#include <gl/glut.h>
#include <stdio.h>

/**
	This program draws 4 squares and do moves on them (translations, rotations, ...)
*/

GLint windowX;
GLint windowY;

GLdouble redTransformationMatrix[16];

void reshape(GLint x, GLint y)
{
	windowX = x;
	windowY = y;

	glViewport(0,0,windowX,windowY);						// Reset The Current Viewport

	glMatrixMode(GL_PROJECTION);						// Select The Projection Matrix
	glLoadIdentity();									// Reset The Projection Matrix

	glMatrixMode(GL_MODELVIEW);							// Select The Modelview Matrix
	glLoadIdentity();									// Reset The Modelview Matrix
}

/**
	\brief	Initializes transformations.
*/
void init()
{
	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();
	glGetDoublev(GL_MODELVIEW_MATRIX, redTransformationMatrix);		//Sets the red square transformation matrix with an identity matrix.
}

/**
	\brief Function that is called when a key is pressed on the keyboard.
	\param key		The ASCII value of the key.
	\param x		The x value of the mouse position at the event.
	\param y		The y value of the mouse position at the event.
*/
void keyboardPressed(unsigned char key, int x, int y)
{
	switch (key)
	{
		case 'D':
		case 'd':
		{
			//Translation of the red square.
			glMatrixMode(GL_MODELVIEW);
			glLoadMatrixd(redTransformationMatrix);
			glTranslated(25.0, 0.0, 0.0);
			glGetDoublev(GL_MODELVIEW, redTransformationMatrix);
			glutPostRedisplay();
			break;
		}

	}
}

/**
	\brief Function that draws a square, knowing the middle point and the length of a side.
	\param middleX		The X coordinate of the middle point.
	\param middleY		The Y coordinate of the middle point.
	\param sideLength	The length of a side of the square.
*/
void DrawSquare(GLdouble middleX, GLdouble middleY, GLdouble sideLength)
{
	glBegin(GL_QUADS);
	glVertex2d(middleX - (sideLength / 2), middleY + (sideLength / 2));
	glVertex2d(middleX + (sideLength / 2), middleY + (sideLength / 2));
	glVertex2d(middleX + (sideLength / 2), middleY - (sideLength / 2));
	glVertex2d(middleX - (sideLength / 2), middleY - (sideLength / 2));
	glEnd();
}

/**
	\brief Function that is called for every display on the screen.
*/
void display()
{
	glMatrixMode(GL_MODELVIEW);
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    // Reset the current modelview matrix
    glLoadIdentity();		//Makes sure that no affine transformation applies here.

	//We need to set the viewport and the orthonormal bounds.
	glViewport(0, 0, windowX, windowY);
	glOrtho(0.0, windowX, 0.0, windowY, -1.0, 1.0);

	//Let's draw the squares.
	//Red square -- trying here to apply the transformation matrix on the red square.
	glPushMatrix();
	glLoadMatrixd(redTransformationMatrix);
	glColor3d(1.0, 0.0, 0.0);
	DrawSquare(200.0, 600.0, 100.0);
	glPopMatrix();

	//Green square
	glColor3d(0.0, 1.0, 0.0);
	DrawSquare(600.0, 600.0, 100.0);
	//Blue square
	glColor3d(0.0, 0.0, 1.0);
	DrawSquare(600.0, 200.0, 100.0);
	//Yellow square
	glColor3d(1.0, 1.0, 0.0);
	DrawSquare(200.0, 200.0, 100.0);

	glutSwapBuffers();		//Very important, because we are using double buffers and we want to print.
}

int main(int argc, char** argv)
{
	glutInit(&argc, argv);

	glClearColor(0.0, 0.0, 0.0, 0.0);		//Black background color.

	windowX = 800;
	windowY = 800;

	glutInitWindowPosition(0, 0);
	glutInitWindowSize(windowX, windowY);

	glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE);

	glutCreateWindow("FourSquares");

	//Basic initialize...
	init();
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

	glutKeyboardFunc(keyboardPressed);
	glutReshapeFunc(reshape);
	glutDisplayFunc(display);

	//The events may start.
	glutMainLoop();

	return 0;
}