*/
const elements = ea.getViewSelectedElements();
const ellipse = elements.filter(el => el.type == "ellipse")[0];
if (!ellipse) return;

let lines = elements.filter(el => el.type == "line" || el.type == "arrow");
if (lines.length == 0) lines = ea.getViewElements().filter(el => el.type == "line" || el.type == "arrow");
const subLines = getSubLines(lines);

const angles = subLines.flatMap(line => {
  return intersectionAngleOfEllipseAndLine(ellipse, line.a, line.b).map(result => ({
    angle: result,
    cuttingLine: line
  }));
});

if (angles.length === 0) angles.push({ angle: 0, cuttingLine: null });

angles.sort((a, b) => a.angle - b.angle);

const closeObject = await utils.suggester(["Yes", "No"], [true, false], "Close object along cutedge?")

ea.style.strokeSharpness = closeObject ? "sharp" : "round";
ea.style.strokeColor = ellipse.strokeColor;
ea.style.strokeWidth = ellipse.strokeWidth;
ea.style.backgroundColor = ellipse.backgroundColor;
ea.style.fillStyle = ellipse.fillStyle;
ea.style.roughness = ellipse.roughness;

angles.forEach((angle, key) => {
  const cuttingLine = angle.cuttingLine;
  angle = angle.angle;
  const nextAngleKey = (key + 1) < angles.length ? key + 1 : 0;
  const nextAngle = angles[nextAngleKey].angle;
  const AngleDelta = nextAngle - angle ? nextAngle - angle : Math.PI*2;
  const pointAmount = Math.ceil((AngleDelta*64)/(Math.PI*2));
  const stepSize = AngleDelta/pointAmount;
  let points = drawEllipse(ellipse.x, ellipse.y, ellipse.width, ellipse.height, ellipse.angle, angle, nextAngle, stepSize);
  if (closeObject && cuttingLine) points = points.concat(getCutLine(points[0], angles[key], angles[nextAngleKey], ellipse));

  const lineId = ea.addLine(points);
  const line = ea.getElement(lineId);
  line.frameId = ellipse.frameId;
  line.groupIds = ellipse.groupIds;
});

ea.deleteViewElements([ellipse]);
ea.addElementsToView(false,false,true);
return;

function getSubLines(lines) {
  return lines.flatMap((line, key) => {
    return line.points.slice(1).map((pointB, i) => ({
      a: addVectors([line.points[i], [line.x, line.y]]),
      b: addVectors([pointB, [line.x, line.y]]),
      originLineIndex: key,
      indexPointA: i,
    }));
  });
}

function intersectionAngleOfEllipseAndLine(ellipse, pointA, pointB) {
  /*
  To understand the code in this function and subfunctions it might help to take a look at this geogebra file
  https://www.geogebra.org/m/apbm3hs6
  */
  const c = multiplyVectorByScalar([ellipse.width, ellipse.height], (1/2));
  const a = rotateVector(
    addVectors([
      pointA,
      invVec([ellipse.x, ellipse.y]),
      invVec(multiplyVectorByScalar([ellipse.width, ellipse.height], (1/2)))
    ]),
    -ellipse.angle
  )
  const l_b = rotateVector(
    addVectors([
      pointB,
      invVec([ellipse.x, ellipse.y]),
      invVec(multiplyVectorByScalar([ellipse.width, ellipse.height], (1/2)))
    ]),
    -ellipse.angle
  );
  const b = addVectors([
    l_b,
    invVec(a)
  ]);
  const solutions = calculateLineSegment(a[0], a[1], b[0], b[1], c[0], c[1]);
  return solutions
    .filter(num => isBetween(num, 0, 1))
    .map(num => {
      const point = [
        (a[0] + b[0] * num) / ellipse.width,
        (a[1] + b[1] * num) / ellipse.height
      ];
      return angleBetweenVectors([1, 0], point);
    });
}

function drawEllipse(x, y, width, height, angle = 0, start = 0, end = Math.PI*2, step = Math.PI/32) {
  const ellipse = (t) => {
    const spanningVector = rotateVector([width/2*Math.cos(t), height/2*Math.sin(t)], angle);
    const baseVector = [x+width/2, y+height/2];
    return addVectors([baseVector, spanningVector]);
  }

  if(end <= start) end = end + Math.PI*2;

  let points = [];
  const almostEnd = end - step/2;
  for (let t = start; t < almostEnd; t = t + step) {
    points.push(ellipse(t));
  }
  points.push(ellipse(end))
  return points;
}

function getCutLine(startpoint, currentAngle, nextAngle, ellipse) {
  if (currentAngle.cuttingLine.originLineIndex != nextAngle.cuttingLine.originLineIndex) return [];
  
  const originLineIndex = currentAngle.cuttingLine.originLineIndex;
  
  if (lines[originLineIndex] == 2) return startpoint;
  
  const originLine = [];
  lines[originLineIndex].points.forEach(p => originLine.push(addVectors([
    p,
    [lines[originLineIndex].x, lines[originLineIndex].y]
  ])));

  const edgepoints = [];
  const direction = isInEllipse(originLine[clamp(nextAngle.cuttingLine.indexPointA - 1, 0, originLine.length - 1)], ellipse) ? -1 : 1
  let i = isInEllipse(originLine[nextAngle.cuttingLine.indexPointA], ellipse) ? nextAngle.cuttingLine.indexPointA : nextAngle.cuttingLine.indexPointA + direction;
  while (isInEllipse(originLine[i], ellipse)) {
    edgepoints.push(originLine[i]);
    i = (i + direction) % originLine.length;
  }
  edgepoints.push(startpoint);
  return edgepoints;
}

function calculateLineSegment(ax, ay, bx, by, cx, cy) {
  const sqrt = Math.sqrt((cx ** 2) * (cy ** 2) * (-(ay ** 2) * (bx ** 2) + 2 * ax * ay * bx * by - (ax ** 2) * (by ** 2) + (bx ** 2) * (cy ** 2) + (by ** 2) * (cx ** 2)));
  const numerator = -(ay * by * (cx ** 2) + ax * bx * (cy ** 2));
  const denominator = ((by ** 2) * (cx ** 2) + (bx ** 2) * (cy ** 2));
  const t1 = (numerator + sqrt) / denominator;
  const t2 = (numerator - sqrt) / denominator;

  return [t1, t2];
}

function isInEllipse(point, ellipse) {
  point = addVectors([point, invVec([ellipse.x, ellipse.y]), invVec(multiplyVectorByScalar([ellipse.width, ellipse.height], 1/2))]);
  point = [point[0]*2/ellipse.width, point[1]*2/ellipse.height];
  const distance = Math.sqrt(point[0]**2 + point[1]**2);
  return distance < 1;
}

function angleBetweenVectors(v1, v2) {
  let dotProduct = v1[0] * v2[0] + v1[1] * v2[1];
  let determinant = v1[0] * v2[1] - v1[1] * v2[0];
  let angle = Math.atan2(determinant, dotProduct);
  return angle < 0 ? angle + 2 * Math.PI : angle;
}

function rotateVector (vec, ang)  {
  var cos = Math.cos(ang);
  var sin = Math.sin(ang);
  return [vec[0] * cos - vec[1] * sin, vec[0] * sin + vec[1] * cos];
}

function addVectors(vectors) {
  return vectors.reduce((acc, vec) => [acc[0] + vec[0], acc[1] + vec[1]], [0, 0]);
}

function invVec(vector) {
  return [-vector[0], -vector[1]];
}

function multiplyVectorByScalar(vector, scalar) {
  return [vector[0] * scalar, vector[1] * scalar];
}

function round(number, precision) {
  var factor = Math.pow(10, precision);
  return Math.round(number * factor) / factor;
}

function isBetween(num, min, max) {
  return (num >= min && num <= max);
}

function clamp(number, min, max) {
  return Math.max(min, Math.min(number, max));
}