random_radius.ts

const rand = (min: number, max: number): number => {
  return Math.random() * (max - min) + min;
}

const roundPrec = (number:number, digits: number = 2): number => {
  return Math.round(number * Math.pow(10, digits)) / Math.pow(10, digits);
}

const randomOnRing = (x: number, y: number, radius: number): Coordinate => {
  const radiusSq = radius ^ 2;
  const xRandSq = rand(0, radiusSq);
  const yRandSq = radiusSq - xRandSq;
  const result = [
    roundPrec(x + Math.sqrt(xRandSq) * (rand(0, 1) ? 1 : -1)),
    roundPrec(y + Math.sqrt(yRandSq) * (rand(0, 1) ? 1 : -1))
  ];
  return result;
}