/*
 * This file is part of Deliantra, the Roguelike Realtime MMORPG.
 * 
 * Copyright (©) 2005,2006,2007,2008 Marc Alexander Lehmann / Robin Redeker / the Deliantra team
 * Copyright (©) 2002,2007 Mark Wedel & Crossfire Development Team
 * Copyright (©) 1992,2007 Frank Tore Johansen
 * 
 * Deliantra 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/>.
 * 
 * The authors can be reached via e-mail to <support@deliantra.net>
 */

/* Nov 95 - inserted USE_LIGHTING code stuff in here - b.t. */

#include <global.h>
#include <cmath>

static void expand_lighted_sight (object *op);

enum {
  LOS_XI = 0x01,
  LOS_YI = 0x02,
};

struct los_info
{
  sint8 xo, yo;  // obscure angle
  sint8 xe, ye;  // angle deviation
  uint8 culled;  // culled from "tree"
  uint8 queued;  // already queued
  uint8 visible;
  uint8 flags;   // LOS_XI/YI
};

// temporary storage for the los algorithm,
// one los_info for each lightable map space
static los_info los[MAP_CLIENT_X][MAP_CLIENT_Y];

struct point
{
  sint8 x, y;
};

// minimum size, but must be a power of two
#define QUEUE_LENGTH ((MAP_CLIENT_X + MAP_CLIENT_Y) * 2)

// a queue of spaces to calculate
static point queue [QUEUE_LENGTH];
static int q1, q2; // queue start, end

/*
 * Clears/initialises the los-array associated to the player
 * controlling the object.
 */
void
player::clear_los (sint8 value)
{
  memset (los, value, sizeof (los));
}

// enqueue a single mapspace, but only if it hasn't
// been enqueued yet.
static void
enqueue (sint8 dx, sint8 dy, uint8 flags = 0)
{
  sint8 x = LOS_X0 + dx;
  sint8 y = LOS_Y0 + dy;

  if (x < 0 || x >= MAP_CLIENT_X) return;
  if (y < 0 || y >= MAP_CLIENT_Y) return;

  los_info &l = los[x][y];

  l.flags |= flags;

  if (l.queued)
    return;

  l.queued = 1;

  queue[q1].x = dx;
  queue[q1].y = dy;

  q1 = (q1 + 1) & (QUEUE_LENGTH - 1);
}

// run the los algorithm
// this is a variant of a spiral los algorithm taken from
// http://www.geocities.com/temerra/los_rays.html
// which has been simplified and changed considerably, but
// still is basically the same algorithm.
static void
do_los (object *op)
{
  player *pl = op->contr;

  int max_radius = max (pl->ns->mapx, pl->ns->mapy) / 2;

  memset (los, 0, sizeof (los));

  q1 = 0; q2 = 0; // initialise queue, not strictly required
  enqueue (0, 0); // enqueue center

  // treat the origin specially
  los[LOS_X0][LOS_Y0].visible = 1;
  pl->los[LOS_X0][LOS_Y0] = 0;

  // loop over all enqueued points until the queue is empty
  // the order in which this is done ensures that we
  // never touch a mapspace whose input spaces we haven't checked
  // yet.
  while (q1 != q2)
    {
      sint8 dx = queue[q2].x;
      sint8 dy = queue[q2].y;

      q2 = (q2 + 1) & (QUEUE_LENGTH - 1);

      sint8 x = LOS_X0 + dx;
      sint8 y = LOS_Y0 + dy;

      //int distance = idistance (dx, dy); if (distance > max_radius) continue;//D
      int distance = 0;//D

      los_info &l = los[x][y];

      if (expect_true (l.flags & (LOS_XI | LOS_YI)))
        {
          l.culled = 1;

          // check contributing spaces, first horizontal
          if (expect_true (l.flags & LOS_XI))
            {
              los_info *xi = &los[x - sign (dx)][y];

	      // don't cull unless obscured
              l.culled &= !xi->visible;

              /* merge input space */
              if (expect_false (xi->xo || xi->yo))
                {
	          // The X input can provide two main pieces of information: 
	          // 1. Progressive X obscurity.
	          // 2. Recessive Y obscurity.
		          
	          // Progressive X obscurity, favouring recessive input angle
	          if (xi->xe > 0 && l.xo == 0)
                    {
                      l.xe = xi->xe - xi->yo;
                      l.ye = xi->ye + xi->yo;
                      l.xo = xi->xo;
                      l.yo = xi->yo;
	            }

	          // Recessive Y obscurity
	          if (xi->ye <= 0 && xi->yo > 0 && xi->xe > 0)
                    {
                      l.ye = xi->yo + xi->ye;
                      l.xe = xi->xe - xi->yo;
                      l.xo = xi->xo;
                      l.yo = xi->yo;
		    }
                }
            }
		
          // check contributing spaces, last vertical, identical structure
          if (expect_true (l.flags & LOS_YI))
            {
              los_info *yi = &los[x][y - sign (dy)];

	      // don't cull unless obscured
              l.culled &= !yi->visible;

              /* merge input space */
              if (expect_false (yi->yo || yi->xo))
                {
	          // The Y input can provide two main pieces of information: 
	          // 1. Progressive Y obscurity.
	          // 2. Recessive X obscurity.
		          
	          // Progressive Y obscurity, favouring recessive input angle
	          if (yi->ye > 0 && l.yo == 0)
                    {
                      l.ye = yi->ye - yi->xo;
                      l.xe = yi->xe + yi->xo;
                      l.yo = yi->yo;
                      l.xo = yi->xo;
	            }

	          // Recessive X obscurity
	          if (yi->xe <= 0 && yi->xo > 0 && yi->ye > 0)
                    {
                      l.xe = yi->xo + yi->xe;
                      l.ye = yi->ye - yi->xo;
                      l.yo = yi->yo;
                      l.xo = yi->xo;
		    }
                }
            }

          // check whether this space blocks the view
          maptile *m = op->map;
          sint16 nx = op->x + dx;
          sint16 ny = op->y + dy;

          if (expect_true (!xy_normalise (m, nx, ny))
              || expect_false (m->at (nx, ny).flags () & P_BLOCKSVIEW))
            {
              l.xo = l.xe = abs (dx);
              l.yo = l.ye = abs (dy);

              // we obscure dependents, but might be visible
              // copy the los from the square towards the player,
              // so outward diagonal corners are lit.
              pl->los[x][y] = los[x - sign0 (dx)][y - sign0 (dy)].visible ? 0 : LOS_BLOCKED;
              l.visible = false;
            }
          else
            {
              // we are not blocked, so calculate visibility, by checking
              // whether we are inside or outside the shadow
              l.visible = (l.xe <= 0 || l.xe > l.xo)
                       && (l.ye <= 0 || l.ye > l.yo);

              pl->los[x][y] = l.culled  ? LOS_BLOCKED
                            : l.visible ? max (0, 2 - max_radius + distance)
                                        : 3;
            }

        }

      // Expands by the unit length in each component's current direction.
      // If a component has no direction, then it is expanded in both of its 
      // positive and negative directions.
      if (!l.culled)
        {
          if (dx >= 0) enqueue (dx + 1, dy, LOS_XI);
          if (dx <= 0) enqueue (dx - 1, dy, LOS_XI);
          if (dy >= 0) enqueue (dx, dy + 1, LOS_YI);
          if (dy <= 0) enqueue (dx, dy - 1, LOS_YI);
	}
    }
}

/* returns true if op carries one or more lights
 * This is a trivial function now days, but it used to
 * be a bit longer.  Probably better for callers to just
 * check the op->glow_radius instead of calling this.
 */
int
has_carried_lights (const object *op)
{
  /* op may glow! */
  if (op->glow_radius > 0)
    return 1;

  return 0;
}

/* radius, distance => lightness adjust */
static sint8 darkness[MAX_LIGHT_RADIUS * 2 + 1][MAX_LIGHT_RADIUS * 3 / 2 + 1];

static struct darkness_init
{
  darkness_init ()
  {
    for (int radius = -MAX_LIGHT_RADIUS; radius <= MAX_LIGHT_RADIUS; ++radius)
      for (int distance = 0; distance <= MAX_LIGHT_RADIUS * 3 / 2; ++distance)
        {
          // max intensity
          int intensity = min (LOS_MAX, abs (radius) + 1);

          // actual intensity
          intensity = max (0, lerp_rd (distance, 0, abs (radius) + 1, intensity, 0));

          darkness [radius + MAX_LIGHT_RADIUS][distance] = radius < 0
            ? min (3, intensity)
            : LOS_MAX - intensity;
        }
  }
} darkness_init;

sint8
los_brighten (sint8 b, sint8 l)
{
  return b == LOS_BLOCKED ? b : min (b, l);
}

sint8
los_darken (sint8 b, sint8 l)
{
  return max (b, l);
}

template<sint8 change_it (sint8, sint8)>
static void
apply_light (object *op, int dx, int dy, int light, const sint8 *darkness_table)
{
  // min or max the circular area around basex, basey
  player *pl = op->contr;

  dx += LOS_X0;
  dy += LOS_Y0;

  int hx = op->contr->ns->mapx / 2;
  int hy = op->contr->ns->mapy / 2;

  int ax0 = max (LOS_X0 - hx, dx - light);
  int ay0 = max (LOS_Y0 - hy, dy - light);
  int ax1 = min (dx + light, LOS_X0 + hx);
  int ay1 = min (dy + light, LOS_Y0 + hy);

  for (int ax = ax0; ax <= ax1; ax++)
    for (int ay = ay0; ay <= ay1; ay++)
      pl->los[ax][ay] =
        change_it (pl->los[ax][ay], darkness_table [idistance (ax - dx, ay - dy)]);
}

/* add light, by finding all (non-null) nearby light sources, then 
 * mark those squares specially.
 */
static void
apply_lights (object *op)
{
  int darklevel, mflags, light, x1, y1;
  maptile *m = op->map;
  sint16 nx, ny;

  darklevel = m->darkness;

  /* If the player can see in the dark, lower the darklevel for him */
  if (QUERY_FLAG (op, FLAG_SEE_IN_DARK))
    darklevel -= LOS_MAX / 2;

  /* Do a sanity check.  If not valid, some code below may do odd
   * things.
   */
  if (darklevel > MAX_DARKNESS)
    {
      LOG (llevError, "Map darkness for %s on %s is too high (%d)\n", &op->name, &op->map->path, darklevel);
      darklevel = MAX_DARKNESS;
    }

  int half_x = op->contr->ns->mapx / 2;
  int half_y = op->contr->ns->mapy / 2;

  int min_x = op->x - half_x - MAX_LIGHT_RADIUS;
  int min_y = op->y - half_y - MAX_LIGHT_RADIUS;
  int max_x = op->x + half_x + MAX_LIGHT_RADIUS;
  int max_y = op->y + half_y + MAX_LIGHT_RADIUS;

  int pass2 = 0; // negative lights have an extra pass

  if (darklevel < 1)
    pass2 = 1;
  else
    {
      /* first, make everything totally dark */
      for (int dx = -half_x; dx <= half_x; dx++)
        for (int dy = -half_x; dy <= half_y; dy++)
          if (op->contr->los[dx + LOS_X0][dy + LOS_Y0] != LOS_BLOCKED)
            op->contr->los[dx + LOS_X0][dy + LOS_Y0] = LOS_MAX;

      /*
       * Only process the area of interest.
       * the basex, basey values represent the position in the op->contr->los
       * array. Its easier to just increment them here (and start with the right
       * value) than to recalculate them down below.
       */
      for (int x = min_x; x <= max_x; x++)
        for (int y = min_y; y <= max_y; y++)
          {
            maptile *m = op->map;
            sint16 nx = x;
            sint16 ny = y;

            if (!xy_normalise (m, nx, ny))
              continue;

            mapspace &ms = m->at (nx, ny);
            ms.update ();
            sint8 light = ms.light;

            if (expect_false (light))
              if (light < 0)
                pass2 = 1;
              else
                apply_light<los_brighten> (op, x - op->x, y - op->y, light, darkness [light + MAX_LIGHT_RADIUS]);
          }

      /* grant some vision to the player, based on the darklevel */
      /* for outdoor maps, ensure some mininum visibility radius */
      {
        int light = clamp (MAX_DARKNESS - darklevel, op->map->outdoor ? 2 : 0, MAX_LIGHT_RADIUS);

        apply_light<los_brighten> (op, 0, 0, light, darkness [light + MAX_LIGHT_RADIUS]);
      }
    }

  // possibly do 2nd pass for rare negative glow radii
  // for effect, those are always considered to be stronger than anything else
  // but they can't darken a place completely
  if (pass2)
    for (int x = min_x; x <= max_x; x++)
      for (int y = min_y; y <= max_y; y++)
        {
          maptile *m = op->map;
          sint16 nx = x;
          sint16 ny = y;

          if (!xy_normalise (m, nx, ny))
            continue;

          mapspace &ms = m->at (nx, ny);
          ms.update ();
          sint8 light = ms.light;

          if (expect_false (light < 0))
            apply_light<los_darken> (op, x - op->x, y - op->y, -light, darkness [light + MAX_LIGHT_RADIUS]);
        }
}

/* blinded_sight() - sets all viewable squares to blocked except 
 * for the one the central one that the player occupies.  A little
 * odd that you can see yourself (and what your standing on), but
 * really need for any reasonable game play.
 */
static void
blinded_sight (object *op)
{
  op->contr->los[LOS_X0][LOS_Y0] = 3;
}

/*
 * update_los() recalculates the array which specifies what is
 * visible for the given player-object.
 */
void
update_los (object *op)
{
  if (QUERY_FLAG (op, FLAG_REMOVED))
    return;

  op->contr->clear_los ();

  if (QUERY_FLAG (op, FLAG_WIZ) /* ||XRAYS(op) */ )
    memset (op->contr->los, 0, sizeof (op->contr->los));
  else if (QUERY_FLAG (op, FLAG_BLIND))      /* player is blind */
    blinded_sight (op);
  else
    {
      do_los (op);
      apply_lights (op);
    }

  if (QUERY_FLAG (op, FLAG_XRAYS))
    for (int dx = -2; dx <= 2; dx++)
      for (int dy = -2; dy <= 2; dy++)
        op->contr->los[dx + LOS_X0][dy + LOS_X0] = 0;
}

/* update all_map_los is like update_all_los below,
 * but updates everyone on the map, no matter where they
 * are. This generally should not be used, as a per
 * specific map change doesn't make much sense when tiling
 * is considered (lowering darkness would certainly be a
 * strange effect if done on a tile map, as it makes
 * the distinction between maps much more obvious to the
 * players, which is should not be.
 * Currently, this function is called from the
 * change_map_light function
 */
void
update_all_map_los (maptile *map)
{
  for_all_players (pl)
    if (pl->ob && pl->ob->map == map)
      pl->do_los = 1;
}

/*
 * This function makes sure that update_los() will be called for all
 * players on the given map within the next frame.
 * It is triggered by removal or inserting of objects which blocks
 * the sight in the map.
 * Modified by MSW 2001-07-12 to take a coordinate of the changed
 * position, and to also take map tiling into account.  This change
 * means that just being on the same map is not sufficient - the
 * space that changes must be withing your viewable area.
 *
 * map is the map that changed, x and y are the coordinates.
 */
void
update_all_los (const maptile *map, int x, int y)
{
  for_all_players (pl)
    {
      /* Player should not have a null map, but do this
       * check as a safety
       */
      if (!pl->ob || !pl->ob->map || !pl->ns)
        continue;

      /* Same map is simple case - see if pl is close enough.
       * Note in all cases, we did the check for same map first,
       * and then see if the player is close enough and update
       * los if that is the case.  If the player is on the
       * corresponding map, but not close enough, then the
       * player can't be on another map that may be closer,
       * so by setting it up this way, we trim processing
       * some.
       */
      if (pl->ob->map == map)
        {
          if ((abs (pl->ob->x - x) <= pl->ns->mapx / 2) && (abs (pl->ob->y - y) <= pl->ns->mapy / 2))
            pl->do_los = 1;
        }

      /* Now we check to see if player is on adjacent
       * maps to the one that changed and also within
       * view.  The tile_maps[] could be null, but in that
       * case it should never match the pl->ob->map, so
       * we want ever try to dereference any of the data in it.
       *
       * The logic for 0 and 3 is to see how far the player is
       * from the edge of the map (height/width) - pl->ob->(x,y)
       * and to add current position on this map - that gives a
       * distance.
       * For 1 and 2, we check to see how far the given
       * coordinate (x,y) is from the corresponding edge,
       * and then add the players location, which gives
       * a distance.
       */
      else if (pl->ob->map == map->tile_map[0])
        {
          if ((abs (pl->ob->x - x) <= pl->ns->mapx / 2) && (abs (y + map->tile_map[0]->height - pl->ob->y) <= pl->ns->mapy / 2))
            pl->do_los = 1;
        }
      else if (pl->ob->map == map->tile_map[2])
        {
          if ((abs (pl->ob->x - x) <= pl->ns->mapx / 2) && (abs (pl->ob->y + map->height - y) <= pl->ns->mapy / 2))
            pl->do_los = 1;
        }
      else if (pl->ob->map == map->tile_map[1])
        {
          if ((abs (pl->ob->x + map->width - x) <= pl->ns->mapx / 2) && (abs (pl->ob->y - y) <= pl->ns->mapy / 2))
            pl->do_los = 1;
        }
      else if (pl->ob->map == map->tile_map[3])
        {
          if ((abs (x + map->tile_map[3]->width - pl->ob->x) <= pl->ns->mapx / 2) && (abs (pl->ob->y - y) <= pl->ns->mapy / 2))
            pl->do_los = 1;
        }
    }
}

/*
 * make_sure_seen: The object is supposed to be visible through walls, thus
 * check if any players are nearby, and edit their LOS array.
 */
void
make_sure_seen (const object *op)
{
  for_all_players (pl)
    if (pl->ob->map == op->map &&
        pl->ob->y - pl->ns->mapy / 2 <= op->y &&
        pl->ob->y + pl->ns->mapy / 2 >= op->y && pl->ob->x - pl->ns->mapx / 2 <= op->x && pl->ob->x + pl->ns->mapx / 2 >= op->x)
      pl->los[op->x - pl->ob->x + LOS_X0][op->y - pl->ob->y + LOS_X0] = 0;
}

/*
 * make_sure_not_seen: The object which is supposed to be visible through
 * walls has just been removed from the map, so update the los of any
 * players within its range
 */
void
make_sure_not_seen (const object *op)
{
  for_all_players (pl)
    if (pl->ob->map == op->map &&
        pl->ob->y - pl->ns->mapy / 2 <= op->y &&
        pl->ob->y + pl->ns->mapy / 2 >= op->y && pl->ob->x - pl->ns->mapx / 2 <= op->x && pl->ob->x + pl->ns->mapx / 2 >= op->x)
      pl->do_los = 1;
}