node_util/node_modules/polygon-clipping/dist/polygon-clipping.esm.js

import SplayTree from 'splaytree';
import { orient2d } from 'robust-predicates';

/**
 * A bounding box has the format:
 *
 *  { ll: { x: xmin, y: ymin }, ur: { x: xmax, y: ymax } }
 *
 */

const isInBbox = (bbox, point) => {
  return bbox.ll.x <= point.x && point.x <= bbox.ur.x && bbox.ll.y <= point.y && point.y <= bbox.ur.y;
};

/* Returns either null, or a bbox (aka an ordered pair of points)
 * If there is only one point of overlap, a bbox with identical points
 * will be returned */
const getBboxOverlap = (b1, b2) => {
  // check if the bboxes overlap at all
  if (b2.ur.x < b1.ll.x || b1.ur.x < b2.ll.x || b2.ur.y < b1.ll.y || b1.ur.y < b2.ll.y) return null;

  // find the middle two X values
  const lowerX = b1.ll.x < b2.ll.x ? b2.ll.x : b1.ll.x;
  const upperX = b1.ur.x < b2.ur.x ? b1.ur.x : b2.ur.x;

  // find the middle two Y values
  const lowerY = b1.ll.y < b2.ll.y ? b2.ll.y : b1.ll.y;
  const upperY = b1.ur.y < b2.ur.y ? b1.ur.y : b2.ur.y;

  // put those middle values together to get the overlap
  return {
    ll: {
      x: lowerX,
      y: lowerY
    },
    ur: {
      x: upperX,
      y: upperY
    }
  };
};

/* Javascript doesn't do integer math. Everything is
 * floating point with percision Number.EPSILON.
 *
 * https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/EPSILON
 */

let epsilon = Number.EPSILON;

// IE Polyfill
if (epsilon === undefined) epsilon = Math.pow(2, -52);
const EPSILON_SQ = epsilon * epsilon;

/* FLP comparator */
const cmp = (a, b) => {
  // check if they're both 0
  if (-epsilon < a && a < epsilon) {
    if (-epsilon < b && b < epsilon) {
      return 0;
    }
  }

  // check if they're flp equal
  const ab = a - b;
  if (ab * ab < EPSILON_SQ * a * b) {
    return 0;
  }

  // normal comparison
  return a < b ? -1 : 1;
};

/**
 * This class rounds incoming values sufficiently so that
 * floating points problems are, for the most part, avoided.
 *
 * Incoming points are have their x & y values tested against
 * all previously seen x & y values. If either is 'too close'
 * to a previously seen value, it's value is 'snapped' to the
 * previously seen value.
 *
 * All points should be rounded by this class before being
 * stored in any data structures in the rest of this algorithm.
 */

class PtRounder {
  constructor() {
    this.reset();
  }
  reset() {
    this.xRounder = new CoordRounder();
    this.yRounder = new CoordRounder();
  }
  round(x, y) {
    return {
      x: this.xRounder.round(x),
      y: this.yRounder.round(y)
    };
  }
}
class CoordRounder {
  constructor() {
    this.tree = new SplayTree();
    // preseed with 0 so we don't end up with values < Number.EPSILON
    this.round(0);
  }

  // Note: this can rounds input values backwards or forwards.
  //       You might ask, why not restrict this to just rounding
  //       forwards? Wouldn't that allow left endpoints to always
  //       remain left endpoints during splitting (never change to
  //       right). No - it wouldn't, because we snap intersections
  //       to endpoints (to establish independence from the segment
  //       angle for t-intersections).
  round(coord) {
    const node = this.tree.add(coord);
    const prevNode = this.tree.prev(node);
    if (prevNode !== null && cmp(node.key, prevNode.key) === 0) {
      this.tree.remove(coord);
      return prevNode.key;
    }
    const nextNode = this.tree.next(node);
    if (nextNode !== null && cmp(node.key, nextNode.key) === 0) {
      this.tree.remove(coord);
      return nextNode.key;
    }
    return coord;
  }
}

// singleton available by import
const rounder = new PtRounder();

/* Cross Product of two vectors with first point at origin */
const crossProduct = (a, b) => a.x * b.y - a.y * b.x;

/* Dot Product of two vectors with first point at origin */
const dotProduct = (a, b) => a.x * b.x + a.y * b.y;

/* Comparator for two vectors with same starting point */
const compareVectorAngles = (basePt, endPt1, endPt2) => {
  const res = orient2d(basePt.x, basePt.y, endPt1.x, endPt1.y, endPt2.x, endPt2.y);
  if (res > 0) return -1;
  if (res < 0) return 1;
  return 0;
};
const length = v => Math.sqrt(dotProduct(v, v));

/* Get the sine of the angle from pShared -> pAngle to pShaed -> pBase */
const sineOfAngle = (pShared, pBase, pAngle) => {
  const vBase = {
    x: pBase.x - pShared.x,
    y: pBase.y - pShared.y
  };
  const vAngle = {
    x: pAngle.x - pShared.x,
    y: pAngle.y - pShared.y
  };
  return crossProduct(vAngle, vBase) / length(vAngle) / length(vBase);
};

/* Get the cosine of the angle from pShared -> pAngle to pShaed -> pBase */
const cosineOfAngle = (pShared, pBase, pAngle) => {
  const vBase = {
    x: pBase.x - pShared.x,
    y: pBase.y - pShared.y
  };
  const vAngle = {
    x: pAngle.x - pShared.x,
    y: pAngle.y - pShared.y
  };
  return dotProduct(vAngle, vBase) / length(vAngle) / length(vBase);
};

/* Get the x coordinate where the given line (defined by a point and vector)
 * crosses the horizontal line with the given y coordiante.
 * In the case of parrallel lines (including overlapping ones) returns null. */
const horizontalIntersection = (pt, v, y) => {
  if (v.y === 0) return null;
  return {
    x: pt.x + v.x / v.y * (y - pt.y),
    y: y
  };
};

/* Get the y coordinate where the given line (defined by a point and vector)
 * crosses the vertical line with the given x coordiante.
 * In the case of parrallel lines (including overlapping ones) returns null. */
const verticalIntersection = (pt, v, x) => {
  if (v.x === 0) return null;
  return {
    x: x,
    y: pt.y + v.y / v.x * (x - pt.x)
  };
};

/* Get the intersection of two lines, each defined by a base point and a vector.
 * In the case of parrallel lines (including overlapping ones) returns null. */
const intersection$1 = (pt1, v1, pt2, v2) => {
  // take some shortcuts for vertical and horizontal lines
  // this also ensures we don't calculate an intersection and then discover
  // it's actually outside the bounding box of the line
  if (v1.x === 0) return verticalIntersection(pt2, v2, pt1.x);
  if (v2.x === 0) return verticalIntersection(pt1, v1, pt2.x);
  if (v1.y === 0) return horizontalIntersection(pt2, v2, pt1.y);
  if (v2.y === 0) return horizontalIntersection(pt1, v1, pt2.y);

  // General case for non-overlapping segments.
  // This algorithm is based on Schneider and Eberly.
  // http://www.cimec.org.ar/~ncalvo/Schneider_Eberly.pdf - pg 244

  const kross = crossProduct(v1, v2);
  if (kross == 0) return null;
  const ve = {
    x: pt2.x - pt1.x,
    y: pt2.y - pt1.y
  };
  const d1 = crossProduct(ve, v1) / kross;
  const d2 = crossProduct(ve, v2) / kross;

  // take the average of the two calculations to minimize rounding error
  const x1 = pt1.x + d2 * v1.x,
    x2 = pt2.x + d1 * v2.x;
  const y1 = pt1.y + d2 * v1.y,
    y2 = pt2.y + d1 * v2.y;
  const x = (x1 + x2) / 2;
  const y = (y1 + y2) / 2;
  return {
    x: x,
    y: y
  };
};

class SweepEvent {
  // for ordering sweep events in the sweep event queue
  static compare(a, b) {
    // favor event with a point that the sweep line hits first
    const ptCmp = SweepEvent.comparePoints(a.point, b.point);
    if (ptCmp !== 0) return ptCmp;

    // the points are the same, so link them if needed
    if (a.point !== b.point) a.link(b);

    // favor right events over left
    if (a.isLeft !== b.isLeft) return a.isLeft ? 1 : -1;

    // we have two matching left or right endpoints
    // ordering of this case is the same as for their segments
    return Segment.compare(a.segment, b.segment);
  }

  // for ordering points in sweep line order
  static comparePoints(aPt, bPt) {
    if (aPt.x < bPt.x) return -1;
    if (aPt.x > bPt.x) return 1;
    if (aPt.y < bPt.y) return -1;
    if (aPt.y > bPt.y) return 1;
    return 0;
  }

  // Warning: 'point' input will be modified and re-used (for performance)
  constructor(point, isLeft) {
    if (point.events === undefined) point.events = [this];else point.events.push(this);
    this.point = point;
    this.isLeft = isLeft;
    // this.segment, this.otherSE set by factory
  }
  link(other) {
    if (other.point === this.point) {
      throw new Error("Tried to link already linked events");
    }
    const otherEvents = other.point.events;
    for (let i = 0, iMax = otherEvents.length; i < iMax; i++) {
      const evt = otherEvents[i];
      this.point.events.push(evt);
      evt.point = this.point;
    }
    this.checkForConsuming();
  }

  /* Do a pass over our linked events and check to see if any pair
   * of segments match, and should be consumed. */
  checkForConsuming() {
    // FIXME: The loops in this method run O(n^2) => no good.
    //        Maintain little ordered sweep event trees?
    //        Can we maintaining an ordering that avoids the need
    //        for the re-sorting with getLeftmostComparator in geom-out?

    // Compare each pair of events to see if other events also match
    const numEvents = this.point.events.length;
    for (let i = 0; i < numEvents; i++) {
      const evt1 = this.point.events[i];
      if (evt1.segment.consumedBy !== undefined) continue;
      for (let j = i + 1; j < numEvents; j++) {
        const evt2 = this.point.events[j];
        if (evt2.consumedBy !== undefined) continue;
        if (evt1.otherSE.point.events !== evt2.otherSE.point.events) continue;
        evt1.segment.consume(evt2.segment);
      }
    }
  }
  getAvailableLinkedEvents() {
    // point.events is always of length 2 or greater
    const events = [];
    for (let i = 0, iMax = this.point.events.length; i < iMax; i++) {
      const evt = this.point.events[i];
      if (evt !== this && !evt.segment.ringOut && evt.segment.isInResult()) {
        events.push(evt);
      }
    }
    return events;
  }

  /**
   * Returns a comparator function for sorting linked events that will
   * favor the event that will give us the smallest left-side angle.
   * All ring construction starts as low as possible heading to the right,
   * so by always turning left as sharp as possible we'll get polygons
   * without uncessary loops & holes.
   *
   * The comparator function has a compute cache such that it avoids
   * re-computing already-computed values.
   */
  getLeftmostComparator(baseEvent) {
    const cache = new Map();
    const fillCache = linkedEvent => {
      const nextEvent = linkedEvent.otherSE;
      cache.set(linkedEvent, {
        sine: sineOfAngle(this.point, baseEvent.point, nextEvent.point),
        cosine: cosineOfAngle(this.point, baseEvent.point, nextEvent.point)
      });
    };
    return (a, b) => {
      if (!cache.has(a)) fillCache(a);
      if (!cache.has(b)) fillCache(b);
      const {
        sine: asine,
        cosine: acosine
      } = cache.get(a);
      const {
        sine: bsine,
        cosine: bcosine
      } = cache.get(b);

      // both on or above x-axis
      if (asine >= 0 && bsine >= 0) {
        if (acosine < bcosine) return 1;
        if (acosine > bcosine) return -1;
        return 0;
      }

      // both below x-axis
      if (asine < 0 && bsine < 0) {
        if (acosine < bcosine) return -1;
        if (acosine > bcosine) return 1;
        return 0;
      }

      // one above x-axis, one below
      if (bsine < asine) return -1;
      if (bsine > asine) return 1;
      return 0;
    };
  }
}

// Give segments unique ID's to get consistent sorting of
// segments and sweep events when all else is identical
let segmentId = 0;
class Segment {
  /* This compare() function is for ordering segments in the sweep
   * line tree, and does so according to the following criteria:
   *
   * Consider the vertical line that lies an infinestimal step to the
   * right of the right-more of the two left endpoints of the input
   * segments. Imagine slowly moving a point up from negative infinity
   * in the increasing y direction. Which of the two segments will that
   * point intersect first? That segment comes 'before' the other one.
   *
   * If neither segment would be intersected by such a line, (if one
   * or more of the segments are vertical) then the line to be considered
   * is directly on the right-more of the two left inputs.
   */
  static compare(a, b) {
    const alx = a.leftSE.point.x;
    const blx = b.leftSE.point.x;
    const arx = a.rightSE.point.x;
    const brx = b.rightSE.point.x;

    // check if they're even in the same vertical plane
    if (brx < alx) return 1;
    if (arx < blx) return -1;
    const aly = a.leftSE.point.y;
    const bly = b.leftSE.point.y;
    const ary = a.rightSE.point.y;
    const bry = b.rightSE.point.y;

    // is left endpoint of segment B the right-more?
    if (alx < blx) {
      // are the two segments in the same horizontal plane?
      if (bly < aly && bly < ary) return 1;
      if (bly > aly && bly > ary) return -1;

      // is the B left endpoint colinear to segment A?
      const aCmpBLeft = a.comparePoint(b.leftSE.point);
      if (aCmpBLeft < 0) return 1;
      if (aCmpBLeft > 0) return -1;

      // is the A right endpoint colinear to segment B ?
      const bCmpARight = b.comparePoint(a.rightSE.point);
      if (bCmpARight !== 0) return bCmpARight;

      // colinear segments, consider the one with left-more
      // left endpoint to be first (arbitrary?)
      return -1;
    }

    // is left endpoint of segment A the right-more?
    if (alx > blx) {
      if (aly < bly && aly < bry) return -1;
      if (aly > bly && aly > bry) return 1;

      // is the A left endpoint colinear to segment B?
      const bCmpALeft = b.comparePoint(a.leftSE.point);
      if (bCmpALeft !== 0) return bCmpALeft;

      // is the B right endpoint colinear to segment A?
      const aCmpBRight = a.comparePoint(b.rightSE.point);
      if (aCmpBRight < 0) return 1;
      if (aCmpBRight > 0) return -1;

      // colinear segments, consider the one with left-more
      // left endpoint to be first (arbitrary?)
      return 1;
    }

    // if we get here, the two left endpoints are in the same
    // vertical plane, ie alx === blx

    // consider the lower left-endpoint to come first
    if (aly < bly) return -1;
    if (aly > bly) return 1;

    // left endpoints are identical
    // check for colinearity by using the left-more right endpoint

    // is the A right endpoint more left-more?
    if (arx < brx) {
      const bCmpARight = b.comparePoint(a.rightSE.point);
      if (bCmpARight !== 0) return bCmpARight;
    }

    // is the B right endpoint more left-more?
    if (arx > brx) {
      const aCmpBRight = a.comparePoint(b.rightSE.point);
      if (aCmpBRight < 0) return 1;
      if (aCmpBRight > 0) return -1;
    }
    if (arx !== brx) {
      // are these two [almost] vertical segments with opposite orientation?
      // if so, the one with the lower right endpoint comes first
      const ay = ary - aly;
      const ax = arx - alx;
      const by = bry - bly;
      const bx = brx - blx;
      if (ay > ax && by < bx) return 1;
      if (ay < ax && by > bx) return -1;
    }

    // we have colinear segments with matching orientation
    // consider the one with more left-more right endpoint to be first
    if (arx > brx) return 1;
    if (arx < brx) return -1;

    // if we get here, two two right endpoints are in the same
    // vertical plane, ie arx === brx

    // consider the lower right-endpoint to come first
    if (ary < bry) return -1;
    if (ary > bry) return 1;

    // right endpoints identical as well, so the segments are idential
    // fall back on creation order as consistent tie-breaker
    if (a.id < b.id) return -1;
    if (a.id > b.id) return 1;

    // identical segment, ie a === b
    return 0;
  }

  /* Warning: a reference to ringWindings input will be stored,
   *  and possibly will be later modified */
  constructor(leftSE, rightSE, rings, windings) {
    this.id = ++segmentId;
    this.leftSE = leftSE;
    leftSE.segment = this;
    leftSE.otherSE = rightSE;
    this.rightSE = rightSE;
    rightSE.segment = this;
    rightSE.otherSE = leftSE;
    this.rings = rings;
    this.windings = windings;
    // left unset for performance, set later in algorithm
    // this.ringOut, this.consumedBy, this.prev
  }
  static fromRing(pt1, pt2, ring) {
    let leftPt, rightPt, winding;

    // ordering the two points according to sweep line ordering
    const cmpPts = SweepEvent.comparePoints(pt1, pt2);
    if (cmpPts < 0) {
      leftPt = pt1;
      rightPt = pt2;
      winding = 1;
    } else if (cmpPts > 0) {
      leftPt = pt2;
      rightPt = pt1;
      winding = -1;
    } else throw new Error(`Tried to create degenerate segment at [${pt1.x}, ${pt1.y}]`);
    const leftSE = new SweepEvent(leftPt, true);
    const rightSE = new SweepEvent(rightPt, false);
    return new Segment(leftSE, rightSE, [ring], [winding]);
  }

  /* When a segment is split, the rightSE is replaced with a new sweep event */
  replaceRightSE(newRightSE) {
    this.rightSE = newRightSE;
    this.rightSE.segment = this;
    this.rightSE.otherSE = this.leftSE;
    this.leftSE.otherSE = this.rightSE;
  }
  bbox() {
    const y1 = this.leftSE.point.y;
    const y2 = this.rightSE.point.y;
    return {
      ll: {
        x: this.leftSE.point.x,
        y: y1 < y2 ? y1 : y2
      },
      ur: {
        x: this.rightSE.point.x,
        y: y1 > y2 ? y1 : y2
      }
    };
  }

  /* A vector from the left point to the right */
  vector() {
    return {
      x: this.rightSE.point.x - this.leftSE.point.x,
      y: this.rightSE.point.y - this.leftSE.point.y
    };
  }
  isAnEndpoint(pt) {
    return pt.x === this.leftSE.point.x && pt.y === this.leftSE.point.y || pt.x === this.rightSE.point.x && pt.y === this.rightSE.point.y;
  }

  /* Compare this segment with a point.
   *
   * A point P is considered to be colinear to a segment if there
   * exists a distance D such that if we travel along the segment
   * from one * endpoint towards the other a distance D, we find
   * ourselves at point P.
   *
   * Return value indicates:
   *
   *   1: point lies above the segment (to the left of vertical)
   *   0: point is colinear to segment
   *  -1: point lies below the segment (to the right of vertical)
   */
  comparePoint(point) {
    if (this.isAnEndpoint(point)) return 0;
    const lPt = this.leftSE.point;
    const rPt = this.rightSE.point;
    const v = this.vector();

    // Exactly vertical segments.
    if (lPt.x === rPt.x) {
      if (point.x === lPt.x) return 0;
      return point.x < lPt.x ? 1 : -1;
    }

    // Nearly vertical segments with an intersection.
    // Check to see where a point on the line with matching Y coordinate is.
    const yDist = (point.y - lPt.y) / v.y;
    const xFromYDist = lPt.x + yDist * v.x;
    if (point.x === xFromYDist) return 0;

    // General case.
    // Check to see where a point on the line with matching X coordinate is.
    const xDist = (point.x - lPt.x) / v.x;
    const yFromXDist = lPt.y + xDist * v.y;
    if (point.y === yFromXDist) return 0;
    return point.y < yFromXDist ? -1 : 1;
  }

  /**
   * Given another segment, returns the first non-trivial intersection
   * between the two segments (in terms of sweep line ordering), if it exists.
   *
   * A 'non-trivial' intersection is one that will cause one or both of the
   * segments to be split(). As such, 'trivial' vs. 'non-trivial' intersection:
   *
   *   * endpoint of segA with endpoint of segB --> trivial
   *   * endpoint of segA with point along segB --> non-trivial
   *   * endpoint of segB with point along segA --> non-trivial
   *   * point along segA with point along segB --> non-trivial
   *
   * If no non-trivial intersection exists, return null
   * Else, return null.
   */
  getIntersection(other) {
    // If bboxes don't overlap, there can't be any intersections
    const tBbox = this.bbox();
    const oBbox = other.bbox();
    const bboxOverlap = getBboxOverlap(tBbox, oBbox);
    if (bboxOverlap === null) return null;

    // We first check to see if the endpoints can be considered intersections.
    // This will 'snap' intersections to endpoints if possible, and will
    // handle cases of colinearity.

    const tlp = this.leftSE.point;
    const trp = this.rightSE.point;
    const olp = other.leftSE.point;
    const orp = other.rightSE.point;

    // does each endpoint touch the other segment?
    // note that we restrict the 'touching' definition to only allow segments
    // to touch endpoints that lie forward from where we are in the sweep line pass
    const touchesOtherLSE = isInBbox(tBbox, olp) && this.comparePoint(olp) === 0;
    const touchesThisLSE = isInBbox(oBbox, tlp) && other.comparePoint(tlp) === 0;
    const touchesOtherRSE = isInBbox(tBbox, orp) && this.comparePoint(orp) === 0;
    const touchesThisRSE = isInBbox(oBbox, trp) && other.comparePoint(trp) === 0;

    // do left endpoints match?
    if (touchesThisLSE && touchesOtherLSE) {
      // these two cases are for colinear segments with matching left
      // endpoints, and one segment being longer than the other
      if (touchesThisRSE && !touchesOtherRSE) return trp;
      if (!touchesThisRSE && touchesOtherRSE) return orp;
      // either the two segments match exactly (two trival intersections)
      // or just on their left endpoint (one trivial intersection
      return null;
    }

    // does this left endpoint matches (other doesn't)
    if (touchesThisLSE) {
      // check for segments that just intersect on opposing endpoints
      if (touchesOtherRSE) {
        if (tlp.x === orp.x && tlp.y === orp.y) return null;
      }
      // t-intersection on left endpoint
      return tlp;
    }

    // does other left endpoint matches (this doesn't)
    if (touchesOtherLSE) {
      // check for segments that just intersect on opposing endpoints
      if (touchesThisRSE) {
        if (trp.x === olp.x && trp.y === olp.y) return null;
      }
      // t-intersection on left endpoint
      return olp;
    }

    // trivial intersection on right endpoints
    if (touchesThisRSE && touchesOtherRSE) return null;

    // t-intersections on just one right endpoint
    if (touchesThisRSE) return trp;
    if (touchesOtherRSE) return orp;

    // None of our endpoints intersect. Look for a general intersection between
    // infinite lines laid over the segments
    const pt = intersection$1(tlp, this.vector(), olp, other.vector());

    // are the segments parrallel? Note that if they were colinear with overlap,
    // they would have an endpoint intersection and that case was already handled above
    if (pt === null) return null;

    // is the intersection found between the lines not on the segments?
    if (!isInBbox(bboxOverlap, pt)) return null;

    // round the the computed point if needed
    return rounder.round(pt.x, pt.y);
  }

  /**
   * Split the given segment into multiple segments on the given points.
   *  * Each existing segment will retain its leftSE and a new rightSE will be
   *    generated for it.
   *  * A new segment will be generated which will adopt the original segment's
   *    rightSE, and a new leftSE will be generated for it.
   *  * If there are more than two points given to split on, new segments
   *    in the middle will be generated with new leftSE and rightSE's.
   *  * An array of the newly generated SweepEvents will be returned.
   *
   * Warning: input array of points is modified
   */
  split(point) {
    const newEvents = [];
    const alreadyLinked = point.events !== undefined;
    const newLeftSE = new SweepEvent(point, true);
    const newRightSE = new SweepEvent(point, false);
    const oldRightSE = this.rightSE;
    this.replaceRightSE(newRightSE);
    newEvents.push(newRightSE);
    newEvents.push(newLeftSE);
    const newSeg = new Segment(newLeftSE, oldRightSE, this.rings.slice(), this.windings.slice());

    // when splitting a nearly vertical downward-facing segment,
    // sometimes one of the resulting new segments is vertical, in which
    // case its left and right events may need to be swapped
    if (SweepEvent.comparePoints(newSeg.leftSE.point, newSeg.rightSE.point) > 0) {
      newSeg.swapEvents();
    }
    if (SweepEvent.comparePoints(this.leftSE.point, this.rightSE.point) > 0) {
      this.swapEvents();
    }

    // in the point we just used to create new sweep events with was already
    // linked to other events, we need to check if either of the affected
    // segments should be consumed
    if (alreadyLinked) {
      newLeftSE.checkForConsuming();
      newRightSE.checkForConsuming();
    }
    return newEvents;
  }

  /* Swap which event is left and right */
  swapEvents() {
    const tmpEvt = this.rightSE;
    this.rightSE = this.leftSE;
    this.leftSE = tmpEvt;
    this.leftSE.isLeft = true;
    this.rightSE.isLeft = false;
    for (let i = 0, iMax = this.windings.length; i < iMax; i++) {
      this.windings[i] *= -1;
    }
  }

  /* Consume another segment. We take their rings under our wing
   * and mark them as consumed. Use for perfectly overlapping segments */
  consume(other) {
    let consumer = this;
    let consumee = other;
    while (consumer.consumedBy) consumer = consumer.consumedBy;
    while (consumee.consumedBy) consumee = consumee.consumedBy;
    const cmp = Segment.compare(consumer, consumee);
    if (cmp === 0) return; // already consumed
    // the winner of the consumption is the earlier segment
    // according to sweep line ordering
    if (cmp > 0) {
      const tmp = consumer;
      consumer = consumee;
      consumee = tmp;
    }

    // make sure a segment doesn't consume it's prev
    if (consumer.prev === consumee) {
      const tmp = consumer;
      consumer = consumee;
      consumee = tmp;
    }
    for (let i = 0, iMax = consumee.rings.length; i < iMax; i++) {
      const ring = consumee.rings[i];
      const winding = consumee.windings[i];
      const index = consumer.rings.indexOf(ring);
      if (index === -1) {
        consumer.rings.push(ring);
        consumer.windings.push(winding);
      } else consumer.windings[index] += winding;
    }
    consumee.rings = null;
    consumee.windings = null;
    consumee.consumedBy = consumer;

    // mark sweep events consumed as to maintain ordering in sweep event queue
    consumee.leftSE.consumedBy = consumer.leftSE;
    consumee.rightSE.consumedBy = consumer.rightSE;
  }

  /* The first segment previous segment chain that is in the result */
  prevInResult() {
    if (this._prevInResult !== undefined) return this._prevInResult;
    if (!this.prev) this._prevInResult = null;else if (this.prev.isInResult()) this._prevInResult = this.prev;else this._prevInResult = this.prev.prevInResult();
    return this._prevInResult;
  }
  beforeState() {
    if (this._beforeState !== undefined) return this._beforeState;
    if (!this.prev) this._beforeState = {
      rings: [],
      windings: [],
      multiPolys: []
    };else {
      const seg = this.prev.consumedBy || this.prev;
      this._beforeState = seg.afterState();
    }
    return this._beforeState;
  }
  afterState() {
    if (this._afterState !== undefined) return this._afterState;
    const beforeState = this.beforeState();
    this._afterState = {
      rings: beforeState.rings.slice(0),
      windings: beforeState.windings.slice(0),
      multiPolys: []
    };
    const ringsAfter = this._afterState.rings;
    const windingsAfter = this._afterState.windings;
    const mpsAfter = this._afterState.multiPolys;

    // calculate ringsAfter, windingsAfter
    for (let i = 0, iMax = this.rings.length; i < iMax; i++) {
      const ring = this.rings[i];
      const winding = this.windings[i];
      const index = ringsAfter.indexOf(ring);
      if (index === -1) {
        ringsAfter.push(ring);
        windingsAfter.push(winding);
      } else windingsAfter[index] += winding;
    }

    // calcualte polysAfter
    const polysAfter = [];
    const polysExclude = [];
    for (let i = 0, iMax = ringsAfter.length; i < iMax; i++) {
      if (windingsAfter[i] === 0) continue; // non-zero rule
      const ring = ringsAfter[i];
      const poly = ring.poly;
      if (polysExclude.indexOf(poly) !== -1) continue;
      if (ring.isExterior) polysAfter.push(poly);else {
        if (polysExclude.indexOf(poly) === -1) polysExclude.push(poly);
        const index = polysAfter.indexOf(ring.poly);
        if (index !== -1) polysAfter.splice(index, 1);
      }
    }

    // calculate multiPolysAfter
    for (let i = 0, iMax = polysAfter.length; i < iMax; i++) {
      const mp = polysAfter[i].multiPoly;
      if (mpsAfter.indexOf(mp) === -1) mpsAfter.push(mp);
    }
    return this._afterState;
  }

  /* Is this segment part of the final result? */
  isInResult() {
    // if we've been consumed, we're not in the result
    if (this.consumedBy) return false;
    if (this._isInResult !== undefined) return this._isInResult;
    const mpsBefore = this.beforeState().multiPolys;
    const mpsAfter = this.afterState().multiPolys;
    switch (operation.type) {
      case "union":
        {
          // UNION - included iff:
          //  * On one side of us there is 0 poly interiors AND
          //  * On the other side there is 1 or more.
          const noBefores = mpsBefore.length === 0;
          const noAfters = mpsAfter.length === 0;
          this._isInResult = noBefores !== noAfters;
          break;
        }
      case "intersection":
        {
          // INTERSECTION - included iff:
          //  * on one side of us all multipolys are rep. with poly interiors AND
          //  * on the other side of us, not all multipolys are repsented
          //    with poly interiors
          let least;
          let most;
          if (mpsBefore.length < mpsAfter.length) {
            least = mpsBefore.length;
            most = mpsAfter.length;
          } else {
            least = mpsAfter.length;
            most = mpsBefore.length;
          }
          this._isInResult = most === operation.numMultiPolys && least < most;
          break;
        }
      case "xor":
        {
          // XOR - included iff:
          //  * the difference between the number of multipolys represented
          //    with poly interiors on our two sides is an odd number
          const diff = Math.abs(mpsBefore.length - mpsAfter.length);
          this._isInResult = diff % 2 === 1;
          break;
        }
      case "difference":
        {
          // DIFFERENCE included iff:
          //  * on exactly one side, we have just the subject
          const isJustSubject = mps => mps.length === 1 && mps[0].isSubject;
          this._isInResult = isJustSubject(mpsBefore) !== isJustSubject(mpsAfter);
          break;
        }
      default:
        throw new Error(`Unrecognized operation type found ${operation.type}`);
    }
    return this._isInResult;
  }
}

class RingIn {
  constructor(geomRing, poly, isExterior) {
    if (!Array.isArray(geomRing) || geomRing.length === 0) {
      throw new Error("Input geometry is not a valid Polygon or MultiPolygon");
    }
    this.poly = poly;
    this.isExterior = isExterior;
    this.segments = [];
    if (typeof geomRing[0][0] !== "number" || typeof geomRing[0][1] !== "number") {
      throw new Error("Input geometry is not a valid Polygon or MultiPolygon");
    }
    const firstPoint = rounder.round(geomRing[0][0], geomRing[0][1]);
    this.bbox = {
      ll: {
        x: firstPoint.x,
        y: firstPoint.y
      },
      ur: {
        x: firstPoint.x,
        y: firstPoint.y
      }
    };
    let prevPoint = firstPoint;
    for (let i = 1, iMax = geomRing.length; i < iMax; i++) {
      if (typeof geomRing[i][0] !== "number" || typeof geomRing[i][1] !== "number") {
        throw new Error("Input geometry is not a valid Polygon or MultiPolygon");
      }
      let point = rounder.round(geomRing[i][0], geomRing[i][1]);
      // skip repeated points
      if (point.x === prevPoint.x && point.y === prevPoint.y) continue;
      this.segments.push(Segment.fromRing(prevPoint, point, this));
      if (point.x < this.bbox.ll.x) this.bbox.ll.x = point.x;
      if (point.y < this.bbox.ll.y) this.bbox.ll.y = point.y;
      if (point.x > this.bbox.ur.x) this.bbox.ur.x = point.x;
      if (point.y > this.bbox.ur.y) this.bbox.ur.y = point.y;
      prevPoint = point;
    }
    // add segment from last to first if last is not the same as first
    if (firstPoint.x !== prevPoint.x || firstPoint.y !== prevPoint.y) {
      this.segments.push(Segment.fromRing(prevPoint, firstPoint, this));
    }
  }
  getSweepEvents() {
    const sweepEvents = [];
    for (let i = 0, iMax = this.segments.length; i < iMax; i++) {
      const segment = this.segments[i];
      sweepEvents.push(segment.leftSE);
      sweepEvents.push(segment.rightSE);
    }
    return sweepEvents;
  }
}
class PolyIn {
  constructor(geomPoly, multiPoly) {
    if (!Array.isArray(geomPoly)) {
      throw new Error("Input geometry is not a valid Polygon or MultiPolygon");
    }
    this.exteriorRing = new RingIn(geomPoly[0], this, true);
    // copy by value
    this.bbox = {
      ll: {
        x: this.exteriorRing.bbox.ll.x,
        y: this.exteriorRing.bbox.ll.y
      },
      ur: {
        x: this.exteriorRing.bbox.ur.x,
        y: this.exteriorRing.bbox.ur.y
      }
    };
    this.interiorRings = [];
    for (let i = 1, iMax = geomPoly.length; i < iMax; i++) {
      const ring = new RingIn(geomPoly[i], this, false);
      if (ring.bbox.ll.x < this.bbox.ll.x) this.bbox.ll.x = ring.bbox.ll.x;
      if (ring.bbox.ll.y < this.bbox.ll.y) this.bbox.ll.y = ring.bbox.ll.y;
      if (ring.bbox.ur.x > this.bbox.ur.x) this.bbox.ur.x = ring.bbox.ur.x;
      if (ring.bbox.ur.y > this.bbox.ur.y) this.bbox.ur.y = ring.bbox.ur.y;
      this.interiorRings.push(ring);
    }
    this.multiPoly = multiPoly;
  }
  getSweepEvents() {
    const sweepEvents = this.exteriorRing.getSweepEvents();
    for (let i = 0, iMax = this.interiorRings.length; i < iMax; i++) {
      const ringSweepEvents = this.interiorRings[i].getSweepEvents();
      for (let j = 0, jMax = ringSweepEvents.length; j < jMax; j++) {
        sweepEvents.push(ringSweepEvents[j]);
      }
    }
    return sweepEvents;
  }
}
class MultiPolyIn {
  constructor(geom, isSubject) {
    if (!Array.isArray(geom)) {
      throw new Error("Input geometry is not a valid Polygon or MultiPolygon");
    }
    try {
      // if the input looks like a polygon, convert it to a multipolygon
      if (typeof geom[0][0][0] === "number") geom = [geom];
    } catch (ex) {
      // The input is either malformed or has empty arrays.
      // In either case, it will be handled later on.
    }
    this.polys = [];
    this.bbox = {
      ll: {
        x: Number.POSITIVE_INFINITY,
        y: Number.POSITIVE_INFINITY
      },
      ur: {
        x: Number.NEGATIVE_INFINITY,
        y: Number.NEGATIVE_INFINITY
      }
    };
    for (let i = 0, iMax = geom.length; i < iMax; i++) {
      const poly = new PolyIn(geom[i], this);
      if (poly.bbox.ll.x < this.bbox.ll.x) this.bbox.ll.x = poly.bbox.ll.x;
      if (poly.bbox.ll.y < this.bbox.ll.y) this.bbox.ll.y = poly.bbox.ll.y;
      if (poly.bbox.ur.x > this.bbox.ur.x) this.bbox.ur.x = poly.bbox.ur.x;
      if (poly.bbox.ur.y > this.bbox.ur.y) this.bbox.ur.y = poly.bbox.ur.y;
      this.polys.push(poly);
    }
    this.isSubject = isSubject;
  }
  getSweepEvents() {
    const sweepEvents = [];
    for (let i = 0, iMax = this.polys.length; i < iMax; i++) {
      const polySweepEvents = this.polys[i].getSweepEvents();
      for (let j = 0, jMax = polySweepEvents.length; j < jMax; j++) {
        sweepEvents.push(polySweepEvents[j]);
      }
    }
    return sweepEvents;
  }
}

class RingOut {
  /* Given the segments from the sweep line pass, compute & return a series
   * of closed rings from all the segments marked to be part of the result */
  static factory(allSegments) {
    const ringsOut = [];
    for (let i = 0, iMax = allSegments.length; i < iMax; i++) {
      const segment = allSegments[i];
      if (!segment.isInResult() || segment.ringOut) continue;
      let prevEvent = null;
      let event = segment.leftSE;
      let nextEvent = segment.rightSE;
      const events = [event];
      const startingPoint = event.point;
      const intersectionLEs = [];

      /* Walk the chain of linked events to form a closed ring */
      while (true) {
        prevEvent = event;
        event = nextEvent;
        events.push(event);

        /* Is the ring complete? */
        if (event.point === startingPoint) break;
        while (true) {
          const availableLEs = event.getAvailableLinkedEvents();

          /* Did we hit a dead end? This shouldn't happen.
           * Indicates some earlier part of the algorithm malfunctioned. */
          if (availableLEs.length === 0) {
            const firstPt = events[0].point;
            const lastPt = events[events.length - 1].point;
            throw new Error(`Unable to complete output ring starting at [${firstPt.x},` + ` ${firstPt.y}]. Last matching segment found ends at` + ` [${lastPt.x}, ${lastPt.y}].`);
          }

          /* Only one way to go, so cotinue on the path */
          if (availableLEs.length === 1) {
            nextEvent = availableLEs[0].otherSE;
            break;
          }

          /* We must have an intersection. Check for a completed loop */
          let indexLE = null;
          for (let j = 0, jMax = intersectionLEs.length; j < jMax; j++) {
            if (intersectionLEs[j].point === event.point) {
              indexLE = j;
              break;
            }
          }
          /* Found a completed loop. Cut that off and make a ring */
          if (indexLE !== null) {
            const intersectionLE = intersectionLEs.splice(indexLE)[0];
            const ringEvents = events.splice(intersectionLE.index);
            ringEvents.unshift(ringEvents[0].otherSE);
            ringsOut.push(new RingOut(ringEvents.reverse()));
            continue;
          }
          /* register the intersection */
          intersectionLEs.push({
            index: events.length,
            point: event.point
          });
          /* Choose the left-most option to continue the walk */
          const comparator = event.getLeftmostComparator(prevEvent);
          nextEvent = availableLEs.sort(comparator)[0].otherSE;
          break;
        }
      }
      ringsOut.push(new RingOut(events));
    }
    return ringsOut;
  }
  constructor(events) {
    this.events = events;
    for (let i = 0, iMax = events.length; i < iMax; i++) {
      events[i].segment.ringOut = this;
    }
    this.poly = null;
  }
  getGeom() {
    // Remove superfluous points (ie extra points along a straight line),
    let prevPt = this.events[0].point;
    const points = [prevPt];
    for (let i = 1, iMax = this.events.length - 1; i < iMax; i++) {
      const pt = this.events[i].point;
      const nextPt = this.events[i + 1].point;
      if (compareVectorAngles(pt, prevPt, nextPt) === 0) continue;
      points.push(pt);
      prevPt = pt;
    }

    // ring was all (within rounding error of angle calc) colinear points
    if (points.length === 1) return null;

    // check if the starting point is necessary
    const pt = points[0];
    const nextPt = points[1];
    if (compareVectorAngles(pt, prevPt, nextPt) === 0) points.shift();
    points.push(points[0]);
    const step = this.isExteriorRing() ? 1 : -1;
    const iStart = this.isExteriorRing() ? 0 : points.length - 1;
    const iEnd = this.isExteriorRing() ? points.length : -1;
    const orderedPoints = [];
    for (let i = iStart; i != iEnd; i += step) orderedPoints.push([points[i].x, points[i].y]);
    return orderedPoints;
  }
  isExteriorRing() {
    if (this._isExteriorRing === undefined) {
      const enclosing = this.enclosingRing();
      this._isExteriorRing = enclosing ? !enclosing.isExteriorRing() : true;
    }
    return this._isExteriorRing;
  }
  enclosingRing() {
    if (this._enclosingRing === undefined) {
      this._enclosingRing = this._calcEnclosingRing();
    }
    return this._enclosingRing;
  }

  /* Returns the ring that encloses this one, if any */
  _calcEnclosingRing() {
    // start with the ealier sweep line event so that the prevSeg
    // chain doesn't lead us inside of a loop of ours
    let leftMostEvt = this.events[0];
    for (let i = 1, iMax = this.events.length; i < iMax; i++) {
      const evt = this.events[i];
      if (SweepEvent.compare(leftMostEvt, evt) > 0) leftMostEvt = evt;
    }
    let prevSeg = leftMostEvt.segment.prevInResult();
    let prevPrevSeg = prevSeg ? prevSeg.prevInResult() : null;
    while (true) {
      // no segment found, thus no ring can enclose us
      if (!prevSeg) return null;

      // no segments below prev segment found, thus the ring of the prev
      // segment must loop back around and enclose us
      if (!prevPrevSeg) return prevSeg.ringOut;

      // if the two segments are of different rings, the ring of the prev
      // segment must either loop around us or the ring of the prev prev
      // seg, which would make us and the ring of the prev peers
      if (prevPrevSeg.ringOut !== prevSeg.ringOut) {
        if (prevPrevSeg.ringOut.enclosingRing() !== prevSeg.ringOut) {
          return prevSeg.ringOut;
        } else return prevSeg.ringOut.enclosingRing();
      }

      // two segments are from the same ring, so this was a penisula
      // of that ring. iterate downward, keep searching
      prevSeg = prevPrevSeg.prevInResult();
      prevPrevSeg = prevSeg ? prevSeg.prevInResult() : null;
    }
  }
}
class PolyOut {
  constructor(exteriorRing) {
    this.exteriorRing = exteriorRing;
    exteriorRing.poly = this;
    this.interiorRings = [];
  }
  addInterior(ring) {
    this.interiorRings.push(ring);
    ring.poly = this;
  }
  getGeom() {
    const geom = [this.exteriorRing.getGeom()];
    // exterior ring was all (within rounding error of angle calc) colinear points
    if (geom[0] === null) return null;
    for (let i = 0, iMax = this.interiorRings.length; i < iMax; i++) {
      const ringGeom = this.interiorRings[i].getGeom();
      // interior ring was all (within rounding error of angle calc) colinear points
      if (ringGeom === null) continue;
      geom.push(ringGeom);
    }
    return geom;
  }
}
class MultiPolyOut {
  constructor(rings) {
    this.rings = rings;
    this.polys = this._composePolys(rings);
  }
  getGeom() {
    const geom = [];
    for (let i = 0, iMax = this.polys.length; i < iMax; i++) {
      const polyGeom = this.polys[i].getGeom();
      // exterior ring was all (within rounding error of angle calc) colinear points
      if (polyGeom === null) continue;
      geom.push(polyGeom);
    }
    return geom;
  }
  _composePolys(rings) {
    const polys = [];
    for (let i = 0, iMax = rings.length; i < iMax; i++) {
      const ring = rings[i];
      if (ring.poly) continue;
      if (ring.isExteriorRing()) polys.push(new PolyOut(ring));else {
        const enclosingRing = ring.enclosingRing();
        if (!enclosingRing.poly) polys.push(new PolyOut(enclosingRing));
        enclosingRing.poly.addInterior(ring);
      }
    }
    return polys;
  }
}

/**
 * NOTE:  We must be careful not to change any segments while
 *        they are in the SplayTree. AFAIK, there's no way to tell
 *        the tree to rebalance itself - thus before splitting
 *        a segment that's in the tree, we remove it from the tree,
 *        do the split, then re-insert it. (Even though splitting a
 *        segment *shouldn't* change its correct position in the
 *        sweep line tree, the reality is because of rounding errors,
 *        it sometimes does.)
 */

class SweepLine {
  constructor(queue) {
    let comparator = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : Segment.compare;
    this.queue = queue;
    this.tree = new SplayTree(comparator);
    this.segments = [];
  }
  process(event) {
    const segment = event.segment;
    const newEvents = [];

    // if we've already been consumed by another segment,
    // clean up our body parts and get out
    if (event.consumedBy) {
      if (event.isLeft) this.queue.remove(event.otherSE);else this.tree.remove(segment);
      return newEvents;
    }
    const node = event.isLeft ? this.tree.add(segment) : this.tree.find(segment);
    if (!node) throw new Error(`Unable to find segment #${segment.id} ` + `[${segment.leftSE.point.x}, ${segment.leftSE.point.y}] -> ` + `[${segment.rightSE.point.x}, ${segment.rightSE.point.y}] ` + "in SweepLine tree.");
    let prevNode = node;
    let nextNode = node;
    let prevSeg = undefined;
    let nextSeg = undefined;

    // skip consumed segments still in tree
    while (prevSeg === undefined) {
      prevNode = this.tree.prev(prevNode);
      if (prevNode === null) prevSeg = null;else if (prevNode.key.consumedBy === undefined) prevSeg = prevNode.key;
    }

    // skip consumed segments still in tree
    while (nextSeg === undefined) {
      nextNode = this.tree.next(nextNode);
      if (nextNode === null) nextSeg = null;else if (nextNode.key.consumedBy === undefined) nextSeg = nextNode.key;
    }
    if (event.isLeft) {
      // Check for intersections against the previous segment in the sweep line
      let prevMySplitter = null;
      if (prevSeg) {
        const prevInter = prevSeg.getIntersection(segment);
        if (prevInter !== null) {
          if (!segment.isAnEndpoint(prevInter)) prevMySplitter = prevInter;
          if (!prevSeg.isAnEndpoint(prevInter)) {
            const newEventsFromSplit = this._splitSafely(prevSeg, prevInter);
            for (let i = 0, iMax = newEventsFromSplit.length; i < iMax; i++) {
              newEvents.push(newEventsFromSplit[i]);
            }
          }
        }
      }

      // Check for intersections against the next segment in the sweep line
      let nextMySplitter = null;
      if (nextSeg) {
        const nextInter = nextSeg.getIntersection(segment);
        if (nextInter !== null) {
          if (!segment.isAnEndpoint(nextInter)) nextMySplitter = nextInter;
          if (!nextSeg.isAnEndpoint(nextInter)) {
            const newEventsFromSplit = this._splitSafely(nextSeg, nextInter);
            for (let i = 0, iMax = newEventsFromSplit.length; i < iMax; i++) {
              newEvents.push(newEventsFromSplit[i]);
            }
          }
        }
      }

      // For simplicity, even if we find more than one intersection we only
      // spilt on the 'earliest' (sweep-line style) of the intersections.
      // The other intersection will be handled in a future process().
      if (prevMySplitter !== null || nextMySplitter !== null) {
        let mySplitter = null;
        if (prevMySplitter === null) mySplitter = nextMySplitter;else if (nextMySplitter === null) mySplitter = prevMySplitter;else {
          const cmpSplitters = SweepEvent.comparePoints(prevMySplitter, nextMySplitter);
          mySplitter = cmpSplitters <= 0 ? prevMySplitter : nextMySplitter;
        }

        // Rounding errors can cause changes in ordering,
        // so remove afected segments and right sweep events before splitting
        this.queue.remove(segment.rightSE);
        newEvents.push(segment.rightSE);
        const newEventsFromSplit = segment.split(mySplitter);
        for (let i = 0, iMax = newEventsFromSplit.length; i < iMax; i++) {
          newEvents.push(newEventsFromSplit[i]);
        }
      }
      if (newEvents.length > 0) {
        // We found some intersections, so re-do the current event to
        // make sure sweep line ordering is totally consistent for later
        // use with the segment 'prev' pointers
        this.tree.remove(segment);
        newEvents.push(event);
      } else {
        // done with left event
        this.segments.push(segment);
        segment.prev = prevSeg;
      }
    } else {
      // event.isRight

      // since we're about to be removed from the sweep line, check for
      // intersections between our previous and next segments
      if (prevSeg && nextSeg) {
        const inter = prevSeg.getIntersection(nextSeg);
        if (inter !== null) {
          if (!prevSeg.isAnEndpoint(inter)) {
            const newEventsFromSplit = this._splitSafely(prevSeg, inter);
            for (let i = 0, iMax = newEventsFromSplit.length; i < iMax; i++) {
              newEvents.push(newEventsFromSplit[i]);
            }
          }
          if (!nextSeg.isAnEndpoint(inter)) {
            const newEventsFromSplit = this._splitSafely(nextSeg, inter);
            for (let i = 0, iMax = newEventsFromSplit.length; i < iMax; i++) {
              newEvents.push(newEventsFromSplit[i]);
            }
          }
        }
      }
      this.tree.remove(segment);
    }
    return newEvents;
  }

  /* Safely split a segment that is currently in the datastructures
   * IE - a segment other than the one that is currently being processed. */
  _splitSafely(seg, pt) {
    // Rounding errors can cause changes in ordering,
    // so remove afected segments and right sweep events before splitting
    // removeNode() doesn't work, so have re-find the seg
    // https://github.com/w8r/splay-tree/pull/5
    this.tree.remove(seg);
    const rightSE = seg.rightSE;
    this.queue.remove(rightSE);
    const newEvents = seg.split(pt);
    newEvents.push(rightSE);
    // splitting can trigger consumption
    if (seg.consumedBy === undefined) this.tree.add(seg);
    return newEvents;
  }
}

// Limits on iterative processes to prevent infinite loops - usually caused by floating-point math round-off errors.
const POLYGON_CLIPPING_MAX_QUEUE_SIZE = typeof process !== "undefined" && process.env.POLYGON_CLIPPING_MAX_QUEUE_SIZE || 1000000;
const POLYGON_CLIPPING_MAX_SWEEPLINE_SEGMENTS = typeof process !== "undefined" && process.env.POLYGON_CLIPPING_MAX_SWEEPLINE_SEGMENTS || 1000000;
class Operation {
  run(type, geom, moreGeoms) {
    operation.type = type;
    rounder.reset();

    /* Convert inputs to MultiPoly objects */
    const multipolys = [new MultiPolyIn(geom, true)];
    for (let i = 0, iMax = moreGeoms.length; i < iMax; i++) {
      multipolys.push(new MultiPolyIn(moreGeoms[i], false));
    }
    operation.numMultiPolys = multipolys.length;

    /* BBox optimization for difference operation
     * If the bbox of a multipolygon that's part of the clipping doesn't
     * intersect the bbox of the subject at all, we can just drop that
     * multiploygon. */
    if (operation.type === "difference") {
      // in place removal
      const subject = multipolys[0];
      let i = 1;
      while (i < multipolys.length) {
        if (getBboxOverlap(multipolys[i].bbox, subject.bbox) !== null) i++;else multipolys.splice(i, 1);
      }
    }

    /* BBox optimization for intersection operation
     * If we can find any pair of multipolygons whose bbox does not overlap,
     * then the result will be empty. */
    if (operation.type === "intersection") {
      // TODO: this is O(n^2) in number of polygons. By sorting the bboxes,
      //       it could be optimized to O(n * ln(n))
      for (let i = 0, iMax = multipolys.length; i < iMax; i++) {
        const mpA = multipolys[i];
        for (let j = i + 1, jMax = multipolys.length; j < jMax; j++) {
          if (getBboxOverlap(mpA.bbox, multipolys[j].bbox) === null) return [];
        }
      }
    }

    /* Put segment endpoints in a priority queue */
    const queue = new SplayTree(SweepEvent.compare);
    for (let i = 0, iMax = multipolys.length; i < iMax; i++) {
      const sweepEvents = multipolys[i].getSweepEvents();
      for (let j = 0, jMax = sweepEvents.length; j < jMax; j++) {
        queue.insert(sweepEvents[j]);
        if (queue.size > POLYGON_CLIPPING_MAX_QUEUE_SIZE) {
          // prevents an infinite loop, an otherwise common manifestation of bugs
          throw new Error("Infinite loop when putting segment endpoints in a priority queue " + "(queue size too big).");
        }
      }
    }

    /* Pass the sweep line over those endpoints */
    const sweepLine = new SweepLine(queue);
    let prevQueueSize = queue.size;
    let node = queue.pop();
    while (node) {
      const evt = node.key;
      if (queue.size === prevQueueSize) {
        // prevents an infinite loop, an otherwise common manifestation of bugs
        const seg = evt.segment;
        throw new Error(`Unable to pop() ${evt.isLeft ? "left" : "right"} SweepEvent ` + `[${evt.point.x}, ${evt.point.y}] from segment #${seg.id} ` + `[${seg.leftSE.point.x}, ${seg.leftSE.point.y}] -> ` + `[${seg.rightSE.point.x}, ${seg.rightSE.point.y}] from queue.`);
      }
      if (queue.size > POLYGON_CLIPPING_MAX_QUEUE_SIZE) {
        // prevents an infinite loop, an otherwise common manifestation of bugs
        throw new Error("Infinite loop when passing sweep line over endpoints " + "(queue size too big).");
      }
      if (sweepLine.segments.length > POLYGON_CLIPPING_MAX_SWEEPLINE_SEGMENTS) {
        // prevents an infinite loop, an otherwise common manifestation of bugs
        throw new Error("Infinite loop when passing sweep line over endpoints " + "(too many sweep line segments).");
      }
      const newEvents = sweepLine.process(evt);
      for (let i = 0, iMax = newEvents.length; i < iMax; i++) {
        const evt = newEvents[i];
        if (evt.consumedBy === undefined) queue.insert(evt);
      }
      prevQueueSize = queue.size;
      node = queue.pop();
    }

    // free some memory we don't need anymore
    rounder.reset();

    /* Collect and compile segments we're keeping into a multipolygon */
    const ringsOut = RingOut.factory(sweepLine.segments);
    const result = new MultiPolyOut(ringsOut);
    return result.getGeom();
  }
}

// singleton available by import
const operation = new Operation();

const union = function (geom) {
  for (var _len = arguments.length, moreGeoms = new Array(_len > 1 ? _len - 1 : 0), _key = 1; _key < _len; _key++) {
    moreGeoms[_key - 1] = arguments[_key];
  }
  return operation.run("union", geom, moreGeoms);
};
const intersection = function (geom) {
  for (var _len2 = arguments.length, moreGeoms = new Array(_len2 > 1 ? _len2 - 1 : 0), _key2 = 1; _key2 < _len2; _key2++) {
    moreGeoms[_key2 - 1] = arguments[_key2];
  }
  return operation.run("intersection", geom, moreGeoms);
};
const xor = function (geom) {
  for (var _len3 = arguments.length, moreGeoms = new Array(_len3 > 1 ? _len3 - 1 : 0), _key3 = 1; _key3 < _len3; _key3++) {
    moreGeoms[_key3 - 1] = arguments[_key3];
  }
  return operation.run("xor", geom, moreGeoms);
};
const difference = function (subjectGeom) {
  for (var _len4 = arguments.length, clippingGeoms = new Array(_len4 > 1 ? _len4 - 1 : 0), _key4 = 1; _key4 < _len4; _key4++) {
    clippingGeoms[_key4 - 1] = arguments[_key4];
  }
  return operation.run("difference", subjectGeom, clippingGeoms);
};
var index = {
  union: union,
  intersection: intersection,
  xor: xor,
  difference: difference
};

export { index as default };