#include <iostream>
#include <SDL.h>
#include <SDL_opengl.h>
#include <gl/GLU.h>

const int WIDTH = 640;
const int HEIGHT = 480;
SDL_Window* gl_win = NULL;
SDL_GLContext gl_context = NULL;
bool gl_isPaint = true;

void errOutSDO(char* prefix) {
	std::cout << "------> " << prefix << ", SDL_GetError()=" << SDL_GetError() << std::endl;
	system("pause");
}

void errOutGL(char* prefix, GLenum glenumErr) {
	std::cout << "------> " << prefix << ", glenumErr=" << glenumErr << ", gluErrorString(glenumErr)=" << gluErrorString(glenumErr) << std::endl;
	system("pause");
}

bool init() {
	/////////////////////////////////////////////////////////////////////////
	//Init SDL
	if (SDL_Init(SDL_INIT_EVERYTHING) < 0) {errOutSDO("if (SDL_Init(SDL_INIT_EVERYTHING) < 0) {");return false;}
	//SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 1);
	//SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 1);
	SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
	SDL_GL_SetAttribute(SDL_GL_RED_SIZE, 5);
	SDL_GL_SetAttribute(SDL_GL_GREEN_SIZE, 6);
	SDL_GL_SetAttribute(SDL_GL_BLUE_SIZE, 5);
	gl_win = SDL_CreateWindow("3D", 1300, 100, WIDTH, HEIGHT, SDL_WINDOW_OPENGL); //SDL_WINDOW_SHOWN
	if (gl_win == nullptr) {errOutSDO("if (win == nullptr) {");return false;}
	gl_context = SDL_GL_CreateContext(gl_win);
	if (gl_context == nullptr) {	errOutSDO("if (gl_g_cont == nullptr) {");return false;	}
	SDL_GL_MakeCurrent(gl_win, gl_context);
	//Init SDL
	/////////////////////////////////////////////////////////////////////////
	/////////////////////////////////////////////////////////////////////////
	//Init OpenGL
	GLenum error = GL_NO_ERROR;
	glClearColor(1.0f, 1.0f, 1.0f, 1.0f);
	glClearDepth(1.0);
	glDepthFunc(GL_LESS);
	glEnable(GL_DEPTH_TEST);
	glShadeModel(GL_SMOOTH);
	//Init OpenGL
	/////////////////////////////////////////////////////////////////////////
	return true;
}

void drawCube() {
	//std::cout << "...." << std::endl;
	glClearColor(0.0, 0.0, 0.0, 1.0);
	glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
	
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	gluPerspective(45, (float)WIDTH / (float)HEIGHT, 1, 500);
	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();

	glBegin(GL_TRIANGLES);
		glVertex3f(0.0, 2.0, -5.0);
		glVertex3f(-2.0, -2.0, -5.0);
		glVertex3f(2.0, -2.0, -5.0);
	glEnd();
}

int main(int argc, char *args[])
{
	if (!init()) return 1;

	while (gl_isPaint) {
		SDL_Event event;
		while (SDL_PollEvent(&event)) {
			if (event.type == SDL_QUIT) gl_isPaint = false;
		}
		drawCube();
		SDL_GL_SwapWindow(gl_win);
	}
	SDL_GL_DeleteContext(gl_context);
	SDL_DestroyWindow(gl_win);
	SDL_Quit();

	return 0;
}