text: // @flow
  
  import {extend, pick} from '../util/util.js';
  
  import {getImage, ResourceType} from '../util/ajax.js';
  import {Event, ErrorEvent, Evented} from '../util/evented.js';
  import loadTileJSON from './load_tilejson.js';
  import {postTurnstileEvent} from '../util/mapbox.js';
  import TileBounds from './tile_bounds.js';
  import Texture from '../render/texture.js';
  import browser from '../util/browser.js';
  
  import {cacheEntryPossiblyAdded} from '../util/tile_request_cache.js';
  
  import type {Source} from './source.js';
  import type {OverscaledTileID} from './tile_id.js';
  import type Map from '../ui/map.js';
  import type Dispatcher from '../util/dispatcher.js';
  import type Tile from './tile.js';
  import type {Callback} from '../types/callback.js';
  import type {Cancelable} from '../types/cancelable.js';
  import type {
      RasterSourceSpecification,
      RasterDEMSourceSpecification
  } from '../style-spec/types.js';
  
  class RasterTileSource extends Evented implements Source {
      type: 'raster' | 'raster-dem';
      id: string;
      minzoom: number;
      maxzoom: number;
      url: string;
      scheme: string;
      tileSize: number;
      zoomOffset: number;
  
      bounds: ?[number, number, number, number];
      tileBounds: TileBounds;
      roundZoom: boolean;
      dispatcher: Dispatcher;
      map: Map;
      tiles: Array<string>;
  
      _loaded: boolean;
      _options: RasterSourceSpecification | RasterDEMSourceSpecification;
      _tileJSONRequest: ?Cancelable;
  
      constructor(id: string, options: RasterSourceSpecification | RasterDEMSourceSpecification, dispatcher: Dispatcher, eventedParent: Evented) {
          super();
          this.id = id;
          this.dispatcher = dispatcher;
          this.setEventedParent(eventedParent);
  
          this.type = 'raster';
          this.minzoom = 0;
          this.maxzoom = 22;
          this.roundZoom = true;
          this.scheme = 'xyz';
          this.tileSize = 512;
          this.zoomOffset = 0;
          this._loaded = false;
  
          this._options = extend({type: 'raster'}, options);
          extend(this, pick(options, ['url', 'scheme', 'tileSize', 'zoomOffset']));
      }
  
      load() {
          this._loaded = false;
          this.fire(new Event('dataloading', {dataType: 'source'}));
          this._tileJSONRequest = loadTileJSON(this._options, this.map._requestManager, (err, tileJSON) => {
              this._tileJSONRequest = null;
              this._loaded = true;
              if (err) {
                  this.fire(new ErrorEvent(err));
              } else if (tileJSON) {
                  extend(this, tileJSON);
                  if (tileJSON.bounds) this.tileBounds = new TileBounds(tileJSON.bounds, this.minzoom, this.maxzoom);
  
                  postTurnstileEvent(tileJSON.tiles);
  
                  // `content` is included here to prevent a race condition where `Style#_updateSources` is called
                  // before the TileJSON arrives. this makes sure the tiles needed are loaded once TileJSON arrives
                  // ref: https://github.com/mapbox/mapbox-gl-js/pull/4347#discussion_r104418088
                  this.fire(new Event('data', {dataType: 'source', sourceDataType: 'metadata'}));
                  this.fire(new Event('data', {dataType: 'source', sourceDataType: 'content'}));
              }
          });
      }
  
      loaded(): boolean {
          return this._loaded;
      }
  
      onAdd(map: Map) {
          this.map = map;
          this.load();
      }
  
      onRemove() {
          if (this._tileJSONRequest) {
              this._tileJSONRequest.cancel();
              this._tileJSONRequest = null;
          }
      }
  
      serialize() {
          return extend({}, this._options);
      }
  
      hasTile(tileID: OverscaledTileID) {
          return !this.tileBounds || this.tileBounds.contains(tileID.canonical);
      }
  
      loadTile(tile: Tile, callback: Callback<void>) {
          const use2x = browser.devicePixelRatio >= 2;
          const url = this.map._requestManager.normalizeTileURL(tile.tileID.canonical.url(this.tiles, this.scheme, this.zoomOffset), use2x, this.tileSize);
          tile.request = getImage(this.map._requestManager.transformRequest(url, ResourceType.Tile), (err, img, cacheControl, expires) => {
              delete tile.request;
  
              if (tile.aborted) {
                  tile.state = 'unloaded';
                  callback(null);
              } else if (err) {
                  tile.state = 'errored';
                  callback(err);
              } else if (img) {
                  if (this.map._refreshExpiredTiles) tile.setExpiryData({cacheControl, expires});
  
                  const context = this.map.painter.context;
                  const gl = context.gl;
                  tile.texture = this.map.painter.getTileTexture(img.width);
                  if (tile.texture) {
                      tile.texture.update(img, {useMipmap: true});
                  } else {
                      tile.texture = new Texture(context, img, gl.RGBA, {useMipmap: true});
                      tile.texture.bind(gl.LINEAR, gl.CLAMP_TO_EDGE, gl.LINEAR_MIPMAP_NEAREST);
  
                      if (context.extTextureFilterAnisotropic) {
                          gl.texParameterf(gl.TEXTURE_2D, context.extTextureFilterAnisotropic.TEXTURE_MAX_ANISOTROPY_EXT, context.extTextureFilterAnisotropicMax);
                      }
                  }
  
                  tile.state = 'loaded';
  
                  cacheEntryPossiblyAdded(this.dispatcher);
  
                  callback(null);
              }
          });
      }
  
      abortTile(tile: Tile, callback: Callback<void>) {
          if (tile.request) {
              tile.request.cancel();
              delete tile.request;
          }
          callback();
      }
  
      unloadTile(tile: Tile, callback: Callback<void>) {
          if (tile.texture) this.map.painter.saveTileTexture(tile.texture);
          callback();
      }
  
      hasTransition() {
          return false;
      }
  }
  
  export default RasterTileSource;
  