/*
 * This is an implementation of the IETF SPF delay algorithm
 * as explained in draft-ietf-rtgwg-backoff-algo-04
 *
 * Created: 25-01-2017 by S. Litkowski
 *
 * Copyright (C) 2017 Orange Labs http://www.orange.com/
 * Copyright (C) 2017 by Christian Franke, Open Source Routing / NetDEF Inc.
 *
 * This file is part of FreeRangeRouting (FRR)
 *
 * FRR 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 2, or (at your option) any
 * later version.
 *
 * FRR 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 this program; see the file COPYING; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include <zebra.h>

#include "spf_backoff.h"

#include "command.h"
#include "memory.h"
#include "thread.h"
#include "vty.h"

DEFINE_MTYPE_STATIC(LIB, SPF_BACKOFF, "SPF backoff")
DEFINE_MTYPE_STATIC(LIB, SPF_BACKOFF_NAME, "SPF backoff name")

static bool debug_spf_backoff = false;
#define backoff_debug(...) \
  do \
    { \
      if (debug_spf_backoff) \
        zlog_debug(__VA_ARGS__); \
    } \
  while (0)

enum spf_backoff_state {
  SPF_BACKOFF_QUIET,
  SPF_BACKOFF_SHORT_WAIT,
  SPF_BACKOFF_LONG_WAIT
};

struct spf_backoff {
  struct thread_master *m;

  /* Timers as per draft */
  long init_delay;
  long short_delay;
  long long_delay;
  long holddown;
  long timetolearn;

  /* State machine */
  enum spf_backoff_state state;
  struct thread *t_holddown;
  struct thread *t_timetolearn;

  /* For debugging */
  char *name;
  struct timeval first_event_time;
  struct timeval last_event_time;
};

static const char *
spf_backoff_state2str(enum spf_backoff_state state)
{
  switch (state)
    {
    case SPF_BACKOFF_QUIET:
      return "QUIET";
    case SPF_BACKOFF_SHORT_WAIT:
      return "SHORT_WAIT";
    case SPF_BACKOFF_LONG_WAIT:
      return "LONG_WAIT";
    }
  return "???";
}

struct spf_backoff *
spf_backoff_new(struct thread_master *m,
                const char *name,
                long init_delay,
                long short_delay,
                long long_delay,
                long holddown,
                long timetolearn)
{
  struct spf_backoff *rv;

  rv = XCALLOC(MTYPE_SPF_BACKOFF, sizeof(*rv));
  rv->m = m;

  rv->init_delay = init_delay;
  rv->short_delay = short_delay;
  rv->long_delay = long_delay;
  rv->holddown = holddown;
  rv->timetolearn = timetolearn;

  rv->state = SPF_BACKOFF_QUIET;

  rv->name = XSTRDUP(MTYPE_SPF_BACKOFF_NAME, name);
  return rv;
}

void
spf_backoff_free(struct spf_backoff *backoff)
{
  if (!backoff)
    return;

  THREAD_TIMER_OFF(backoff->t_holddown);
  THREAD_TIMER_OFF(backoff->t_timetolearn);
  XFREE(MTYPE_SPF_BACKOFF_NAME, backoff->name);

  XFREE(MTYPE_SPF_BACKOFF, backoff);
}

static int
spf_backoff_timetolearn_elapsed(struct thread *thread)
{
  struct spf_backoff *backoff = THREAD_ARG(thread);

  backoff->t_timetolearn = NULL;
  backoff->state = SPF_BACKOFF_LONG_WAIT;
  backoff_debug("SPF Back-off(%s) TIMETOLEARN elapsed, move to state %s",
                backoff->name, spf_backoff_state2str(backoff->state));
  return 0;
}

static int
spf_backoff_holddown_elapsed(struct thread *thread)
{
  struct spf_backoff *backoff = THREAD_ARG(thread);

  backoff->t_holddown = NULL;
  THREAD_TIMER_OFF(backoff->t_timetolearn);
  timerclear(&backoff->first_event_time);
  backoff->state = SPF_BACKOFF_QUIET;
  backoff_debug("SPF Back-off(%s) HOLDDOWN elapsed, move to state %s",
                backoff->name, spf_backoff_state2str(backoff->state));
  return 0;
}

long spf_backoff_schedule(struct spf_backoff *backoff)
{
  long rv;
  struct timeval now;

  gettimeofday(&now, NULL);

  backoff_debug("SPF Back-off(%s) schedule called in state %s",
                backoff->name, spf_backoff_state2str(backoff->state));

  backoff->last_event_time = now;

  switch (backoff->state)
    {
    case SPF_BACKOFF_QUIET:
      backoff->state = SPF_BACKOFF_SHORT_WAIT;
      thread_add_timer_msec(backoff->m, spf_backoff_timetolearn_elapsed,
                            backoff, backoff->timetolearn,
                            &backoff->t_timetolearn);
      thread_add_timer_msec(backoff->m, spf_backoff_holddown_elapsed, backoff,
                            backoff->holddown, &backoff->t_holddown);
      backoff->first_event_time = now;
      rv = backoff->init_delay;
      break;
    case SPF_BACKOFF_SHORT_WAIT:
    case SPF_BACKOFF_LONG_WAIT:
      THREAD_TIMER_OFF(backoff->t_holddown);
      thread_add_timer_msec(backoff->m, spf_backoff_holddown_elapsed, backoff,
                            backoff->holddown, &backoff->t_holddown);
      if (backoff->state == SPF_BACKOFF_SHORT_WAIT)
        rv = backoff->short_delay;
      else
        rv = backoff->long_delay;
      break;
    default:
      zlog_warn("SPF Back-off(%s) in unknown state", backoff->name);
      rv = backoff->init_delay;
    }

  backoff_debug("SPF Back-off(%s) changed state to %s and returned %ld delay",
                backoff->name, spf_backoff_state2str(backoff->state), rv);
  return rv;
}

static const char *
timeval_format(struct timeval *tv)
{
  struct tm tm_store;
  struct tm *tm;
  static char timebuf[256];

  if (!tv->tv_sec && !tv->tv_usec)
    return "(never)";

  tm = localtime_r(&tv->tv_sec, &tm_store);
  if (!tm || strftime(timebuf, sizeof(timebuf),
                      "%Z %a %Y-%m-%d %H:%M:%S", tm) == 0)
    {
      return "???";
    }

  size_t offset = strlen(timebuf);
  snprintf(timebuf + offset, sizeof(timebuf) - offset, ".%ld", tv->tv_usec);

  return timebuf;
}

void
spf_backoff_show(struct spf_backoff *backoff, struct vty *vty,
                 const char *prefix)
{
  vty_out (vty, "%sCurrent state:     %s\n", prefix,
          spf_backoff_state2str(backoff->state));
  vty_out (vty, "%sInit timer:        %ld msec\n", prefix,
          backoff->init_delay);
  vty_out (vty, "%sShort timer:       %ld msec\n", prefix,
          backoff->short_delay);
  vty_out (vty, "%sLong timer:        %ld msec\n", prefix,
          backoff->long_delay);
  vty_out (vty, "%sHolddown timer:    %ld msec\n", prefix,
          backoff->holddown);
  if (backoff->t_holddown)
    {
      struct timeval remain = thread_timer_remain(backoff->t_holddown);
      vty_out (vty, "%s                   Still runs for %ld msec\n",
              prefix, remain.tv_sec * 1000 + remain.tv_usec / 1000);
    }
  else
    {
      vty_out (vty, "%s                   Inactive\n", prefix);
    }

  vty_out (vty, "%sTimeToLearn timer: %ld msec\n", prefix,
          backoff->timetolearn);
  if (backoff->t_timetolearn)
    {
      struct timeval remain = thread_timer_remain(backoff->t_timetolearn);
      vty_out (vty, "%s                   Still runs for %ld msec\n",
              prefix, remain.tv_sec * 1000 + remain.tv_usec / 1000);
    }
  else
    {
      vty_out (vty, "%s                   Inactive\n", prefix);
    }

  vty_out (vty, "%sFirst event:       %s\n", prefix,
          timeval_format(&backoff->first_event_time));
  vty_out (vty, "%sLast event:        %s\n", prefix,
          timeval_format(&backoff->last_event_time));
}

DEFUN(spf_backoff_debug,
      spf_backoff_debug_cmd,
      "debug spf-delay-ietf",
      DEBUG_STR
      "SPF Back-off Debugging\n")
{
  debug_spf_backoff = true;
  return CMD_SUCCESS;
}

DEFUN(no_spf_backoff_debug,
      no_spf_backoff_debug_cmd,
      "no debug spf-delay-ietf",
      NO_STR
      DEBUG_STR
      "SPF Back-off Debugging\n")
{
  debug_spf_backoff = false;
  return CMD_SUCCESS;
}

int
spf_backoff_write_config(struct vty *vty)
{
  int written = 0;

  if (debug_spf_backoff)
    {
      vty_out (vty, "debug spf-delay-ietf\n");
      written++;
    }

  return written;
}

void
spf_backoff_cmd_init(void)
{
  install_element(ENABLE_NODE, &spf_backoff_debug_cmd);
  install_element(CONFIG_NODE, &spf_backoff_debug_cmd);
  install_element(ENABLE_NODE, &no_spf_backoff_debug_cmd);
  install_element(CONFIG_NODE, &no_spf_backoff_debug_cmd);
}

long
spf_backoff_init_delay(struct spf_backoff *backoff)
{
  return backoff->init_delay;
}

long
spf_backoff_short_delay(struct spf_backoff *backoff)
{
  return backoff->short_delay;
}

long
spf_backoff_long_delay(struct spf_backoff *backoff)
{
  return backoff->long_delay;
}

long
spf_backoff_holddown(struct spf_backoff *backoff)
{
  return backoff->holddown;
}

long
spf_backoff_timetolearn(struct spf_backoff *backoff)
{
  return backoff->timetolearn;
}