////////////////////////////////////////////////////////////////////////
//
// Copyright (C) 1993-2022 The Octave Project Developers
//
// See the file COPYRIGHT.md in the top-level directory of this
// distribution or <https://octave.org/copyright/>.
//
// This file is part of Octave.
//
// Octave is free software: you can redistribute it and/or modify it
// under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Octave is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Octave; see the file COPYING.  If not, see
// <https://www.gnu.org/licenses/>.
//
////////////////////////////////////////////////////////////////////////

#if ! defined (octave_pager_h)
#define octave_pager_h 1

#include "octave-config.h"

#include <fstream>
#include <iosfwd>
#include <sstream>
#include <string>

class octave_value;
class octave_value_list;

OCTAVE_NAMESPACE_BEGIN

  class interpreter;
  class oprocstream;

  class
  OCTINTERP_API
  pager_buf : public std::stringbuf
  {
  public:

    pager_buf (void) : std::stringbuf (), m_diary_skip (0) { }

    void flush_current_contents_to_diary (void);

    void set_diary_skip (void);

  protected:

    int sync (void);

  private:

    std::size_t m_diary_skip;
  };

  class
  OCTINTERP_API
  pager_stream : public std::ostream
  {
  public:

    pager_stream (void);

    // No copying!

    pager_stream (const pager_stream&) = delete;

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

    ~pager_stream (void);

    void flush_current_contents_to_diary (void);

    void set_diary_skip (void);

    std::ostream& stream (void);

    void reset (void);

  private:

    pager_buf *m_pb;
  };

  class
  OCTINTERP_API
  diary_buf : public std::stringbuf
  {
  public:

    diary_buf (void) : std::stringbuf () { }

  protected:

    int sync (void);
  };

  class
  OCTINTERP_API
  diary_stream : public std::ostream
  {
  public:

    diary_stream (void);

    // No copying!

    diary_stream (const diary_stream&) = delete;

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

    ~diary_stream (void);

    std::ostream& stream (void);

    void reset (void);

  private:

    diary_buf *m_db;
  };

  extern OCTINTERP_API void flush_stdout (void);

  class output_system
  {
  public:

    output_system (interpreter& interp);

    output_system (const output_system&) = delete;

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

    ~output_system (void) = default;

    pager_stream& pager (void) { return m_pager_stream; }

    diary_stream& diary (void) { return m_diary_stream; }

    std::string diary_file_name (void) const { return m_diary_file_name; }

    std::string diary_file_name (const std::string& nm)
    {
      std::string val = m_diary_file_name;
      m_diary_file_name = nm.empty () ? "diary" : nm;
      return val;
    }

    octave_value PAGER (const octave_value_list& args, int nargout);

    std::string PAGER (void) const { return m_PAGER; }

    std::string PAGER (const std::string& s)
    {
      std::string val = m_PAGER;
      m_PAGER = s;
      return val;
    }

    octave_value PAGER_FLAGS (const octave_value_list& args, int nargout);

    std::string PAGER_FLAGS (void) const { return m_PAGER_FLAGS; }

    std::string PAGER_FLAGS (const std::string& s)
    {
      std::string val = m_PAGER_FLAGS;
      m_PAGER_FLAGS = s;
      return val;
    }

    octave_value page_output_immediately (const octave_value_list& args,
                                          int nargout);

    bool page_output_immediately (void) const
    {
      return m_page_output_immediately;
    }

    bool page_output_immediately (bool flag)
    {
      bool val = m_page_output_immediately;
      m_page_output_immediately = flag;
      return val;
    }

    octave_value page_screen_output (const octave_value_list& args,
                                     int nargout);

    bool page_screen_output (void) const { return m_page_screen_output; }

    bool page_screen_output (bool flag)
    {
      bool val = m_page_screen_output;
      m_page_screen_output = flag;
      return val;
    }

    bool write_to_diary_file (void) const
    {
      return m_write_to_diary_file;
    }

    bool write_to_diary_file (bool flag)
    {
      bool val = m_write_to_diary_file;
      m_write_to_diary_file = flag;
      return val;
    }

    bool really_flush_to_pager (void) const
    {
      return m_really_flush_to_pager;
    }

    bool really_flush_to_pager (bool flag)
    {
      bool val = m_really_flush_to_pager;
      m_really_flush_to_pager = flag;
      return val;
    }

    bool flushing_output_to_pager (void) const
    {
      return m_flushing_output_to_pager;
    }

    bool flushing_output_to_pager (bool flag)
    {
      bool val = m_flushing_output_to_pager;
      m_flushing_output_to_pager = flag;
      return val;
    }

    std::string pager_command (void) const;

    std::ofstream& external_diary_file (void) { return m_external_diary_file; }

    void reset (void);

    void flush_stdout (void);

    bool sync (const char *msg, int len);

    void clear_external_pager (void);

    void open_diary (void);

    void close_diary (void);

    std::ostream& __stdout__ (void) { return m_pager_stream.stream (); }

    std::ostream& __diary__ (void) { return m_diary_stream.stream (); }

  private:

    interpreter& m_interpreter;

    pager_stream m_pager_stream;

    diary_stream m_diary_stream;

    // Our actual connection to the external pager.
    oprocstream *m_external_pager = nullptr;

    // The diary file.
    std::ofstream m_external_diary_file;

    // The name of the current diary file.
    std::string m_diary_file_name;

    // The shell command to run as the pager.
    std::string m_PAGER;

    // The options to pass to the pager.
    std::string m_PAGER_FLAGS;

    // TRUE means that if output is going to the pager, it is sent as soon
    // as it is available.  Otherwise, it is buffered and only sent to the
    // pager when it is time to print another prompt.
    bool m_page_output_immediately;

    // TRUE means all output intended for the screen should be passed
    // through the pager.
    bool m_page_screen_output;

    // TRUE means we write to the diary file.
    bool m_write_to_diary_file;

    bool m_really_flush_to_pager;

    bool m_flushing_output_to_pager;

    void start_external_pager (void);

    void do_sync (const char *msg, int len, bool bypass_pager);
  };

  extern OCTINTERP_API std::ostream& __stdout__ (void);

  extern OCTINTERP_API std::ostream& __diary__ (void);

OCTAVE_NAMESPACE_END

#define octave_stdout (octave::__stdout__ ())

#define octave_diary (octave::__diary__ ())

#endif