// -*- C++ -*-
//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCPP___FORMAT_FORMAT_PARSE_CONTEXT_H
#define _LIBCPP___FORMAT_FORMAT_PARSE_CONTEXT_H

#include <__config>
#include <__format/format_error.h>
#include <string_view>

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#pragma GCC system_header
#endif

_LIBCPP_BEGIN_NAMESPACE_STD

#if _LIBCPP_STD_VER > 17

// TODO FMT Remove this once we require compilers with proper C++20 support.
// If the compiler has no concepts support, the format header will be disabled.
// Without concepts support enable_if needs to be used and that too much effort
// to support compilers with partial C++20 support.
#if !defined(_LIBCPP_HAS_NO_CONCEPTS) && !defined(_LIBCPP_HAS_NO_BUILTIN_IS_CONSTANT_EVALUATED)

template <class _CharT>
class _LIBCPP_TEMPLATE_VIS _LIBCPP_AVAILABILITY_FORMAT basic_format_parse_context {
public:
  using char_type = _CharT;
  using const_iterator = typename basic_string_view<_CharT>::const_iterator;
  using iterator = const_iterator;

  _LIBCPP_HIDE_FROM_ABI
  constexpr explicit basic_format_parse_context(basic_string_view<_CharT> __fmt,
                                                size_t __num_args = 0) noexcept
      : __begin_(__fmt.begin()),
        __end_(__fmt.end()),
        __indexing_(__unknown),
        __next_arg_id_(0),
        __num_args_(__num_args) {}

  basic_format_parse_context(const basic_format_parse_context&) = delete;
  basic_format_parse_context&
  operator=(const basic_format_parse_context&) = delete;

  _LIBCPP_HIDE_FROM_ABI constexpr const_iterator begin() const noexcept {
    return __begin_;
  }
  _LIBCPP_HIDE_FROM_ABI constexpr const_iterator end() const noexcept {
    return __end_;
  }
  _LIBCPP_HIDE_FROM_ABI constexpr void advance_to(const_iterator __it) {
    __begin_ = __it;
  }

  _LIBCPP_HIDE_FROM_ABI constexpr size_t next_arg_id() {
    if (__indexing_ == __manual)
      __throw_format_error("Using automatic argument numbering in manual "
                           "argument numbering mode");

    if (__indexing_ == __unknown)
      __indexing_ = __automatic;
    return __next_arg_id_++;
  }
  _LIBCPP_HIDE_FROM_ABI constexpr void check_arg_id(size_t __id) {
    if (__indexing_ == __automatic)
      __throw_format_error("Using manual argument numbering in automatic "
                           "argument numbering mode");

    if (__indexing_ == __unknown)
      __indexing_ = __manual;

    // Throws an exception to make the expression a non core constant
    // expression as required by:
    // [format.parse.ctx]/11
    //   Remarks: Call expressions where id >= num_args_ are not core constant
    //   expressions ([expr.const]).
    // Note: the Throws clause [format.parse.ctx]/10 doesn't specify the
    // behavior when id >= num_args_.
    if (is_constant_evaluated() && __id >= __num_args_)
      __throw_format_error("Argument index outside the valid range");
  }

private:
  iterator __begin_;
  iterator __end_;
  enum _Indexing { __unknown, __manual, __automatic };
  _Indexing __indexing_;
  size_t __next_arg_id_;
  size_t __num_args_;
};

using format_parse_context = basic_format_parse_context<char>;
using wformat_parse_context = basic_format_parse_context<wchar_t>;

#endif // !defined(_LIBCPP_HAS_NO_CONCEPTS)

#endif //_LIBCPP_STD_VER > 17

_LIBCPP_END_NAMESPACE_STD

#endif // _LIBCPP___FORMAT_FORMAT_PARSE_CONTEXT_H
