/**
 A loading storage keeping all of the related property, associated to single image request
 */
@interface SDWebImageLoadStorage

// Description is same as current property
@property (nonatomic, strong, readonly, nullable) NSURL *imageURL;
@property (nonatomic, strong, null_resettable) NSProgress *imageProgress;
@property (nonatomic, strong, nullable) SDWebImageTransition *imageTransition;
@property (nonatomic, strong, nullable) id<SDWebImageIndicator> imageIndicator;

@end


@interface UIView (WebCache)

/**
 Return the loading storage for specify operation key.
 */
- (nullable SDWebImageLoadStorage *)sd_imageLoadStorageForKey:(nullable NSString *)key;
/**
 Specify a desired loading storage for opeartion key.
 */
- (void)sd_setImageLoadStorage:(nullable SDWebImageLoadStorage *)storage forKey:(nullable NSString *)key;

@end

- (void)testUIButton {
    NSURL *url;
    NSURL *disabledUrl;
    
    // Normal
    SDWebImageLoadStorage *storage = [SDWebImageLoadStorage new];
    UIButton *button = [UIButton new];
    UIControlState state = UIControlStateNormal;
    NSString *key = [UIButton sd_imageOperationKeyForState:state];
    [button sd_setImageLoadStorage:storage forKey:key];
    
    [self.KVOController observe:storage.imageProgress keyPath:NSStringFromSelector(@selector(fractionCompleted)) options:NSKeyValueObservingOptionNew block:^(id  _Nullable observer, id  _Nonnull object, NSDictionary<NSString *,id> * _Nonnull change) {
        // ....
    }];
    [button sd_setImageWithURL:url forState:state];
    
    // Disabled
    state = UIControlStateDisabled;
    key = [UIButton sd_imageOperationKeyForState:state];
    SDWebImageLoadStorage *disabledStorage = [SDWebImageLoadStorage new];
    [button sd_setImageLoadStorage:disabledStorage forKey:key];
    
    [self.KVOController observe:disabledStorage.imageProgress keyPath:NSStringFromSelector(@selector(fractionCompleted)) options:NSKeyValueObservingOptionNew block:^(id  _Nullable observer, id  _Nonnull object, NSDictionary<NSString *,id> * _Nonnull change) {
        // ....
    }];
    [button sd_setImageWithURL:disabledUrl forState:state];
}

- (void)testUIImageView {
    NSURL *url;
    NSURL *highlightedUrl;
    
    // image
    UIImageView *imageView = [UIImageView new];
    SDWebImageLoadStorage *storage = [SDWebImageLoadStorage new];
    storage.imageTransition = SDWebImageTransition.fadeTransition;
    NSString *key = [UIImageView sd_imageOperationKey]; // actually is nil, or `NSStringFromClass`
    [imageView sd_setImageLoadStorage:storage forKey:key];
    [imageView sd_setImageWithURL:url];
    
    // highlighted image
    key = [UIImageView sd_highlightedImageOperationKey];
    SDWebImageLoadStorage *backgroundStorage = [SDWebImageLoadStorage new];
    backgroundStorage.imageTransition = SDWebImageTransition.flipFromTopTransition;
    [imageView sd_setHighlightedImageWithURL:highlightedUrl];
}

@interface UIButton (WebCache)
/**
 Get the image progress for a control state.
 */
- (nullable NSProgress *)sd_imageProgressForState:(UIControlState)state;
/**
 Get the background image progress for a control state.
 */
- (nullable NSProgress *)sd_backgroundImageProgressForState:(UIControlState)state;
@end

@implementation UIButton (WebCache)

- (NSProgress *)sd_imageProgressForState:(UIControlState)state {
    NSString *key = [UIButton sd_imageOperationKeyForState:state];
    SDWebImageLoadStorage *storage = [self sd_imageLoadStorageForKey:key];
    return storage.imageProgress;
}

- (NSProgress *)sd_backgroundImageProgressForState:(UIControlState)state {
    NSString *key = [UIButton sd_backgroundImageOperationKeyForState:state];
    SDWebImageLoadStorage *storage = [self sd_imageLoadStorageForKey:key];
    return storage.imageProgress;
}

@end