landxml/lib/converter.js

import xml2js from 'xml2js';

import { featureCollection } from '@turf/helpers';
import area from '@turf/area';
import proj4 from 'proj4';
import { Proj4Defs } from './projection';
import { getProp } from './util';

import { convertSurfaces } from './surface';
import { convertParcels } from './parcel';
import { convertPipeNetworks } from './pipe-network';
import { convertCGPoints } from './cg-point';

export const PROJECTION_AUTO_DETECT = 'auto_detect';
export const CONVERT_SURFACES = 'surfaces';
export const CONVERT_PARCELS = 'parcels';
export const CONVERT_PIPE_NETWORKS = 'pipe_networks';
export const CONVERT_CG_POINTS = 'cg_points';

const converters = {
  [CONVERT_PARCELS]: convertParcels,
  [CONVERT_SURFACES]: convertSurfaces,
  [CONVERT_PIPE_NETWORKS]: convertPipeNetworks,
  [CONVERT_CG_POINTS]: convertCGPoints,
}

// Based on alexgleith's preliminary work
// github.com/alexgleith/land-xml-to-geojson
export class Converter {

  defaultOptions = {
    projection: PROJECTION_AUTO_DETECT,
    enabledConverters: [ CONVERT_SURFACES, CONVERT_PARCELS, CONVERT_PIPE_NETWORKS, CONVERT_CG_POINTS ],
    parser: {
      normalize: true
    },
    proj4Defs: [
      [
        "EPSG:28355",
        "+proj=utm +zone=55 +south +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs",
      ],
      ...Proj4Defs,
    ],
    featureMapper: (feature, opts) => feature,
    colorOpts: {
      hue: 'blue',
      luminosity: 'dark',
      seed: 1,
    },
  }

  toGeoJSON(xml, opts = {}) {
    const parserOptions = Object.assign({}, this.defaultOptions.parser, opts.parser);
    const parser = new xml2js.Parser(parserOptions);

    this.configureProj4(opts.proj4Defs);

    return new Promise((resolve, reject) => {
      parser.parseString(xml, (err, xmlObj) => {
        if (err) return reject(err);

        let geojson;
        try {
          geojson = this.convertToGeoJSON(xmlObj, opts);
        } catch(err) {
          return reject(err);
        }

        return resolve(geojson);
      });
    });
  }

  convertToGeoJSON(xmlObj, opts = {}) {

    const options = Object.assign({}, this.defaultOptions, opts);

    // Use specified projection or try to find one in the LandXML file
    const projection = this.getLandXMLProjection(xmlObj, options.projection || this.defaultOptions.projection);
    if (!projection) throw new Error("Source projection can not be found !");

    // List enabled converters
    const enabledConverters = Array.isArray(opts.enabledConverters) ? 
      opts.enabledConverters : 
      this.defaultOptions.enabledConverters
    ;

    let features = [];

    // Convert LandXML entities to GeoJSON features
    enabledConverters.forEach(c => {
      if (!(c in converters)) return;
      console.log("Executing convert '%s'...", c);
      const newFeatures = converters[c](xmlObj, projection, options);
      features.push(...newFeatures);
    });

    // Apply features mapper function if defined
    if (typeof options.featureMapper === 'function') {
      features = features.map(f => {
        return options.featureMapper(f, options);
      });
    }

    // Sort feature by reverse area
    // to ease rendering
    features.sort((a, b) => {
      if (area(a) > area(b)) return -1;
      if (area(a) < area(b)) return 1;
      return 0;
    });

    // Return extracted features as a feature collection
    return featureCollection(features);

  }

  configureProj4(additionalProj4Defs) {
    const proj4Defs = this.defaultOptions.proj4Defs.slice(0)
    if (Array.isArray(additionalProj4Defs)) proj4Defs.push(...additionalProj4Defs);
    proj4.defs(proj4Defs);
  }

  getLandXMLProjection(xmlObj, manualProjection) {
    if (manualProjection !== PROJECTION_AUTO_DETECT) return manualProjection;
    let projection = null;
    if(!projection) projection = this.findUTMProjection(xmlObj);
    return projection;
  }

  findUTMProjection(xmlObj) {
    const projection = getProp(xmlObj, "LandXML", "CoordinateSystem", 0, "$", "datum");
    const zone = getProp(xmlObj, "LandXML", "CgPoints", 0, "$", "zoneNumber");
    let utmProjection = null
    if (projection && zone) {
      utmProjection = `+proj=utm +zone=${zone} +south +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs `;
    }
    return utmProjection;
  }

}