function mixin(obj1, obj2) {
	for(var i in obj2) {
		if(obj2.hasOwnProperty(i)) {
			obj1[i] = obj2[i];
		}
	}
};

function EventEmitter() {
	this._events = {};
};
EventEmitter.prototype.on = function(evtn, fn) {
	if(!this._events.hasOwnProperty(evtn)) this._events[evtn] = [];
	this._events[evtn].push(fn);
};
EventEmitter.prototype.off = function(evtn, fn) {
	if(!this._events.hasOwnProperty(evtn)) return;
	var idx = this._events[evtn].indexOf(fn);
	if(idx < 0) return;
	this._events[evtn].splice(idx, 1);
};
EventEmitter.prototype.emit = function(evtn) {
	if(!this._events.hasOwnProperty(evtn)) return;
	var fns = this._events[evtn].slice(0);
	if(fns.length < 1) return;
	var args = Array.prototype.slice.call(arguments, 1);
	for(var i = 0; i < fns.length; i++) fns[i].apply(this, args);
};

function hashFnv32a(str, asString, seed) {
    /*jshint bitwise:false */
    var i, l,
        hval = (seed === undefined) ? 0x811c9dc5 : seed;

    for (i = 0, l = str.length; i < l; i++) {
        hval ^= str.charCodeAt(i);
        hval += (hval << 1) + (hval << 4) + (hval << 7) + (hval << 8) + (hval << 24);
    }
    if( asString ){
        // Convert to 8 digit hex string
        return ("0000000" + (hval >>> 0).toString(16)).substr(-8);
    }
    return hval >>> 0;
}

function round(number, increment, offset) {
	return Math.round((number - offset) / increment ) * increment + offset;
}

// knob
var Knob = function(canvas, min, max, step, value, name, unit) {
	EventEmitter.call(this);

	this.min = min || 0;
	this.max = max || 10;
	this.step = step || 0.01;
	this.value = value || this.min;
	this.knobValue = (this.value - this.min) / (this.max - this.min);
	this.name = name || "";
	this.unit = unit || "";

	var ind = step.toString().indexOf(".");
	if(ind == -1) ind = step.toString().length - 1;
	this.fixedPoint = step.toString().substr(ind).length - 1;

	this.dragY = 0;
	this.mouse_over = false;

	this.canvas = canvas;
	this.ctx = canvas.getContext("2d");

	// knob image
	this.radius = this.canvas.width * 0.3333;
	this.baseImage = document.createElement("canvas");
	this.baseImage.width = canvas.width;
	this.baseImage.height = canvas.height;
	var ctx = this.baseImage.getContext("2d");
	ctx.fillStyle = "#444";
	ctx.shadowColor = "rgba(0, 0, 0, 0.5)";
	ctx.shadowBlur = 5;
	ctx.shadowOffsetX = this.canvas.width * 0.02;
	ctx.shadowOffsetY = this.canvas.width * 0.02;
	ctx.beginPath();
	ctx.arc(this.canvas.width / 2, this.canvas.height /2, this.radius,
		0, Math.PI * 2);
	ctx.fill();

	// events
	var self = this;
	var dragging = false;
	// dragging
	(function() {
		function mousemove(evt) {
			if(evt.screenY !== self.dragY) {
				var delta = -(evt.screenY - self.dragY);
				var scale = 0.0075;
				if(evt.ctrlKey) scale *= 0.05;
				self.setKnobValue(self.knobValue + delta * scale);
				self.dragY = evt.screenY;
				self.redraw();
			}
			evt.preventDefault();
			showTip();
		}
		function mouseout(evt) {
			if(evt.toElement === null && evt.relatedTarget === null) {
				mouseup();
			}
		}
		function mouseup() {
			document.removeEventListener("mousemove", mousemove);
			document.removeEventListener("mouseout", mouseout);
			document.removeEventListener("mouseup", mouseup);
			self.emit("release", self);
			dragging = false;
			if(!self.mouse_over) removeTip();
		}
		canvas.addEventListener("mousedown", function(evt) {
			var pos = self.translateMouseEvent(evt);
			if(self.contains(pos.x, pos.y)) {
				dragging = true;
				self.dragY = evt.screenY;
				showTip();
				document.addEventListener("mousemove", mousemove);
				document.addEventListener("mouseout", mouseout);
				document.addEventListener("mouseup", mouseup);
			}
		});
		canvas.addEventListener("keydown", function(evt) {
			if(evt.keyCode == 38) {
				self.setValue(self.value + self.step);
				showTip();
			} else if(evt.keyCode == 40) {
				self.setValue(self.value - self.step);
				showTip();
			}
		});
	})();
	// tooltip
	function showTip() {
		var div = document.getElementById("tooltip");
		if(!div) {
			div = document.createElement("div");
			document.body.appendChild(div);
			div.id = "tooltip";
			var rect = self.canvas.getBoundingClientRect();
			div.style.left = rect.left + "px";
			div.style.top = rect.bottom + "px";
		}
		div.textContent = self.name;
		if(self.name) div.textContent += ": ";
		div.textContent += self.valueString() + self.unit;
	}
	function removeTip() {
		var div = document.getElementById("tooltip");
		if(div) {
			div.parentElement.removeChild(div);
		}
	}
	function ttmousemove(evt) {
		var pos = self.translateMouseEvent(evt);
		if(self.contains(pos.x, pos.y)) {
			self.mouse_over = true;
			showTip();
		} else {
			self.mouse_over = false;
			if(!dragging) removeTip();
		}
	}
	function ttmouseout(evt) {
		self.mouse_over = false;
		if(!dragging) removeTip();
	}
	self.canvas.addEventListener("mousemove", ttmousemove);
	self.canvas.addEventListener("mouseout", ttmouseout);

	this.redraw();
}
mixin(Knob.prototype, EventEmitter.prototype);
Knob.prototype.redraw = function() {
	var dot_distance = 0.28 * this.canvas.width;
	var dot_radius = 0.03 * this.canvas.width;
	this.ctx.clearRect(0, 0, this.canvas.width, this.canvas.height);
	this.ctx.drawImage(this.baseImage, 0, 0);

	var a = this.knobValue;
	a *= Math.PI * 2 * 0.8;
	a += Math.PI / 2;
	a += Math.PI * 2 * 0.1;
	var half_width = this.canvas.width / 2;
	var x = Math.cos(a) * dot_distance + half_width;
	var y = Math.sin(a) * dot_distance + half_width;
	this.ctx.fillStyle = "#fff";
	this.ctx.beginPath();
	this.ctx.arc(x, y, dot_radius, 0, Math.PI * 2);
	this.ctx.fill();
};
Knob.prototype.setKnobValue = function(value) {
	if(value < 0) value = 0;
	else if(value > 1) value = 1;
	this.knobValue = value;
	this.setValue(value * (this.max - this.min) + this.min);
};
Knob.prototype.setValue = function(value) {
	var old = value;
	value = round(value, this.step, this.min);
	if(value < this.min) value = this.min;
	else if(value > this.max) value = this.max;
	if(this.value !== value) {
		this.value = value;
		this.knobValue = (value - this.min) / (this.max - this.min);
		this.redraw();
		this.emit("change", this);
	}
};
Knob.prototype.valueString = function() {
	return this.value.toFixed(this.fixedPoint);
};
Knob.prototype.contains = function(x, y) {
	x -= this.canvas.width / 2;
	y -= this.canvas.height / 2;
	return Math.sqrt(Math.pow(x, 2) + Math.pow(y, 2)) < this.radius;
};
Knob.prototype.translateMouseEvent = function(evt) {
	var element = evt.target;
	return {
		x: (evt.clientX - element.getBoundingClientRect().left - element.clientLeft + element.scrollLeft),
		y: evt.clientY - (element.getBoundingClientRect().top - element.clientTop + element.scrollTop)
	}
};