#include <time.h>
#include <stdlib.h>
#include <glut.h>

int n = 30, m = 20;
int scale = 25;

int w = scale * n;
int h = scale * m;

int dir, num = 4;

bool controls_arrows = true;

struct
{
	int x, y;
}
s[100];

class Apple
{
public:
	int x, y;

	void New()
	{
		x = rand() % n;
		y = rand() % m;
	}

	void Draw_apple()
	{
		glColor3f(0.0, 0.0, 1.0);
		glRectf(x * scale, y * scale, (x + 1) * scale, (y + 1) * scale);
	}
}
m[10];

void Draw_snake()
{
	glColor3f(0.0, 0.0, 1.0);

	for (int i = 0; i < num; i++)
		glRectf(s[i].x * scale, s[i].y * scale, (s[i].x + 0.9) * scale, (s[i].y + 0.9) * scale);
}

void Tick()
{
	for (int i = num; i > 0; --i)
	{
		s[i].x = s[i - 1].x;
		s[i].y = s[i - 1].y;
	}

	if (dir == 0) s[0].y += 1;
	if (dir == 1) s[0].x -= 1;
	if (dir == 2) s[0].x += 1;
	if (dir == 3) s[0].y -= 1;

	for (int i = 0; i<10; i++)
	if ((s[0].x == m[i].x) && (s[0].y == m[i].y))
	{
		num++; m[i].New();
	}

	if (s[0].x > n) dir = 1;
	if (s[0].x < 0) dir = 2;
	if (s[0].y > m) dir = 3;
	if (s[0].y < 0) dir = 0;

	for (int i = 0; i < num; i++)
	if (s[0].x == s[i].x && s[0].y == s[i].y) num = i;
}

void Draw_field()
{
	glColor3f(0.0, 7.0, 0.0);
	glBegin(GL_LINES);
	for (int i = 0; i < w; i += scale)
	{
		glVertex2f(i, 0);
		glVertex2f(i, h);
	}

	for (int j = 0; j < w; j += scale)
	{
		glVertex2f(0, j);
		glVertex2f(w, j);
	}

	glEnd();
}

void Display()
{
	glClear(GL_COLOR_BUFFER_BIT);

	Draw_field();

	Draw_snake();

	for (int i = 0; i < 10; i++)
		m[i].Draw_apple();

	glFlush();
	glutSwapBuffers();
}

void Keyboard(int key, int a, int b)
{
	switch (key)
	{
		if (controls_arrows == true) case 101: dir = 0; break;
		if (controls_arrows == true) case 102: dir = 2; break;
		if (controls_arrows == true) case 100: dir = 1; break;
		if (controls_arrows == true) case 103: dir = 3; break;
	}
}

void Timer(int i = 0)
{
	Display();

	Tick();

	glutTimerFunc(50, Timer, 0);
}

int main(int argc, char **argv)
{
	srand(time(0));

 	for (int i = 0; i < 10; i++)
 		m[i].New();

	s[i].x = 10;
	s[i].y = 10;

	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
	glutInitWindowSize(w, h);
	glutCreateWindow("Snake");
	glClearColor(1.0, 1.0, 0.6, 1.0);
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	gluOrtho2D(0, w, 0, h);
	glutDisplayFunc(Display);
	glutSpecialFunc(Keyboard);
	glutTimerFunc(50, Timer, 0);
	glutMainLoop();
}