TiledMapLayer.js

import L from 'leaflet';
import {warn, cleanUrl} from '../Util';
import mapService from '../Services/MapService';

export var TiledMapLayer = L.TileLayer.extend({
  options: {
    zoomOffsetAllowance: 0.1
  },

  statics: {
    MercatorZoomLevels: {
      '0': 156543.03392799999,
      '1': 78271.516963999893,
      '2': 39135.758482000099,
      '3': 19567.879240999901,
      '4': 9783.9396204999593,
      '5': 4891.9698102499797,
      '6': 2445.9849051249898,
      '7': 1222.9924525624899,
      '8': 611.49622628138002,
      '9': 305.74811314055802,
      '10': 152.874056570411,
      '11': 76.437028285073197,
      '12': 38.218514142536598,
      '13': 19.109257071268299,
      '14': 9.5546285356341496,
      '15': 4.7773142679493699,
      '16': 2.38865713397468,
      '17': 1.1943285668550501,
      '18': 0.59716428355981699,
      '19': 0.29858214164761698,
      '20': 0.14929107082381,
      '21': 0.07464553541191,
      '22': 0.0373227677059525,
      '23': 0.0186613838529763
    }
  },

  initialize: function (options) {
    options.url = cleanUrl(options.url);
    options = L.Util.setOptions(this, options);

    // set the urls
    this.tileUrl = options.url + 'tile/{z}/{y}/{x}';
    this.service = mapService(options);
    this.service.addEventParent(this);

    var arcgisonline = new RegExp(/tiles.arcgis(online)?\.com/g);
    if (arcgisonline.test(options.url)) {
      this.tileUrl = this.tileUrl.replace('://tiles', '://tiles{s}');
      options.subdomains = ['1', '2', '3', '4'];
    }

    if (this.options.token) {
      this.tileUrl += ('?token=' + this.options.token);
    }

    // init layer by calling TileLayers initialize method
    L.TileLayer.prototype.initialize.call(this, this.tileUrl, options);
  },

  getTileUrl: function (tilePoint) {
    return L.Util.template(this.tileUrl, L.extend({
      s: this._getSubdomain(tilePoint),
      z: (this._lodMap && this._lodMap[tilePoint.z]) ? this._lodMap[tilePoint.z] : tilePoint.z, // try lod map first, then just defualt to zoom level
      x: tilePoint.x,
      y: tilePoint.y
    }, this.options));
  },

  createTile:  function (coords, done){
    var tile = document.createElement('img');

    L.DomEvent.on(tile, 'load', L.bind(this._tileOnLoad, this, done, tile));
    L.DomEvent.on(tile, 'error', L.bind(this._tileOnError, this, done, tile));

    if (this.options.crossOrigin) {
      tile.crossOrigin = '';
    }

    /*
     Alt tag is set to empty string to keep screen readers from reading URL and for compliance reasons
     http://www.w3.org/TR/WCAG20-TECHS/H67
    */
    tile.alt = '';

    // if there is no lod map or an lod map with a proper zoom load the tile
    // otherwise wait for the lod map to become available
    if(!this._lodMap || (this._lodMap && this._lodMap[coords.z])) {
      tile.src = this.getTileUrl(coords);
    } else {
      this.once('lodmap', function () {
        tile.src = this.getTileUrl(coords);
      }, this);
    }

    return tile;
  },

  onAdd: function (map) {
    if (map.options.crs === L.CRS.EPSG3857 && !this._lodMap) {
      this._lodMap = {};
      this.metadata(function (error, metadata) {
        if (!error) {
          var sr = metadata.spatialReference.latestWkid || metadata.spatialReference.wkid;
          if (sr === 102100 || sr === 3857) {
            // create the zoom level data
            var arcgisLODs = metadata.tileInfo.lods;
            var correctResolutions = TiledMapLayer.MercatorZoomLevels;

            for (var i = 0; i < arcgisLODs.length; i++) {
              var arcgisLOD = arcgisLODs[i];
              for (var ci in correctResolutions) {
                var correctRes = correctResolutions[ci];

                if (this._withinPercentage(arcgisLOD.resolution, correctRes, this.options.zoomOffsetAllowance)) {
                  this._lodMap[ci] = arcgisLOD.level;
                  break;
                }
              }
            }

            this.fire('lodmap');
          } else {
            warn('L.esri.TiledMapLayer is using a non-mercator spatial reference. Support may be available through Proj4Leaflet http://esri.github.io/esri-leaflet/examples/non-mercator-projection.html');
          }
        }
      }, this);
    }

    L.TileLayer.prototype.onAdd.call(this, map);
  },

  metadata: function (callback, context) {
    this.service.metadata(callback, context);
    return this;
  },

  identify: function () {
    return this.service.identify();
  },

  find: function () {
    return this.service.find();
  },

  query: function () {
    return this.service.query();
  },

  authenticate: function (token) {
    var tokenQs = '?token=' + token;
    this.tileUrl = (this.options.token) ? this.tileUrl.replace(/\?token=(.+)/g, tokenQs) : this.tileUrl + tokenQs;
    this.options.token = token;
    this.service.authenticate(token);
    return this;
  },

  _withinPercentage: function (a, b, percentage) {
    var diff = Math.abs((a / b) - 1);
    return diff < percentage;
  }
});

export function tiledMapLayer (url, options) {
  return new TiledMapLayer(url, options);
}

export default tiledMapLayer;