/*******************************************************************************
  Copyright (c) 2011, 2012 Dmitry Matveev <me@dmitrymatveev.co.uk>

  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files (the "Software"), to deal
  in the Software without restriction, including without limitation the rights
  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  copies of the Software, and to permit persons to whom the Software is
  furnished to do so, subject to the following conditions:

  The above copyright notice and this permission notice shall be included in
  all copies or substantial portions of the Software.

  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  THE SOFTWARE.
*******************************************************************************/

#include "config.h"

#include <sys/types.h>
#include <sys/event.h>
#include <sys/time.h>
#include <sys/socket.h>
#include <sys/stat.h>

#include <errno.h>
#include <fcntl.h>
#include <string.h>

#include <glib-object.h>
#include <gio/gfilemonitor.h>
#include <gio/glocalfilemonitor.h>
#include <gio/giomodule.h>
#include <gio/gpollfilemonitor.h>
#include <gio/gfile.h>
#include <glib-unix.h>
#include "glib-private.h"

#include "kqueue-helper.h"
#include "dep-list.h"

G_LOCK_DEFINE_STATIC (kq_lock);
static GSource       *kq_source;
static int	      kq_queue = -1;

#define G_TYPE_KQUEUE_FILE_MONITOR	(g_kqueue_file_monitor_get_type ())
#define G_KQUEUE_FILE_MONITOR(inst)	(G_TYPE_CHECK_INSTANCE_CAST ((inst), \
					G_TYPE_KQUEUE_FILE_MONITOR, GKqueueFileMonitor))

typedef GLocalFileMonitorClass GKqueueFileMonitorClass;

typedef struct
{
  GLocalFileMonitor parent_instance;

  kqueue_sub *sub;
#ifndef O_EVTONLY
  GFileMonitor *fallback;
  GFile *fbfile;
#endif
} GKqueueFileMonitor;

GType g_kqueue_file_monitor_get_type (void);
G_DEFINE_TYPE_WITH_CODE (GKqueueFileMonitor, g_kqueue_file_monitor, G_TYPE_LOCAL_FILE_MONITOR,
	g_io_extension_point_implement (G_LOCAL_FILE_MONITOR_EXTENSION_POINT_NAME,
		g_define_type_id,
                "kqueue",
		20))

#ifndef O_EVTONLY
#define O_KQFLAG O_RDONLY
#else
#define O_KQFLAG O_EVTONLY
#endif

#define NOTE_ALL (NOTE_DELETE|NOTE_WRITE|NOTE_EXTEND|NOTE_ATTRIB|NOTE_RENAME)

static gboolean g_kqueue_file_monitor_cancel (GFileMonitor* monitor);
static gboolean g_kqueue_file_monitor_is_supported (void);

static kqueue_sub	*_kqsub_new (const gchar *, GLocalFileMonitor *, GFileMonitorSource *);
static void		 _kqsub_free (kqueue_sub *);
static gboolean		 _kqsub_cancel (kqueue_sub *);


#ifndef O_EVTONLY
static void
_fallback_callback (GFileMonitor      *unused,
                    GFile             *first,
                    GFile             *second,
                    GFileMonitorEvent  event,
                    gpointer           udata)
{
  GKqueueFileMonitor *kq_mon = G_KQUEUE_FILE_MONITOR (udata);

  g_file_monitor_emit_event (G_FILE_MONITOR (kq_mon), first, second, event);
}

/*
 * _ke_is_excluded:
 * @full_path - a path to file to check.
 *
 * Returns: TRUE if the file should be excluded from the kqueue-powered
 *      monitoring, FALSE otherwise.
 **/
gboolean
_ke_is_excluded (const char *full_path)
{
  GFile *f = NULL;
  GMount *mount = NULL;

  f = g_file_new_for_path (full_path);

  if (f != NULL) {
    mount = g_file_find_enclosing_mount (f, NULL, NULL);
    g_object_unref (f);
  }

  if ((mount != NULL && (g_mount_can_unmount (mount))) || g_str_has_prefix (full_path, "/mnt/"))
  {
    g_warning ("Excluding %s from kernel notification, falling back to poll", full_path);
    if (mount)
      g_object_unref (mount);
    return TRUE;
  }

  return FALSE;
}
#endif /* !O_EVTONLY */

static void
g_kqueue_file_monitor_finalize (GObject *object)
{
  GKqueueFileMonitor *kqueue_monitor = G_KQUEUE_FILE_MONITOR (object);

  if (kqueue_monitor->sub)
    {
      _kqsub_cancel (kqueue_monitor->sub);
      _kqsub_free (kqueue_monitor->sub);
      kqueue_monitor->sub = NULL;
    }

#ifndef O_EVTONLY
  if (kqueue_monitor->fallback)
    g_object_unref (kqueue_monitor->fallback);

  if (kqueue_monitor->fbfile)
    g_object_unref (kqueue_monitor->fbfile);
#endif

  if (G_OBJECT_CLASS (g_kqueue_file_monitor_parent_class)->finalize)
    (*G_OBJECT_CLASS (g_kqueue_file_monitor_parent_class)->finalize) (object);
}

static void
g_kqueue_file_monitor_start (GLocalFileMonitor *local_monitor,
                             const gchar *dirname,
                             const gchar *basename,
                             const gchar *filename,
                             GFileMonitorSource *source)
{
  GKqueueFileMonitor *kqueue_monitor = G_KQUEUE_FILE_MONITOR (local_monitor);
  kqueue_sub *sub;
  const gchar *path;

  path = filename;
  if (path == NULL)
    path = dirname;

#ifndef O_EVTONLY
  if (_ke_is_excluded (path))
    {
      GFile *file = g_file_new_for_path (path);
      kqueue_monitor->fbfile = file;
      kqueue_monitor->fallback = _g_poll_file_monitor_new (file);
      g_signal_connect (kqueue_monitor->fallback, "changed",
			G_CALLBACK (_fallback_callback), kqueue_monitor);
      return;
    }
#endif

  /* For a directory monitor, create a subscription object anyway.
   * It will be used for directory diff calculation routines. 
   * Wait, directory diff in a GKqueueFileMonitor?
   * Yes, it is. When a file monitor is started on an non-existent
   * file, GIO uses a GKqueueFileMonitor object for that. If a directory
   * will be created under that path, GKqueueFileMonitor will have to
   * handle the directory notifications. */
  sub = _kqsub_new (path, local_monitor, source);
  if (sub == NULL)
    return;

  kqueue_monitor->sub = sub;
  if (!_kqsub_start_watching (sub))
    _km_add_missing (sub);
}

static void
g_kqueue_file_monitor_class_init (GKqueueFileMonitorClass *klass)
{
  GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
  GFileMonitorClass *file_monitor_class = G_FILE_MONITOR_CLASS (klass);
  GLocalFileMonitorClass *local_file_monitor_class = G_LOCAL_FILE_MONITOR_CLASS (klass);

  gobject_class->finalize = g_kqueue_file_monitor_finalize;
  file_monitor_class->cancel = g_kqueue_file_monitor_cancel;

  local_file_monitor_class->is_supported = g_kqueue_file_monitor_is_supported;
  local_file_monitor_class->start = g_kqueue_file_monitor_start;
  local_file_monitor_class->mount_notify = TRUE; /* TODO: ??? */
}

static void
g_kqueue_file_monitor_init (GKqueueFileMonitor *monitor)
{
}

static gboolean
g_kqueue_file_monitor_callback (gint fd, GIOCondition condition, gpointer user_data)
{
  gint64 now = g_source_get_time (kq_source);
  kqueue_sub *sub;
  GFileMonitorSource *source;
  struct kevent ev;
  struct timespec ts;

  memset (&ts, 0, sizeof(ts));
  while (kevent(fd, NULL, 0, &ev, 1, &ts) > 0)
    {
        GFileMonitorEvent mask = 0;

        if (ev.filter != EVFILT_VNODE || ev.udata == NULL)
          continue;

	sub = ev.udata;
        source = sub->source;

        if (ev.flags & EV_ERROR)
          ev.fflags = NOTE_REVOKE;

        if (ev.fflags & (NOTE_DELETE | NOTE_REVOKE))
          {
            _kqsub_cancel (sub);
            _km_add_missing (sub);
          }

        if (sub->is_dir && ev.fflags & (NOTE_WRITE | NOTE_EXTEND))
          {
            _kh_dir_diff (sub);
            ev.fflags &= ~(NOTE_WRITE | NOTE_EXTEND);
          }

        if (ev.fflags & NOTE_DELETE)
          {
            mask = G_FILE_MONITOR_EVENT_DELETED;
          }
        else if (ev.fflags & NOTE_ATTRIB)
          {
            mask = G_FILE_MONITOR_EVENT_ATTRIBUTE_CHANGED;
          }
        else if (ev.fflags & (NOTE_WRITE | NOTE_EXTEND))
          {
            mask = G_FILE_MONITOR_EVENT_CHANGED;
          }
        else if (ev.fflags & NOTE_RENAME)
          {
            /* Since there’s apparently no way to get the new name of the
             * file out of kqueue(), all we can do is say that this one has
             * been deleted. */
            mask = G_FILE_MONITOR_EVENT_DELETED;
          }
        else if (ev.fflags & NOTE_REVOKE)
          {
            mask = G_FILE_MONITOR_EVENT_UNMOUNTED;
          }

        if (mask)
          g_file_monitor_source_handle_event (source, mask, NULL, NULL, NULL, now);
    }

  return TRUE;
}

static gboolean
g_kqueue_file_monitor_is_supported (void)
{
  int errsv;

  G_LOCK (kq_lock);

  if (kq_queue == -1)
    {
      kq_queue = kqueue ();
      errsv = errno;

      if (kq_queue == -1)
        {
          g_warning ("Unable to create a kqueue: %s", g_strerror (errsv));
          G_UNLOCK (kq_lock);
          return FALSE;
        }

      kq_source = g_unix_fd_source_new (kq_queue, G_IO_IN);
      g_source_set_callback (kq_source, (GSourceFunc) g_kqueue_file_monitor_callback, NULL, NULL);
      g_source_attach (kq_source, GLIB_PRIVATE_CALL (g_get_worker_context) ());
    }

  G_UNLOCK (kq_lock);

  return TRUE;
}

static gboolean
g_kqueue_file_monitor_cancel (GFileMonitor *monitor)
{
  GKqueueFileMonitor *kqueue_monitor = G_KQUEUE_FILE_MONITOR (monitor);

  if (kqueue_monitor->sub)
    {
      _kqsub_cancel (kqueue_monitor->sub);
      _kqsub_free (kqueue_monitor->sub);
      kqueue_monitor->sub = NULL;
    }
#ifndef O_EVTONLY
  else if (kqueue_monitor->fallback)
    {
      g_signal_handlers_disconnect_by_func (kqueue_monitor->fallback, _fallback_callback, kqueue_monitor);
      g_file_monitor_cancel (kqueue_monitor->fallback);
    }
#endif

  if (G_FILE_MONITOR_CLASS (g_kqueue_file_monitor_parent_class)->cancel)
    (*G_FILE_MONITOR_CLASS (g_kqueue_file_monitor_parent_class)->cancel) (monitor);

  return TRUE;
}

static kqueue_sub *
_kqsub_new (const gchar *filename, GLocalFileMonitor *mon, GFileMonitorSource *source)
{
  kqueue_sub *sub;

  sub = g_slice_new (kqueue_sub);
  sub->filename = g_strdup (filename);
  sub->mon = mon;
  g_source_ref ((GSource *) source);
  sub->source = source;
  sub->fd = -1;
  sub->deps = NULL;
  sub->is_dir = 0;

  return sub;
}

static void
_kqsub_free (kqueue_sub *sub)
{
  g_assert (sub->deps == NULL);
  g_assert (sub->fd == -1);

  g_source_unref ((GSource *) sub->source);
  g_free (sub->filename);
  g_slice_free (kqueue_sub, sub);
}

static gboolean
_kqsub_cancel (kqueue_sub *sub)
{
  struct kevent ev;

  if (sub->deps)
    {
      dl_free (sub->deps);
      sub->deps = NULL;
    }

  _km_remove (sub);

  /* Only in the missing list?  We're done! */
  if (sub->fd == -1)
    return TRUE;

  EV_SET (&ev, sub->fd, EVFILT_VNODE, EV_DELETE, NOTE_ALL, 0, sub);
  if (kevent (kq_queue, &ev, 1, NULL, 0, NULL) == -1)
    {
      g_warning ("Unable to remove event for %s: %s", sub->filename, g_strerror (errno));
      return FALSE;
    }

  close (sub->fd);
  sub->fd = -1;

  return TRUE;
}

gboolean
_kqsub_start_watching (kqueue_sub *sub)
{
  struct stat st;
  struct kevent ev;

  sub->fd = open (sub->filename, O_KQFLAG);
  if (sub->fd == -1)
      return FALSE;

  if (fstat (sub->fd, &st) == -1)
    {
      g_warning ("fstat failed for %s: %s", sub->filename, g_strerror (errno));
      close (sub->fd);
      sub->fd = -1;
      return FALSE;
    }

  sub->is_dir = (st.st_mode & S_IFDIR) ? 1 : 0;
  if (sub->is_dir)
    {
      if (sub->deps)
        dl_free (sub->deps);

      sub->deps = dl_listing (sub->filename);
    }

  EV_SET (&ev, sub->fd, EVFILT_VNODE, EV_ADD | EV_CLEAR, NOTE_ALL, 0, sub);
  if (kevent (kq_queue, &ev, 1, NULL, 0, NULL) == -1)
    {
      g_warning ("Unable to add event for %s: %s", sub->filename, g_strerror (errno));
      close (sub->fd);
      sub->fd = -1;
      return FALSE;
    }

  return TRUE;
}