/* Copyright (c) 2014-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 */

#import <CoreGraphics/CoreGraphics.h>
#import <Foundation/Foundation.h>

@protocol ASImageCacheProtocol <NSObject>

@required
/**
  @abstract Attempts to fetch an image with the given URL from the cache.
  @param URL The URL of the image to retrieve from the cache.
  @param callbackQueue The queue to call `completion` on. If this value is nil, @{ref completion} will be invoked on the main-queue.
  @param completion The block to be called when the cache has either hit or missed.
  @param imageFromCache The image that was retrieved from the cache, if the image could be retrieved; nil otherwise.
  @discussion If `URL` is nil, `completion` will be invoked immediately with a nil image.
 */
- (void)fetchCachedImageWithURL:(NSURL *)URL
                  callbackQueue:(dispatch_queue_t)callbackQueue
                     completion:(void (^)(CGImageRef imageFromCache))completion;

@end

@protocol ASImageDownloaderProtocol <NSObject>

@required
/**
  @abstract Downloads an image with the given URL.
  @param URL The URL of the image to download.
  @param callbackQueue The queue to call `downloadProgressBlock` and `completion` on. If this value is nil, both blocks will be invoked on the main-queue.
  @param downloadProgressBlock The block to be invoked when the download of `URL` progresses.
  @param progress The progress of the download, in the range of (0.0, 1.0), inclusive.
  @param completion The block to be invoked when the download has completed, or has failed.
  @param image The image that was downloaded, if the image could be successfully downloaded; nil otherwise.
  @param error An error describing why the download of `URL` failed, if the download failed; nil otherwise.
  @discussion If `URL` is nil, `completion` will be invoked immediately with a nil image and an error describing why the download failed.
  @result An opaque identifier to be used in canceling the download, via `cancelImageDownloadForIdentifier:`. You must retain the identifier if you wish to use it later.
 */
- (id)downloadImageWithURL:(NSURL *)URL
             callbackQueue:(dispatch_queue_t)callbackQueue
     downloadProgressBlock:(void (^)(CGFloat progress))downloadProgressBlock
                completion:(void (^)(CGImageRef image, NSError *error))completion;

/**
  @abstract Cancels an image download.
  @param downloadIdentifier The opaque download identifier object returned from `downloadImageWithURL:callbackQueue:downloadProgressBlock:completion:`.
  @discussion This method has no effect if `downloadIdentifier` is nil.
 */
- (void)cancelImageDownloadForIdentifier:(id)downloadIdentifier;

@end