/*
  This file is part of LilyPond, the GNU music typesetter.

  Copyright (C) 2002--2020 Han-Wen Nienhuys <hanwen@xs4all.nl>

  LilyPond 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.

  LilyPond 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 LilyPond.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "music.hh"
#include "sequential-iterator.hh"
#include "context.hh"
#include "lily-imports.hh"

using std::string;

class Volta_repeat_iterator final : public Sequential_iterator
{
public:
  DECLARE_SCHEME_CALLBACK (constructor, ());
  Volta_repeat_iterator () = default;

  void add_repeat_command (SCM);
protected:
  SCM get_music_list () const override;
  void next_element () override;
  void create_children () override;
  void process (Moment) override;
  void derived_mark () const override;

  bool first_time_ = true;
  // It seems silly not to have a body, but we're trying to be robust.
  bool have_body_ = false;
  int alt_count_ = 0;
  int rep_count_ = 0;
  int done_count_ = 0;
  SCM alt_restores_ = SCM_EOL;
};

void
Volta_repeat_iterator::derived_mark () const
{
  scm_gc_mark (alt_restores_);
  Sequential_iterator::derived_mark ();
}

SCM
Volta_repeat_iterator::get_music_list ()const
{
  return scm_cons (get_property (get_music (), "element"),
                   Sequential_iterator::get_music_list ());
}

void
Volta_repeat_iterator::create_children ()
{
  if (auto *body = unsmob<Music> (get_property (get_music (), "element")))
    {
      have_body_ = (body->get_length () > 0) || body->start_mom ().grace_part_;
    }

  Sequential_iterator::create_children ();

  SCM alts = get_property (get_music (), "elements");

  alt_count_ = int (scm_ilength (alts));
  rep_count_ = scm_to_int (get_property (get_music (), "repeat-count"));
  done_count_ = 0;
}

/*
  TODO: add source information for debugging
*/
void
Volta_repeat_iterator::add_repeat_command (SCM what)
{
  SCM reps = ly_symbol2scm ("repeatCommands");
  SCM current_reps = SCM_EOL;
  Context *where = get_context ()->where_defined (reps, &current_reps);

  if (where && ly_cheap_is_list (current_reps))
    {
      current_reps = scm_cons (what, current_reps);
      set_property (where, reps, current_reps);
    }
}

void
Volta_repeat_iterator::next_element ()
{
  done_count_++;

  Sequential_iterator::next_element ();

  if (alt_count_)
    {
      string repstr = std::to_string (rep_count_ - alt_count_ + done_count_) + ".";
      if (done_count_ <= 1)
        {
          alt_restores_ = SCM_EOL;
          if (from_scm<bool> (get_property (get_context (), "timing")))
            {
              for (SCM lst = get_property (get_context (), "alternativeRestores");
                   scm_is_pair (lst);
                   lst = scm_cdr (lst))
                {
                  SCM res = SCM_EOL;
                  Context *t = get_context ()->where_defined (scm_car (lst),
                                                              &res);
                  if (t)
                    {
                      alt_restores_ = scm_cons
                                      (scm_list_3 (t->self_scm (), scm_car (lst), res),
                                       alt_restores_);
                    }
                }
            }
        }
      else
        {

          add_repeat_command (scm_list_2 (ly_symbol2scm ("volta"), SCM_BOOL_F));

          if (done_count_ - 1 < alt_count_)
            {
              if (have_body_)
                add_repeat_command (ly_symbol2scm ("end-repeat"));

              if (from_scm<bool> (get_property (get_context (), "timing")))
                {
                  SCM mps = ly_symbol2scm ("measurePosition");
                  for (SCM p = alt_restores_; scm_is_pair (p); p = scm_cdr (p))
                    {
                      SCM ls = scm_car (p);
                      if (scm_is_eq (scm_cadr (ls), mps))
                        // Repeats may have different grace timing, so
                        // we need to adjust the measurePosition grace
                        // timing to that of the current alternative
                        // rather than that of the first.  The
                        // Timing_translator does this already but is
                        // too late to avoid bad side-effects
                        {
                          Moment mp (unsmob<Moment> (scm_caddr (ls))->main_part_,
                                     get_context ()->now_mom ().grace_part_);
                          Lily::ly_context_set_property_x (scm_car (ls),
                                                           mps,
                                                           mp.smobbed_copy ());
                        }
                      else
                        scm_apply_0 (Lily::ly_context_set_property_x, ls);
                    }
                }
            }
        }

      if (done_count_ == 1 && alt_count_ < rep_count_)
        repstr = "1.--" + std::to_string (rep_count_ - alt_count_ + done_count_) + ".";

      if (done_count_ <= alt_count_)
        add_repeat_command (scm_list_2 (ly_symbol2scm ("volta"),
                                        ly_string2scm (repstr)));
    }
  else
    {
      if (have_body_)
        add_repeat_command (ly_symbol2scm ("end-repeat"));
    }
}

void
Volta_repeat_iterator::process (Moment m)
{
  if (first_time_)
    {
      if (have_body_)
        add_repeat_command (ly_symbol2scm ("start-repeat"));
      first_time_ = false;
    }
  Sequential_iterator::process (m);
}

IMPLEMENT_CTOR_CALLBACK (Volta_repeat_iterator);
