/*
  dispatcher.cc -- implement Dispatcher

  source file of the GNU LilyPond music typesetter

  (c) 2005-2006 Erik Sandberg  <address@hidden>
*/

#include "dispatcher.hh"
#include "international.hh"
#include "ly-smobs.icc"
#include "stream-event.hh"
#include "warn.hh"

// ES todo: move to lily-guile.hh
SCM appendable_list ();
void appendable_list_append (SCM l, SCM elt);

IMPLEMENT_SMOBS (Dispatcher);
IMPLEMENT_TYPE_P (Dispatcher, "dispatcher");
IMPLEMENT_DEFAULT_EQUAL_P (Dispatcher);

Dispatcher::~Dispatcher ()
{
}

Dispatcher::Dispatcher ()
{
  self_scm_ = SCM_EOL;
  listeners_ = SCM_EOL;
  dispatchers_ = SCM_EOL;
  listen_classes_ = SCM_EOL;
  smobify_self ();
  //TODO use resizable hash
  listeners_ = scm_c_make_hash_table (17);
  priority_count_ = 0;
}

SCM
Dispatcher::mark_smob (SCM sm)
{
  Dispatcher *me = (Dispatcher *) SCM_CELL_WORD_1 (sm);
  scm_gc_mark (me->dispatchers_);
  scm_gc_mark (me->listen_classes_);
  return me->listeners_;
}

int
Dispatcher::print_smob (SCM s, SCM p, scm_print_state*)
{
  Dispatcher *me = (Dispatcher *) SCM_CELL_WORD_1 (s);
  scm_puts ("#<Dispatcher ", p);
  scm_write (scm_vector_to_list (me->listeners_), p);
  scm_puts (">", p);
  return 1;
}

/*
Event dispatching:
- Collect a list of listeners for each relevant class
- Send the event to each of these listeners, in increasing priority order.
  This is done by keeping a bubble-sorted temporary list of listener lists,
  and iteratively send the event to the lowest-priority listener.
- An event is never sent twice to listeners with equal priority.
*/
IMPLEMENT_LISTENER (Dispatcher, dispatch) (Stream_event *ev)
{
  SCM class_symbol = ev->get_property ("class");
  if (!scm_symbol_p (class_symbol))
    {
      warning (_f ("Unknown event class %s", ly_symbol2string (class_symbol).c_str ()));
      return;
    }

  SCM class_list = scm_primitive_eval (class_symbol);
  bool sent = false;

  // TODO: fix this loop.
  int num_classes = 0;
  for (SCM cl = class_list; cl != SCM_EOL; cl = scm_cdr (cl))
    num_classes++;

  // Collect all listener lists.
  struct { int prio; SCM list; } lists[num_classes+1];
  int i = 0;
  for (SCM cl = class_list; cl != SCM_EOL; cl = scm_cdr (cl))
    {
      SCM list = scm_hashq_ref (listeners_, scm_car (cl), SCM_EOL);
      if (list == SCM_EOL)
	num_classes--;
      else 
	{
          // bubblesort.
          int prio = scm_to_int (scm_caar (list));
	  int j;
	  for (j = i; j > 0 && lists[j-1].prio > prio; j--)
	    lists[j] = lists[j-1];
	  lists[j].prio = prio;
	  lists[j].list = list;
	  i++;
        }
    }
  lists[num_classes].prio = INT_MAX;

  // Never send an event to two listeners with equal priority.
  int last_priority = -1;
  // Iteratively process all event classes, in increasing priority.
  while (num_classes)
    {
      // Send the event, if we haven't already sent it to this target.
      if (lists[0].prio != last_priority)
        {
          // process the listener
          assert (lists[0].prio > last_priority);
          last_priority = lists[0].prio;

          Listener *l = unsmob_listener (scm_cdar (lists[0].list));
          l->listen (ev);
          sent = true;
        }
      // go to the next listener; bubble-sort the class list.
      SCM next = scm_cdr (lists[0].list);
      if (next == SCM_EOL)
        num_classes--;
      int prio = (next == SCM_EOL) ? INT_MAX : scm_to_int (scm_caar (next));
      for (i = 0; prio > lists[i+1].prio; i++)
        lists[i] = lists[i+1];
      lists[i].prio = prio;
      lists[i].list = next;
    }

  if (!sent)
    warning (_f ("Junking event: %s", ly_symbol2string (class_symbol).c_str ()));
}

void
Dispatcher::add_listener (Listener l, SCM ev_class)
{
  internal_add_listener (l, ev_class, ++priority_count_);
}

#if 0
/*
 New listeners are appended to the end of the list.
 This way, listeners will listen to an event in the order they were added.
*/
inline void
Dispatcher::internal_add_listener (Listener l, SCM ev_class, int priority)
{
  SCM list = scm_hashq_ref (listeners_, ev_class, SCM_EOL);
  if (list == SCM_EOL)
    {
      list = appendable_list ();
      scm_hashq_set_x (listeners_, ev_class, list);
      /* Register with all dispatchers. */
      for (SCM disp = dispatchers_; disp != SCM_EOL; disp = scm_cdr (disp))
	{
	  int priority = scm_cdar (disp);
	  Dispatcher *d = unsmob_dispatcher (scm_caar (disp));
	  d->internal_add_listener (dispatch (), ev_class, priority);
	}
      listen_classes_ = scm_cons (ev_class, listen_classes_);
    }

  appendable_list_append (list, l.smobbed_copy ());
}
#endif

inline void
Dispatcher::internal_add_listener (Listener l, SCM ev_class, int priority)
{
  SCM list = scm_hashq_ref (listeners_, ev_class, SCM_EOL);
  if (list == SCM_EOL)
    {
      /* Register with all dispatchers. */
      for (SCM disp = dispatchers_; disp != SCM_EOL; disp = scm_cdr (disp))
	{
	  int priority = scm_to_int (scm_cdar (disp));
	  Dispatcher *d = unsmob_dispatcher (scm_caar (disp));
	  d->internal_add_listener (dispatch (), ev_class, priority);
	}
      listen_classes_ = scm_cons (ev_class, listen_classes_);
    }
  SCM entry = scm_cons (scm_int2num (priority), l.smobbed_copy ());
  list = scm_merge_x (list, scm_list_1 (entry), scm_primitive_eval (ly_symbol2scm ("car<")));
  scm_hashq_set_x (listeners_, ev_class, list);
}

void
Dispatcher::remove_listener (Listener l, SCM ev_class)
{
  SCM list = scm_hashq_ref (listeners_, ev_class, SCM_EOL);

  if (list == SCM_EOL)
    {
      programming_error ("remove_listener called with incorrect class.");
      return;
    }

  // We just remove the listener once.
  bool first = true;

  SCM dummy = scm_cons (SCM_EOL, list);
  SCM e = dummy;
  while (scm_cdr (e) != SCM_EOL)
    if (*unsmob_listener (scm_cdadr (e)) == l && first)
      {
	scm_set_cdr_x (e, scm_cddr(e));
	first = false;
	break;
      }
    else
      e = scm_cdr (e);
  list = scm_cdr (dummy);

#if 0 // obsolete appandable-list code
  SCM e = list;
  while (scm_cdr (e) != SCM_EOL)
    if (*unsmob_listener (scm_cadr (e)) == l && first)
      {
	scm_set_cdr_x (e, scm_cddr(e));
	first = false;
      }
    else
      e = scm_cdr (e);
  scm_set_car_x (list, e);
#endif

  if (first)
    warning ("Attempting to remove nonexisting listener.");
  else if (list == SCM_EOL)
    {
      /* Unregister with all dispatchers. */
      for (SCM disp = dispatchers_; disp != SCM_EOL; disp = scm_cdr (disp))
	{
	  Dispatcher *d = unsmob_dispatcher (scm_caar (disp));
	  d->remove_listener (dispatch (), ev_class);
	}
      listen_classes_ = scm_delq_x (ev_class, listen_classes_);
    }
}

/* Register as a listener to another dispatcher. */
void
Dispatcher::register_as_listener (Dispatcher *disp)
{
  int priority = ++disp->priority_count_;

  // Don't register twice to the same dispatcher.
  if (scm_assq (disp->self_scm (), dispatchers_) != SCM_BOOL_F)
    {
      warning ("Already listening to dispatcher, ignoring request");
      return;
    }

  dispatchers_ = scm_acons (disp->self_scm (), scm_int2num (priority), dispatchers_);

  Listener list = dispatch ();
  for (SCM cl = listen_classes_; cl != SCM_EOL; cl = scm_cdr (cl))
    {
      disp->internal_add_listener (list, scm_car (cl), priority);
    }
}

/* Unregister as a listener to another dispatcher. */
void
Dispatcher::unregister_as_listener (Dispatcher *disp)
{
#ifndef NDEBUG
//  assert (SCM_EOL == scm_hashq_ref (listeners_, ly_symbol2scm ("StreamEvent"), SCM_EOL));
#endif

  dispatchers_ = scm_assq_remove_x (dispatchers_, disp->self_scm ());

  Listener list = dispatch ();
  for (SCM cl = listen_classes_; cl != SCM_EOL; cl = scm_cdr (cl))
    {
      disp->remove_listener (list, scm_car (cl));
    }
}

LY_DEFINE (ly_make_dispatcher, "ly:make-dispatcher",
	   0, 0, 0, (),
	   "Returns a newly created dispatcher.")
{
  return (new Dispatcher ())->unprotect ();
}

LY_DEFINE (ly_register_dispatcher, "ly:connect-dispatchers",
	   2, 0, 0, (SCM to, SCM from),
	   "Makes the dispatcher @var{to} listen to events from @var{from}." )
{
  Dispatcher *t = unsmob_dispatcher (to);
  Dispatcher *f = unsmob_dispatcher (from);
  SCM_ASSERT_TYPE (t, from, SCM_ARG1, __FUNCTION__, "dispatcher");
  SCM_ASSERT_TYPE (f, to, SCM_ARG2, __FUNCTION__, "dispatcher");
  t->register_as_listener (f);

  return SCM_UNDEFINED;
}

LY_DEFINE (ly_add_listener, "ly:add-listener",
	   2, 0, 1, (SCM list, SCM disp, SCM cl),
	   "Adds the listener @var{list} to the dispatcher @var{disp}.\n"
	   " Whenever @var{disp} hears an event of class @var{cl}, it will be forwarded to @var{list}.\n" )
{
  Listener *l = unsmob_listener (list);
  Dispatcher *d = unsmob_dispatcher (disp);
  SCM_ASSERT_TYPE (l, list, SCM_ARG1, __FUNCTION__, "listener");
  SCM_ASSERT_TYPE (d, disp, SCM_ARG2, __FUNCTION__, "dispatcher");
  
  for (int arg=SCM_ARG3; cl != SCM_EOL; cl = scm_cdr (cl), arg++)
    {
      SCM_ASSERT_TYPE (scm_symbol_p (cl), cl, arg, __FUNCTION__, "symbol");
      d->add_listener (*l, scm_car (cl));
    }

  return SCM_UNDEFINED;
}

LY_DEFINE (ly_broadcast, "ly:broadcast",
	   2, 0, 0, (SCM disp, SCM ev),
	   "Sends the stream event @var{ev} to the dispatcher\n"
	   "@var{disp}.")
{
  Dispatcher *d = unsmob_dispatcher (disp);
  Stream_event *e = unsmob_stream_event (ev);
  SCM_ASSERT_TYPE (d, disp, SCM_ARG1, __FUNCTION__, "dispatcher");
  SCM_ASSERT_TYPE (e, ev, SCM_ARG2, __FUNCTION__, "stream event");
  d->broadcast (e);
  return SCM_UNDEFINED;
}