var ctx = null;

var gameTime = 0, lastFrameTime = 0;
var currentSecond = 0, frameCount = 0, framesLastSecond = 0;
var showFramerate = false;

var offsetX = 0;
var offsetY = 0;

var mouseState = {
	x	: 0,
	y	: 0,
	click	: null
};

var gameState = {
	screen		: 'menu',
	
	dir		: 0,
	moveDelay	: 300,
	lastMove	: 0,
	
	snake		: [],
	newBlock	: null,
	
	mapW		: 14,
	mapH		: 14,
	tileW		: 20,
	tileH		: 20,
	
	score		: 0,
	newBest		: false,
	bestScore	: 0
};

function startGame()
{
	gameTime	= 0;
	lastFrameTime	= 0;

	gameState.snake.length	= 0;
	gameState.dir		= 0;
	gameState.score		= 0;
	gameState.lastMove	= 0;
	gameState.screen	= 'playing';
	gameState.newBest	= false;

	gameState.snake.push([
		Math.floor(gameState.mapW / 2),
		Math.floor(gameState.mapH / 2)
	]);

	placeNewBlock();
}

function placeNewBlock()
{
	do {
		var x = Math.floor(Math.random() * gameState.mapW);
		var y = Math.floor(Math.random() * gameState.mapH);
		
		var onSnake = false;
		
		for(var s in gameState.snake)
		{
			if(gameState.snake[s][0]==x &&
				gameState.snake[s][1]==y)
			{
				onSnake = true;
				break;
			}
		}
		
		if(!onSnake)
		{
			gameState.newBlock = [x, y];
			break;
		}

	} while(true);
}

function updateGame()
{
	
	if(gameState.screen=='menu')
	{
		if(mouseState.click!=null)
		{
			if(mouseState.click[1] >= 150 &&
				mouseState.click[1]<= 220)
			{
				startGame();
			}
		}

		mouseState.click = null;
	}
	else if(gameState.screen=='playing')
	{
		if((gameTime - gameState.lastMove) < gameState.moveDelay)
		{
			return;
		}

		var tmp = gameState.snake[0];
		var head = [tmp[0], tmp[1]];
		var dir = gameState.dir;

		if(dir==0 && head[1]==0) { gameOver(); }
		else if(dir==2 && head[1]==(gameState.mapH-1)) { gameOver(); }
		else if(dir==3 && head[0]==0) { gameOver(); }
		else if(dir==1 && head[0]==(gameState.mapW-1)) { gameOver(); }

		if(dir==0) { head[1]-= 1; }
		else if(dir==2) { head[1]+= 1; }
		else if(dir==1) { head[0]+= 1; }
		else if(dir==3) { head[0]-= 1; }

		for(var s in gameState.snake)
		{
			if(s==(gameState.snake.length-1)) { break; }
	
			if(gameState.snake[s][0]==head[0] &&
				gameState.snake[s][1]==head[1])
			{
				gameOver();
				break;
			}
		}

		if(gameState.screen=='menu') { return; }

		gameState.snake.unshift(head);
		gameState.lastMove = gameTime;

		if(gameState.newBlock[0]==head[0] &&
			gameState.newBlock[1]==head[1])
		{
			gameState.score+= 1;
			placeNewBlock();
		}
		else { gameState.snake.pop(); }
	}
}

function gameOver()
{
	gameState.screen = 'menu';
	if(gameState.score > gameState.bestScore)
	{

		gameState.bestScore
	= gameState.score;
		gameState.newBest	= true;
	}
}

window.onload = function()
{
	ctx = document.getElementById('game').getContext('2d');

	offsetX = Math.floor((document.getElementById('game').width -
		(gameState.mapW * gameState.tileW)) / 2);
	offsetY = Math.floor((document.getElementById('game').height -
		(gameState.mapH * gameState.tileH)) / 2);
	
	document.getElementById('game').addEventListener('click', function(e) {

		var pos = realPos(e.pageX, e.pageY);
		mouseState.click = pos;
	});
	document.getElementById('game').addEventListener('mousemove',
	function(e) {
		var pos = realPos(e.pageX, e.pageY);
		mouseState.x = pos[0];
		mouseState.y = pos[1];
	});
	
	window.addEventListener('keydown', function(e) {
		if(e.keyCode==38) { gameState.dir = 0; }
		else if(e.keyCode==39) { gameState.dir = 1; }
		else if(e.keyCode==40) { gameState.dir = 2; }
		else if(e.keyCode==37) { gameState.dir = 3; }
		else if(e.keyCode==70) { showFramerate = !showFramerate; }
	});

	requestAnimationFrame(drawGame);
};

function drawMenu()
{
	ctx.textAlign	= "center";
	ctx.font	= "bold italic 20pt sans-serif";

	ctx.fillStyle = ((mouseState.y>=150 && mouseState.y<=220) ?
		"#0000aa" : "#000000");
	
	ctx.fillText("Nowa Gra", 150, 180);

	ctx.font		= "italic 12pt sans-serif";
	ctx.fillText("Najlepszy wynik: " + gameState.bestScore, 150, 210);
	
	if(gameState.newBest)
	{
		ctx.fillText("Najlepszy wynik!", 150, 240);
	}
	if(gameState.score>0)
	{
		ctx.fillText("Wynik: " + gameState.score, 150, 260);
	}
}

function drawPlaying()
{
	ctx.strokeStyle = "#2c6b00";
	ctx.fillStyle	= "#2c6b00";

	ctx.strokeRect(offsetX, offsetY,
		(gameState.mapW * gameState.tileW),
		(gameState.mapH * gameState.tileH));
	
	for(var s in gameState.snake)
	{
		ctx.fillRect(offsetX + (gameState.snake[s][0] * gameState.tileW),
			offsetY + (gameState.snake[s][1] * gameState.tileH),
			gameState.tileW, gameState.tileH);
	}
	ctx.font = "12pt sans-serif";
	ctx.textAlign = "right";
	ctx.fillText("Wynik: " + gameState.score, 290, 20);

	ctx.fillStyle	= "#e00b00";
	ctx.fillRect(offsetX + (gameState.newBlock[0] * gameState.tileW),
		offsetY + (gameState.newBlock[1] * gameState.tileH),
		gameState.tileW, gameState.tileH);
}

function drawGame()
{
	if(ctx==null) { return; }

	var currentFrameTime = Date.now();
	var timeElapsed = currentFrameTime - lastFrameTime;
	gameTime+= timeElapsed;

	updateGame();

	var sec = Math.floor(Date.now()/1000);
	if(sec!=currentSecond)
	{
		currentSecond = sec;
		framesLastSecond = frameCount;
		frameCount = 1;
	}
	else { frameCount++; }

	ctx.fillStyle = "#ddddee";
	ctx.fillRect(0, 0, 300, 400);

	if(showFramerate)
	{
		ctx.textAlign = "left";
		ctx.font = "10pt sans-serif";
		ctx.fillStyle = "#000000";
		ctx.fillText("Frames: " + framesLastSecond, 5, 15);
	}

	if(gameState.screen=='menu')		{ drawMenu(); }
	else if(gameState.screen=='playing')	{ drawPlaying(); }

	lastFrameTime = currentFrameTime;

	requestAnimationFrame(drawGame);
}

function realPos(x, y)
{
	var p = document.getElementById('game');
	
	do {
		x-= p.offsetLeft;
		y-= p.offsetTop;
		
		p = p.offsetParent;
	} while(p!=null);
	
	return [x, y];
}