/* GIMP - The GNU Image Manipulation Program
 * Copyright (C) 1995 Spencer Kimball and Peter Mattis
 *
 * This program 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 3 of the License, or
 * (at your option) any later version.
 *
 * This program 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.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "config.h"

#include <errno.h>
#include <fcntl.h>
#include <sys/types.h>

#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

#include <glib-object.h>
#include <glib/gstdio.h>

#include "libgimpbase/gimpbase.h"
#include "libgimpconfig/gimpconfig.h"

#ifdef G_OS_WIN32
#include <windows.h>
#include "libgimpbase/gimpwin32-io.h"
#endif

#include "base-types.h"

#ifndef _O_BINARY
#define _O_BINARY 0
#endif
#ifndef _O_TEMPORARY
#define _O_TEMPORARY 0
#endif

#include "base-utils.h"
#include "tile.h"
#include "tile-rowhints.h"
#include "tile-swap.h"
#include "tile-private.h"
#include "tile-cache.h"

#include "gimp-intl.h"

typedef enum
{
  SWAP_IN = 1,
  SWAP_OUT,
  SWAP_DELETE
} SwapCommand;

typedef gint (* SwapFunc) (gint         fd,
                           Tile        *tile,
                           SwapCommand  cmd);



#define MAX_OPEN_SWAP_FILES  16


typedef struct _SwapFile     SwapFile;
typedef struct _SwapFileGap  SwapFileGap;

struct _SwapFile
{
  gchar   *filename;
  gint     fd;
  GList   *gaps;
  gint64   swap_file_end;
  gint64   cur_position;
};

struct _SwapFileGap
{
  gint64 start;
  gint64 end;
};


static void          tile_swap_command        (Tile        *tile,
                                               gint         command);
static void          tile_swap_default_in     (SwapFile    *swap_file,
                                               Tile        *tile);
static void          tile_swap_default_out    (SwapFile    *swap_file,
                                               Tile        *tile);
static void          tile_swap_default_delete (SwapFile    *swap_file,
                                               Tile        *tile);

static gint64        tile_swap_find_offset    (SwapFile    *swap_file,
                                               gint64       bytes);
static void          tile_swap_open           (SwapFile    *swap_file);
static void          tile_swap_resize         (SwapFile    *swap_file,
                                               gint64       new_size);
static SwapFileGap * tile_swap_gap_new        (gint64       start,
                                               gint64       end);
static void          tile_swap_gap_destroy    (SwapFileGap *gap);


static SwapFile     * gimp_swap_file   = NULL;

static const gint64   swap_file_grow   = 1024 * TILE_WIDTH * TILE_HEIGHT * 4;

static gboolean       seek_err_msg     = TRUE;
static gboolean       read_err_msg     = TRUE;
static gboolean       write_err_msg    = TRUE;

#ifdef TILE_PROFILING
static gulong         tile_total_seek = 0;

/* how many tiles were swapped out under cache pressure but never
   swapped back in?  This does not count idle swapped tiles, as those
   do not contribute to any perceived load or latency */
static gulong         tile_total_wasted_swapout  = 0;

/* total tile flushes under cache pressure */
gulong                tile_total_zorched          = 0;
gulong                tile_total_zorched_swapout  = 0;
static gulong         tile_total_zorched_swapin   = 0;

/* total tiles swapped out to swap file (not total calls to swap out;
   this only counts actual flushes to disk) */
static gulong         tile_total_swapout          = 0;
static gulong         tile_unique_swapout         = 0;
gulong                tile_idle_swapout           = 0;

/* total tiles swapped in from swap file (not total calls to swap in;
   this only counts actual tile reads from disk) */
static gulong         tile_total_swapin           = 0;
static gulong         tile_unique_swapin          = 0;

/* total dead time spent waiting to read or write */
static glong          tile_total_swapwait_sec     = 0;
static glong          tile_total_swapwait_usec    = 0;

/* total time spent in tile cache due to cache pressure */
glong                 tile_total_interactive_sec  = 0;
glong                 tile_total_interactive_usec = 0;

#endif

#ifdef G_OS_WIN32

#define LARGE_SEEK(f, o, w) _lseeki64 (f, o, w)
#define LARGE_TRUNCATE(f, s) win32_large_truncate (f, s)

static gint
win32_large_truncate (gint   fd,
		      gint64 size)
{
  if (LARGE_SEEK (fd, size, SEEK_SET) == size &&
      SetEndOfFile ((HANDLE) _get_osfhandle (fd)))
    return 0;
  else
    return -1;
}

#else

#define LARGE_SEEK(f, o, t) lseek (f, o, t)
#define LARGE_TRUNCATE(f, s) ftruncate (f, s)

#endif


#ifdef GIMP_UNSTABLE
static void
tile_swap_print_gaps (SwapFile *swap_file)
{
  GList *list;

  for (list = swap_file->gaps; list; list = list->next)
    {
      SwapFileGap *gap = list->data;

      g_print ("  %"G_GINT64_FORMAT" - %"G_GINT64_FORMAT"\n",
               gap->start, gap->end);
    }
}
#endif

void
tile_swap_init (const gchar *path)
{
  gchar *basename;
  gchar *dirname;

  g_return_if_fail (gimp_swap_file == NULL);
  g_return_if_fail (path != NULL);

  dirname  = gimp_config_path_expand (path, TRUE, NULL);
  basename = g_strdup_printf ("gimpswap.%lu", (unsigned long) get_pid ());

  /*  create the swap directory if it doesn't exist */
  if (! g_file_test (dirname, G_FILE_TEST_EXISTS))
    g_mkdir_with_parents (dirname,
                          S_IRUSR | S_IXUSR | S_IWUSR |
                          S_IRGRP | S_IXGRP |
                          S_IROTH | S_IXOTH);

  gimp_swap_file = g_slice_new (SwapFile);

  gimp_swap_file->filename      = g_build_filename (dirname, basename, NULL);
  gimp_swap_file->gaps          = NULL;
  gimp_swap_file->swap_file_end = 0;
  gimp_swap_file->cur_position  = 0;
  gimp_swap_file->fd            = -1;

  g_free (basename);
  g_free (dirname);
}

void
tile_swap_exit (void)
{

#ifdef TILE_PROFILING
  extern int tile_exist_peak;

  g_printerr ("\n\nPeak Tile usage: %d Tile structs\n\n",
              tile_exist_peak);

  g_printerr ("Total tiles swapped out to disk: %lu\n", tile_total_swapout);
  g_printerr ("Unique tiles swapped out to disk: %lu\n", tile_unique_swapout);
  g_printerr ("Total tiles swapped in from disk: %lu\n", tile_total_swapin);
  g_printerr ("Unique tiles swapped in from disk: %lu\n", tile_unique_swapin);
  g_printerr ("Tiles swapped out by idle swapper: %lu\n", tile_idle_swapout);
  g_printerr ("Total seeks during swapping: %lu\n", tile_total_seek);
  g_printerr ("Total time spent in swap: %f seconds\n\n",
              tile_total_swapwait_sec + 0.000001 * tile_total_swapwait_usec);

  g_printerr ("Total zorched tiles: %lu\n", tile_total_zorched);
  g_printerr ("Total zorched tiles swapped out: %lu\n",
              tile_total_zorched_swapout);
  g_printerr ("Total zorched tiles swapped back in: %lu\n",
              tile_total_zorched_swapin);
  g_printerr ("Total zorched tiles wasted after swapping out: %lu\n",
              tile_total_wasted_swapout);
  g_printerr ("Total interactive swap/cache delay: %f seconds\n\n",
              tile_total_interactive_sec +
              0.000001 * tile_total_interactive_usec);

#endif

  if (tile_global_refcount () != 0)
    g_warning ("tile ref count balance: %d\n", tile_global_refcount ());

  g_return_if_fail (gimp_swap_file != NULL);

#ifdef GIMP_UNSTABLE
  if (gimp_swap_file->swap_file_end != 0)
    {
      g_warning ("swap file not empty: \"%s\"\n",
                 gimp_filename_to_utf8 (gimp_swap_file->filename));
      tile_swap_print_gaps (gimp_swap_file);
    }
#endif

#ifdef G_OS_WIN32
  /* should close before unlink */
  if (gimp_swap_file->fd > 0)
    {
      close (gimp_swap_file->fd);
      gimp_swap_file->fd = -1;
    }
#endif

  g_unlink (gimp_swap_file->filename);

  g_free (gimp_swap_file->filename);
  g_slice_free (SwapFile, gimp_swap_file);

  gimp_swap_file = NULL;
}

/* check if we can open a swap file */
gboolean
tile_swap_test (void)
{
  g_return_val_if_fail (gimp_swap_file != NULL, FALSE);

  /* make sure this duplicates the open() call from tile_swap_open() */
  gimp_swap_file->fd = g_open (gimp_swap_file->filename,
                               O_CREAT | O_RDWR | _O_BINARY | _O_TEMPORARY,
                               S_IRUSR | S_IWUSR);

  if (gimp_swap_file->fd != -1)
    {
      close (gimp_swap_file->fd);
      gimp_swap_file->fd = -1;
      g_unlink (gimp_swap_file->filename);

      return TRUE;
    }

  return FALSE;
}

void
tile_swap_in (Tile *tile)
{
  if (tile->swap_offset == -1)
    {
      tile_alloc (tile);
      return;
    }

  tile_swap_command (tile, SWAP_IN);
}

void
tile_swap_out (Tile *tile)
{
  tile_swap_command (tile, SWAP_OUT);
}

void
tile_swap_delete (Tile *tile)
{
  tile_swap_command (tile, SWAP_DELETE);
}

static void
tile_swap_command (Tile *tile,
                   gint  command)
{
  if (gimp_swap_file->fd == -1)
    {
      tile_swap_open (gimp_swap_file);

      if (G_UNLIKELY (gimp_swap_file->fd == -1))
        return;
    }

  switch (command)
    {
    case SWAP_IN:
      tile_swap_default_in (gimp_swap_file, tile);
      break;
    case SWAP_OUT:
      tile_swap_default_out (gimp_swap_file, tile);
      break;
    case SWAP_DELETE:
      tile_swap_default_delete (gimp_swap_file, tile);
      break;
    }
}

/* The actual swap file code. The swap file consists of tiles
 *  which have been moved out to disk in order to conserve memory.
 *  The swap file format is free form. Any tile in memory may
 *  end up anywhere on disk.
 * An actual tile in the swap file consists only of the tile data.
 *  The offset of the tile on disk is stored in the tile data structure
 *  in memory.
 */

static void
tile_swap_default_in (SwapFile *swap_file,
                      Tile     *tile)
{
  gint   nleft;
  gint64 offset;
#ifdef TILE_PROFILING
  GTimeVal now;
  GTimeVal later;
#endif

  if (tile->data)
    return;

  tile_cache_suspend_idle_swapper();

#ifdef TILE_PROFILING
  g_get_current_time (&now);
  tile_total_swapin++;

  if (tile->zorched)
    tile_total_zorched_swapin++;

  if (!tile->inonce)
    tile_unique_swapin++;

  tile->inonce = TRUE;
#endif

  if (swap_file->cur_position != tile->swap_offset)
    {
      swap_file->cur_position = tile->swap_offset;

#ifdef TILE_PROFILING
      tile_total_seek++;
#endif

      offset = LARGE_SEEK (swap_file->fd, tile->swap_offset, SEEK_SET);
      if (offset == -1)
        {
          if (seek_err_msg)
            g_message ("unable to seek to tile location on disk: %s",
                       g_strerror (errno));
          seek_err_msg = FALSE;
          return;
        }
    }

  tile_alloc (tile);

  nleft = tile->size;
  while (nleft > 0)
    {
      gint err;

      do
        {
          err = read (swap_file->fd, tile->data + tile->size - nleft, nleft);
        }
      while ((err == -1) && ((errno == EAGAIN) || (errno == EINTR)));

      if (err <= 0)
        {
          if (read_err_msg)
            g_message ("unable to read tile data from disk: "
                       "%s (%d/%d bytes read)",
                       g_strerror (errno), err, nleft);
          read_err_msg = FALSE;
          return;
        }

      nleft -= err;
    }

#ifdef TILE_PROFILING
  g_get_current_time (&later);
  tile_total_swapwait_usec += later.tv_usec - now.tv_usec;
  tile_total_swapwait_sec += later.tv_sec - now.tv_sec;

  if (tile_total_swapwait_usec < 0)
    {
      tile_total_swapwait_usec += 1000000;
      tile_total_swapwait_sec--;
    }

  if (tile_total_swapwait_usec > 1000000)
    {
      tile_total_swapwait_usec -= 1000000;
      tile_total_swapwait_sec++;
    }

  tile_total_interactive_usec += later.tv_usec - now.tv_usec;
  tile_total_interactive_sec += later.tv_sec - now.tv_sec;

  if (tile_total_interactive_usec < 0)
    {
      tile_total_interactive_usec += 1000000;
      tile_total_interactive_sec--;
    }

  if (tile_total_interactive_usec > 1000000)
    {
      tile_total_interactive_usec -= 1000000;
      tile_total_interactive_sec++;
    }

  tile->zorched = FALSE;
  tile->zorchout = FALSE;
#endif

  swap_file->cur_position += tile->size;

  /*  Do not delete the swap from the file  */
  /*  tile_swap_default_delete (swap_file, fd, tile);  */

  read_err_msg = seek_err_msg = TRUE;
}

static void
tile_swap_default_out (SwapFile *swap_file,
                       Tile     *tile)
{
  gint   bytes;
  gint   nleft;
  gint64 offset;
  gint64 newpos;
#ifdef TILE_PROFILING
  GTimeVal now;
  GTimeVal later;
  g_get_current_time(&now);
  tile_total_swapout++;

  if (!tile->outonce)
    tile_unique_swapout++;

  tile->outonce = TRUE;
#endif

  bytes = TILE_WIDTH * TILE_HEIGHT * tile->bpp;

  /*  If there is already a valid swap_offset, use it  */
  if (tile->swap_offset == -1)
    newpos = tile_swap_find_offset (swap_file, bytes);
  else
    newpos = tile->swap_offset;

  if (swap_file->cur_position != newpos)
    {

#ifdef TILE_PROFILING
      tile_total_seek++;
#endif

      offset = LARGE_SEEK (swap_file->fd, newpos, SEEK_SET);

      if (offset == -1)
        {
          if (seek_err_msg)
            g_message ("unable to seek to tile location on disk: %s",
                       g_strerror (errno));
          seek_err_msg = FALSE;
          return;
        }

      swap_file->cur_position = newpos;
    }

  nleft = tile->size;
  while (nleft > 0)
    {
      gint err = write (swap_file->fd, tile->data + tile->size - nleft, nleft);

      if (err <= 0)
        {
          if (write_err_msg)
            g_message ("unable to write tile data to disk: "
                       "%s (%d/%d bytes written)",
                       g_strerror (errno), err, nleft);
          write_err_msg = FALSE;
          return;
        }

      nleft -= err;
    }

#ifdef TILE_PROFILING
  g_get_current_time (&later);
  tile_total_swapwait_usec += later.tv_usec - now.tv_usec;
  tile_total_swapwait_sec += later.tv_sec - now.tv_sec;

  if (tile_total_swapwait_usec < 0)
    {
      tile_total_swapwait_usec += 1000000;
      tile_total_swapwait_sec--;
    }

  if (tile_total_swapwait_usec > 1000000)
    {
      tile_total_swapwait_usec -= 1000000;
      tile_total_swapwait_sec++;
    }

#endif

  swap_file->cur_position += tile->size;

  /* Do NOT free tile->data because we may be pre-swapping.
   * tile->data is freed in tile_cache_zorch_next
   */
  tile->dirty = FALSE;
  tile->swap_offset = newpos;

  write_err_msg = seek_err_msg = TRUE;
}

static void
tile_swap_default_delete (SwapFile *swap_file,
                          Tile     *tile)
{
  SwapFileGap *gap;
  SwapFileGap *gap2;
  GList       *tmp;
  GList       *tmp2;
  gint64       start;
  gint64       end;

  if (tile->swap_offset == -1)
    return;

#ifdef TILE_PROFILING
  if (tile->zorchout)
    tile_total_wasted_swapout++;

  tile->zorched=FALSE;
  tile->zorchout=FALSE;
#endif

  start = tile->swap_offset;
  end = start + TILE_WIDTH * TILE_HEIGHT * tile->bpp;
  tile->swap_offset = -1;

  tmp = swap_file->gaps;
  while (tmp)
    {
      gap = tmp->data;

      if (end == gap->start)
        {
          gap->start = start;

          if (tmp->prev)
            {
              gap2 = tmp->prev->data;

              if (gap->start == gap2->end)
                {
                  gap2->end = gap->end;
                  tile_swap_gap_destroy (gap);
                  swap_file->gaps =
                    g_list_remove_link (swap_file->gaps, tmp);
                  g_list_free (tmp);
                }
            }
          break;
        }
      else if (start == gap->end)
        {
          gap->end = end;

          if (tmp->next)
            {
              gap2 = tmp->next->data;

              if (gap->end == gap2->start)
                {
                  gap2->start = gap->start;
                  tile_swap_gap_destroy (gap);
                  swap_file->gaps =
                    g_list_remove_link (swap_file->gaps, tmp);
                  g_list_free (tmp);
                }
            }
          break;
        }
      else if (end < gap->start)
        {
          gap = tile_swap_gap_new (start, end);

          tmp2 = g_list_alloc ();
          tmp2->data = gap;
          tmp2->next = tmp;
          tmp2->prev = tmp->prev;
          if (tmp->prev)
            tmp->prev->next = tmp2;
          tmp->prev = tmp2;

          if (tmp == swap_file->gaps)
            swap_file->gaps = tmp2;
          break;
        }
      else if (!tmp->next)
        {
          gap = tile_swap_gap_new (start, end);
          tmp->next = g_list_alloc ();
          tmp->next->data = gap;
          tmp->next->prev = tmp;
          break;
        }

      tmp = tmp->next;
    }

  if (!swap_file->gaps)
    {
      gap = tile_swap_gap_new (start, end);
      swap_file->gaps = g_list_append (swap_file->gaps, gap);
    }

  tmp = g_list_last (swap_file->gaps);
  gap = tmp->data;

  if (gap->end == swap_file->swap_file_end)
    {
      tile_swap_resize (swap_file, gap->start);
      tile_swap_gap_destroy (gap);
      swap_file->gaps = g_list_remove_link (swap_file->gaps, tmp);
      g_list_free (tmp);
    }
}

static void
tile_swap_open (SwapFile *swap_file)
{
  g_return_if_fail (swap_file->fd == -1);

  /* duplicate this open() call in tile_swap_test() */
  swap_file->fd = g_open (swap_file->filename,
                          O_CREAT | O_RDWR | _O_BINARY | _O_TEMPORARY,
                          S_IRUSR | S_IWUSR);

  if (swap_file->fd == -1)
    g_message (_("Unable to open swap file. GIMP has run out of memory "
                 "and cannot use the swap file. Some parts of your images "
                 "may be corrupted. Try to save your work using different "
                 "filenames, restart GIMP and check the location of the "
                 "swap directory in your Preferences."));
}

static void
tile_swap_resize (SwapFile *swap_file,
                  gint64    new_size)
{
  if (swap_file->swap_file_end > new_size)
    {
      if (LARGE_TRUNCATE (swap_file->fd, new_size) != 0)
        {
          g_message (_("Failed to resize swap file: %s"), g_strerror (errno));
          return;
        }
    }

  swap_file->swap_file_end = new_size;
}

static gint64
tile_swap_find_offset (SwapFile *swap_file,
                       gint64    bytes)
{
  SwapFileGap *gap;
  GList       *tmp;
  gint64       offset;

  tmp = swap_file->gaps;
  while (tmp)
    {
      gap = tmp->data;

      if ((gap->end - gap->start) >= bytes)
        {
          offset = gap->start;
          gap->start += bytes;

          if (gap->start == gap->end)
            {
              tile_swap_gap_destroy (gap);
              swap_file->gaps = g_list_remove_link (swap_file->gaps, tmp);
              g_list_free (tmp);
            }

          return offset;
        }

      tmp = tmp->next;
    }

  offset = swap_file->swap_file_end;

  tile_swap_resize (swap_file, swap_file->swap_file_end + swap_file_grow);

  if ((offset + bytes) < (swap_file->swap_file_end))
    {
      gap = tile_swap_gap_new (offset + bytes, swap_file->swap_file_end);
      swap_file->gaps = g_list_append (swap_file->gaps, gap);
    }

  return offset;
}

static SwapFileGap *
tile_swap_gap_new (gint64 start,
                   gint64 end)
{
  SwapFileGap *gap = g_slice_new (SwapFileGap);

  gap->start = start;
  gap->end   = end;

  return gap;
}

static void
tile_swap_gap_destroy (SwapFileGap *gap)
{
  g_slice_free (SwapFileGap, gap);
}