    return format_to(out, compiled, std::forward<Args>(args)...);
  }
}
#endif

template <typename OutputIt, typename S, typename... Args,
          FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
format_to_n_result<OutputIt> format_to_n(OutputIt out, size_t n,
                                         const S& format_str, Args&&... args) {
  auto it = format_to(detail::truncating_iterator<OutputIt>(out, n), format_str,
                      std::forward<Args>(args)...);
  return {it.base(), it.count()};
}

template <typename S, typename... Args,
          FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
size_t formatted_size(const S& format_str, const Args&... args) {
  return format_to(detail::counting_iterator(), format_str, args...).count();
}

template <typename S, typename... Args,
          FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
void print(std::FILE* f, const S& format_str, const Args&... args) {
  memory_buffer buffer;
  format_to(std::back_inserter(buffer), format_str, args...);
  detail::print(f, {buffer.data(), buffer.size()});
}

template <typename S, typename... Args,
          FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
void print(const S& format_str, const Args&... args) {
  print(stdout, format_str, args...);
}

#if FMT_USE_NONTYPE_TEMPLATE_PARAMETERS
inline namespace literals {
template <detail::fixed_string Str>
constexpr detail::udl_compiled_string<
    remove_cvref_t<decltype(Str.data[0])>,
    sizeof(Str.data) / sizeof(decltype(Str.data[0])), Str>
operator""_cf() {
  return {};
}
}  // namespace literals
#endif

FMT_MODULE_EXPORT_END
FMT_END_NAMESPACE

#endif  // FMT_COMPILE_H_