/*
 (c) 2017, Vladimir Agafonkin
 Simplify.js, a high-performance JS polyline simplification library
 mourner.github.io/simplify-js
*/
// to suit your point format, run search/replace for '.x' and '.y';
// for 3D version, see 3d branch (configurability would draw significant performance overhead)
// square distance between 2 points
function getSqDist(p1, p2) {
  var dx = p1.x - p2.x,
    dy = p1.y - p2.y;
  return dx * dx + dy * dy;
}
// square distance from a point to a segment
function getSqSegDist(p, p1, p2) {
  var x = p1.x,
    y = p1.y,
    dx = p2.x - x,
    dy = p2.y - y;
  if (dx !== 0 || dy !== 0) {
    var t = ((p.x - x) * dx + (p.y - y) * dy) / (dx * dx + dy * dy);
    if (t > 1) {
      x = p2.x;
      y = p2.y;
    } else if (t > 0) {
      x += dx * t;
      y += dy * t;
    }
  }
  dx = p.x - x;
  dy = p.y - y;
  return dx * dx + dy * dy;
}
// rest of the code doesn't care about point format
// basic distance-based simplification
function simplifyRadialDist(points, sqTolerance) {
  var prevPoint = points[0],
    newPoints = [prevPoint],
    point;
  for (var i = 1, len = points.length; i < len; i++) {
    point = points[i];
    if (getSqDist(point, prevPoint) > sqTolerance) {
      newPoints.push(point);
      prevPoint = point;
    }
  }
  if (prevPoint !== point) newPoints.push(point);
  return newPoints;
}
function simplifyDPStep(points, first, last, sqTolerance, simplified) {
  var maxSqDist = sqTolerance,
    index;
  for (var i = first + 1; i < last; i++) {
    var sqDist = getSqSegDist(points[i], points[first], points[last]);
    if (sqDist > maxSqDist) {
      index = i;
      maxSqDist = sqDist;
    }
  }
  if (maxSqDist > sqTolerance) {
    if (index - first > 1) simplifyDPStep(points, first, index, sqTolerance, simplified);
    simplified.push(points[index]);
    if (last - index > 1) simplifyDPStep(points, index, last, sqTolerance, simplified);
  }
}
// simplification using Ramer-Douglas-Peucker algorithm
function simplifyDouglasPeucker(points, sqTolerance) {
  var last = points.length - 1;
  var simplified = [points[0]];
  simplifyDPStep(points, 0, last, sqTolerance, simplified);
  simplified.push(points[last]);
  return simplified;
}
// both algorithms combined for awesome performance
export function simplify(points, tolerance, highestQuality) {
  if (points.length <= 2) return points;
  var sqTolerance = tolerance !== undefined ? tolerance * tolerance : 1;
  points = highestQuality ? points : simplifyRadialDist(points, sqTolerance);
  points = simplifyDouglasPeucker(points, sqTolerance);
  return points;
}