// source: https://github.com/bryc/code/blob/master/jshash/PRNGs.md
function mulberry32(a) {
  return function () {
    a |= 0;
    a = (a + 0x6d2b79f5) | 0;
    var t = Math.imul(a ^ (a >>> 15), 1 | a);
    t = (t + Math.imul(t ^ (t >>> 7), 61 | t)) ^ t;
    return ((t ^ (t >>> 14)) >>> 0) / 4294967296;
  };
}

const pointInRect = ({ x1, y1, x2, y2 }, { x, y }) =>
  x > x1 && x < x2 && y > y1 && y < y2;

function circleIntersect(x0, y0, r0, x1, y1, r1) {
  return Math.hypot(x0 - x1, y0 - y1) <= r0 + r1;
}

class DropCap {
  static get inputProperties() {
    return ["--dropcap-seed"];
  }

  paint(ctx, geometry, props) {
    const seed = props.get("--dropcap-seed").toString().trim();

    const random = mulberry32(seed);

    const colors = ["#352970", "#FFD53D", "#F25C54", "#48CB8A", "#F25C54"];

    const center = {
      x: geometry.width / 2,
      y: geometry.height / 2
    };

    // Estimate the bounding rect of the dropcap's letter (this could be much nicer!)
    const letterBoundingRect = {
      x1: geometry.width / 2 - 20,
      y1: geometry.height / 2 - 20,
      x2: geometry.height / 2 + 20,
      y2: geometry.height / 2 + 20
    };

    const circles = [];

    for (let i = 0; i < 32; i++) {
      let x;
      let y;
      let radius;

      // Try and plot a circle that does not intersect the dropcap's letter, or any other circle. Again, this could be much cleaner!
      for (let j = 0; j < 30; j++) {
        x = random() * geometry.width;
        y = random() * geometry.height;
        radius = 0.25 + random() * 4;

        let overlapsWithOtherCircles = false;

        for (let i = 0; i < circles.length; i++) {
          var dx = x - circles[i].x;
          var dy = y - circles[i].y;
          var distance = Math.sqrt(dx * dx + dy * dy);

          if (distance < radius * 2 + circles[i].radius) {
            overlapsWithOtherCircles = true;
          }
        }

        if (
          !overlapsWithOtherCircles &&
          !pointInRect(letterBoundingRect, { x, y })
        ) {
          break;
        }
      }

      if (!x || !y) continue;

      circles.push({
        x,
        y,
        radius
      });

      ctx.fillStyle = colors[~~(random() * colors.length)];
      ctx.beginPath();
      ctx.arc(x, y, radius, 0, 2 * Math.PI);
      ctx.fill();
    }
  }
}

if (typeof registerPaint !== "undefined") {
  registerPaint("dropCap", DropCap);
}