/*
  note-spacing.cc -- implement Note_spacing

  source file of the GNU LilyPond music typesetter

  (c) 2001--2007  Han-Wen Nienhuys <hanwen@xs4all.nl>
*/

#include "note-spacing.hh"

#include "bar-line.hh"
#include "directional-element-interface.hh"
#include "grob-array.hh"
#include "paper-column.hh"
#include "moment.hh"
#include "note-column.hh"
#include "warn.hh"
#include "stem.hh"
#include "separation-item.hh"
#include "spacing-interface.hh"
#include "staff-spacing.hh"
#include "accidental-placement.hh"
#include "output-def.hh"
#include "pointer-group-interface.hh"

/*
  TODO: detect hshifts due to collisions, and account for them in
  spacing?
*/

Spring
Note_spacing::get_spacing (Grob *me, Item *right_col,
			   Real base_space, Real increment)
{
  vector<Item*> note_columns = Spacing_interface::left_note_columns (me);
  Real left_head_end = 0;

  for (vsize i = 0; i < note_columns.size (); i++)
    {
       SCM r = note_columns[i]->get_object ("rest");
       Grob *g = unsmob_grob (r);
       Grob *col = note_columns[i]->get_column ();

       if (!g)
	 g = Note_column::first_head (note_columns[i]);

       /*
	 Ugh. If Stem is switched off, we don't know what the
	 first note head will be.
       */
       if (g)
	 {
	   if (g->common_refpoint (col, X_AXIS) != col)
	     programming_error ("Note_spacing::get_spacing (): Common refpoint incorrect");
	   else
	     left_head_end = g->extent (col, X_AXIS)[RIGHT];
	 }
    }

  /*
    The main factor that determines the amount of space is the width of the
    note head (or the rest). For example, a quarter rest gets almost 0.5 ss
    less horizontal space than a note.

    The other parts of a note column (eg. flags, accidentals, etc.) don't get
    the full amount of space. We give them half the amount of space, but then
    adjust things so there are no collisions.
  */
  Drul_array<Skyline> skys = Spacing_interface::skylines (me, right_col);
  Real distance = skys[LEFT].distance (skys[RIGHT]);
  Real min_dist = max (0.0, distance);
  Real min_desired_space = left_head_end + (min_dist - left_head_end + base_space - increment) / 2;
  Real ideal = base_space - increment + left_head_end;

  /* If we have a NonMusical column on the right, we measure the ideal distance
     to the bar-line (if present), not the start of the column. */
  if (!Paper_column::is_musical (right_col)
      && !skys[RIGHT].is_empty ()
      && to_boolean (me->get_property ("space-to-barline")))
    {
      Grob *bar = Pointer_group_interface::find_grob (right_col,
						      ly_symbol2scm ("elements"),
						      Bar_line::has_interface);

      if (bar)
	{
	  Real shift = bar->extent (right_col, X_AXIS)[LEFT];
	  ideal -= shift;
	  min_desired_space -= max (shift, 0.0);
	}
      else
	ideal -= right_col->extent (right_col, X_AXIS)[RIGHT];
    }

  ideal = max (ideal, min_desired_space);
  stem_dir_correction (me, right_col, increment, &ideal, &min_desired_space);

  /* TODO: grace notes look bad when things are stretched. Should we increase
     their stretch strength? */
  Spring ret (max (0.0, ideal), min_dist);
  ret.set_inverse_compress_strength (max (0.0, ideal - min_desired_space));
  ret.set_inverse_stretch_strength (max (0.1, base_space - increment));
  return ret;
}

static Real
knee_correction (Grob *note_spacing, Grob *right_stem, Real increment)
{
  Real note_head_width = increment;
  Grob *head = right_stem ? Stem::support_head (right_stem) : 0;
  Grob *rcolumn = dynamic_cast<Item*> (head)->get_column ();

  Interval head_extent;
  if (head)
    {
      head_extent = head->extent (rcolumn, X_AXIS);

      if (!head_extent.is_empty ())
	note_head_width = head_extent[RIGHT];

      note_head_width -= Stem::thickness (right_stem);
    }

  return -note_head_width * get_grob_direction (right_stem)
    * robust_scm2double (note_spacing->get_property ("knee-spacing-correction"), 0);
}

static Real
different_directions_correction (Grob *note_spacing,
				 Drul_array<Interval> stem_posns,
				 Direction left_stem_dir)
{
  Real ret = 0.0;
  Interval intersect = stem_posns[LEFT];
  intersect.intersect (stem_posns[RIGHT]);

  if (!intersect.is_empty ())
    {
      ret = abs (intersect.length ());

      /*
	Ugh. 7 is hardcoded.
      */
      ret = min (ret / 7, 1.0)
	* left_stem_dir
	* robust_scm2double (note_spacing->get_property ("stem-spacing-correction"), 0);
    }
  return ret;
}

static Real
same_direction_correction (Grob *note_spacing, Drul_array<Interval> head_posns)
{
  /*
    Correct for the following situation:
    
    X      X
    |      |
    |      |
    |   X  |
    |  |   |
    ========
    
    ^ move the center one to the left.
    
    
    this effect seems to be much more subtle than the
    stem-direction stuff (why?), and also does not scale with the
    difference in stem length.
    
  */

  Interval hp = head_posns[LEFT];
  hp.intersect (head_posns[RIGHT]);
  if (!hp.is_empty ())
    return 0;
  
  Direction lowest
    = (head_posns[LEFT][DOWN] > head_posns[RIGHT][UP]) ? RIGHT : LEFT;
  
  Real delta = head_posns[-lowest][DOWN] - head_posns[lowest][UP];
  Real corr = robust_scm2double (note_spacing->get_property ("same-direction-correction"), 0);
  
  return (delta > 1) ? -lowest * corr : 0;
}


/**
   Correct for optical illusions. See [Wanske] p. 138. The combination
   up-stem + down-stem should get extra space, the combination
   down-stem + up-stem less.

   TODO: have to check whether the stems are in the same staff.
*/
void
Note_spacing::stem_dir_correction (Grob *me, Item *rcolumn,
				   Real increment,
				   Real *space, Real *fixed)
{
  Drul_array<Direction> stem_dirs (CENTER, CENTER);
  Drul_array<Interval> stem_posns;
  Drul_array<Interval> head_posns;
  Drul_array<SCM> props (me->get_object ("left-items"),
			 me->get_object ("right-items"));

  Drul_array<Spanner *> beams_drul (0, 0);
  Drul_array<Grob *> stems_drul (0, 0);

  stem_dirs[LEFT] = stem_dirs[RIGHT] = CENTER;
  Interval intersect;
  Interval bar_xextent;
  Interval bar_yextent;

  Direction d = LEFT;

  Grob *bar = Spacing_interface::extremal_break_aligned_grob (me, RIGHT,
							      rcolumn->break_status_dir (),
							      &bar_xextent);
  if (bar && dynamic_cast<Item*> (bar)->get_column () == rcolumn)
    bar_yextent = Staff_spacing::bar_y_positions (bar);

  do
    {
      vector<Grob*> const &items (ly_scm2link_array (props [d]));
      for (vsize i = 0; i < items.size (); i++)
	{
	  Item *it = dynamic_cast<Item *> (items[i]);
	  if (!Note_column::has_interface (it))
	    continue;

	  /*
	    don't correct if accidentals are sticking out of the right side.
	  */
	  if (d == RIGHT && Note_column::accidentals (it))
	    return;

	  Grob *stem = Note_column::get_stem (it);

	  if (!stem || !stem->is_live () || Stem::is_invisible (stem))
	    return;

	  stems_drul[d] = stem;
	  beams_drul[d] = Stem::get_beam (stem);

	  Direction stem_dir = get_grob_direction (stem);
	  if (stem_dirs[d] && stem_dirs[d] != stem_dir)
	    return;

	  stem_dirs[d] = stem_dir;

	  /*
	    Correction doesn't seem appropriate  when there is a large flag
	    hanging from the note.
	  */
	  if (d == LEFT
	      && Stem::duration_log (stem) > 2 && !Stem::get_beam (stem))
	    return;

	  Interval hp = Stem::head_positions (stem);
	  if (!hp.is_empty ())
	    {
	      Real chord_start = hp[stem_dir];

	      /*
		can't look at stem-end-position, since that triggers
		beam slope computations.
	      */
	      Real stem_end = hp[stem_dir] +
		stem_dir * robust_scm2double (stem->get_property ("length"), 7);

	      stem_posns[d] = Interval (min (chord_start, stem_end),
					max (chord_start, stem_end));
	      head_posns[d].unite (hp);
	    }
	}
    }
  while (flip (&d) != LEFT);

  Real correction = 0.0;

  if (!bar_yextent.is_empty ())
    {
      stem_dirs[RIGHT] = -stem_dirs[LEFT];
      stem_posns[RIGHT] = bar_yextent;
      stem_posns[RIGHT] *= 2;
    }

  if (stem_dirs[LEFT] * stem_dirs[RIGHT] == -1)
    {
      if (beams_drul[LEFT] && beams_drul[LEFT] == beams_drul[RIGHT])
	{
	  correction = knee_correction (me, stems_drul[RIGHT], increment);
	  *fixed += correction;
	}
      else
	{
	  correction = different_directions_correction (me, stem_posns, stem_dirs[LEFT]);

	  if (!bar_yextent.is_empty ())
	    correction *= 0.5;
	}
    }
  else if (stem_dirs[LEFT] * stem_dirs[RIGHT] == 1)
    correction = same_direction_correction (me, head_posns);

  *space += correction;

  /* there used to be a correction for bar_xextent () here, but
     it's unclear what that was good for ?
  */
}

ADD_INTERFACE (Note_spacing,
	       "This object calculates spacing wishes for individual voices.",

	       
	       "knee-spacing-correction "
	       "left-items "
	       "right-items "
	       "same-direction-correction "
	       "stem-spacing-correction "
	       "space-to-barline "

	       );

