/*
 *  Copyright (C) 2018-2020 - Vito Caputo - <vcaputo@pengaru.com>
 *
 *  This program is free software: you can redistribute it and/or modify it
 *  under the terms of the GNU General Public License version 3 as published
 *  by the Free Software Foundation.
 *
 *  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 <SDL.h>

#include <stage.h>

#include "glad.h"
#include "m4f.h"
#include "checker-node.h"
#include "shader-node.h"
#include "v3f.h"


static const char	*checker_vs = ""
	"#version 120\n"

	"uniform mat4 model_x;"

	"attribute vec3 i_vertex;"
	"attribute vec2 i_texcoord;"

	"void main()"
	"{"
	"	gl_TexCoord[0].xy = i_texcoord;"
	"	gl_Position = model_x * vec4(i_vertex, 1.f);"
	"}"
"";


static const char	*checker_fs = ""
	"#version 120\n"

	"uniform float alpha;"
	"uniform vec3 color;"

	"void main()"
	"{"
	"	int	x = int(mod(gl_TexCoord[0].x * 20, 2));"
	"	int	y = int(mod(gl_TexCoord[0].y * 20, 2));"

	"	if (x == y) {"
	"		gl_FragColor = vec4(1.f - color, alpha);"
	"	} else {"
	"		gl_FragColor = vec4(.25f * color, alpha);"
	"	}"
	"}"
"";


static void checker_uniforms(shader_t *shader, void *uniforms_ctxt, void *render_ctxt, unsigned n_uniforms, const int *uniforms, const m4f_t *model_x, float alpha)
{
	v3f_t	*color = uniforms_ctxt;

	glUniform1f(uniforms[0], alpha);
	glUniformMatrix4fv(uniforms[1], 1, GL_FALSE, &model_x->m[0][0]);
	glUniform3f(uniforms[2], color->x, color->y, color->z);
}


/* create checker pattern rendering stage */
stage_t * checker_node_new(const stage_conf_t *conf, const m4f_t *model_x, const v3f_t *color)
{
	assert(model_x);
	assert(color);

	return	shader_node_new_src(conf, checker_vs, checker_fs, model_x, checker_uniforms, (void *)color, 3,
			(const char *[]){
				"alpha",
				"model_x",
				"color",
			}
		);
}