/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*- */

#define _GNU_SOURCE /* For M_PI */

#include <math.h>

#include "compositor-private.h"
#include "shadow.h"
#include "tidy/tidy-texture-frame.h"

#define SHADOW_RADIUS 8
#define SHADOW_OPACITY	0.9
#define SHADOW_OFFSET_X	(SHADOW_RADIUS)
#define SHADOW_OFFSET_Y	(SHADOW_RADIUS)

#define MAX_TILE_SZ 8 	/* Must be <= shaddow radius */
#define TILE_WIDTH  (3*MAX_TILE_SZ)
#define TILE_HEIGHT (3*MAX_TILE_SZ)

static unsigned char* shadow_gaussian_make_tile (void);

ClutterActor *
meta_create_shadow_frame (MetaCompositor *compositor)
{
  ClutterActor *frame;

  if (!compositor->shadow_src)
    {
      guchar *data;

      data = shadow_gaussian_make_tile ();

      compositor->shadow_src = clutter_texture_new ();

      clutter_texture_set_from_rgb_data (CLUTTER_TEXTURE (compositor->shadow_src),
                                         data,
                                         TRUE,
                                         TILE_WIDTH,
                                         TILE_HEIGHT,
                                         TILE_WIDTH*4,
                                         4,
                                         0,
                                         NULL);
      g_free (data);
    }

  frame = tidy_texture_frame_new (CLUTTER_TEXTURE (compositor->shadow_src),
                                  MAX_TILE_SZ,
                                  MAX_TILE_SZ,
                                  MAX_TILE_SZ,
                                  MAX_TILE_SZ);

  clutter_actor_set_position (frame,
                              SHADOW_OFFSET_X , SHADOW_OFFSET_Y);

  return frame;
}

typedef struct GaussianMap
{
  int	   size;
  double * data;
} GaussianMap;

static double
gaussian (double r, double x, double y)
{
  return ((1 / (sqrt (2 * M_PI * r))) *
	  exp ((- (x * x + y * y)) / (2 * r * r)));
}


static GaussianMap *
make_gaussian_map (double r)
{
  GaussianMap  *c;
  int	          size = ((int) ceil ((r * 3)) + 1) & ~1;
  int	          center = size / 2;
  int	          x, y;
  double          t = 0.0;
  double          g;

  c = g_malloc (sizeof (GaussianMap) + size * size * sizeof (double));
  c->size = size;

  c->data = (double *) (c + 1);

  for (y = 0; y < size; y++)
    for (x = 0; x < size; x++)
      {
	g = gaussian (r, (double) (x - center), (double) (y - center));
	t += g;
	c->data[y * size + x] = g;
      }

  for (y = 0; y < size; y++)
    for (x = 0; x < size; x++)
      c->data[y*size + x] /= t;

  return c;
}

static unsigned char
sum_gaussian (GaussianMap * map, double opacity,
              int x, int y, int width, int height)
{
  int	           fx, fy;
  double         * g_data;
  double         * g_line = map->data;
  int	           g_size = map->size;
  int	           center = g_size / 2;
  int	           fx_start, fx_end;
  int	           fy_start, fy_end;
  double           v;
  unsigned int     r;

  /*
   * Compute set of filter values which are "in range",
   * that's the set with:
   *	0 <= x + (fx-center) && x + (fx-center) < width &&
   *  0 <= y + (fy-center) && y + (fy-center) < height
   *
   *  0 <= x + (fx - center)	x + fx - center < width
   *  center - x <= fx	fx < width + center - x
   */

  fx_start = center - x;
  if (fx_start < 0)
    fx_start = 0;
  fx_end = width + center - x;
  if (fx_end > g_size)
    fx_end = g_size;

  fy_start = center - y;
  if (fy_start < 0)
    fy_start = 0;
  fy_end = height + center - y;
  if (fy_end > g_size)
    fy_end = g_size;

  g_line = g_line + fy_start * g_size + fx_start;

  v = 0;
  for (fy = fy_start; fy < fy_end; fy++)
    {
      g_data = g_line;
      g_line += g_size;

      for (fx = fx_start; fx < fx_end; fx++)
	v += *g_data++;
    }
  if (v > 1)
    v = 1;

  v *= (opacity * 255.0);

  r = (unsigned int) v;

  return (unsigned char) r;
}

static unsigned char *
shadow_gaussian_make_tile ()
{
  unsigned char              * data;
  int		               size;
  int		               center;
  int		               x, y;
  unsigned char                d;
  int                          pwidth, pheight;
  double                       opacity = SHADOW_OPACITY;
  static GaussianMap       * gaussian_map = NULL;

  struct _mypixel
  {
    unsigned char r;
    unsigned char g;
    unsigned char b;
    unsigned char a;
  } * _d;


  if (!gaussian_map)
    gaussian_map =
      make_gaussian_map (SHADOW_RADIUS);

  size   = gaussian_map->size;
  center = size / 2;

  /* Top & bottom */

  pwidth  = MAX_TILE_SZ;
  pheight = MAX_TILE_SZ;

  data = g_malloc0 (4 * TILE_WIDTH * TILE_HEIGHT);

  _d = (struct _mypixel*) data;

  /* N */
  for (y = 0; y < pheight; y++)
    {
      d = sum_gaussian (gaussian_map, opacity,
                        center, y - center,
                        TILE_WIDTH, TILE_HEIGHT);
      for (x = 0; x < pwidth; x++)
	{
	  _d[y*3*pwidth + x + pwidth].r = 0;
	  _d[y*3*pwidth + x + pwidth].g = 0;
	  _d[y*3*pwidth + x + pwidth].b = 0;
	  _d[y*3*pwidth + x + pwidth].a = d;
	}

    }

  /* S */
  pwidth = MAX_TILE_SZ;
  pheight = MAX_TILE_SZ;

  for (y = 0; y < pheight; y++)
    {
      d = sum_gaussian (gaussian_map, opacity,
                        center, y - center,
                        TILE_WIDTH, TILE_HEIGHT);
      for (x = 0; x < pwidth; x++)
	{
	  _d[(pheight-y-1)*3*pwidth + 6*pwidth*pheight + x + pwidth].r = 0;
	  _d[(pheight-y-1)*3*pwidth + 6*pwidth*pheight + x + pwidth].g = 0;
	  _d[(pheight-y-1)*3*pwidth + 6*pwidth*pheight + x + pwidth].b = 0;
	  _d[(pheight-y-1)*3*pwidth + 6*pwidth*pheight + x + pwidth].a = d;
	}

    }


  /* w */
  pwidth = MAX_TILE_SZ;
  pheight = MAX_TILE_SZ;

  for (x = 0; x < pwidth; x++)
    {
      d = sum_gaussian (gaussian_map, opacity,
                        x - center, center,
                        TILE_WIDTH, TILE_HEIGHT);
      for (y = 0; y < pheight; y++)
	{
	  _d[y*3*pwidth + 3*pwidth*pheight + x].r = 0;
	  _d[y*3*pwidth + 3*pwidth*pheight + x].g = 0;
	  _d[y*3*pwidth + 3*pwidth*pheight + x].b = 0;
	  _d[y*3*pwidth + 3*pwidth*pheight + x].a = d;
	}

    }

  /* E */
  for (x = 0; x < pwidth; x++)
    {
      d = sum_gaussian (gaussian_map, opacity,
					       x - center, center,
					       TILE_WIDTH, TILE_HEIGHT);
      for (y = 0; y < pheight; y++)
	{
	  _d[y*3*pwidth + 3*pwidth*pheight + (pwidth-x-1) + 2*pwidth].r = 0;
	  _d[y*3*pwidth + 3*pwidth*pheight + (pwidth-x-1) + 2*pwidth].g = 0;
	  _d[y*3*pwidth + 3*pwidth*pheight + (pwidth-x-1) + 2*pwidth].b = 0;
	  _d[y*3*pwidth + 3*pwidth*pheight + (pwidth-x-1) + 2*pwidth].a = d;
	}

    }

  /* NW */
  pwidth = MAX_TILE_SZ;
  pheight = MAX_TILE_SZ;

  for (x = 0; x < pwidth; x++)
    for (y = 0; y < pheight; y++)
      {
	d = sum_gaussian (gaussian_map, opacity,
                          x-center, y-center,
                          TILE_WIDTH, TILE_HEIGHT);

	_d[y*3*pwidth + x].r = 0;
	_d[y*3*pwidth + x].g = 0;
	_d[y*3*pwidth + x].b = 0;
	_d[y*3*pwidth + x].a = d;
      }

  /* SW */
  for (x = 0; x < pwidth; x++)
    for (y = 0; y < pheight; y++)
      {
	d = sum_gaussian (gaussian_map, opacity,
                          x-center, y-center,
                          TILE_WIDTH, TILE_HEIGHT);

	_d[(pheight-y-1)*3*pwidth + 6*pwidth*pheight + x].r = 0;
	_d[(pheight-y-1)*3*pwidth + 6*pwidth*pheight + x].g = 0;
	_d[(pheight-y-1)*3*pwidth + 6*pwidth*pheight + x].b = 0;
	_d[(pheight-y-1)*3*pwidth + 6*pwidth*pheight + x].a = d;
      }

  /* SE */
  for (x = 0; x < pwidth; x++)
    for (y = 0; y < pheight; y++)
      {
	d = sum_gaussian (gaussian_map, opacity,
                          x-center, y-center,
                          TILE_WIDTH, TILE_HEIGHT);

	_d[(pheight-y-1)*3*pwidth + 6*pwidth*pheight + (pwidth-x-1) +
	   2*pwidth].r = 0;
	_d[(pheight-y-1)*3*pwidth + 6*pwidth*pheight + (pwidth-x-1) +
	   2*pwidth].g = 0;
	_d[(pheight-y-1)*3*pwidth + 6*pwidth*pheight + (pwidth-x-1) +
	   2*pwidth].b = 0;
	_d[(pheight-y-1)*3*pwidth + 6*pwidth*pheight + (pwidth-x-1) +
	   2*pwidth].a = d;
      }

  /* NE */
  for (x = 0; x < pwidth; x++)
    for (y = 0; y < pheight; y++)
      {
	d = sum_gaussian (gaussian_map, opacity,
                          x-center, y-center,
                          TILE_WIDTH, TILE_HEIGHT);

	_d[y*3*pwidth + (pwidth - x - 1) + 2*pwidth].r = 0;
	_d[y*3*pwidth + (pwidth - x - 1) + 2*pwidth].g = 0;
	_d[y*3*pwidth + (pwidth - x - 1) + 2*pwidth].b = 0;
	_d[y*3*pwidth + (pwidth - x - 1) + 2*pwidth].a = d;
      }

  /* center */
  pwidth = MAX_TILE_SZ;
  pheight = MAX_TILE_SZ;

  d = sum_gaussian (gaussian_map, opacity,
                    center, center, TILE_WIDTH, TILE_HEIGHT);

  for (x = 0; x < pwidth; x++)
    for (y = 0; y < pheight; y++)
      {
	_d[y*3*pwidth + 3*pwidth*pheight + x + pwidth].r = 0;
	_d[y*3*pwidth + 3*pwidth*pheight + x + pwidth].g = 0;
	_d[y*3*pwidth + 3*pwidth*pheight + x + pwidth].b = 0;
	_d[y*3*pwidth + 3*pwidth*pheight + x + pwidth].a = 0;
      }

  return data;
}