#include <libmaxsi/platform.h>
#include <libmaxsi/io.h>
#include <libmaxsi/thread.h>
#include <libmaxsi/keyboard.h>
#include <libmaxsi/sortix-vga.h>
#include <libmaxsi/sortix-keyboard.h>

using namespace Maxsi;
using namespace Maxsi::Keyboard;

const int width = 80;
const int height = 25;

const int buffersize = height * width;

System::VGA::Frame* frame;

int posx;
int posy;
int velx;
int vely;
int tailx;
int taily;
int taillen;
int tailmax;
int animalx;
int animaly;

char direction[buffersize];

uint16_t animal = '%' | (COLOR8_RED<<8);
uint16_t snake = ' ' | (COLOR8_GREEN<<12);

const int defaultspeed = 75;
const int speedincrease = -5;
const int maxspeed = 40;
volatile int speed;

// HACK: Sortix has no random number generator yet!
int random_seed=1337;
int rand(int max) 
{
	int tmpmax=max;
	random_seed = random_seed + 37 * 1103515245 + 12345;
	return (unsigned int) (random_seed / 65536) % tmpmax; 
}

void Clear()
{
	// Reset the game data.
	for ( int i = 0; i < buffersize; i++ ) { frame->text[i] = ' '; direction[i] = -1; }
}

void Reset()
{
	Clear();
	tailx = posx = width/2;
	taily = posy = height/2;
	switch ( rand(4) )
	{
		case 0: velx = -1; vely = 0; break;
		case 1: velx = 1; vely = 0; break; 
		case 2: velx = 0; vely = -1; break;
		case 3: velx = 0; vely = -1; break;
	}

	animalx = 2 + rand(width-4);
	animaly = 2 + rand(height-4);

	taillen = 0;
	tailmax = 3;

	frame->text[animaly * width + animalx] = animal;

	speed = defaultspeed;
}

int Init()
{
	// Create a VGA frame we can render onto.
	frame = System::VGA::CreateFrame();
	if ( frame == NULL )
	{
		Print("Could not create VGA frame\n");
		return -1;
	}

	System::VGA::ChangeFrame(frame->fd);

	Reset();

	return 0;
}

void Update()
{
	int newvelx = velx;
	int newvely = vely;

	// Read the keyboard input from the user.
	unsigned method = System::Keyboard::POLL;
	uint32_t codepoint;
	while ( (codepoint = System::Keyboard::ReceieveKeystroke(method) ) != 0 )
	{
		bool keyup = codepoint & DEPRESSED;
		if ( keyup ) { continue; }
		codepoint &= ~DEPRESSED;

		if ( codepoint == '\n' ) { Reset(); return; }
		if ( codepoint == 'w' || codepoint == 'W' ) { newvelx = 0; newvely = -1; }
		if ( codepoint == 'a' || codepoint == 'A' ) { newvelx = -1; newvely = 0; }
		if ( codepoint == 's' || codepoint == 'S' ) { newvelx = 0; newvely = 1; }
		if ( codepoint == 'd' || codepoint == 'D' ) { newvelx = 1; newvely = 0; }
	}

	// Make sure we don't do a 180.
	if ( !(velx == -1 && newvelx == 1) &&
	     !(velx == 1 && newvelx == -1) &&
	     !(vely == -1 && newvely == 1) &&
	     !(vely == 1 && newvely == -1) )
	{
		velx = newvelx; vely = newvely;
	}

	// Don't collide with the border!
	if ( posx + velx < 0 || width <= posx + velx ||
	     posy + vely < 0 || height <= posy + vely ) { Reset(); return; }

	int newx = posx + velx;
	int newy = posy + vely;

	// Move the tail, if needed.
	if ( taillen == tailmax )
	{
		frame->text[taily * width + tailx] = ' '; taillen--;
		switch ( direction[taily * width + tailx] )
		{
			case 0: tailx--; break;
			case 1: tailx++; break; 
			case 2: taily--; break;
			case 3: taily++; break;
		}
	}

	// Check for collision.
	if ( frame->text[newy * width + newx] == snake ) { Reset(); return; }

	// Check for food.
	if ( newx == animalx && newy == animaly )
	{
		tailmax++;
		animalx = 2 + rand(width-4);
		animaly = 2 + rand(height-4);
		if ( maxspeed < speed ) { speed += speedincrease; }
	}

	frame->text[animaly * width + animalx] = animal;

	// Remember where we are going.
	int dir = 0;
	if ( velx < 0 ) { dir = 0; }
	if ( velx > 0 ) { dir = 1; }
	if ( vely < 0 ) { dir = 2; }
	if ( vely > 0 ) { dir = 3; }
	direction[posy * width + posx] = dir;

	// Move the head.
	posx = newx;
	posy = newy;
	frame->text[posy * width + posx] = snake; taillen++;
}

int main(int argc, char* argv[])
{
	int result = Init();
	if ( result != 0 ) { return result; }

	// Update the game every once in a while.
	while ( true )
	{
		Thread::USleep(speed * 1000);
		Update();
	}

	return 0;
}