//  
// Example code for OpenGL programming
//
#include <stdio.h>
#include <stdlib.h>
#include <GL/glew.h>
#include <GL/glut.h>

int nFPS = 60;
float fRotateAngle = 0.f;
float randomVar = 1;
float heyThisGetsSentToAShader = 0;

GLuint vs;

GLuint program;
const GLchar* vertex_shader_code = "\
	uniform float thisCameFromC;\
	vec4 p;\
	void main(void){\
		p = gl_Vertex;\
		p.x = p.x + sin(thisCameFromC)*sin(p.y);\
		p.y = p.y + cos(thisCameFromC)*sin(p.x);\
		p.z = sin(5.0*p.x+thisCameFromC )*0.25;\
		gl_Position = gl_ProjectionMatrix * gl_ModelViewMatrix * p;\
	}";
const GLchar* fragment_shader_code = "\
	void main(void) {\
	    gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);\
	}";

void printShaderInfoLog(GLuint obj);
GLint uniformLocation;

void init(void)
{
	// init your data, setup OpenGL environment here
	glClearColor(0.3,0.3,0.3,1.0); // clear color is gray		
	glPolygonMode(GL_FRONT_AND_BACK, GL_LINE); // uncomment this function if you only want to draw wireframe model

	//Shader time!
	GLuint vs = glCreateShader(GL_VERTEX_SHADER);
	glShaderSource(vs, 1, (const GLchar **) &vertex_shader_code, NULL);
	glCompileShader(vs);
	printShaderInfoLog(vs);
	
	GLuint fs = glCreateShader(GL_FRAGMENT_SHADER);
	glShaderSource(fs, 1, (const GLchar **) &fragment_shader_code, NULL);
	glCompileShader(fs);
	printShaderInfoLog(fs);
	
	program = glCreateProgram();
	glAttachShader(program, vs);
	glAttachShader(program, fs);
	glLinkProgram(program);

	uniformLocation = glGetUniformLocation(program,"thisCameFromC");
	
	glUseProgram(program);

}

/* 
Tastefully borrowed from 
http://zach.in.tu-clausthal.de/teaching/cg2_07/literatur/glsl_tutorial/index.html
for your convenience 
*/
void printShaderInfoLog(GLuint obj)
{
	int infologLength = 0;
	int charsWritten  = 0;
	char *infoLog;

	glGetShaderiv(obj, GL_INFO_LOG_LENGTH,&infologLength);

	if (infologLength > 0)
	{
		infoLog = (char *)malloc(infologLength);
		glGetShaderInfoLog(obj, infologLength, &charsWritten, infoLog);
		printf("%s\n",infoLog);
		free(infoLog);
	}
}


void display(void)
{
	// put your OpenGL display commands here
	glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
	
	glUniform1f(uniformLocation, heyThisGetsSentToAShader );

	// reset OpenGL transformation matrix
	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity(); // reset transformation matrix to identity

	// setup look at transformation so that 
	// eye is at : (0,0,3)
	// look at center is at : (0,0,0)
	// up direction is +y axis
	gluLookAt(0.f,0.f,6.f,0.f,0.f,0.f,0.f,1.f,0.f);


	//glScalef(2,1,0);
	//glTranslatef(2,-2,1);
	//
	glPushMatrix();
		glRotatef(fRotateAngle,0.f,0.f,1.f);
		glRotatef(90.0, 0.0, 0.0, 1.0);
		glTranslatef(2.0, 2.0, 0.0);
		glScalef(1.0, 1.5, 1.0);
		glRotatef(fRotateAngle*3,0.f,0.f,1.f);

		// Test drawing a solid teapot
		glColor3f(1.0,0.0,0.0); // set current color to Red
		glutSolidTeapot(1.f); // call glut utility to draw a solid teapot 
	glPopMatrix();

	
	glPushMatrix();
		//glScalef(1,1,randomVar);
		//glScalef(2,2,2);
		glScalef(randomVar,randomVar,randomVar);

		glColor3f(1.0,1.0,0.0); // set current color to Red
		glutSolidTeapot(1.f); // call glut utility to draw a solid teapot 

	glPopMatrix();



	glutSwapBuffers();	// swap front/back framebuffer to avoid flickering 
}

void reshape (int w, int h)
{
	// reset viewport ( drawing screen ) size
	glViewport(0, 0, w, h);
	float fAspect = ((float)w)/h; 
	// reset OpenGL projection matrix
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	gluPerspective(70.f,fAspect,0.001f,30.f); 
}



void keyboard(unsigned char key, int x, int y)
{
	printf(" Key has been pressed: %c\n", key);
	if (key == 'w') {
		glPolygonMode(GL_FRONT_AND_BACK, GL_LINE); // uncomment this function if you only want to draw wireframe model
	} else if (key == 'f') {
		glPolygonMode(GL_FRONT_AND_BACK, GL_FILL); // uncomment this function if you only want to draw wireframe model
	}

	// put your keyboard control here
	if (key == 27) 
	{
		// ESC hit, so quit
		printf("demonstration finished.\n");
		exit(0);
	}
}

void mouse(int button, int state, int x, int y)
{
	// process your mouse control here
	if (button == GLUT_LEFT_BUTTON && state == GLUT_DOWN)
		printf("push left mouse button.\n");
}
void motion(int x, int y)
{
	//printf("mouse has been moved at %d,%d\n", x, y);
	randomVar = (float)x/30.f;

}


void timer(int v)
{
	fRotateAngle += 1.f; // change rotation angles
	glutTimerFunc(1000/nFPS,timer,v); // restart timer again
	heyThisGetsSentToAShader += 0.01f;
	//glutTimerFunc(0,timer,v); // restart timer again
	glutPostRedisplay(); // trigger display function by sending redraw into message queue
}

int main(int argc, char* argv[])
{
	glutInit(&argc, (char**)argv);
	// set up for double-buffering & RGB color buffer & depth test
	glutInitDisplayMode (GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH); 
	glutInitWindowSize (500, 500); 
	glutInitWindowPosition (100, 100);
	glutCreateWindow ((const char*)"Hello Triangle");

	// initalize glew
        GLenum res = glewInit();
        if (res != GLEW_OK)
        {
          fprintf(stderr, "Error: '%s'\n", glewGetErrorString(res));
          return 1;
        }


	init(); // setting up user data & OpenGL environment
	
	// set up the call-back functions 
	glutDisplayFunc(display);  // called when drawing 
	glutReshapeFunc(reshape);  // called when change window size
	glutKeyboardFunc(keyboard); // called when received keyboard interaction
	glutMouseFunc(mouse);	    // called when received mouse interaction
	glutMotionFunc(motion);	    // called when received mouse interaction
	glutTimerFunc(100,timer,nFPS); // a periodic timer. Usually used for updating animation
	
	glutMainLoop(); // start the main message-callback loop

	return 0;
}