vizicities/src/layer/tile/MVTTile.js

import GeoJSONTile from './GeoJSONTile';
import extend from 'lodash.assign';

import Pbf from 'pbf';
import {VectorTile} from '@mapbox/vector-tile';

// TODO: Process raw MVT data rather than convert to GeoJSON
// TODO: Make it so full request and processing cycle occurs within a worker

class MVTTile extends GeoJSONTile {
  constructor(quadcode, path, layer, options) {
    var defaults = {
      mvt: true,
      fetch: true
    };

    options = extend({}, defaults, options);

    super(quadcode, path, layer, options);

    this._controller;
    this._signal;
  }

  _requestTile() {
    var urlParams = {
      x: this._tile[0],
      y: this._tile[1],
      z: this._tile[2]
    };

    var url = this._getTileURL(urlParams);

    if ('AbortController' in window) {
      // Abort any previous requests
      if (this._controller) {
        this._controller.abort();
      }

      // Create a fresh abort controller so old ones don't cause problems
      this._controller = new AbortController();
      this._signal = this._controller.signal;
    }

    this._aborted = false;

    fetch(url, {
      signal: this._signal
    }).then((response) => {
      return response.arrayBuffer();
    }).then((data) => {
      var buffer = new Pbf(data);
      var vt = new VectorTile(buffer);

      var fc = {type: 'FeatureCollection', features: []};

      var layers = [];

      if (this._options.layers) {
        layers = this._options.layers;
      }

      // Process defined layers (otherwise all)
      for (var key in vt.layers) {
        if (layers.length > 0) {
          if (!layers.includes(key)) {
            continue;
          }
        }

        var layer = vt.layers[key];
        for (var f = 0; f < layer.length; f++) {
          var feature = layer.feature(f);
          fc.features.push(feature.toGeoJSON(urlParams.x, urlParams.y, urlParams.z));
        }
      }

      this._processTileData(fc);

      // Clean up
      buffer = null;
      vt = null;
      layers = null;
      fc = null;
    }).catch((err) => {
      if (err.name === 'AbortError') {
        return;
      }

      console.error(err);
    });
  }
}

export default MVTTile;

var noNew = function(path, options) {
  return new MVTTile(path, options);
};

export {noNew as mvtTile};