common/lib/earcut.js

/* eslint-disable */
export function earcut(data, holeIndices, dim) {

  dim = dim || 2;

  var hasHoles = holeIndices && holeIndices.length,
      outerLen = hasHoles ? holeIndices[0] * dim : data.length,
      outerNode = linkedList(data, 0, outerLen, dim, true),
      triangles = [];

  if (!outerNode || outerNode.next === outerNode.prev) return triangles;

  var minX, minY, maxX, maxY, x, y, invSize;

  if (hasHoles) outerNode = eliminateHoles(data, holeIndices, outerNode, dim);

  // if the shape is not too simple, we'll use z-order curve hash later; calculate polygon bbox
  if (data.length > 80 * dim) {
      minX = maxX = data[0];
      minY = maxY = data[1];

      for (var i = dim; i < outerLen; i += dim) {
          x = data[i];
          y = data[i + 1];
          if (x < minX) minX = x;
          if (y < minY) minY = y;
          if (x > maxX) maxX = x;
          if (y > maxY) maxY = y;
      }

      // minX, minY and invSize are later used to transform coords into integers for z-order calculation
      invSize = Math.max(maxX - minX, maxY - minY);
      invSize = invSize !== 0 ? 1 / invSize : 0;
  }

  earcutLinked(outerNode, triangles, dim, minX, minY, invSize);

  return triangles;
}

// create a circular doubly linked list from polygon points in the specified winding order
function linkedList(data, start, end, dim, clockwise) {
  var i, last;

  if (clockwise === (signedArea(data, start, end, dim) > 0)) {
      for (i = start; i < end; i += dim) last = insertNode(i, data[i], data[i + 1], last);
  } else {
      for (i = end - dim; i >= start; i -= dim) last = insertNode(i, data[i], data[i + 1], last);
  }

  if (last && equals(last, last.next)) {
      removeNode(last);
      last = last.next;
  }

  return last;
}

// eliminate colinear or duplicate points
function filterPoints(start, end) {
  if (!start) return start;
  if (!end) end = start;

  var p = start,
      again;
  do {
      again = false;

      if (!p.steiner && (equals(p, p.next) || area(p.prev, p, p.next) === 0)) {
          removeNode(p);
          p = end = p.prev;
          if (p === p.next) break;
          again = true;

      } else {
          p = p.next;
      }
  } while (again || p !== end);

  return end;
}

// main ear slicing loop which triangulates a polygon (given as a linked list)
function earcutLinked(ear, triangles, dim, minX, minY, invSize, pass) {
  if (!ear) return;

  // interlink polygon nodes in z-order
  if (!pass && invSize) indexCurve(ear, minX, minY, invSize);

  var stop = ear,
      prev, next;

  // iterate through ears, slicing them one by one
  while (ear.prev !== ear.next) {
      prev = ear.prev;
      next = ear.next;

      if (invSize ? isEarHashed(ear, minX, minY, invSize) : isEar(ear)) {
          // cut off the triangle
          triangles.push(prev.i / dim);
          triangles.push(ear.i / dim);
          triangles.push(next.i / dim);

          removeNode(ear);

          // skipping the next vertex leads to less sliver triangles
          ear = next.next;
          stop = next.next;

          continue;
      }

      ear = next;

      // if we looped through the whole remaining polygon and can't find any more ears
      if (ear === stop) {
          // try filtering points and slicing again
          if (!pass) {
              earcutLinked(filterPoints(ear), triangles, dim, minX, minY, invSize, 1);

          // if this didn't work, try curing all small self-intersections locally
          } else if (pass === 1) {
              ear = cureLocalIntersections(filterPoints(ear), triangles, dim);
              earcutLinked(ear, triangles, dim, minX, minY, invSize, 2);

          // as a last resort, try splitting the remaining polygon into two
          } else if (pass === 2) {
              splitEarcut(ear, triangles, dim, minX, minY, invSize);
          }

          break;
      }
  }
}

// check whether a polygon node forms a valid ear with adjacent nodes
function isEar(ear) {
  var a = ear.prev,
      b = ear,
      c = ear.next;

  if (area(a, b, c) >= 0) return false; // reflex, can't be an ear

  // now make sure we don't have other points inside the potential ear
  var p = ear.next.next;

  while (p !== ear.prev) {
      if (pointInTriangle(a.x, a.y, b.x, b.y, c.x, c.y, p.x, p.y) &&
          area(p.prev, p, p.next) >= 0) return false;
      p = p.next;
  }

  return true;
}

function isEarHashed(ear, minX, minY, invSize) {
  var a = ear.prev,
      b = ear,
      c = ear.next;

  if (area(a, b, c) >= 0) return false; // reflex, can't be an ear

  // triangle bbox; min & max are calculated like this for speed
  var minTX = a.x < b.x ? (a.x < c.x ? a.x : c.x) : (b.x < c.x ? b.x : c.x),
      minTY = a.y < b.y ? (a.y < c.y ? a.y : c.y) : (b.y < c.y ? b.y : c.y),
      maxTX = a.x > b.x ? (a.x > c.x ? a.x : c.x) : (b.x > c.x ? b.x : c.x),
      maxTY = a.y > b.y ? (a.y > c.y ? a.y : c.y) : (b.y > c.y ? b.y : c.y);

  // z-order range for the current triangle bbox;
  var minZ = zOrder(minTX, minTY, minX, minY, invSize),
      maxZ = zOrder(maxTX, maxTY, minX, minY, invSize);

  var p = ear.prevZ,
      n = ear.nextZ;

  // look for points inside the triangle in both directions
  while (p && p.z >= minZ && n && n.z <= maxZ) {
      if (p !== ear.prev && p !== ear.next &&
          pointInTriangle(a.x, a.y, b.x, b.y, c.x, c.y, p.x, p.y) &&
          area(p.prev, p, p.next) >= 0) return false;
      p = p.prevZ;

      if (n !== ear.prev && n !== ear.next &&
          pointInTriangle(a.x, a.y, b.x, b.y, c.x, c.y, n.x, n.y) &&
          area(n.prev, n, n.next) >= 0) return false;
      n = n.nextZ;
  }

  // look for remaining points in decreasing z-order
  while (p && p.z >= minZ) {
      if (p !== ear.prev && p !== ear.next &&
          pointInTriangle(a.x, a.y, b.x, b.y, c.x, c.y, p.x, p.y) &&
          area(p.prev, p, p.next) >= 0) return false;
      p = p.prevZ;
  }

  // look for remaining points in increasing z-order
  while (n && n.z <= maxZ) {
      if (n !== ear.prev && n !== ear.next &&
          pointInTriangle(a.x, a.y, b.x, b.y, c.x, c.y, n.x, n.y) &&
          area(n.prev, n, n.next) >= 0) return false;
      n = n.nextZ;
  }

  return true;
}

// go through all polygon nodes and cure small local self-intersections
function cureLocalIntersections(start, triangles, dim) {
  var p = start;
  do {
      var a = p.prev,
          b = p.next.next;

      if (!equals(a, b) && intersects(a, p, p.next, b) && locallyInside(a, b) && locallyInside(b, a)) {

          triangles.push(a.i / dim);
          triangles.push(p.i / dim);
          triangles.push(b.i / dim);

          // remove two nodes involved
          removeNode(p);
          removeNode(p.next);

          p = start = b;
      }
      p = p.next;
  } while (p !== start);

  return filterPoints(p);
}

// try splitting polygon into two and triangulate them independently
function splitEarcut(start, triangles, dim, minX, minY, invSize) {
  // look for a valid diagonal that divides the polygon into two
  var a = start;
  do {
      var b = a.next.next;
      while (b !== a.prev) {
          if (a.i !== b.i && isValidDiagonal(a, b)) {
              // split the polygon in two by the diagonal
              var c = splitPolygon(a, b);

              // filter colinear points around the cuts
              a = filterPoints(a, a.next);
              c = filterPoints(c, c.next);

              // run earcut on each half
              earcutLinked(a, triangles, dim, minX, minY, invSize);
              earcutLinked(c, triangles, dim, minX, minY, invSize);
              return;
          }
          b = b.next;
      }
      a = a.next;
  } while (a !== start);
}

// link every hole into the outer loop, producing a single-ring polygon without holes
function eliminateHoles(data, holeIndices, outerNode, dim) {
  var queue = [],
      i, len, start, end, list;

  for (i = 0, len = holeIndices.length; i < len; i++) {
      start = holeIndices[i] * dim;
      end = i < len - 1 ? holeIndices[i + 1] * dim : data.length;
      list = linkedList(data, start, end, dim, false);
      if (list === list.next) list.steiner = true;
      queue.push(getLeftmost(list));
  }

  queue.sort(compareX);

  // process holes from left to right
  for (i = 0; i < queue.length; i++) {
      eliminateHole(queue[i], outerNode);
      outerNode = filterPoints(outerNode, outerNode.next);
  }

  return outerNode;
}

function compareX(a, b) {
  return a.x - b.x;
}

// find a bridge between vertices that connects hole with an outer ring and and link it
function eliminateHole(hole, outerNode) {
  outerNode = findHoleBridge(hole, outerNode);
  if (outerNode) {
      var b = splitPolygon(outerNode, hole);

      // filter collinear points around the cuts
      filterPoints(outerNode, outerNode.next);
      filterPoints(b, b.next);
  }
}

// David Eberly's algorithm for finding a bridge between hole and outer polygon
function findHoleBridge(hole, outerNode) {
  var p = outerNode,
      hx = hole.x,
      hy = hole.y,
      qx = -Infinity,
      m;

  // find a segment intersected by a ray from the hole's leftmost point to the left;
  // segment's endpoint with lesser x will be potential connection point
  do {
      if (hy <= p.y && hy >= p.next.y && p.next.y !== p.y) {
          var x = p.x + (hy - p.y) * (p.next.x - p.x) / (p.next.y - p.y);
          if (x <= hx && x > qx) {
              qx = x;
              if (x === hx) {
                  if (hy === p.y) return p;
                  if (hy === p.next.y) return p.next;
              }
              m = p.x < p.next.x ? p : p.next;
          }
      }
      p = p.next;
  } while (p !== outerNode);

  if (!m) return null;

  if (hx === qx) return m; // hole touches outer segment; pick leftmost endpoint

  // look for points inside the triangle of hole point, segment intersection and endpoint;
  // if there are no points found, we have a valid connection;
  // otherwise choose the point of the minimum angle with the ray as connection point

  var stop = m,
      mx = m.x,
      my = m.y,
      tanMin = Infinity,
      tan;

  p = m;

  do {
      if (hx >= p.x && p.x >= mx && hx !== p.x &&
              pointInTriangle(hy < my ? hx : qx, hy, mx, my, hy < my ? qx : hx, hy, p.x, p.y)) {

          tan = Math.abs(hy - p.y) / (hx - p.x); // tangential

          if (locallyInside(p, hole) &&
              (tan < tanMin || (tan === tanMin && (p.x > m.x || (p.x === m.x && sectorContainsSector(m, p)))))) {
              m = p;
              tanMin = tan;
          }
      }

      p = p.next;
  } while (p !== stop);

  return m;
}

// whether sector in vertex m contains sector in vertex p in the same coordinates
function sectorContainsSector(m, p) {
  return area(m.prev, m, p.prev) < 0 && area(p.next, m, m.next) < 0;
}

// interlink polygon nodes in z-order
function indexCurve(start, minX, minY, invSize) {
  var p = start;
  do {
      if (p.z === null) p.z = zOrder(p.x, p.y, minX, minY, invSize);
      p.prevZ = p.prev;
      p.nextZ = p.next;
      p = p.next;
  } while (p !== start);

  p.prevZ.nextZ = null;
  p.prevZ = null;

  sortLinked(p);
}

// Simon Tatham's linked list merge sort algorithm
// http://www.chiark.greenend.org.uk/~sgtatham/algorithms/listsort.html
function sortLinked(list) {
  var i, p, q, e, tail, numMerges, pSize, qSize,
      inSize = 1;

  do {
      p = list;
      list = null;
      tail = null;
      numMerges = 0;

      while (p) {
          numMerges++;
          q = p;
          pSize = 0;
          for (i = 0; i < inSize; i++) {
              pSize++;
              q = q.nextZ;
              if (!q) break;
          }
          qSize = inSize;

          while (pSize > 0 || (qSize > 0 && q)) {

              if (pSize !== 0 && (qSize === 0 || !q || p.z <= q.z)) {
                  e = p;
                  p = p.nextZ;
                  pSize--;
              } else {
                  e = q;
                  q = q.nextZ;
                  qSize--;
              }

              if (tail) tail.nextZ = e;
              else list = e;

              e.prevZ = tail;
              tail = e;
          }

          p = q;
      }

      tail.nextZ = null;
      inSize *= 2;

  } while (numMerges > 1);

  return list;
}

// z-order of a point given coords and inverse of the longer side of data bbox
function zOrder(x, y, minX, minY, invSize) {
  // coords are transformed into non-negative 15-bit integer range
  x = 32767 * (x - minX) * invSize;
  y = 32767 * (y - minY) * invSize;

  x = (x | (x << 8)) & 0x00FF00FF;
  x = (x | (x << 4)) & 0x0F0F0F0F;
  x = (x | (x << 2)) & 0x33333333;
  x = (x | (x << 1)) & 0x55555555;

  y = (y | (y << 8)) & 0x00FF00FF;
  y = (y | (y << 4)) & 0x0F0F0F0F;
  y = (y | (y << 2)) & 0x33333333;
  y = (y | (y << 1)) & 0x55555555;

  return x | (y << 1);
}

// find the leftmost node of a polygon ring
function getLeftmost(start) {
  var p = start,
      leftmost = start;
  do {
      if (p.x < leftmost.x || (p.x === leftmost.x && p.y < leftmost.y)) leftmost = p;
      p = p.next;
  } while (p !== start);

  return leftmost;
}

// check if a point lies within a convex triangle
function pointInTriangle(ax, ay, bx, by, cx, cy, px, py) {
  return (cx - px) * (ay - py) - (ax - px) * (cy - py) >= 0 &&
         (ax - px) * (by - py) - (bx - px) * (ay - py) >= 0 &&
         (bx - px) * (cy - py) - (cx - px) * (by - py) >= 0;
}

// check if a diagonal between two polygon nodes is valid (lies in polygon interior)
function isValidDiagonal(a, b) {
  return a.next.i !== b.i && a.prev.i !== b.i && !intersectsPolygon(a, b) && // dones't intersect other edges
         (locallyInside(a, b) && locallyInside(b, a) && middleInside(a, b) && // locally visible
          (area(a.prev, a, b.prev) || area(a, b.prev, b)) || // does not create opposite-facing sectors
          equals(a, b) && area(a.prev, a, a.next) > 0 && area(b.prev, b, b.next) > 0); // special zero-length case
}

// signed area of a triangle
function area(p, q, r) {
  return (q.y - p.y) * (r.x - q.x) - (q.x - p.x) * (r.y - q.y);
}

// check if two points are equal
function equals(p1, p2) {
  return p1.x === p2.x && p1.y === p2.y;
}

// check if two segments intersect
function intersects(p1, q1, p2, q2) {
  var o1 = sign(area(p1, q1, p2));
  var o2 = sign(area(p1, q1, q2));
  var o3 = sign(area(p2, q2, p1));
  var o4 = sign(area(p2, q2, q1));

  if (o1 !== o2 && o3 !== o4) return true; // general case

  if (o1 === 0 && onSegment(p1, p2, q1)) return true; // p1, q1 and p2 are collinear and p2 lies on p1q1
  if (o2 === 0 && onSegment(p1, q2, q1)) return true; // p1, q1 and q2 are collinear and q2 lies on p1q1
  if (o3 === 0 && onSegment(p2, p1, q2)) return true; // p2, q2 and p1 are collinear and p1 lies on p2q2
  if (o4 === 0 && onSegment(p2, q1, q2)) return true; // p2, q2 and q1 are collinear and q1 lies on p2q2

  return false;
}

// for collinear points p, q, r, check if point q lies on segment pr
function onSegment(p, q, r) {
  return q.x <= Math.max(p.x, r.x) && q.x >= Math.min(p.x, r.x) && q.y <= Math.max(p.y, r.y) && q.y >= Math.min(p.y, r.y);
}

function sign(num) {
  return num > 0 ? 1 : num < 0 ? -1 : 0;
}

// check if a polygon diagonal intersects any polygon segments
function intersectsPolygon(a, b) {
  var p = a;
  do {
      if (p.i !== a.i && p.next.i !== a.i && p.i !== b.i && p.next.i !== b.i &&
              intersects(p, p.next, a, b)) return true;
      p = p.next;
  } while (p !== a);

  return false;
}

// check if a polygon diagonal is locally inside the polygon
function locallyInside(a, b) {
  return area(a.prev, a, a.next) < 0 ?
      area(a, b, a.next) >= 0 && area(a, a.prev, b) >= 0 :
      area(a, b, a.prev) < 0 || area(a, a.next, b) < 0;
}

// check if the middle point of a polygon diagonal is inside the polygon
function middleInside(a, b) {
  var p = a,
      inside = false,
      px = (a.x + b.x) / 2,
      py = (a.y + b.y) / 2;
  do {
      if (((p.y > py) !== (p.next.y > py)) && p.next.y !== p.y &&
              (px < (p.next.x - p.x) * (py - p.y) / (p.next.y - p.y) + p.x))
          inside = !inside;
      p = p.next;
  } while (p !== a);

  return inside;
}

// link two polygon vertices with a bridge; if the vertices belong to the same ring, it splits polygon into two;
// if one belongs to the outer ring and another to a hole, it merges it into a single ring
function splitPolygon(a, b) {
  var a2 = new Node(a.i, a.x, a.y),
      b2 = new Node(b.i, b.x, b.y),
      an = a.next,
      bp = b.prev;

  a.next = b;
  b.prev = a;

  a2.next = an;
  an.prev = a2;

  b2.next = a2;
  a2.prev = b2;

  bp.next = b2;
  b2.prev = bp;

  return b2;
}

// create a node and optionally link it with previous one (in a circular doubly linked list)
function insertNode(i, x, y, last) {
  var p = new Node(i, x, y);

  if (!last) {
      p.prev = p;
      p.next = p;

  } else {
      p.next = last.next;
      p.prev = last;
      last.next.prev = p;
      last.next = p;
  }
  return p;
}

function removeNode(p) {
  p.next.prev = p.prev;
  p.prev.next = p.next;

  if (p.prevZ) p.prevZ.nextZ = p.nextZ;
  if (p.nextZ) p.nextZ.prevZ = p.prevZ;
}

function Node(i, x, y) {
  // vertex index in coordinates array
  this.i = i;

  // vertex coordinates
  this.x = x;
  this.y = y;

  // previous and next vertex nodes in a polygon ring
  this.prev = null;
  this.next = null;

  // z-order curve value
  this.z = null;

  // previous and next nodes in z-order
  this.prevZ = null;
  this.nextZ = null;

  // indicates whether this is a steiner point
  this.steiner = false;
}

// return a percentage difference between the polygon area and its triangulation area;
// used to verify correctness of triangulation
earcut.deviation = function (data, holeIndices, dim, triangles) {
  var hasHoles = holeIndices && holeIndices.length;
  var outerLen = hasHoles ? holeIndices[0] * dim : data.length;

  var polygonArea = Math.abs(signedArea(data, 0, outerLen, dim));
  if (hasHoles) {
      for (var i = 0, len = holeIndices.length; i < len; i++) {
          var start = holeIndices[i] * dim;
          var end = i < len - 1 ? holeIndices[i + 1] * dim : data.length;
          polygonArea -= Math.abs(signedArea(data, start, end, dim));
      }
  }

  var trianglesArea = 0;
  for (i = 0; i < triangles.length; i += 3) {
      var a = triangles[i] * dim;
      var b = triangles[i + 1] * dim;
      var c = triangles[i + 2] * dim;
      trianglesArea += Math.abs(
          (data[a] - data[c]) * (data[b + 1] - data[a + 1]) -
          (data[a] - data[b]) * (data[c + 1] - data[a + 1]));
  }

  return polygonArea === 0 && trianglesArea === 0 ? 0 :
      Math.abs((trianglesArea - polygonArea) / polygonArea);
};

function signedArea(data, start, end, dim) {
  var sum = 0;
  for (var i = start, j = end - dim; i < end; i += dim) {
      sum += (data[j] - data[i]) * (data[i + 1] + data[j + 1]);
      j = i;
  }
  return sum;
}

// turn a polygon in a multi-dimensional array form (e.g. as in GeoJSON) into a form Earcut accepts
earcut.flatten = function (data) {
  var dim = data[0][0].length,
      result = {vertices: [], holes: [], dimensions: dim},
      holeIndex = 0;

  for (var i = 0; i < data.length; i++) {
      for (var j = 0; j < data[i].length; j++) {
          for (var d = 0; d < dim; d++) result.vertices.push(data[i][j][d]);
      }
      if (i > 0) {
          holeIndex += data[i - 1].length;
          result.holes.push(holeIndex);
      }
  }
  return result;
};