SVGElement.prototype.getTransformToElement = SVGElement.prototype.getTransformToElement ||        function(toElement) {

  return toElement.getScreenCTM().inverse().multiply(this.getScreenCTM());

};

function ns_elem () { if (typeof arguments[0] === "undefined") { console.log('There was an error in the element assist function. Called with no valid tag name!');} var elem; if (typeof arguments[1] === "string") { elem = document.createElementNS(arguments[1], arguments[0]); for (var i=2; i<arguments.length; i+=2) { if (typeof arguments[i+1] === "undefined") { for (var key in arguments[i]) { elem.setAttribute(key, arguments[i][key]); } break; } else { for (var key in arguments[i]) { elem.setAttributeNS(arguments[i+1], key, arguments[i][key]); } } } } else { elem = document.createElement(arguments[0]); for (var i=1; i<arguments.length; i+=2) { if (typeof arguments[i+1] === "undefined") { for (var key in arguments[i]) { elem.setAttribute(key, arguments[i][key]); } break; } else { for (var key in arguments[i]) { elem.setAttributeNS(arguments[i+1], key, arguments[i][key]); } } } } return elem;}


var svg_ns = "http://www.w3.org/2000/svg";
var xlink_ns = "http://www.w3.org/1999/xlink";

function norm (vector) {
	var norm = Math.sqrt(vector.x*vector.x + vector.y*vector.y);
	return {x: vector.x / norm, y: vector.y / norm};
}
function len (vector) {
	return Math.sqrt(vector.x*vector.x + vector.y*vector.y);
}
function sub (a, b) { return {x: a.x-b.x, y: a.y-b.y}; }
function add (a, b) { return {x: a.x+b.x, y: a.y+b.y}; }
function mul (a, b) {
	if ("x" in a) { return {x: a.x*b, y: a.y*b}; }
	return a*b;
}

function remove_class(element, classname) {
	var classlist = $(element).attr("class");
	if (classlist) {
		classlist = classlist.split(" ");
	}
	var newclasslist = "";
	for (const x in classlist) {
		newclasslist += (classname != classlist[x]) ? " " + classlist[x] : "";
	}
	$(element).attr("class", newclasslist);
}

function add_class(element, classname) {
	const classlist = $(element).attr("class");
	$(element).attr("class", classlist  + " " + classname);
}

function svg_from_dom(point, svg) {
	const pt = svg.createSVGPoint();
	pt.x = point.x;
	pt.y = point.y;

	return pt.matrixTransform(svg.getScreenCTM().inverse());
}
function dom_from_svg(point, svg) {
	const pt = svg.createSVGPoint();
	pt.x = point.x;
	pt.y = point.y;

	return pt.matrixTransform(svg.getScreenCTM());
}
function point_from_circle(circle) {
	return {x:parseFloat(circle.attr('cx')), y:parseFloat(circle.attr('cy'))};
}
var previous_mouse_position = {x:0,y:0};

function set_transform(element, point, rotation) {
	const transform_string = `translate(${point.x},${point.y}) rotate(${180*rotation/Math.PI})`;

	return $(element).attr("transform", transform_string);
}

function remove(list, element) {
	const index = list.indexOf(element);
	if (index > -1) { // only splice array when item is found
		list.splice(index, 1); // 2nd parameter means remove one item only
	}
}

function appropriate_angle(point) {
	return -Math.atan2(point.x, point.y);
}

function newsvg(element) {
	document.createElementNS(svg_ns, element);
}
function set_loc(elem, point) { return $(elem).attr("cx", point.x).attr("cy",point.y)}

function get_global_point_at_length(svg, path, distance) {
	return path.getPointAtLength(distance).matrixTransform(path.getTransformToElement(svg));
}