/* GStreamer
 * Copyright (C) 1999,2000 Erik Walthinsen <omega@cse.ogi.edu>
 *                    2005 Wim Taymans <wim@fluendo.com>
 *                    2005 Andy Wingo <wingo@pobox.com>
 *
 * gstnetclientclock.h: clock that synchronizes itself to a time provider over
 * the network
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library 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
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <unistd.h>

#include "gstnettimepacket.h"
#include "gstnetclientclock.h"

GST_DEBUG_CATEGORY (ncc_debug);
#define GST_CAT_DEFAULT (ncc_debug)

/* the select call is also performed on the control sockets, that way
 * we can send special commands to unblock or restart the select call */
#define CONTROL_RESTART        'R'      /* restart the select call */
#define CONTROL_STOP           'S'      /* stop the select call */
#define CONTROL_SOCKETS(self)   self->control_sock
#define WRITE_SOCKET(self)      self->control_sock[1]
#define READ_SOCKET(self)       self->control_sock[0]

#define SEND_COMMAND(self, command)             	\
G_STMT_START {                                 	\
  unsigned char c; c = command;                	\
  write (WRITE_SOCKET(self), &c, 1);         	\
} G_STMT_END

#define READ_COMMAND(self, command, res)        	\
G_STMT_START {                                	\
  res = read(READ_SOCKET(self), &command, 1);    \
} G_STMT_END

#define DEFAULT_ADDRESS		"127.0.0.1"
#define DEFAULT_PORT		5637
#define DEFAULT_WINDOW_SIZE	32
#define DEFAULT_TIMEOUT		GST_SECOND

enum
{
  PROP_0,
  PROP_ADDRESS,
  PROP_PORT,
  PROP_WINDOW_SIZE,
  PROP_TIMEOUT
};

#define _do_init(type) \
  GST_DEBUG_CATEGORY_INIT (ncc_debug, "netclock", 0, "Network client clock");

GST_BOILERPLATE_FULL (GstNetClientClock, gst_net_client_clock,
    GstSystemClock, GST_TYPE_SYSTEM_CLOCK, _do_init);

static void gst_net_client_clock_finalize (GObject * object);
static void gst_net_client_clock_set_property (GObject * object, guint prop_id,
    const GValue * value, GParamSpec * pspec);
static void gst_net_client_clock_get_property (GObject * object, guint prop_id,
    GValue * value, GParamSpec * pspec);

static void gst_net_client_clock_stop (GstNetClientClock * self);

static void
gst_net_client_clock_base_init (gpointer g_class)
{
  /* nop */
}

static void
gst_net_client_clock_class_init (GstNetClientClockClass * klass)
{
  GObjectClass *gobject_class;

  gobject_class = (GObjectClass *) klass;

  gobject_class->finalize = gst_net_client_clock_finalize;
  gobject_class->get_property = gst_net_client_clock_get_property;
  gobject_class->set_property = gst_net_client_clock_set_property;

  g_object_class_install_property (gobject_class, PROP_ADDRESS,
      g_param_spec_string ("address", "address",
          "The address of the machine providing a time server, "
          "as a dotted quad (x.x.x.x)", DEFAULT_ADDRESS, G_PARAM_READWRITE));
  g_object_class_install_property (G_OBJECT_CLASS (klass), PROP_PORT,
      g_param_spec_int ("port", "port",
          "The port on which the remote server is listening", 0, G_MAXUINT16,
          DEFAULT_PORT, G_PARAM_READWRITE));
  g_object_class_install_property (G_OBJECT_CLASS (klass), PROP_WINDOW_SIZE,
      g_param_spec_int ("window-size", "Window size",
          "The size of the window used to calculate rate and offset", 2, 1024,
          DEFAULT_WINDOW_SIZE, G_PARAM_READWRITE));
  g_object_class_install_property (G_OBJECT_CLASS (klass), PROP_TIMEOUT,
      g_param_spec_uint64 ("timeout", "Timeout",
          "The amount of time, in nanoseconds, to wait for replies", 0,
          G_MAXUINT64, DEFAULT_TIMEOUT, G_PARAM_READWRITE));
}

static void
gst_net_client_clock_init (GstNetClientClock * self,
    GstNetClientClockClass * g_class)
{
  self->port = DEFAULT_PORT;
  self->address = g_strdup (DEFAULT_ADDRESS);
  self->window_size = DEFAULT_WINDOW_SIZE;
  self->timeout = DEFAULT_TIMEOUT;

  self->sock = -1;
  self->thread = NULL;

  self->filling = TRUE;
  self->time_index = 0;
  self->local_times = g_new0 (GstClockTime, self->window_size);
  self->remote_times = g_new0 (GstClockTime, self->window_size);

  self->servaddr = NULL;

  READ_SOCKET (self) = -1;
  WRITE_SOCKET (self) = -1;
}

static void
gst_net_client_clock_finalize (GObject * object)
{
  GstNetClientClock *self = GST_NET_CLIENT_CLOCK (object);

  if (self->thread) {
    gst_net_client_clock_stop (self);
    g_assert (self->thread == NULL);
  }

  if (READ_SOCKET (self) != -1) {
    close (READ_SOCKET (self));
    close (WRITE_SOCKET (self));
    READ_SOCKET (self) = -1;
    WRITE_SOCKET (self) = -1;
  }

  g_free (self->address);
  self->address = NULL;

  g_free (self->servaddr);
  self->servaddr = NULL;

  g_free (self->local_times);
  self->local_times = NULL;

  g_free (self->remote_times);
  self->remote_times = NULL;

  G_OBJECT_CLASS (parent_class)->finalize (object);
}

static void
gst_net_client_clock_set_property (GObject * object, guint prop_id,
    const GValue * value, GParamSpec * pspec)
{
  GstNetClientClock *self = GST_NET_CLIENT_CLOCK (object);

  switch (prop_id) {
    case PROP_ADDRESS:
      g_free (self->address);
      if (g_value_get_string (value) == NULL)
        self->address = g_strdup (DEFAULT_ADDRESS);
      else
        self->address = g_strdup (g_value_get_string (value));
      break;
    case PROP_PORT:
      self->port = g_value_get_int (value);
      break;
    case PROP_WINDOW_SIZE:
      self->window_size = g_value_get_int (value);
      break;
    case PROP_TIMEOUT:
      self->timeout = g_value_get_uint64 (value);
      break;
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      break;
  }
}

static void
gst_net_client_clock_get_property (GObject * object, guint prop_id,
    GValue * value, GParamSpec * pspec)
{
  GstNetClientClock *self = GST_NET_CLIENT_CLOCK (object);

  switch (prop_id) {
    case PROP_ADDRESS:
      g_value_set_string (value, self->address);
      break;
    case PROP_PORT:
      g_value_set_int (value, self->port);
      break;
    case PROP_WINDOW_SIZE:
      g_value_set_int (value, self->window_size);
      break;
    case PROP_TIMEOUT:
      g_value_set_uint64 (value, self->timeout);
      break;
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      break;
  }
}

/* http://mathworld.wolfram.com/LeastSquaresFitting.html */
static void
do_linear_regression (GstClockTime * x, GstClockTime * y, gint n, gdouble * m,
    gdouble * b, gdouble * r_squared)
{
  gdouble sxx, syy, sxy, xbar, ybar;
  gint i;

  sxx = syy = sxy = xbar = ybar = 0.0;

  /* we lose precision with the doubles, but there's no other way except to use
     ~80 bit arithmetic */
  for (i = 0; i < n; i++) {
    xbar += x[i];
    ybar += y[i];
  }
  xbar /= n;
  ybar /= n;

  for (i = 0; i < n; i++) {
    sxx += ((double) x[i]) * x[i];
    syy += ((double) y[i]) * y[i];
    sxy += ((double) x[i]) * y[i];
  }
  sxx -= ((double) n) * xbar * xbar;
  syy -= ((double) n) * ybar * ybar;
  sxy -= ((double) n) * xbar * ybar;

  *m = sxy / sxx;
  *b = ybar - xbar * *m;
  *r_squared = (sxy * sxy) / (sxx * syy);
}

static void
gst_net_client_clock_observe_times (GstNetClientClock * self,
    GstClockTime local_1, GstClockTime remote, GstClockTime local_2)
{
  GstClockTime local_avg;
  gdouble m, b, r_squared;

  if (local_2 < local_1)
    goto bogus_observation;

  local_avg = (local_2 - local_1) / 2;

  self->local_times[self->time_index] = local_avg;
  self->remote_times[self->time_index] = remote;

  self->time_index++;
  if (self->time_index == self->window_size) {
    self->filling = FALSE;
    self->time_index = 0;
  }

  if (!self->filling || self->time_index >= 4) {
    /* need to allow tuning of the "4" parameter -- means that we need 4 samples
     * before beginning to adjust the clock */
    do_linear_regression (self->local_times, self->remote_times,
        self->filling ? self->time_index : self->window_size, &m, &b,
        &r_squared);

    GST_LOG_OBJECT (self, "adjusting clock to m=%g, b=%g (rsquared=%g)", m, b,
        r_squared);

    gst_clock_set_rate_offset (GST_CLOCK (self), m, b);
  }

  if (self->filling) {
    self->current_timeout = 0;
  } else {
    /* geto formula */
    self->current_timeout =
        (1e-3 / (1 - MIN (r_squared, 0.99999))) * GST_SECOND;
    self->current_timeout = MIN (self->current_timeout, self->timeout);
  }

  return;

bogus_observation:
  {
    GST_WARNING_OBJECT (self, "time packet receive time < send time (%",
        GST_TIME_FORMAT, " < %" GST_TIME_FORMAT ")", GST_TIME_ARGS (local_1),
        GST_TIME_ARGS (local_2));
    return;
  }
}

static gint
gst_net_client_clock_do_select (GstNetClientClock * self, fd_set * readfds)
{
  gint max_sock;
  gint ret;

  while (TRUE) {
    FD_ZERO (readfds);
    FD_SET (self->sock, readfds);
    FD_SET (READ_SOCKET (self), readfds);
    max_sock = MAX (self->sock, READ_SOCKET (self));

    GST_LOG_OBJECT (self, "doing select");
    {
      GstClockTime diff;
      GTimeVal tv, *ptv = &tv;

      diff = gst_clock_get_internal_time (GST_CLOCK (self));
      GST_TIME_TO_TIMEVAL (self->current_timeout, tv);

      ret = select (max_sock + 1, readfds, NULL, NULL, (struct timeval *) ptv);

      diff = gst_clock_get_internal_time (GST_CLOCK (self)) - diff;

      if (diff > self->current_timeout)
        self->current_timeout = 0;
      else
        self->current_timeout -= diff;
    }
    GST_LOG_OBJECT (self, "select returned %d", ret);

    if (ret < 0) {
      if (errno != EAGAIN && errno != EINTR)
        goto select_error;
      else
        continue;
    } else {
      return ret;
    }

    g_assert_not_reached ();

    /* log errors and keep going */
  select_error:
    {
      GST_WARNING_OBJECT (self, "select error %d: %s (%d)", ret,
          g_strerror (errno), errno);
      continue;
    }
  }

  g_assert_not_reached ();
  return -1;
}

static gpointer
gst_net_client_clock_thread (gpointer data)
{
  GstNetClientClock *self = data;
  struct sockaddr_in tmpaddr;
  socklen_t len;
  fd_set read_fds;
  GstNetTimePacket *packet;
  gint ret;

  while (TRUE) {
    ret = gst_net_client_clock_do_select (self, &read_fds);

    if (FD_ISSET (READ_SOCKET (self), &read_fds)) {
      /* got control message */
      while (TRUE) {
        gchar command;
        int res;

        READ_COMMAND (self, command, res);
        if (res < 0) {
          GST_LOG_OBJECT (self, "no more commands");
          break;
        }

        switch (command) {
          case CONTROL_STOP:
            /* break out of the select loop */
            GST_LOG_OBJECT (self, "stop");
            goto stopped;
          default:
            GST_WARNING_OBJECT (self, "unknown message: '%c'", command);
            g_warning ("netclientclock: unknown control message received");
            continue;
        }

        g_assert_not_reached ();
      }

      continue;
    } else if (ret == 0) {
      /* timed out, let's send another packet */
      packet = gst_net_time_packet_new (NULL);

      packet->local_time = gst_clock_get_internal_time (GST_CLOCK (self));

      gst_net_time_packet_send (packet, self->sock,
          (struct sockaddr *) self->servaddr, sizeof (struct sockaddr_in));

      g_free (packet);

      /* reset timeout */
      self->current_timeout = self->timeout;
      continue;
    } else if (FD_ISSET (READ_SOCKET (self), &read_fds)) {
      /* got data in */
      GstClockTime new_local = gst_clock_get_internal_time (GST_CLOCK (self));

      len = sizeof (struct sockaddr);
      packet = gst_net_time_packet_receive (self->sock,
          (struct sockaddr *) &tmpaddr, &len);

      if (!packet)
        goto receive_error;

      /* observe_times will reset the timeout */
      gst_net_client_clock_observe_times (self, packet->local_time,
          packet->remote_time, new_local);

      g_free (packet);
      continue;
    } else {
      GST_WARNING_OBJECT (self, "unhandled select return state?");
      continue;
    }

    g_assert_not_reached ();

  stopped:
    {
      GST_DEBUG_OBJECT (self, "shutting down");
      /* socket gets closed in _stop() */
      return NULL;
    }
  receive_error:
    {
      GST_WARNING_OBJECT (self, "receive error");
      continue;
    }

    g_assert_not_reached ();

  }

  g_assert_not_reached ();

  return NULL;
}

static gboolean
gst_net_client_clock_start (GstNetClientClock * self)
{
  struct sockaddr_in servaddr, myaddr;
  socklen_t len;
  gint ret;
  GError *error;

  g_return_val_if_fail (self->address != NULL, FALSE);
  g_return_val_if_fail (self->servaddr == NULL, FALSE);

  if ((ret = socket (AF_INET, SOCK_DGRAM, 0)) < 0)
    goto no_socket;

  self->sock = ret;

  len = sizeof (myaddr);
  ret = getsockname (self->sock, (struct sockaddr *) &myaddr, &len);
  if (ret < 0)
    goto getsockname_error;

  GST_DEBUG_OBJECT (self, "socket opened on UDP port %hd",
      ntohs (servaddr.sin_port));

  memset (&servaddr, 0, sizeof (servaddr));
  servaddr.sin_family = AF_INET;        /* host byte order */
  servaddr.sin_port = htons (self->port);       /* short, network byte order */
  if (!inet_aton (self->address, &servaddr.sin_addr))
    goto bad_address;

  self->servaddr = g_malloc (sizeof (struct sockaddr_in));
  memcpy (self->servaddr, &servaddr, sizeof (servaddr));

  GST_DEBUG_OBJECT (self, "will communicate with %s:%d", self->address,
      self->port);

  self->thread = g_thread_create (gst_net_client_clock_thread, self, TRUE,
      &error);
  if (!self->thread)
    goto no_thread;

  return TRUE;

  /* ERRORS */
no_socket:
  {
    GST_ERROR_OBJECT (self, "socket failed %d: %s (%d)", ret,
        g_strerror (errno), errno);
    return FALSE;
  }
getsockname_error:
  {
    GST_ERROR_OBJECT (self, "getsockname failed %d: %s (%d)", ret,
        g_strerror (errno), errno);
    close (self->sock);
    self->sock = -1;
    return FALSE;
  }
bad_address:
  {
    GST_ERROR_OBJECT (self, "inet_aton failed %d: %s (%d)", ret,
        g_strerror (errno), errno);
    close (self->sock);
    self->sock = -1;
    return FALSE;
  }
no_thread:
  {
    GST_ERROR_OBJECT (self, "could not create thread: %s", error->message);
    close (self->sock);
    self->sock = -1;
    g_free (self->servaddr);
    self->servaddr = NULL;
    g_error_free (error);
    return FALSE;
  }
}

static void
gst_net_client_clock_stop (GstNetClientClock * self)
{
  SEND_COMMAND (self, CONTROL_STOP);
  g_thread_join (self->thread);
  self->thread = NULL;

  if (self->sock != -1) {
    close (self->sock);
    self->sock = -1;
  }
}

GstClock *
gst_net_client_clock_new (gchar * name, const gchar * remote_address,
    gint remote_port, GstClockTime base_time)
{
  GstNetClientClock *ret;
  GstClockTime internal;
  GstClockTimeDiff offset;
  gint iret;

  g_return_val_if_fail (remote_address != NULL, NULL);
  g_return_val_if_fail (remote_port > 0, NULL);
  g_return_val_if_fail (remote_port <= G_MAXUINT16, NULL);
  g_return_val_if_fail (base_time != GST_CLOCK_TIME_NONE, NULL);

  ret = g_object_new (GST_TYPE_NET_CLIENT_CLOCK, "address", remote_address,
      "port", remote_port, NULL);

  /* gst_clock_get_time() values are guaranteed to be increasing. because no one
   * has called get_time on this clock yet we are free to adjust to any value
   * without worrying about worrying about MAX() issues with the clock's
   * internal time.
   */

  /* update our internal time so get_time() give something around base_time.
     assume that the rate is 1 in the beginning. */
  internal = gst_clock_get_internal_time (GST_CLOCK (ret));
  /* MAXINT64 + 1 so as to avoid overflow */
  if ((base_time > internal
          && base_time - internal > ((guint64) G_MAXINT64) + 1)
      || (base_time < internal && internal - base_time > G_MAXINT64))
    goto bad_base_time;

  offset = base_time > internal ? (base_time - internal)
      : -(gint64) (internal - base_time);

  gst_clock_set_rate_offset (GST_CLOCK (ret), 1.0, offset);

  {
    GstClockTime now = gst_clock_get_time (GST_CLOCK (ret));

    if (now < base_time || now > base_time + GST_SECOND)
      g_warning ("unable to set the base time, expect sync problems!");
  }

  GST_DEBUG_OBJECT (ret, "creating socket pair");
  if ((iret = socketpair (PF_UNIX, SOCK_STREAM, 0, CONTROL_SOCKETS (ret))) < 0)
    goto no_socket_pair;

  fcntl (READ_SOCKET (ret), F_SETFL, O_NONBLOCK);
  fcntl (WRITE_SOCKET (ret), F_SETFL, O_NONBLOCK);

  if (!gst_net_client_clock_start (ret))
    goto failed_start;

  /* all systems go, cap'n */
  return (GstClock *) ret;

bad_base_time:
  {
    GST_ERROR_OBJECT (ret, "base time (%" GST_TIME_FORMAT ") too far off from "
        "internal time (%" GST_TIME_FORMAT ")", GST_TIME_ARGS (base_time),
        GST_TIME_ARGS (internal));
    gst_object_unref (ret);
    return NULL;
  }
no_socket_pair:
  {
    GST_ERROR_OBJECT (ret, "no socket pair %d: %s (%d)", iret,
        g_strerror (errno), errno);
    gst_object_unref (ret);
    return NULL;
  }
failed_start:
  {
    /* already printed a nice error */
    gst_object_unref (ret);
    return NULL;
  }
}