var MOUSE_TIMEOUT = 1000;
var mouseTimeout;

$('body').mousemove(function() {
    hideAll();

    if (mouseTimeout)
	clearTimeout(mouseTimeout);
    mouseTimeout = setTimeout(onMouseTimeout, MOUSE_TIMEOUT);
});

function onMouseTimeout() {
    canSpawn();
}


var MAX_BUGS = 5;
var bugs = [];
var SPAWN_INTERVAL = 2000;
var spawnInterval;
function canSpawn() {
    if (!spawnInterval)
	spawnInterval = setInterval(spawn, SPAWN_INTERVAL);
}

function spawn() {
    bugs = bugs.filter(function(bug) {
	return !bug.shouldHide;
    });
    /*console.log("spawn", bugs.length, "/", MAX_BUGS);*/
    if (bugs.length >= MAX_BUGS)
	return;

    bugs.push(new Bug());
}

function hideAll() {
    if (spawnInterval) {
	clearInterval(spawnInterval);
	spawnInterval = null;
	hideAll();
    }

    for(var i = 0; i < bugs.length; i++) {
	bugs[i].shouldHide = true;
    }
    bugs = [];
}

function Bug() {
    this.alpha = 0;
    this.rotation = 0;
    this.x = $('body').scrollLeft() + Math.floor(window.innerWidth * Math.random());
    this.y = $('body').scrollTop() + Math.floor(window.innerHeight * Math.random());
    this.selectTarget();

    this.el = $('<img src="images/derbug.png">');
    this.el.css({ position: 'absolute',
		  width: "28px",
		  height: "28px"
		});
    $('body').append(this.el);
    /*console.log("new bug", this, this.x, this.y);*/

    this.think();
}
Bug.prototype = {
    update: function() {
	this.el.css({ left: Math.floor(this.x) + "px",
		      top: Math.floor(this.y) + "px",
		      opacity: this.alpha,
		      transform: "rotate(" + this.rotation + "rad)",
		      '-webkitTransform': "rotate(" + this.rotation + "rad)",
		      '-mozTransform': "rotate(" + this.rotation + "rad)"
		    });
    },
    selectTarget: function() {
	this.targetRotation = 2 * Math.PI * (Math.random() - 0.5);
	this.targetSteps = 5 + Math.ceil(10 * Math.random());
    },
    think: function() {
	if (this.shouldHide && this.alpha > 0) {
	    /* fading out */
	    this.alpha -= 0.1;
	} else if (this.shouldHide) {
	    this.el.remove();
	    /* destroy
	     * HACK: Avoid nextTick() */
	    return;
	} else if (this.alpha < 1) {
	    /* fading in */
	    this.alpha += 0.1;
	}

	var dr = this.targetRotation - this.rotation;
	if (Math.abs(dr) > 1) {
	    this.rotation += Math.random() * dr / 10;
	}
	if (this.targetSteps > 0) {
	    this.targetSteps--;
	    this.x += Math.sin(this.rotation);
	    this.y -= Math.cos(this.rotation);

	    /* Emergency suicide: */
	    if (this.x < 16 ||
		this.x > $('body').innerWidth() - 16 ||
		this.y < 16 ||
		this.y > $('body').innerHeight() - 16) {
		this.shouldHide = true;
	    }
	} else {
	    this.selectTarget();
	}

	this.update();
	nextTick(this.think.bind(this));
    }
};

var nextTick =
    window.requestAnimationFrame ||
    window.webkitRequestAnimationFrame ||
    window.mozRequestAnimationFrame ||
    window.msRequestAnimationFrame ||
    window.oRequestAnimationFrame ||
    function(f) {
	window.setTimeout(f, 40);
    };