/*
 *	BIRD -- Route Export Mechanisms
 *
 *	(c) 2024       Maria Matejka <mq@jmq.cz>
 *
 *	Can be freely distributed and used under the terms of the GNU GPL.
 */

#include "nest/bird.h"
#include "nest/route.h"

_Thread_local static struct rt_export_union reu;

static inline enum rt_export_state
rt_export_change_state(struct rt_export_receiver *r, u32 expected_mask, enum rt_export_state state)
{
  r->last_state_change = current_time();
  enum rt_export_state old = atomic_exchange_explicit(&r->export_state, state, memory_order_acq_rel);
  if (!((1 << old) & expected_mask))
    bug("Unexpected export state change from %s to %s, expected mask %02x",
      rt_export_state_name(old),
      rt_export_state_name(state),
      expected_mask
      );

  return old;
}

const struct rt_export_union *
rt_export_get(struct rt_export_receiver *r)
{
  switch (rt_export_get_state_r(r))
  {
    case TES_DOWN:
      bug("Tried to get an export from a stopped receiver");

    case TES_STOP:
      reu.kind = RT_EXPORT_STOP;
      return &reu;

    case TES_PARTIAL:
    case TES_FEEDING:
      /* TODO: implement feeds */
      bug("not implemented yet");

    case TES_READY:
      break;

    case TES_HUNGRY:
    case TES_MAX:
      bug("invalid export state");
  }

  /* Process sequence number reset event */
  if (lfjour_reset_seqno(&r->r))
    bmap_reset(&r->seq_map, 4);

  reu.update = SKIP_BACK(struct rt_export_item, li, lfjour_get(&r->r));

  if (!reu.update)
    return NULL;

  reu.kind = RT_EXPORT_UPDATE;

  if (bmap_test(&r->seq_map, reu.update->seq))
  {
//    log(L_DEBUG "seen, ignoring %p", reu.update);
    rt_export_release(r, &reu);
    return rt_export_get(r);
  }
  else
  {
//    log(L_DEBUG "getting %p", reu.update);
    return &reu;
  }
}

void
rt_export_release(struct rt_export_receiver *r, const struct rt_export_union *u)
{
  ASSERT_DIE(u == &reu);

  switch (reu.kind)
  {
    case RT_EXPORT_UPDATE:
//      log(L_DEBUG "releaseing %p", u.update);
      lfjour_release(&r->r);
      reu.kind = RT_EXPORT_NONE;
      return;

    case RT_EXPORT_FEED:
      bug("not implemented yet");

    case RT_EXPORT_STOP:
      /* Checking that we have indeed stopped the exporter */
      ASSERT_DIE(rt_export_get_state_r(r) == TES_DOWN);
      break;

    default:
      bug("strange export kind");
  }
}

void
rt_export_processed(struct rt_export_receiver *r, const struct rt_export_item *u)
{
//  log(L_DEBUG "processed %p", u);

  /* Check sequence number reset event */
  if (lfjour_reset_seqno(&r->r))
    bmap_reset(&r->seq_map, 4);

  ASSERT_DIE(!bmap_test(&r->seq_map, u->seq));
  bmap_set(&r->seq_map, u->seq);
}

void
rt_export_subscribe(struct rt_exporter *e, struct rt_export_receiver *r)
{
  rt_export_change_state(r, BIT32_ALL(TES_DOWN), TES_FEEDING);

  lfjour_register(&e->journal, &r->r);

  r->stats = (struct rt_export_stats) {};
  r->last_state_change = current_time();
  bmap_init(&r->seq_map, r->pool, 4);

  /* We should init feeding but this is not implemented yet */
  rt_export_change_state(r, BIT32_ALL(TES_FEEDING), TES_READY);
}

void
rt_export_unsubscribe(struct rt_exporter *e UNUSED, struct rt_export_receiver *r)
{
  switch (rt_export_change_state(r, BIT32_ALL(TES_FEEDING, TES_PARTIAL, TES_READY, TES_STOP), TES_DOWN))
  {
    case TES_FEEDING:
    case TES_PARTIAL:
    case TES_READY:
    case TES_STOP:
      lfjour_unregister(&r->r);
      break;
    default:
      bug("not implemented");
  }
}

static void
rt_exporter_cleanup_done(struct lfjour *j, u64 begin_seq UNUSED, u64 end_seq UNUSED)
{
  SKIP_BACK_DECLARE(struct rt_exporter, e, journal, j);

  /* TODO: log the begin_seq / end_seq values */

  CALL(e->cleanup_done, e);
  if (e->stopped && (lfjour_count_recipients(j) == 0))
  {
    settle_cancel(&j->announce_timer);
    ev_postpone(&j->cleanup_event);
    e->stopped(e);
  }
}

void
rt_exporter_init(struct rt_exporter *e, struct settle_config *scf)
{
  e->journal.cleanup_done = rt_exporter_cleanup_done;
  lfjour_init(&e->journal, scf);
}

const struct rt_export_item *
rt_exporter_push(struct rt_exporter *e, const struct rt_export_item *uit)
{
  /* Get the object */
  SKIP_BACK_DECLARE(struct rt_export_item, it, li, lfjour_push_prepare(&e->journal));

  /* Copy the data, keeping the header */
  memcpy(&it->data, &uit->data, e->journal.item_size - OFFSETOF(struct rt_export_item, data));

  /* Commit the update */
/*  log(L_DEBUG "pushing %p %016lx %016lx %016lx %016lx", it,
      ((u64 *)it->data)[0],
      ((u64 *)it->data)[1],
      ((u64 *)it->data)[2],
      ((u64 *)it->data)[3]);*/

  lfjour_push_commit(&e->journal);

  /* Return the update pointer */
  return it;
}

void
rt_exporter_shutdown(struct rt_exporter *e, void (*stopped)(struct rt_exporter *))
{
  /* We have to tell every receiver to stop */
  _Bool done = 1;
  WALK_TLIST(lfjour_recipient, r, &e->journal.recipients)
  {
    done = 0;
    rt_export_change_state(
	SKIP_BACK(struct rt_export_receiver, r, r),
	BIT32_ALL(TES_FEEDING, TES_PARTIAL, TES_READY, TES_STOP),
	TES_STOP);
  }

  /* The rest is done via the cleanup routine */
  lfjour_do_cleanup_now(&e->journal);

  if (done)
  {
    ev_postpone(&e->journal.cleanup_event);
    settle_cancel(&e->journal.announce_timer);
    CALL(stopped, e);
  }
  else
//  e->stopped = stopped;
    bug("not implemented yet");
}