#include <GL/glut.h>
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#include <string.h>

#define WINDSIZEX 100
#define WINDSIZEY 100

#define SIZEW 4
#define SIZEH 4

// Draw function used by many test casses
static void Draw()
{
	GLfloat fragcolor [] = {0.4, 0.4, 0.4, 0.8};
	int i, k;

	glColor4fv(fragcolor);

	glBegin(GL_POINTS);
	for(k=0; k < SIZEH; k++){
		for(i=0; i < SIZEW; i++){
			glVertex3f(i, k, 0.5);
		}
	}
	glEnd();
}


void init(void)
{
	glClearColor (1,1,1,1);
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	glShadeModel(GL_FLAT);
	glDisable (GL_DITHER);
	glBlendFunc(GL_ZERO, GL_SRC_ALPHA);
}

static void test(void)
{    
	GLfloat *buf;
	static char *cmd1 = "!!ARBfp1.0\nOUTPUT outcolor = result.color;\nATTRIB attrib_fragpos = fragment.position;\nTEMP temp_fpos;\nMUL temp_fpos, attrib_fragpos, {0.2, 0.1, 0.4, 0.7};\nMOV outcolor, temp_fpos;\nEND";
	GLuint programName;

	glGenProgramsARB(1, &programName);
	// bind a program to the name
	glBindProgramARB(GL_FRAGMENT_PROGRAM_ARB, programName);
	glProgramStringARB(GL_FRAGMENT_PROGRAM_ARB, GL_PROGRAM_FORMAT_ASCII_ARB,
			(GLint) strlen(cmd1), cmd1);
	if(glGetError() == GL_INVALID_OPERATION) {
		printf("\nError loading program: check the error\n%s",
				glGetString(GL_PROGRAM_ERROR_STRING_ARB));
		exit(1);
	}
	glEnable(GL_FRAGMENT_PROGRAM_ARB);

	glClear(GL_COLOR_BUFFER_BIT);
	Draw();
	//////////////////////////////////////

	buf = (GLfloat *)malloc(SIZEW * SIZEH *sizeof(GLfloat) * 3);
	glReadPixels(0, 0, SIZEW, SIZEH, GL_RGB, GL_FLOAT, buf);
	printf("get pixel at (0, 0): %f %f, %f\n", buf[0], buf[1], buf[2]);
	printf("should be: 0, 0, *\n");
}

void display(void)
{
	glViewport(0, 0, WINDSIZEX, WINDSIZEY);
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	gluOrtho2D(0, WINDSIZEX, 0, WINDSIZEY);
	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();

	test();
}

int main(int argc, char** argv)
{
	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
	glutInitWindowSize(WINDSIZEX, WINDSIZEY);
	glutInitWindowPosition(100, 100);
	glutCreateWindow(argv[0]);
	init();
	glutDisplayFunc(display);
	glutMainLoop();
	return 0; 
}