@interface GHImageLoader : NSObject {}

+ (void)loadImageAtURL:(NSURL *)imageURL completionBlock:(void (^)(NSImage *image))block;

@end




#import "GHImageLoader.h"

static NSUInteger kMaxCuncurrentOperations = 4;

@interface GHImageLoader ()
@property (nonatomic, retain) NSOperationQueue *operationQueue;
+ (GHImageLoader *)imageLoader;
- (void)loadImageAtURL:(NSURL *)imageURL completionBlock:(void (^)(NSImage *image))block;
@end


@implementation GHImageLoader

@synthesize operationQueue;

- (void)dealloc {

	self.operationQueue = nil;
	[super dealloc];
}

+ (GHImageLoader *)imageLoader {

	static GHImageLoader *imageLoaderSingleton = nil;
	return imageLoaderSingleton ? : (imageLoaderSingleton = [[GHImageLoader alloc] init]);
}

- (id)init {

	self = [super init];
	if (self) {
		self.operationQueue = [[[NSOperationQueue alloc] init] autorelease];
		[self.operationQueue setMaxConcurrentOperationCount:kMaxCuncurrentOperations];
	}

	return self;
}

+ (void)loadImageAtURL:(NSURL *)imageURL completionBlock:(void (^)(NSImage *image))block {

	[[self imageLoader] loadImageAtURL:imageURL completionBlock:block];
}

- (void)loadImageAtURL:(NSURL *)imageURL completionBlock:(void (^)(NSImage *image))block {

	[self.operationQueue addOperationWithBlock:^{
		NSImage *imageLoaded = [[[NSImage alloc] initWithContentsOfURL:imageURL] autorelease];
		dispatch_async(dispatch_get_main_queue(), ^{
				block(imageLoaded);
		});
	}];
}

@end