DCTAuthPlatform.h

@import Foundation;

typedef void(^DCTAuthPlatformCompletion)(BOOL success);
typedef void(^DCTAuthPlatformURLOpener)(NSURL *URL, DCTAuthPlatformCompletion completion);

typedef void(^DCTAuthPlatformExpirationHandler)();
typedef id(^DCTAuthPlatformBeginBackgroundTaskBlock)(DCTAuthPlatformExpirationHandler expirationHandler);
typedef void(^DCTAuthPlatformEndBackgroundTaskBlock)(id identifier);

@interface DCTAuthPlatform : NSObject

+ (instancetype)sharedPlatform;

@property (nonatomic, copy) DCTAuthPlatformURLOpener URLOpener;
@property (nonatomic, copy) DCTAuthPlatformBeginBackgroundTaskBlock beginBackgroundTaskHandler;
@property (nonatomic, copy) DCTAuthPlatformEndBackgroundTaskBlock endBackgroundTaskHandler;

- (void)openURL:(NSURL *)URL completion:(DCTAuthPlatformCompletion)completion;

- (id)beginBackgroundTaskWithExpirationHandler:(DCTAuthPlatformExpirationHandler)handler;

- (void)endBackgroundTask:(id)identifier;

@end

DCTAuthPlatform.m

@implementation DCTAuthPlatform

+ (instancetype)sharedPlatform {
	static DCTAuthPlatform *platform;
	static dispatch_once_t onceToken;
	dispatch_once(&onceToken, ^{
		platform = [self new];
	});
	return platform;
}

- (void)openURL:(NSURL *)URL completion:(DCTAuthPlatformCompletion)completion {

	if (!completion) {
		completion = ^(BOOL success) {};
	}

	if (!self.URLOpener) {
		completion(NO);
		return;
	}

	self.URLOpener(URL, completion);
}

- (id)beginBackgroundTaskWithExpirationHandler:(DCTAuthPlatformExpirationHandler)handler {

	if (!self.beginBackgroundTaskHandler) {
		return nil;
	}

	return self.beginBackgroundTaskHandler(handler);
}

- (void)endBackgroundTask:(id)identifier {

	if (!self.endBackgroundTaskHandler) {
		return;
	}

	self.endBackgroundTaskHandler(identifier);
}

@end