/**
 * @module ol/source/TileArcGISRest
 */

import {createEmpty} from '../extent.js';
import {modulo} from '../math.js';
import {assign} from '../obj.js';
import {toSize, scale as scaleSize} from '../size.js';
import TileImage from './TileImage.js';
import {hash as tileCoordHash} from '../tilecoord.js';
import {appendParams} from '../uri.js';

/**
 * @typedef {Object} Options
 * @property {import("./Source.js").AttributionLike} [attributions] Attributions.
 * @property {number} [cacheSize] Tile cache size. The default depends on the screen size. Will increase if too small.
 * @property {null|string} [crossOrigin] The `crossOrigin` attribute for loaded images.  Note that
 * you must provide a `crossOrigin` value if you want to access pixel data with the Canvas renderer.
 * See https://developer.mozilla.org/en-US/docs/Web/HTML/CORS_enabled_image for more detail.
 * @property {Object<string,*>} [params] ArcGIS Rest parameters. This field is optional. Service defaults will be
 * used for any fields not specified. `FORMAT` is `PNG32` by default. `F` is `IMAGE` by
 * default. `TRANSPARENT` is `true` by default.  `BBOX`, `SIZE`, `BBOXSR`,
 * and `IMAGESR` will be set dynamically. Set `LAYERS` to
 * override the default service layer visibility. See
 * http://resources.arcgis.com/en/help/arcgis-rest-api/index.html#/Export_Map/02r3000000v7000000/
 * for further reference.
 * @property {import("../tilegrid/TileGrid.js").default} [tileGrid] Tile grid. Base this on the resolutions,
 * tilesize and extent supported by the server.
 * If this is not defined, a default grid will be used: if there is a projection
 * extent, the grid will be based on that; if not, a grid based on a global
 * extent with origin at 0,0 will be used.
 * @property {import("../proj.js").ProjectionLike} [projection] Projection. Default is the view projection.
 * @property {number} [reprojectionErrorThreshold=0.5] Maximum allowed reprojection error (in pixels).
 * Higher values can increase reprojection performance, but decrease precision.
 * @property {import("../Tile.js").LoadFunction} [tileLoadFunction] Optional function to load a tile given a URL.
 * The default is
 * ```js
 * function(imageTile, src) {
 *   imageTile.getImage().src = src;
 * };
 * ```
 * @property {string} [url] ArcGIS Rest service URL for a Map Service or Image Service. The
 * url should include /MapServer or /ImageServer.
 * @property {boolean} [wrapX=true] Whether to wrap the world horizontally.
 * @property {number} [transition] Duration of the opacity transition for rendering.  To disable the opacity
 * transition, pass `transition: 0`.
 * @property {Array<string>} [urls] ArcGIS Rest service urls. Use this instead of `url` when the ArcGIS
 * Service supports multiple urls for export requests.
 */


/**
 * @classdesc
 * Layer source for tile data from ArcGIS Rest services. Map and Image
 * Services are supported.
 *
 * For cached ArcGIS services, better performance is available using the
 * {@link module:ol/source/XYZ~XYZ} data source.
 * @api
 */
class TileArcGISRest extends TileImage {
  /**
   * @param {Options=} opt_options Tile ArcGIS Rest options.
   */
  constructor(opt_options) {

    const options = opt_options || /** @type {Options} */ ({});

    super({
      attributions: options.attributions,
      cacheSize: options.cacheSize,
      crossOrigin: options.crossOrigin,
      projection: options.projection,
      reprojectionErrorThreshold: options.reprojectionErrorThreshold,
      tileGrid: options.tileGrid,
      tileLoadFunction: options.tileLoadFunction,
      tileUrlFunction: tileUrlFunction,
      url: options.url,
      urls: options.urls,
      wrapX: options.wrapX !== undefined ? options.wrapX : true,
      transition: options.transition
    });

    /**
     * @private
     * @type {!Object}
     */
    this.params_ = options.params || {};

    /**
     * @private
     * @type {import("../extent.js").Extent}
     */
    this.tmpExtent_ = createEmpty();

    this.setKey(this.getKeyForParams_());
  }

  /**
   * @private
   * @return {string} The key for the current params.
   */
  getKeyForParams_() {
    let i = 0;
    const res = [];
    for (const key in this.params_) {
      res[i++] = key + '-' + this.params_[key];
    }
    return res.join('/');
  }

  /**
   * Get the user-provided params, i.e. those passed to the constructor through
   * the "params" option, and possibly updated using the updateParams method.
   * @return {Object} Params.
   * @api
   */
  getParams() {
    return this.params_;
  }

  /**
   * @param {import("../tilecoord.js").TileCoord} tileCoord Tile coordinate.
   * @param {import("../size.js").Size} tileSize Tile size.
   * @param {import("../extent.js").Extent} tileExtent Tile extent.
   * @param {number} pixelRatio Pixel ratio.
   * @param {import("../proj/Projection.js").default} projection Projection.
   * @param {Object} params Params.
   * @return {string|undefined} Request URL.
   * @private
   */
  getRequestUrl_(tileCoord, tileSize, tileExtent, pixelRatio, projection, params) {

    const urls = this.urls;
    if (!urls) {
      return undefined;
    }

    // ArcGIS Server only wants the numeric portion of the projection ID.
    const srid = projection.getCode().split(':').pop();

    params['SIZE'] = tileSize[0] + ',' + tileSize[1];
    params['BBOX'] = tileExtent.join(',');
    params['BBOXSR'] = srid;
    params['IMAGESR'] = srid;
    params['DPI'] = Math.round(
      params['DPI'] ? params['DPI'] * pixelRatio : 90 * pixelRatio
    );

    let url;
    if (urls.length == 1) {
      url = urls[0];
    } else {
      const index = modulo(tileCoordHash(tileCoord), urls.length);
      url = urls[index];
    }

    const modifiedUrl = url
      .replace(/MapServer\/?$/, 'MapServer/export')
      .replace(/ImageServer\/?$/, 'ImageServer/exportImage');
    return appendParams(modifiedUrl, params);
  }

  /**
   * @inheritDoc
   */
  getTilePixelRatio(pixelRatio) {
    return /** @type {number} */ (pixelRatio);
  }

  /**
   * Update the user-provided params.
   * @param {Object} params Params.
   * @api
   */
  updateParams(params) {
    assign(this.params_, params);
    this.setKey(this.getKeyForParams_());
  }
}

/**
 * @param {import("../tilecoord.js").TileCoord} tileCoord The tile coordinate
 * @param {number} pixelRatio The pixel ratio
 * @param {import("../proj/Projection.js").default} projection The projection
 * @return {string|undefined} The tile URL
 * @this {TileArcGISRest}
 */
function tileUrlFunction(tileCoord, pixelRatio, projection) {

  let tileGrid = this.getTileGrid();
  if (!tileGrid) {
    tileGrid = this.getTileGridForProjection(projection);
  }

  if (tileGrid.getResolutions().length <= tileCoord[0]) {
    return undefined;
  }

  const tileExtent = tileGrid.getTileCoordExtent(
    tileCoord, this.tmpExtent_);
  let tileSize = toSize(
    tileGrid.getTileSize(tileCoord[0]), this.tmpSize);

  if (pixelRatio != 1) {
    tileSize = scaleSize(tileSize, pixelRatio, this.tmpSize);
  }

  // Apply default params and override with user specified values.
  const baseParams = {
    'F': 'image',
    'FORMAT': 'PNG32',
    'TRANSPARENT': true
  };
  assign(baseParams, this.params_);

  return this.getRequestUrl_(tileCoord, tileSize, tileExtent,
    pixelRatio, projection, baseParams);
}


export default TileArcGISRest;