/*
 * This file is part of Shimatta OpenGL.
 *
* Foobar is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* Shimatta OpenGL 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 GtkGraphView. If not, see <https://www.gnu.org/licenses/>.
*/

#include <shimatta-opengl-program.h>
#include <epoxy/gl.h>

struct _ShimattaOpenglProgram {
	GObject super;
};

typedef struct {
	GLuint shader_id;
	gboolean compiled;
	char *fragment_file;
	char *vertex_file;
	char *geometry_file;
	char *fragment_src;
	char *vertex_src;
	char *geometry_src;

} ShimattaOpenglProgramPrivate;

G_DEFINE_TYPE_WITH_PRIVATE(ShimattaOpenglProgram, shimatta_opengl_program, G_TYPE_OBJECT);

static void shimatta_opengl_program_dispose(GObject *self)
{
	ShimattaOpenglProgram *prog;
	ShimattaOpenglProgramPrivate *priv;

	g_return_if_fail(SHIMATTA_IS_OPENGL_PROGRAM(self));

	prog = SHIMATTA_OPENGL_PROGRAM(self);
	priv = shimatta_opengl_program_get_instance_private(prog);
	if (priv->compiled) {
		priv->compiled = false;
		glDeleteProgram(priv->shader_id);
	}

	if (priv->fragment_src)
		g_free(priv->fragment_src);
	if (priv->geometry_src)
		g_free(priv->geometry_src);
	if (priv->vertex_src)
		g_free(priv->vertex_src);
	if (priv->vertex_file)
		g_free(priv->vertex_file);
	if (priv->fragment_file)
		g_free(priv->fragment_file);
	if (priv->geometry_file)
		g_free(priv->geometry_file);

}

static void shimatta_opengl_program_class_init(ShimattaOpenglProgramClass *klass)
{
	(void)klass;
	GObjectClass *oclass;

	oclass = G_OBJECT_CLASS(klass);
	oclass->dispose = shimatta_opengl_program_dispose;

	return;
}

static void shimatta_opengl_program_init(ShimattaOpenglProgram *self)
{
	ShimattaOpenglProgramPrivate *priv;

	priv = shimatta_opengl_program_get_instance_private(self);

	priv->shader_id = 0;
	priv->vertex_src = NULL;
	priv->vertex_file = NULL;
	priv->fragment_src = NULL;
	priv->geometry_src = NULL;
	priv->fragment_file = NULL;
	priv->geometry_file = NULL;
	priv->compiled = false;
}

ShimattaOpenglProgram *shimatta_opengl_program_new_from_data(const char *vertex_shader, const char *geometry_shader,
								const char *fragment_shader)
{
	ShimattaOpenglProgram *ret;
	ShimattaOpenglProgramPrivate *priv;

	ret = g_object_new(SHIMATTA_TYPE_OPENGL_PROGRAM, NULL);
	priv = shimatta_opengl_program_get_instance_private(ret);

	priv->fragment_src = g_strdup(fragment_shader);
	priv->geometry_src = g_strdup(geometry_shader);
	priv->vertex_src= g_strdup(vertex_shader);

	return ret;
}

ShimattaOpenglProgram *shimatta_opengl_program_new_from_file(const char *vertex_shader, const char *geometry_shader,
							     const char *fragment_shader)
{
	ShimattaOpenglProgram *ret;
	ShimattaOpenglProgramPrivate *priv;

	ret = g_object_new(SHIMATTA_TYPE_OPENGL_PROGRAM, NULL);
	priv = shimatta_opengl_program_get_instance_private(ret);

	priv->vertex_file = g_strdup(vertex_shader);
	priv->geometry_file = g_strdup(geometry_shader);
	priv->fragment_file = g_strdup(fragment_shader);

	return ret;
}

int shimatta_opengl_program_use(ShimattaOpenglProgram *program)
{
	ShimattaOpenglProgramPrivate *priv;

	g_return_val_if_fail(SHIMATTA_IS_OPENGL_PROGRAM(program), -1001);

	if (!shimatta_opengl_program_is_compiled(program))
		return -1;

	priv = shimatta_opengl_program_get_instance_private(program);

	glUseProgram(priv->shader_id);

	return 0;
}

gboolean shimatta_opengl_program_is_compiled(ShimattaOpenglProgram *program)
{
	ShimattaOpenglProgramPrivate *priv;

	g_return_val_if_fail(SHIMATTA_IS_OPENGL_PROGRAM(program), FALSE);
	priv = shimatta_opengl_program_get_instance_private(program);

	return priv->compiled;
}

static char *load_shader_from_source_file(const char *src_file)
{

}

static int compile_shader(const char *src, char *error_text, size_t error_text_size, gboolean use_error,
			     GLuint shader_type, GLuint *shader_id_out)
{
	GLuint shader_id;
	GLint success;
	int ret = 0;

	if (!shader_id_out || !src)
		return -1000;

	shader_id = glCreateShader(shader_type);
	glShaderSource(shader_id, 1, &src, NULL);
	glCompileShader(shader_id);
	glGetShaderiv(shader_id, GL_COMPILE_STATUS, &success);

	if (!success) {
		ret = -1;
		if (use_error) {
			glGetShaderInfoLog(shader_id, error_text_size, NULL, error_text);
		}
		glDeleteShader(shader_id);
	} else {
		*shader_id_out = shader_id;
	}

	return ret;
}

int shimatta_opengl_program_compile(ShimattaOpenglProgram *program, char *error_text, size_t error_text_size)
{
	gboolean use_error = FALSE;
	ShimattaOpenglProgramPrivate *priv;
	char *shader_source_code;
	int ret_val = 0;
	int status;
	GLint success;
	GLuint vertex_shader, fragment_shader, geometry_shader;
	gboolean vertex_built = FALSE, fragment_built = FALSE, geometry_built = FALSE;

	g_return_val_if_fail(SHIMATTA_IS_OPENGL_PROGRAM(program), -1001);

	if (error_text && error_text_size > 0)
		use_error = TRUE;

	priv = shimatta_opengl_program_get_instance_private(program);

	if (priv->compiled == TRUE) {
		return 1;
	}

	priv->shader_id = glCreateProgram();

	if (priv->vertex_src) {
		shader_source_code = priv->vertex_src;
	} else if (priv->vertex_file) {
		shader_source_code = load_shader_from_source_file(priv->vertex_file);
		if (!shader_source_code) {
			ret_val = -1;
			goto return_value;
		}

	} else {
		shader_source_code = NULL;
	}

	/* Build the vertex shader */
	if (shader_source_code) {
		status = compile_shader(shader_source_code, error_text, error_text_size, use_error, GL_VERTEX_SHADER,
					&vertex_shader);

		free(shader_source_code);

		if (status) {
			ret_val = -2;
			goto return_value;
		}
		vertex_built = TRUE;
		glAttachShader(priv->shader_id, vertex_shader);
	}

	/* Build the fragment shader */
	if (priv->fragment_src) {
		shader_source_code = priv->fragment_src;
	} else if (priv->fragment_file) {
		shader_source_code = load_shader_from_source_file(priv->fragment_file);
		if (!shader_source_code) {
			ret_val = -1;
			goto return_value;
		}
	} else {
		shader_source_code = NULL;
	}

	if (shader_source_code) {
		status = compile_shader(shader_source_code, error_text, error_text_size, use_error, GL_FRAGMENT_SHADER,
					&fragment_shader);

		free(shader_source_code);

		if (status) {
			ret_val = -2;
			goto return_value;
		}
		fragment_built = TRUE;
		glAttachShader(priv->shader_id, fragment_shader);
	}

	/* Build the geometry shader */
	if (priv->geometry_src) {
		shader_source_code = priv->geometry_src;
	} else if (priv->geometry_file) {
		shader_source_code = load_shader_from_source_file(priv->geometry_file);
		if (!shader_source_code) {
			ret_val = -1;
			goto return_value;
		}
	} else {
		shader_source_code = NULL;
	}

	if (shader_source_code) {
		status = compile_shader(shader_source_code, error_text, error_text_size, use_error, GL_GEOMETRY_SHADER,
					&geometry_shader);

		free(shader_source_code);

		if (status) {
			ret_val = -2;
			goto return_value;
		}
		geometry_built = TRUE;
		glAttachShader(priv->shader_id, geometry_shader);
	}

	glLinkProgram(priv->shader_id);
	glGetShaderiv(priv->shader_id, GL_LINK_STATUS, &success);
	if (!success) {
		if (use_error)
			glGetShaderInfoLog(priv->shader_id, error_text_size, NULL, error_text);
		ret_val = -3;
		glDeleteProgram(priv->shader_id);
	} else {
		priv->compiled = TRUE;
	}

return_value:
	if (vertex_built)
		glDeleteShader(vertex_shader);
	if (geometry_built)
		glDeleteShader(geometry_shader);
	if (fragment_built)
		glDeleteShader(fragment_shader);

	return ret_val;
}