#include <stdio.h>
#include <stdlib.h>
#include <conio.h>
#include <windows.h>
#include <unistd.h>

#define High 20
#define Width 30

int moveDirection;
int canvas[High][Width] = {0};

void gotoxy(int x, int y)
{
	HANDLE handle = GetStdHandle(STD_OUTPUT_HANDLE);
	COORD pos;
	pos.X = x;
	pos.Y = y;
	SetConsoleCursorPosition(handle,pos);
}

void moveSnakeByDirection()
{
	int i, j;
	for(i = 0; i < High - 1; i++ )
		for(j = 0; j < Width - 1; j++)
			if(canvas[i][j] > 0)
				canvas[i][j]++;
				
	int oldTail_i,oldTail_j,oldHead_i,oldHead_j;
	int max = 0;
	
	for(i = 0; i < High - 1; i++)
		for(j = 0; j < Width - 1; j++)
			if(canvas[i][j] > 0)
			{
				if(max < canvas[i][j])
				{
					max = canvas[i][j];
					oldTail_i = i;
					oldTail_j = j;
				}
				
				if(canvas[i][j] == 2)
				{
					oldHead_i = i;
					oldHead_j = j;
				}
			}
			
	canvas[oldTail_i][oldTail_j] = 0;

	if(moveDirection == 1)
		canvas[oldHead_i - 1][oldHead_j] = 1;
	if(moveDirection == 2)
		canvas[oldHead_i + 1][oldHead_j] = 1;
	if(moveDirection == 3)
		canvas[oldHead_i][oldHead_j - 1] = 1;
	if(moveDirection == 4)
		canvas[oldHead_i][oldHead_j + 1] = 1;		
}

void startup()
{
	int i, j;
	
	for(i = 0; i < High; i++)
	{
		canvas[i][0] = -1;
		canvas[i][Width - 1] = -1;
	}
	
	for(j = 0; j < Width; j++)
	{
		canvas[0][j] = -1;
		canvas[High - 1][j] = -1;
	}
	
	canvas[High / 2][Width / 2] = 1;
	
	for(i = 0; i <= 4; i++)
		canvas[High / 2][(Width / 2 )- 1] = i + 1;
		
	moveDirection = 4;
}

void show ()
{
	gotoxy(0,0);
	int i, j;
	for(i = 0; i < High ; i++)
	{
		for(j = 0; j < Width; j++)
		{
			if(canvas[i][j] = 0)
				printf(" ");
		 	else if(canvas[i][j] == -1)
		 		printf("#");
		 	else if(canvas[i][j] == 1)
		 		printf("@");
		 	else if(canvas[i][j] > 0)
		 		printf("*");
		}
		printf("\n");
	}
	usleep(100000);
}

void updateWithoutInput()
{
	moveSnakeByDirection;
}

void updateWithInput()
{
	char input;
	if(kbhit())
	{
		input = getch();
		if(input == 'a')
		{
			moveDirection = 3;
			moveSnakeByDirection();
		}
		
		else if(input == 'd')
		{
			moveDirection = 4;
			moveSnakeByDirection();
		}
		
		else if(input == 'w')
		{
			moveDirection = 1;
			moveSnakeByDirection();
		}
		
		else if(input == 's')
		{
			moveDirection = 2;
			moveSnakeByDirection();
		}
	}
}

int main()
{
	startup();
	while(1)
	{
		show();
		updateWithoutInput();
		updateWithInput();
	}
	return 0;
}