OIDExternalUserAgentIOSSafariViewController.h

// Original source from AppAuth: https://gist.github.com/WilliamDenniss/18f3779b4a310361bb955cf4e534f29c
// NOTE: If you use this for LOGIN, you probably want to use it for LOGOUT, too.

#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>
#import <SafariServices/SafariServices.h>

#import "OIDExternalUserAgent.h"

NS_ASSUME_NONNULL_BEGIN

/*! @brief Allows library consumers to bootstrap an @c SFSafariViewController as they see fit.
    @remarks Useful for customizing tint colors and presentation styles.
 */
@protocol OIDSafariViewControllerFactoryExternal

/*! @brief Creates and returns a new @c SFSafariViewController.
    @param URL The URL which the @c SFSafariViewController should load initially.
 */
- (SFSafariViewController *)safariViewControllerWithURL:(NSURL *)URL;

@end

/*! @brief A special-case iOS external user-agent that always uses \SFSafariViewController. Most applications should use the more generic @c OIDExternalUserAgentIOS to get the default AppAuth user-agent handling with the benefits of Single Sign-on (SSO) for all supported versions of iOS.
 */
@interface OIDExternalUserAgentIOSSafariViewController : NSObject<OIDExternalUserAgent>

/*! @brief Allows library consumers to change the @c OIDSafariViewControllerFactory used to create new instances of @c SFSafariViewController.
    @remarks Useful for customizing tint colors and presentation styles.
    @param factory The @c OIDSafariViewControllerFactory to use for creating new instances of @c SFSafariViewController.
 */
+ (void)setSafariViewControllerFactory:(id<OIDSafariViewControllerFactoryExternal>)factory;

/*! @internal
    @brief Unavailable. Please use @c initWithPresentingViewController:
 */
- (nonnull instancetype)init NS_UNAVAILABLE;

/*! @brief The designated initializer.
    @param presentingViewController The view controller from which to present the \SFSafariViewController.
 */
- (nullable instancetype)initWithPresentingViewController:(UIViewController *)presentingViewController NS_DESIGNATED_INITIALIZER;

@end

NS_ASSUME_NONNULL_END

OIDExternalUserAgentIOSSafariViewController.m

// Original source from AppAuth: https://gist.github.com/WilliamDenniss/18f3779b4a310361bb955cf4e534f29c
// NOTE: If you use this for LOGIN, you probably want to use it for LOGOUT, too.

#import "OIDExternalUserAgentIOSSafariViewController.h"

#import "OIDErrorUtilities.h"
#import "OIDExternalUserAgentSession.h"
#import "OIDExternalUserAgentRequest.h"

NS_ASSUME_NONNULL_BEGIN

/** @brief The global/shared Safari view controller factory. Responsible for creating all new instances of @c SFSafariViewController.
 */
static id<OIDSafariViewControllerFactoryExternal> __nullable gSafariViewControllerFactoryExternal;

/** @brief The default @c OIDSafariViewControllerFactory which creates new instances of  @c SFSafariViewController using known best practices.
 */
@interface MSKDefaultSafariViewControllerFactory : NSObject<OIDSafariViewControllerFactoryExternal>
@end

@interface OIDExternalUserAgentIOSSafariViewController() <SFSafariViewControllerDelegate>
@end

@implementation OIDExternalUserAgentIOSSafariViewController {
    UIViewController *_presentingViewController;

    BOOL _externalUserAgentFlowInProgress;
    __weak id<OIDExternalUserAgentSession> _session;
    __weak SFSafariViewController *_safariVC;
}

/** @brief Obtains the current @c OIDSafariViewControllerFactory; creating a new default instance if required.
 */
+ (id<OIDSafariViewControllerFactoryExternal>)safariViewControllerFactory {
    if (!gSafariViewControllerFactoryExternal) {
        gSafariViewControllerFactoryExternal = [[MSKDefaultSafariViewControllerFactory alloc] init];
    }

    return gSafariViewControllerFactoryExternal;
}

+ (void)setSafariViewControllerFactory:(id<OIDSafariViewControllerFactoryExternal>)factory {
     NSAssert(factory, @"Parameter: |factory| must be non-nil.");
     gSafariViewControllerFactoryExternal = factory;
}

- (nullable instancetype)initWithPresentingViewController: (UIViewController *)presentingViewController {
    self = [super init];
    if (self) {
        _presentingViewController = presentingViewController;
    }
    return self;
}

- (BOOL)presentExternalUserAgentRequest:(id<OIDExternalUserAgentRequest>)request
                                session:(id<OIDExternalUserAgentSession>)session {
    if (_externalUserAgentFlowInProgress) {
        // TODO: Handle errors as authorization is already in progress.
        return NO;
    }

    _externalUserAgentFlowInProgress = YES;
    _session = session;
    BOOL openedSafari = NO;
    NSURL *requestURL = [request externalUserAgentRequestURL];

    SFSafariViewController *safariVC = [[[self class] safariViewControllerFactory] safariViewControllerWithURL:requestURL];
    safariVC.delegate = self;
    _safariVC = safariVC;
    [_presentingViewController presentViewController:safariVC animated:YES completion:nil];
    openedSafari = YES;

    if (!openedSafari) {
        [self cleanUp];
        NSError *safariError = [OIDErrorUtilities errorWithCode:OIDErrorCodeSafariOpenError
                                                underlyingError:nil
                                                    description:@"Unable to open Safari."];
        [session failExternalUserAgentFlowWithError:safariError];
    }
    
    return openedSafari;
}

- (void)dismissExternalUserAgentAnimated:(BOOL)animated completion:(void (^)(void))completion {
    if (!_externalUserAgentFlowInProgress) {
        // Ignore this call if there is no authorization flow in progress.
        return;
    }
  
    SFSafariViewController *safariVC = _safariVC;
  
    [self cleanUp];
  
    if (safariVC) {
        [safariVC dismissViewControllerAnimated:YES completion:completion];
    } else {
        if (completion) completion();
    }
}

- (void)cleanUp {
    // The weak references to |_safariVC| and |_session| are set to nil to avoid accidentally using them while not in an authorization flow.
    _safariVC = nil;
    _session = nil;
    _externalUserAgentFlowInProgress = NO;
}

#pragma mark - SFSafariViewControllerDelegate

- (void)safariViewControllerDidFinish:(SFSafariViewController *)controller {
    if (controller != _safariVC) {
        // Ignore this call if the safari view controller do not match.
        return;
    }
    if (!_externalUserAgentFlowInProgress) {
        // Ignore this call if there is no authorization flow in progress.
        return;
    }
    
    id<OIDExternalUserAgentSession> session = _session;
    [self cleanUp];
    NSError *error = [OIDErrorUtilities errorWithCode:OIDErrorCodeProgramCanceledAuthorizationFlow
                                      underlyingError:nil
                                          description:nil];
    
    [session failExternalUserAgentFlowWithError:error];
}

@end

@implementation MSKDefaultSafariViewControllerFactory

- (SFSafariViewController *)safariViewControllerWithURL:(NSURL *)URL {
    SFSafariViewController *safariViewController = [[SFSafariViewController alloc] initWithURL:URL
                                                                       entersReaderIfAvailable:NO];
    return safariViewController;
}

@end

NS_ASSUME_NONNULL_END