'use strict';

var buildArc = require('./buildArc.js');

"use strict";
function buildArcTo(points, x1, y1, x2, y2, radius) {
  const fromX = points[points.length - 2];
  const fromY = points[points.length - 1];
  const a1 = fromY - y1;
  const b1 = fromX - x1;
  const a2 = y2 - y1;
  const b2 = x2 - x1;
  const mm = Math.abs(a1 * b2 - b1 * a2);
  if (mm < 1e-8 || radius === 0) {
    if (points[points.length - 2] !== x1 || points[points.length - 1] !== y1) {
      points.push(x1, y1);
    }
    return;
  }
  const dd = a1 * a1 + b1 * b1;
  const cc = a2 * a2 + b2 * b2;
  const tt = a1 * a2 + b1 * b2;
  const k1 = radius * Math.sqrt(dd) / mm;
  const k2 = radius * Math.sqrt(cc) / mm;
  const j1 = k1 * tt / dd;
  const j2 = k2 * tt / cc;
  const cx = k1 * b2 + k2 * b1;
  const cy = k1 * a2 + k2 * a1;
  const px = b1 * (k2 + j1);
  const py = a1 * (k2 + j1);
  const qx = b2 * (k1 + j2);
  const qy = a2 * (k1 + j2);
  const startAngle = Math.atan2(py - cy, px - cx);
  const endAngle = Math.atan2(qy - cy, qx - cx);
  buildArc.buildArc(
    points,
    cx + x1,
    cy + y1,
    radius,
    startAngle,
    endAngle,
    b1 * a2 > b2 * a1
  );
}

exports.buildArcTo = buildArcTo;
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