// file      : libbutl/char-scanner.cxx -*- C++ -*-
// copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
// license   : MIT; see accompanying LICENSE file

#ifndef __cpp_modules_ts
#include <libbutl/char-scanner.mxx>
#endif

// C includes.

#ifndef __cpp_lib_modules_ts
#include <string>  // char_traits
#include <cstdint> // uint64_t
#include <istream>
#endif

// Other includes.

#ifdef __cpp_modules_ts
module butl.char_scanner;

// Only imports additional to interface.
#ifdef __clang__
#ifdef __cpp_lib_modules_ts
import std.core;
import std.io;
#endif
import butl.fdstream;
#endif

#endif

using namespace std;

namespace butl
{
  char_scanner::
  char_scanner (istream& is, bool crlf, uint64_t l, uint64_t p)
      : line (l),
        column (1),
        position (p),
        is_ (is),
        buf_ (dynamic_cast<fdbuf*> (is.rdbuf ())),
        gptr_ (nullptr),
        egptr_ (nullptr),
        crlf_ (crlf)
  {
  }

  auto char_scanner::
  peek () -> xchar
  {
    if (unget_)
      return ungetc_;

    if (unpeek_)
      return unpeekc_;

    if (eos_)
      return xchar (xchar::traits_type::eof (), line, column, position);

    int_type v (peek_ ());

    if (v == xchar::traits_type::eof ())
      eos_ = true;
    else if (crlf_ && v == '\r')
    {
      int_type v1;
      do
      {
        get_ ();
        v1 = peek_ ();
      }
      while (v1 == '\r');

      if (v1 != '\n')
      {
        // We need to make sure subsequent calls to peek() return newline.
        //
        unpeek_ = true;
        unpeekc_ = xchar ('\n', line, column, position);

        if (v1 == xchar::traits_type::eof ())
          eos_ = true;
      }

      v = '\n';
    }

    return xchar (v, line, column, position);
  }

  void char_scanner::
  get (const xchar& c)
  {
    if (unget_)
      unget_ = false;
    else
    {
      if (unpeek_)
      {
        unpeek_ = false;
      }
      // When is_.get () returns eof, the failbit is also set (stupid,
      // isn't?) which may trigger an exception. To work around this
      // we will call peek() first and only call get() if it is not
      // eof. But we can only call peek() on eof once; any subsequent
      // calls will spoil the failbit (even more stupid).
      //
      else if (!eos (c))
        get_ ();

      if (!eos (c))
      {
        if (c == '\n')
        {
          line++;
          column = 1;
        }
        else
          column++;

        position = pos_ ();
      }
    }
  }
}