turf/packages/turf-boolean-valid/index.ts

import { Feature, Geometry, Position } from "geojson";
import { getGeom } from "@turf/invariant";
import { polygon, lineString } from "@turf/helpers";
import { booleanDisjoint } from "@turf/boolean-disjoint";
import { booleanCrosses } from "@turf/boolean-crosses";
import { lineIntersect } from "@turf/line-intersect";
import { booleanPointOnLine as isPointOnLine } from "@turf/boolean-point-on-line";

/**
 * booleanValid checks if the geometry is a valid according to the OGC Simple Feature Specification.
 *
 * @function
 * @param {Geometry|Feature<any>} feature GeoJSON Feature or Geometry
 * @returns {boolean} true/false
 * @example
 * var line = turf.lineString([[1, 1], [1, 2], [1, 3], [1, 4]]);
 *
 * turf.booleanValid(line); // => true
 * turf.booleanValid({foo: "bar"}); // => false
 */
function booleanValid(feature: Feature<any> | Geometry) {
  // Automatic False
  if (!feature.type) return false;

  // Parse GeoJSON
  const geom = getGeom(feature);
  const type = geom.type;
  const coords = geom.coordinates;

  switch (type) {
    case "Point":
      return coords.length > 1;
    case "MultiPoint":
      for (var i = 0; i < coords.length; i++) {
        if (coords[i].length < 2) return false;
      }
      return true;
    case "LineString":
      if (coords.length < 2) return false;
      for (var i = 0; i < coords.length; i++) {
        if (coords[i].length < 2) return false;
      }
      return true;
    case "MultiLineString":
      if (coords.length < 2) return false;
      for (var i = 0; i < coords.length; i++) {
        if (coords[i].length < 2) return false;
      }
      return true;
    case "Polygon":
      for (var i = 0; i < geom.coordinates.length; i++) {
        if (coords[i].length < 4) return false;
        if (!checkRingsClose(coords[i])) return false;
        if (checkRingsForSpikesPunctures(coords[i])) return false;
        if (i > 0) {
          if (
            lineIntersect(polygon([coords[0]]), polygon([coords[i]])).features
              .length > 1
          )
            return false;
        }
      }
      return true;
    case "MultiPolygon":
      for (var i = 0; i < geom.coordinates.length; i++) {
        var poly: any = geom.coordinates[i];

        for (var ii = 0; ii < poly.length; ii++) {
          if (poly[ii].length < 4) return false;
          if (!checkRingsClose(poly[ii])) return false;
          if (checkRingsForSpikesPunctures(poly[ii])) return false;
          if (ii === 0) {
            if (!checkPolygonAgainstOthers(poly, geom.coordinates, i))
              return false;
          }
          if (ii > 0) {
            if (
              lineIntersect(polygon([poly[0]]), polygon([poly[ii]])).features
                .length > 1
            )
              return false;
          }
        }
      }
      return true;
    default:
      return false;
  }
}

function checkRingsClose(geom: Position[]) {
  return (
    geom[0][0] === geom[geom.length - 1][0] &&
    geom[0][1] === geom[geom.length - 1][1]
  );
}

function checkRingsForSpikesPunctures(geom: Position[]) {
  for (var i = 0; i < geom.length - 1; i++) {
    var point = geom[i];
    for (var ii = i + 1; ii < geom.length - 2; ii++) {
      var seg = [geom[ii], geom[ii + 1]];
      if (isPointOnLine(point, lineString(seg))) return true;
    }
  }
  return false;
}

function checkPolygonAgainstOthers(
  poly: Position[][],
  geom: Position[][][],
  index: number
) {
  var polyToCheck = polygon(poly);
  for (var i = index + 1; i < geom.length; i++) {
    if (!booleanDisjoint(polyToCheck, polygon(geom[i]))) {
      if (booleanCrosses(polyToCheck, lineString(geom[i][0]))) return false;
    }
  }
  return true;
}

export { booleanValid };
export default booleanValid;