/**
 * Copyright (c) Nicolas Gallagher.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * @flow
 */
const dataUriPattern = /^data:/;
declare export class ImageUriCache {
  static _maximumEntries: number,
  static _entries: any,
  static has(uri: string): boolean,
  static add(uri: string): any,
  static remove(uri: string): any,
  static _cleanUpIfNeeded(): any,
}
let id = 0;
const requests = {};
const ImageLoader = {
  abort(requestId: number) {
    let image = requests[`${requestId}`];

    if (image) {
      image.onerror = null;
      image.onload = null;
      image = null;
      delete requests[`${requestId}`];
    }
  },

  getSize(uri: string, success: (width: number, height: number) => void, failure: () => void) {
    let complete = false;
    const interval = setInterval(callback, 16);
    const requestId = ImageLoader.load(uri, callback, errorCallback);
    declare function callback(): any;
    declare function errorCallback(): any;
  },

  has(uri: string): boolean {
    return ImageUriCache.has(uri);
  },

  load(uri: string, onLoad: Function, onError: Function): number {
    id += 1;
    const image = new window.Image();
    image.onerror = onError;

    image.onload = e => {
      // avoid blocking the main thread
      declare var onDecode: () => any;

      if (typeof image.decode === 'function') {
        // Safari currently throws exceptions when decoding svgs.
        // We want to catch that error and allow the load handler
        // to be forwarded to the onLoad handler in this case
        image.decode().then(onDecode, onDecode);
      } else {
        setTimeout(onDecode, 0);
      }
    };

    image.src = uri;
    requests[`${id}`] = image;
    return id;
  },

  prefetch(uri: string): Promise<void> {
    return new Promise((resolve, reject) => {
      ImageLoader.load(uri, () => {
        // Add the uri to the cache so it can be immediately displayed when used
        // but also immediately remove it to correctly reflect that it has no active references
        ImageUriCache.add(uri);
        ImageUriCache.remove(uri);
        resolve();
      }, reject);
    });
  },

  queryCache(uris: Array<string>): Promise<{|
    [uri: string]: 'disk/memory'
  |}> {
    const result = {};
    uris.forEach(u => {
      if (ImageUriCache.has(u)) {
        result[u] = 'disk/memory';
      }
    });
    return Promise.resolve(result);
  }

};
export default ImageLoader;