#include <GL/glew.h>
#include <GL/glut.h>

#include <stdlib.h>
#include <stdio.h>
#include <math.h>

void init();
void reshape(int width, int height);
void display();

int const fbo_width = 512;
int const fbo_height = 512;

GLuint fb, color, depth;

int main(int argc, char *argv[])
{
	glutInit(&argc, argv);
	glutInitDisplayMode( GLUT_RGBA | GLUT_DOUBLE | GLUT_DEPTH );

	glutCreateWindow("FBO test");
	glutDisplayFunc(display);
	glutIdleFunc(glutPostRedisplay);

	glewInit();

	init();
	glutMainLoop();

	return 0;
}

void CHECK_FRAMEBUFFER_STATUS()
{                                                         
	GLenum status;
	status = glCheckFramebufferStatus(GL_DRAW_FRAMEBUFFER); 
	switch(status) {
	case GL_FRAMEBUFFER_COMPLETE:
		break;

	case GL_FRAMEBUFFER_UNSUPPORTED:
	/* choose different formats */
		break;

	default:
		/* programming error; will fail on all hardware */
		fputs("Framebuffer Error\n", stderr);
		exit(-1);
	}
}

float const light_dir[]={1,1,1,0};
float const light_color[]={1,0.95,0.9,1};

void init()
{
	glGenFramebuffers(1, &fb);
	glGenTextures(1, &color);
	glGenRenderbuffers(1, &depth);

	glBindFramebuffer(GL_FRAMEBUFFER, fb);

	glBindTexture(GL_TEXTURE_2D, color);
	glTexImage2D(	GL_TEXTURE_2D, 
			0, 
			GL_RGBA, 
			fbo_width, fbo_height,
			0, 
			GL_RGBA, 
			GL_UNSIGNED_BYTE, 
			NULL);
	
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
	glFramebufferTexture2D(GL_DRAW_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, color, 0);

	glBindRenderbuffer(GL_RENDERBUFFER, depth);
	glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT24, fbo_width, fbo_height);
	glFramebufferRenderbuffer(GL_DRAW_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depth);

	CHECK_FRAMEBUFFER_STATUS();
}

void prepare()
{
	static float a=0, b=0, c=0;

	glBindTexture(GL_TEXTURE_2D, 0);
	glEnable(GL_TEXTURE_2D);
	glBindFramebuffer(GL_FRAMEBUFFER, fb);

	glViewport(0,0, fbo_width, fbo_height);

	glClearColor(1,1,1,0);
	glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );

	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	gluPerspective(45, 1, 1, 10);

	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();

	glEnable(GL_LIGHT0);
	glEnable(GL_LIGHTING);

	glEnable(GL_DEPTH_TEST);
	glDisable(GL_CULL_FACE);

	glLightfv(GL_LIGHT0, GL_POSITION, light_dir);
	glLightfv(GL_LIGHT0, GL_DIFFUSE, light_color);

	glTranslatef(0,0,-5);

	glRotatef(a, 1, 0, 0);
	glRotatef(b, 0, 1, 0);
	glRotatef(c, 0, 0, 1);

	glutSolidTeapot(0.75);

	a=fmod(a+0.1, 360.);
	b=fmod(b+0.5, 360.);
	c=fmod(c+0.25, 360.);
}

void final()
{
	static float a=0, b=0, c=0;

	const int win_width  = glutGet(GLUT_WINDOW_WIDTH);
	const int win_height = glutGet(GLUT_WINDOW_HEIGHT);
	const float aspect = (float)win_width/(float)win_height;

	glBindFramebuffer(GL_FRAMEBUFFER, 0);
	
	glViewport(0,0, win_width, win_height);

	glClearColor(1.,1.,1.,0.);
	glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );

	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	gluPerspective(45, aspect, 1, 10);

	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();
	glTranslatef(0,0,-5);

	glRotatef(b, 0, 1, 0);

	b=fmod(b+0.5, 360.);

	glEnable(GL_TEXTURE_2D);
	glBindTexture(GL_TEXTURE_2D, color);

	glEnable(GL_DEPTH_TEST);
	glEnable(GL_CULL_FACE);

	glEnable(GL_BLEND);
	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

	glDisable(GL_LIGHTING);

	float cube[][5]=
	{
		{-1, -1, -1,  0,  0},
		{ 1, -1, -1,  1,  0},
		{ 1,  1, -1,  1,  1},
		{-1,  1, -1,  0,  1},

		{-1, -1,  1, -1,  0},
		{ 1, -1,  1,  0,  0},
		{ 1,  1,  1,  0,  1},
		{-1,  1,  1, -1,  1},
	};
	unsigned int faces[]=
	{
		0, 1, 2, 3,
		1, 5, 6, 2,
		5, 4, 7, 6,
		4, 0, 3, 7,
		3, 2, 6, 7,
		4, 5, 1, 0
	};

	glEnableClientState(GL_VERTEX_ARRAY);
	glEnableClientState(GL_TEXTURE_COORD_ARRAY);

	glVertexPointer(3, GL_FLOAT, 5*sizeof(float), &cube[0][0]);
	glTexCoordPointer(2, GL_FLOAT, 5*sizeof(float), &cube[0][3]);

	glCullFace(GL_BACK);
	glDrawElements(GL_QUADS, 24, GL_UNSIGNED_INT, faces);

	glCullFace(GL_FRONT);
	glDrawElements(GL_QUADS, 24, GL_UNSIGNED_INT, faces);

	glDisableClientState(GL_VERTEX_ARRAY);
	glDisableClientState(GL_TEXTURE_COORD_ARRAY);

}

void display()
{
	prepare();
	final();

	glutSwapBuffers();
}