/* Simplified OpenGL 4.5 demo
 * Seth Long, Fall 2020
 * This is a *very* short demo which displays a triangle
 * Many of these functions can fail, and return error values
 * I doubt it can be done much shorter without leaving vertices in only main memory or some such
 */

#include<stdio.h>
#include<stdlib.h>
#include<fcntl.h>
#include<unistd.h>
#include<GL/glew.h>
#include<GLFW/glfw3.h>
#include<glm/glm.hpp>
#include<glm/gtc/matrix_transform.hpp>
#include<glm/gtc/type_ptr.hpp>
#include<SOIL/SOIL.h>
#include "scolor.hpp"

const float height = 2560;
const float width = 1600;

// Will be used for a lot of stuff throughout the demo
// NOTE:  general_buffer is NOT thread safe.  Don't try to load shaders in parallel!
// NOTE on the NOTE:  You probably shouldn't do that anyway!
#define GBLEN (1024*32)
char *general_buffer;

GLuint make_shader(const char *filename, GLenum shaderType){
	int fd = open(filename, O_RDONLY);
	size_t readlen = read(fd, general_buffer, GBLEN);
	close(fd);
	if(readlen == GBLEN){
		printf(RED("Buffer Length of %d bytes Inadequate for File %s\n").c_str(), GBLEN, filename);
		return 0;
	}
	general_buffer[readlen] = 0;
	printf(DGREEN("Read shader in file %s (%d bytes)\n").c_str(), filename, readlen);
	puts(general_buffer);
	unsigned int s_reference = glCreateShader(shaderType);
	glShaderSource(s_reference, 1, (const char**)&general_buffer, 0);
	glCompileShader(s_reference);
	glGetShaderInfoLog(s_reference, GBLEN, NULL, general_buffer);
	puts(general_buffer);
	GLint compile_ok;
	glGetShaderiv(s_reference, GL_COMPILE_STATUS, &compile_ok);
	if(compile_ok){
		puts(GREEN("Compile Success").c_str());
		return s_reference;
	}
	puts(RED("Compile Failed\n").c_str());
	return 0;
}

int main(int argc, char ** argv){
	general_buffer = (char*)malloc(GBLEN);
	glfwInit();
	GLFWwindow* window = glfwCreateWindow(width, height, "Simple OpenGL 4.0+ Demo", 0, 0);
	glfwMakeContextCurrent(window);
	glewInit();

	GLuint program = glCreateProgram();
	GLuint shader = make_shader("image_filter.glsl", GL_COMPUTE_SHADER);
	glAttachShader(program, shader);
	glLinkProgram(program);
	GLint link_ok;
	glGetProgramiv(program, GL_LINK_STATUS, &link_ok);
	if(!link_ok){
		glGetProgramInfoLog(program, GBLEN, NULL, general_buffer);
		puts(general_buffer);
		puts(RED("Link Failed").c_str());
		return 1;
	}
	glUseProgram(program);

	int width, height;
	unsigned char* image = SOIL_load_image("brick.jpg", &width, &height, 0, SOIL_LOAD_RGBA); 
	if(!image)
		puts(RED("No image, giving up!").c_str());
	else
		printf(PURPLE("Image size:  %d by %d\n").c_str(), width, height);
	unsigned int image_buffer;
	glGenBuffers(1, &image_buffer);
	glBindBuffer(GL_SHADER_STORAGE_BUFFER, image_buffer);
	glBufferData(GL_SHADER_STORAGE_BUFFER, 4 * width * height, image, GL_STATIC_DRAW);

	glBindBufferBase(GL_SHADER_STORAGE_BUFFER, 0, image_buffer);
	glDispatchCompute(width*height, 1, 1);
	glMemoryBarrier(GL_SHADER_STORAGE_BARRIER_BIT);
	glGetBufferSubData(GL_SHADER_STORAGE_BUFFER, 0, width*height*sizeof(int), image);

	// write image
	SOIL_save_image("done.bmp", SOIL_SAVE_TYPE_BMP, width, height, 4, image);
	puts(GREEN("Saved image as done.bmp").c_str());

	glDeleteProgram(program);
	glfwDestroyWindow(window);
	glfwTerminate();
	free(general_buffer);
}
// g++ load_object.cpp -lGL -lglfw -lGLEW