#include <cstdio>
#include <cmath>
#include <GL/glut.h>

using namespace std;

int SCORE1 = 0, SCORE2 = 0;
float PX1 = -230, PY1 = 0, PX2 = 230, PY2 = 0;
float PADDLE_WIDTH = 10, PADDLE_HEIGHT = 80, PADDLE_SPEED = 8;
float BALLX = 0, BALLY = 0, BALL_SIZE = 10;
float DIRX = 1, DIRY = 1, SPEEDX = 4, SPEEDY = 4;
char MESSAGE[60];
bool KEYS_NORMAL[256], KEYS_SPECIAL[256], GAME_OVER = false;

void type_text(char *str, float x, float y, float s)
{
	char *c;
	glPushMatrix();
	glTranslatef(x, y, 0);
	glScalef(0.1 * s, 0.1 * s, 0);
	for (c = str; *c != '\0'; c++)
		glutStrokeCharacter(GLUT_STROKE_ROMAN, *c);
	glScalef(1, 1, 1);
	glPopMatrix();
}

void draw_middle_line()
{
    glPushAttrib(GL_ALL_ATTRIB_BITS);
    glEnable(GL_LINE_STIPPLE);
    glLineStipple(1, 0x00FF);
    glLineWidth(4);
    glColor3ub(128, 128, 128);
	glBegin(GL_LINES);
		glVertex2i(0, 180);
		glVertex2i(0, -180);
	glEnd();
	glDisable(GL_LINE_STIPPLE);
	glPopAttrib();
}

void draw_ball(float cx, float cy, float s)
{
    float x, y, r = s / 2;
    glBegin(GL_TRIANGLE_FAN);
    glVertex2f(cx, cy);
    for(int angle = 0; angle <= 360; angle++)
    {
        x = cx + r * cos(M_PI * angle / 180);
        y = cy + r * sin(M_PI * angle / 180);
        glVertex2f(x, y);
    }
    glEnd();
}

void draw_paddle(float x, float y, float w, float h)
{
    glRectf(x - w / 2, y - h / 2, x + w / 2, y + h / 2);
}

void check_collisions()
{
	if(BALLY > 180 - BALL_SIZE / 2) DIRY *= -1;
	if(BALLY < -180 + BALL_SIZE / 2) DIRY *= -1;

	if(BALLX >= PX1 - PADDLE_WIDTH / 2 - BALL_SIZE / 2 &&
       BALLX <= PX1 + PADDLE_WIDTH / 2 + BALL_SIZE / 2 &&
       BALLY <= PY1 + PADDLE_HEIGHT / 2 + BALL_SIZE / 2 &&
       BALLY >= PY1 - PADDLE_HEIGHT / 2 - BALL_SIZE / 2 )
        DIRX *= -1;

	if(BALLX >= PX2 - PADDLE_WIDTH / 2 - BALL_SIZE / 2 &&
       BALLX <= PX2 + PADDLE_WIDTH / 2 + BALL_SIZE / 2 &&
       BALLY <= PY2 + PADDLE_HEIGHT / 2 + BALL_SIZE / 2 &&
       BALLY >= PY2 - PADDLE_HEIGHT / 2 - BALL_SIZE / 2 )
        DIRX *= -1;

    if(BALLX >= 240 - BALL_SIZE / 2)
    {
        SCORE1++;
        BALLX = 0;
        BALLY = 0;
        DIRX = -1;
        DIRY = 1;
    }

    if(BALLX <= -240 + BALL_SIZE / 2)
    {
        SCORE2++;
        BALLX = 0;
        BALLY = 0;
        DIRX = 1;
        DIRY = 1;
    }
}

void check_keyboard()
{
    if (KEYS_SPECIAL[GLUT_KEY_UP] && PY2 < (180 - PADDLE_HEIGHT / 2)) PY2 += PADDLE_SPEED;
    if (KEYS_SPECIAL[GLUT_KEY_DOWN] && PY2 > (-180 + PADDLE_HEIGHT / 2)) PY2 -= PADDLE_SPEED;
    if ((KEYS_NORMAL['W'] || KEYS_NORMAL['w']) && PY1 < (180 - PADDLE_HEIGHT / 2)) PY1 += PADDLE_SPEED;
    if ((KEYS_NORMAL['S'] || KEYS_NORMAL['s']) && PY1 > (-180 + PADDLE_HEIGHT / 2)) PY1 -= PADDLE_SPEED;
}

void display()
{
	glClearColor(1,1,1,1);
	glClear(GL_COLOR_BUFFER_BIT);

	if(GAME_OVER)
    {
        // Show game vver
        type_text("GAME OVER", -195, 0, 5);
    }
    else
    {
        // Draw middle line
        draw_middle_line();

        // Player 1 paddle
        glColor3ub(255, 0, 0);
        draw_paddle(PX1, PY1, PADDLE_WIDTH, PADDLE_HEIGHT);

        // Player 2 paddle
        glColor3ub(0, 0, 255);
        draw_paddle(PX2, PY2, PADDLE_WIDTH, PADDLE_HEIGHT);

        // Draw ball
        glColor3ub(0, 0, 0);
        draw_ball(BALLX, BALLY, BALL_SIZE);

        // Move ball
        BALLX += DIRX * SPEEDX;
        BALLY += DIRY * SPEEDY;

        // Collisions
        check_collisions();

        // Keyboard
        check_keyboard();

        // Score
        sprintf(MESSAGE, "%d", SCORE1);
        type_text(MESSAGE, -120, 100, 5);
        sprintf(MESSAGE, "%d", SCORE2);
        type_text(MESSAGE, 120, 100, 5);
        if(SCORE1 == 5 || SCORE2 == 5) GAME_OVER = true;
    }

	glutSwapBuffers();
}

void keyboard_normal(unsigned char key, int x, int y) { KEYS_NORMAL[key] = true; }
void keyboard_normal_up(unsigned char key, int x, int y) { KEYS_NORMAL[key] = false; }
void keyboard_special(int key, int x, int y) { KEYS_SPECIAL[key] = true; }
void keyboard_special_up(int key, int x, int y) { KEYS_SPECIAL[key] = false; }

void timer(int value)
{
    glutPostRedisplay();
    glutTimerFunc(1000.0 / 60.0, timer, 0);
}

int main(int argc, char** argv)
{
	glutInit(&argc,argv);
	glutInitWindowPosition(250, 50);
	glutInitWindowSize(480,360);
	glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
	glutCreateWindow("PONG");
	glMatrixMode(GL_PROJECTION);
	gluOrtho2D(-240, 240, -180, 180);
	glutDisplayFunc(display);
	glutKeyboardFunc(keyboard_normal);
	glutKeyboardUpFunc(keyboard_normal_up);
	glutSpecialFunc(keyboard_special);
	glutSpecialUpFunc(keyboard_special_up);
	glutTimerFunc(1000.0 / 60.0, timer, 0);
	glutMainLoop();
	return 0;
}