/*
  context-property.cc -- implement manipulation of immutable Grob
  property lists.

  source file of the GNU LilyPond music typesetter

  (c) 2004--2006 Han-Wen Nienhuys <hanwen@xs4all.nl>
*/

#include "context.hh"
#include "engraver.hh"
#include "international.hh"
#include "item.hh"
#include "main.hh"
#include "simple-closure.hh"
#include "spanner.hh"
#include "warn.hh"

SCM
lookup_nested_property (SCM alist,
			SCM grob_property_path)
{
  if (scm_is_pair (grob_property_path))
    {
      SCM sym = scm_car (grob_property_path);
      SCM handle = scm_assq (sym, alist);

      if (handle == SCM_BOOL_F)
	return SCM_EOL;
      else
	return lookup_nested_property (scm_cdr (handle),
				       scm_cdr (grob_property_path));
    }
  else 
    return alist;
}

/*
  copy ALIST leaving out SYMBOL. Copying stops at ALIST_END
*/
SCM
evict_from_alist (SCM symbol,
		  SCM alist,
		  SCM alist_end)
{
  SCM new_alist = SCM_EOL;
  SCM *tail = &new_alist;

  while (alist != alist_end)
    {
      if (ly_is_equal (scm_caar (alist), symbol))
	{
	  alist = scm_cdr (alist);
	  break;
	}

      *tail = scm_cons (scm_car (alist), SCM_EOL);
      tail = SCM_CDRLOC (*tail);
      alist = scm_cdr (alist);
    }

  *tail = alist;
  return new_alist;
}

void
general_pushpop_property (Context *context,
			  SCM context_property,
			  SCM grob_property_path,
			  SCM new_value			  
			  )
{
  if (!scm_is_symbol (context_property)
      || !scm_is_symbol (scm_car (grob_property_path)))
    {
      warning (_ ("need symbol arguments for \\override and \\revert"));
      if (do_internal_type_checking_global)
	assert (false);
    }

  execute_general_pushpop_property (context, context_property,
				    grob_property_path, new_value);
}


/*
  
  Grob descriptions (ie. alists with layout properties) are
  represented as a (ALIST . BASED-ON) pair, where BASED-ON is the
  alist defined in a parent context. BASED-ON should always be a tail
  of ALIST.

  Push or pop (depending on value of VAL) a single entry entry from a
  translator property list by name of PROP.  GROB_PROPERTY_PATH
  indicates nested alists, eg. '(beamed-stem-lengths details)
  
*/
void
execute_general_pushpop_property (Context *context,
				  SCM context_property,
				  SCM grob_property_path,
				  SCM new_value
				  )
{
  SCM current_context_val = SCM_EOL;
  if (new_value != SCM_UNDEFINED)
    {
      Context *where = context->where_defined (context_property, &current_context_val);

      /*
	Don't mess with MIDI.
      */
      if (!where)
	return;

      if (where != context)
	{
	  SCM base = updated_grob_properties (context, context_property);
	  current_context_val = scm_cons (base, base);
	  context->set_property (context_property, current_context_val);
	}

      if (!scm_is_pair (current_context_val))
	{
	  programming_error ("Grob definition should be cons");
	  return;
	}

      SCM prev_alist = scm_car (current_context_val);
      SCM symbol = scm_car (grob_property_path);
      SCM target_alist
	= lookup_nested_property (prev_alist,
				  scm_reverse (scm_cdr (grob_property_path)));

      target_alist = scm_acons (symbol, new_value, target_alist);

      bool ok = true;
      if (!scm_is_pair (scm_cdr (grob_property_path)))
	{
	  if (!ly_is_procedure (new_value)
	      && !is_simple_closure (new_value))
	    ok = type_check_assignment (symbol, new_value,
					ly_symbol2scm ("backend-type?"));

	  /*
	    tack onto alist.  We can use set_car, since
	    updated_grob_properties() in child contexts will check
	    for changes in the car.
	  */
	  if (ok)
	    {
	      scm_set_car_x (current_context_val, target_alist);
	    }
	}
      else
	{
	  execute_general_pushpop_property (context,
					    context_property,
					    scm_cdr (grob_property_path),
					    target_alist
					    );
	}
    }
  else if (context->where_defined (context_property, &current_context_val) == context)
    {
      SCM current_value = scm_car (current_context_val);
      SCM daddy = scm_cdr (current_context_val);

      if (!scm_is_pair (grob_property_path)
	  || !scm_is_symbol (scm_car (grob_property_path)))
	{
	  programming_error ("Grob property path should be list of symbols.");
	  return;
	}
      
      SCM symbol = scm_car (grob_property_path);
      SCM new_alist = evict_from_alist (symbol, current_value, daddy);

      if (new_alist == daddy)
	context->unset_property (context_property);
      else
	context->set_property (context_property, scm_cons (new_alist, daddy));
    }
}

void
execute_pushpop_property (Context *context,
			  SCM context_property,
			  SCM grob_property,
			  SCM new_value
			  )
{
  general_pushpop_property (context, context_property,
			    scm_list_1 (grob_property),
			    new_value);
}
  
/*
  PRE_INIT_OPS is in the order specified, and hence must be reversed.
*/
void
apply_property_operations (Context *tg, SCM pre_init_ops)
{
  SCM correct_order = scm_reverse (pre_init_ops);
  for (SCM s = correct_order; scm_is_pair (s); s = scm_cdr (s))
    {
      SCM entry = scm_car (s);
      SCM type = scm_car (entry);
      entry = scm_cdr (entry);

      if (type == ly_symbol2scm ("push"))
	{
	  SCM context_prop = scm_car (entry);
	  SCM val = scm_cadr (entry);
	  SCM grob_prop_path = scm_cddr (entry);
	  execute_general_pushpop_property (tg, context_prop, grob_prop_path, val);
	}
      else if (type == ly_symbol2scm ("pop"))
	{
	  SCM context_prop = scm_car (entry);
	  SCM val = SCM_UNDEFINED;
	  SCM grob_prop_path = scm_cdr (entry);
	  execute_general_pushpop_property (tg, context_prop, grob_prop_path, val);
	}
      else if (type == ly_symbol2scm ("assign"))
	tg->set_property (scm_car (entry), scm_cadr (entry));
    }
}

/*
  Return the object alist for SYM, checking if its base in enclosing
  contexts has changed. The alist is updated if necessary.
*/
SCM
updated_grob_properties (Context *tg, SCM sym)
{
  assert (scm_is_symbol (sym));

  SCM props;
  tg = tg->where_defined (sym, &props);
  if (!tg)
    return SCM_EOL;

  SCM daddy_props
    = (tg->get_parent_context ())
    ? updated_grob_properties (tg->get_parent_context (), sym)
    : SCM_EOL;

  if (!scm_is_pair (props))
    {
      programming_error ("grob props not a pair?");
      return SCM_EOL;
    }

  SCM based_on = scm_cdr (props);
  if (based_on == daddy_props)
    return scm_car (props);
  else
    {
      SCM copy = daddy_props;
      SCM *tail = &copy;
      SCM p = scm_car (props);
      while (p != based_on)
	{
	  *tail = scm_cons (scm_car (p), daddy_props);
	  tail = SCM_CDRLOC (*tail);
	  p = scm_cdr (p);
	}

      scm_set_car_x (props, copy);
      scm_set_cdr_x (props, daddy_props);

      return copy;
    }
}
