// file      : build/lexer -*- C++ -*-
// copyright : Copyright (c) 2014-2015 Code Synthesis Tools CC
// license   : MIT; see accompanying LICENSE file

#ifndef BUILD_LEXER
#define BUILD_LEXER

#include <string>
#include <iosfwd>
#include <cstdint> // uint64_t
#include <exception>

#include <build/token>

namespace build
{
  // The handler must assume the diagnostics has already been issued.
  //
  struct lexer_error: std::exception {};

  class lexer
  {
  public:
    lexer (std::istream& is, const std::string& name, std::ostream& diag)
        : is_ (is), name_ (name), diag_ (diag) {}

    token
    next ();

    // Character interface.
    //
  private:
    class xchar
    {
    public:
      typedef std::char_traits<char> traits_type;
      typedef traits_type::int_type int_type;
      typedef traits_type::char_type char_type;

      xchar (int_type v, std::uint64_t l, std::uint64_t c)
          : v_ (v), l_ (l), c_ (c) {}

      operator char_type () const {return static_cast<char_type> (v_);}

      int_type
      value () const {return v_;}

      std::uint64_t line () const {return l_;}
      std::uint64_t column () const {return c_;}

    private:
      int_type v_;
      std::uint64_t l_;
      std::uint64_t c_;
    };

    xchar
    peek ();

    xchar
    get ();

    void
    unget (const xchar&);

    // Tests.
    //
    bool
    is_eos (const xchar& c) const
    {
      return c.value () == xchar::traits_type::eof ();
    }

    // Scanner.
    //
  private:
    xchar
    escape ();

    void
    skip_spaces ();

    token
    name (xchar);

    // Utilities.
    //
  private:
    std::ostream&
    error (const xchar&);

  private:
    std::istream& is_;
    std::string name_;
    std::ostream& diag_;

    std::uint64_t l_ {1};
    std::uint64_t c_ {1};

    bool eos_ {false};

    bool unget_ {false};
    xchar buf_ {0, 0, 0};
  };
}

#endif // BUILD_LEXER