mars.js

const compare = (a, b) => {
  return a.x === b.x && a.y === b.y;
};

const distance = (a, b) => {
  return Math.sqrt((a.x - b.x) ** 2 + (a.y - b.y) ** 2);
};


const draaien = (a, b, c) => {
  if (compare(a, b) || compare(b, c) || compare(a, c)) {
    throw "AssertionError: drie punten moeten verschillend zijn";
  }

  let calc = ((b.x - a.x) * (c.y - a.y)) - ((b.y - a.y) * (c.x - a.x));

  if (!calc) {
    return calc;
  } else {
    return Math.abs(calc) / calc;
  }
};

const volgende = (point, pointset, flag) => {
  let current = undefined;
  let check = 1;
  if (!flag) {
    check = -1;
  }

  pointset.filter((o) => !compare(o, point)).forEach(
    (p) => {
      if (!current) {
        current = p;
      } else if (draaien(point, current, p) === check) {
        current = p;

      } else if (draaien(point, current, p) === 0) {
        if (distance(point, current) < distance(point, p)) {
          current = p;
        }
      }

    });
  return current;


};

const contour = (pointset, flag) => {
  let first = pointset.reduce((prev, cur) => {
    if (prev.x === cur.x) {
      if (cur.y < prev.y) {
        return cur;
      } else {
        return prev;
      }
    } else {
      if (cur.x < prev.x) {
        return cur;
      }
      return prev;
    }
  });

  let rslt = [first];
  let next = volgende(first, pointset, flag);
  while (!compare(next, first)) {
    rslt.push(next);
    next = volgende(next, pointset, flag);
  }
  return rslt;
};