wellknown/index.js

convert wkt to geojson

/*eslint-disable no-cond-assign */
module.exports = parse;
module.exports.parse = parse;
module.exports.stringify = stringify;

var numberRegexp = /[-+]?([0-9]*\.[0-9]+|[0-9]+)([eE][-+]?[0-9]+)?/;
// Matches sequences like '100 100' or '100 100 100'.
var tuples = new RegExp('^' + numberRegexp.source + '(\\s' + numberRegexp.source + '){1,}');

/*
 * Parse WKT and return GeoJSON.
 *
 * @param {string} _ A WKT geometry
 * @return {?Object} A GeoJSON geometry object
 */
function parse (input) {
  var parts = input.split(';');
  var _ = parts.pop();
  var srid = (parts.shift() || '').split('=').pop();

  var i = 0;

  function $ (re) {
    var match = _.substring(i).match(re);
    if (!match) return null;
    else {
      i += match[0].length;
      return match[0];
    }
  }

  function crs (obj) {
    if (obj && srid.match(/\d+/)) {
      obj.crs = {
        type: 'name',
        properties: {
          name: 'urn:ogc:def:crs:EPSG::' + srid
        }
      };
    }

    return obj;
  }

  function white () { $(/^\s*/); }

  function multicoords () {
    white();
    var depth = 0;
    var rings = [];
    var stack = [rings];
    var pointer = rings;
    var elem;

    while (elem =
           $(/^(\()/) ||
             $(/^(\))/) ||
               $(/^(,)/) ||
                 $(tuples)) {
      if (elem === '(') {
        stack.push(pointer);
        pointer = [];
        stack[stack.length - 1].push(pointer);
        depth++;
      } else if (elem === ')') {
        // For the case: Polygon(), ...
        if (pointer.length === 0) return null;

        pointer = stack.pop();
        // the stack was empty, input was malformed
        if (!pointer) return null;
        depth--;
        if (depth === 0) break;
      } else if (elem === ',') {
        pointer = [];
        stack[stack.length - 1].push(pointer);
      } else if (!elem.split(/\s/g).some(isNaN)) {
        Array.prototype.push.apply(pointer, elem.split(/\s/g).map(parseFloat));
      } else {
        return null;
      }
      white();
    }

    if (depth !== 0) return null;

    return rings;
  }

  function coords () {
    var list = [];
    var item;
    var pt;
    while (pt =
           $(tuples) ||
             $(/^(,)/)) {
      if (pt === ',') {
        list.push(item);
        item = [];
      } else if (!pt.split(/\s/g).some(isNaN)) {
        if (!item) item = [];
        Array.prototype.push.apply(item, pt.split(/\s/g).map(parseFloat));
      }
      white();
    }

    if (item) list.push(item);
    else return null;

    return list.length ? list : null;
  }

  function point () {
    if (!$(/^(point(\sz)?)/i)) return null;
    white();
    if (!$(/^(\()/)) return null;
    var c = coords();
    if (!c) return null;
    white();
    if (!$(/^(\))/)) return null;
    return {
      type: 'Point',
      coordinates: c[0]
    };
  }

  function multipoint () {
    if (!$(/^(multipoint)/i)) return null;
    white();
    var newCoordsFormat = _
      .substring(_.indexOf('(') + 1, _.length - 1)
      .replace(/\(/g, '')
      .replace(/\)/g, '');
    _ = 'MULTIPOINT (' + newCoordsFormat + ')';
    var c = multicoords();
    if (!c) return null;
    white();
    return {
      type: 'MultiPoint',
      coordinates: c
    };
  }

  function multilinestring () {
    if (!$(/^(multilinestring)/i)) return null;
    white();
    var c = multicoords();
    if (!c) return null;
    white();
    return {
      type: 'MultiLineString',
      coordinates: c
    };
  }

  function linestring () {
    if (!$(/^(linestring(\sz)?)/i)) return null;
    white();
    if (!$(/^(\()/)) return null;
    var c = coords();
    if (!c) return null;
    if (!$(/^(\))/)) return null;
    return {
      type: 'LineString',
      coordinates: c
    };
  }

  function polygon () {
    if (!$(/^(polygon(\sz)?)/i)) return null;
    white();
    var c = multicoords();
    if (!c) return null;
    return {
      type: 'Polygon',
      coordinates: c
    };
  }

  function multipolygon () {
    if (!$(/^(multipolygon)/i)) return null;
    white();
    var c = multicoords();
    if (!c) return null;
    return {
      type: 'MultiPolygon',
      coordinates: c
    };
  }

  function geometrycollection () {
    var geometries = [];
    var geometry;

    if (!$(/^(geometrycollection)/i)) return null;
    white();

    if (!$(/^(\()/)) return null;
    while (geometry = root()) {
      geometries.push(geometry);
      white();
      $(/^(,)/);
      white();
    }
    if (!$(/^(\))/)) return null;

    return {
      type: 'GeometryCollection',
      geometries: geometries
    };
  }

  function root () {
    return point() ||
      linestring() ||
      polygon() ||
      multipoint() ||
      multilinestring() ||
      multipolygon() ||
      geometrycollection();
  }

  return crs(root());
}

/**
 * Stringifies a GeoJSON object into WKT
 */
function stringify (gj) {
  if (gj.type === 'Feature') {
    gj = gj.geometry;
  }

  function pairWKT (c) {
    return c.join(' ');
  }

  function ringWKT (r) {
    return r.map(pairWKT).join(', ');
  }

  function ringsWKT (r) {
    return r.map(ringWKT).map(wrapParens).join(', ');
  }

  function multiRingsWKT (r) {
    return r.map(ringsWKT).map(wrapParens).join(', ');
  }

  function wrapParens (s) { return '(' + s + ')'; }

  switch (gj.type) {
    case 'Point':
      return 'POINT (' + pairWKT(gj.coordinates) + ')';
    case 'LineString':
      return 'LINESTRING (' + ringWKT(gj.coordinates) + ')';
    case 'Polygon':
      return 'POLYGON (' + ringsWKT(gj.coordinates) + ')';
    case 'MultiPoint':
      return 'MULTIPOINT (' + ringWKT(gj.coordinates) + ')';
    case 'MultiPolygon':
      return 'MULTIPOLYGON (' + multiRingsWKT(gj.coordinates) + ')';
    case 'MultiLineString':
      return 'MULTILINESTRING (' + ringsWKT(gj.coordinates) + ')';
    case 'GeometryCollection':
      return 'GEOMETRYCOLLECTION (' + gj.geometries.map(stringify).join(', ') + ')';
    default:
      throw new Error('stringify requires a valid GeoJSON Feature or geometry object as input');
  }
}