changeset-map/lib/getChangeset.js

import adiffParser from 'osm-adiff-parser-saxjs';
import jsonParser from 'real-changesets-parser';
import { query } from './query';
import { config } from './config';

export function getChangeset(changesetID, overpassBase = config.overpassBase) {
    return query(changesetID).then(changeset => {
        var url = config.S3_URL + changesetID + '.json';
        return fetch(url)
      .then(r => {
          if (r.ok) return r.json();
        // Fallback to overpass
          return Promise.reject();
      })
      .then(r => {
          var geojson = jsonParser(r);
          var featureMap = getFeatureMap(geojson);
          var ret = {
              geojson: geojson,
              featureMap: featureMap,
              changeset: changeset
          };
          return ret;
      })
      .catch(() => fetchFromOverPass(changesetID, changeset, overpassBase));
    });
}

function fetchFromOverPass(changesetID, changeset, overpassBase) {
    var data = getDataParam(changeset);
    var bbox = getBboxParam(changeset.bbox);
    var url = overpassBase + '?data=' + data + '&bbox=' + bbox;

    return fetch(url, {
        'Response-Type': 'application/osm3s+xml'
    })
    .then(r => r.text())
    .then(response => {
        return new Promise((res, rej) => {
            adiffParser(response, null, (err, json) => {
                if (err) {
                    return rej({
                        msg: 'Failed to parser adiff xml.',
                        error: err
                    });
                }
                var geojson = jsonParser({
                    elements: json[changesetID]
                });
                var featureMap = getFeatureMap(geojson);

                var ret = {
                    geojson: geojson,
                    featureMap: featureMap,
                    changeset: changeset
                };
                return res(ret);
            });
        });
    })
    .catch(err =>
      Promise.reject({
          msg: 'Overpass query failed.',
          error: err
      })
    );
}

function getDataParam(c) {
    return (
    '[out:xml][adiff:%22' +
    c.from.toString() +
    ',%22,%22' +
    c.to.toString() +
    '%22];(node(bbox)(changed);way(bbox)(changed);relation(bbox)(changed));out%20meta%20geom(bbox);'
    );
}

function getBboxParam(bbox) {
    return [bbox.left, bbox.bottom, bbox.right, bbox.top].join(',');
}

function getFeatureMap(geojson) {
    var features = geojson.features;
    var featureMap = {};

    for (var i = 0, len = features.length; i < len; i++) {
        var id = features[i].properties.id;
        featureMap[id] = featureMap[id] || [];
        featureMap[id].push(features[i]);
    }

    return featureMap;
}