/*

    ......... 2015-2018 Ivan Mahonin

    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: licenses="" www.gnu.org="">.</http:>

*/

#pragma OPENCL EXTENSION cl_khr_int64_base_atomics: enable

#define ONE       65536

#define TWO      131072               // (ONE)*2

#define HALF      32768               // (ONE)/2

#define ONE_F     65536.f             // (float)(ONE)

#define DIV_ONE_F 0.0000152587890625f // 1.f/(ONE_F)

kernel void clear(

	int width,

	int height,

	global int4 *marks )

{

	int id = get_global_id(0);

	int c = id % width;

	marks[id] = (int4)(0, 0, c | (c + 1), 0);

}

kernel void path(

	int width,

	int height,

	global int *marks,

	global float2 *points,

	int4 bounds )

{

	int id = get_global_id(0);

	float2 p0 = points[id];

	float2 p1 = points[id + 1];

	bool flipx = p1.x < p0.x;

	bool flipy = p1.y < p0.y;

	if (flipx) { p0.x = (float)width - p0.x; p1.x = (float)width - p1.x; }

	if (flipy) { p0.y = (float)height - p0.y; p1.y = (float)height - p1.y; }

	float2 d = p1 - p0;

	float kx = d.x/d.y;

	float ky = d.y/d.x;

	int w1 = width - 1;

	int h1 = height - 1;

	global int *row;

	float2 px, py, pp1;

	float cover, area;

	int ix, iy, iix;

	while(p0.x != p1.x || p0.y != p1.y) {

		ix = (int)p0.x;

		iy = max((int)p0.y, 0);

		if (iy > h1) return;

		px.x = (float)(ix + 1);

		px.y = p0.y + ky*(px.x - p0.x);

		py.y = (float)(iy + 1);

		py.x = p0.x + kx*(py.y - p0.y);

		pp1 = p1;

		if (pp1.x > px.x) pp1 = px;

		if (pp1.y > py.y) pp1 = py;

		cover = (pp1.y - p0.y)*ONE_F;

		area = px.x - 0.5f*(p0.x + pp1.x);

		if (flipx) { ix = w1 - ix; area = 1.f - area; }

		if (flipy) { iy = h1 - iy; cover = -cover; }

		ix = clamp(ix, 0, w1);

		row = marks + 4*iy*width;

		atomic_add((global long*)(row + 4*ix), upsample((int)cover, (int)(area*cover)));

		//atomic_add(row + 4*ix, (int)(area*cover));

		//atomic_add(row + 4*ix + 1, (int)cover);

		row += 2;

		iix = (ix & (ix + 1)) - 1;

		while(iix >= bounds.s0) {

			atomic_min(row + 4*iix, ix);

			iix = (iix & (iix + 1)) - 1;

		}

		p0 = pp1;

	}

}

// TODO:

// different implementations for:

//   antialiased, transparent, inverted, evenodd contours and combinations (total 16 implementations)

kernel void fill(

	int width,

	global int4 *marks,

	global float4 *image,

	float4 color,

	int2 boundsx )

{

	int id = width*(int)get_global_id(0);

	marks += id;

	image += id;

	global int4 *mark;

	global float4 *pixel;

	//prefetch(row       + boundsx.s0, boundsx.s1 - boundsx.s0);

	//prefetch(image_row + boundsx.s0, boundsx.s1 - boundsx.s0);

	int4 m;

	float alpha;

	//int ialpha;

	int icover = 0, c0 = boundsx.s0, c1 = boundsx.s0;

	while(c1 < boundsx.s1) {

		//ialpha = abs(icover);

		//ialpha = evenodd ? ONE - abs((ialpha % TWO) - ONE)

		//				 : min(ialpha, ONE);

		//if (invert) ialpha = ONE - ialpha;

		if (abs(icover) > HALF)

			while(c0 < c1)

				image[c0++] = color;

		mark = &marks[c1];

		m = *mark;

		*mark = (int4)(0, 0, c1 | (c1 + 1), 0); 

		//ialpha = abs(mark.x + icover);

		//ialpha = evenodd ? ONE - abs((ialpha % TWO) - ONE)

		//				 : min(ialpha, ONE);

		//if (invert) ialpha = ONE - ialpha;  

		alpha = (float)abs(m.x + icover)*DIV_ONE_F;

		pixel = &image[c1];

		*pixel = *pixel*(1.f - alpha) + color*alpha;

		icover += m.y;

		c0 = c1 + 1;

		c1 = m.z;

	}

}