/*
 File: JAHPAuthenticatingHTTPProtocol.h
 Abstract: An NSURLProtocol subclass that overrides the built-in HTTP/HTTPS protocol.
 Version: 1.1
 
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@import Foundation;

@protocol JAHPAuthenticatingHTTPProtocolDelegate;

/*! An NSURLProtocol subclass that overrides the built-in HTTP/HTTPS protocol to intercept
 *  authentication challenges for subsystems, ilke UIWebView, that don't otherwise allow it.
 *  To use this class you should set up your delegate (+setDelegate:) and then call +start.
 *  If you don't call +start the class is completely benign.
 *
 *  The really tricky stuff here is related to the authentication challenge delegate
 *  callbacks; see the docs for JAHPAuthenticatingHTTPProtocolDelegate for the details.
 */

@interface JAHPAuthenticatingHTTPProtocol : NSURLProtocol

/*! Call this to start the module.  Prior to this the module is just dormant, and
 *  all HTTP requests proceed as normal.  After this all HTTP and HTTPS requests
 *  go through this module.
 */

+ (void)start;

/*! 
 Unregisters the protocol
 */
+ (void)stop;

/*! Sets the delegate for the class.
 *  \details Note that there's one delegate for the entire class, not one per
 *  instance of the class as is more normal.  The delegate is not retained in general,
 *  but is retained for the duration of any given call.  Once you set the delegate to nil
 *  you can be assured that it won't be called unretained (that is, by the time that
 *  -setDelegate: returns, we've already done all possible retains on the delegate).
 *
 *  The delegate is weakly referenced, so there's no risk of a crash if you don't
 *  explicitly nil it.
 *  \param newValue The new delegate to use; may be nil.
 */

+ (void)setDelegate:(nullable id<JAHPAuthenticatingHTTPProtocolDelegate>)newValue;

/*! Returns the class delegate.
 */

+ (nullable id<JAHPAuthenticatingHTTPProtocolDelegate>)delegate;

/*! Sets the user agent token
 *  \details This token is appended to the system default user agent.
 */
+ (void)setUserAgentToken:(nullable NSString *)userAgentToken;

/*! Returns the user agent token.
 */
+ (nullable NSString *)userAgentToken;

+ (void)resetSharedDemux;

@property (atomic, strong, readonly)  NSURLAuthenticationChallenge * __nullable     pendingChallenge;   ///< The current authentication challenge; it's only safe to access this from the main thread.

/*! Call this method to resolve an authentication challeng.  This must be called on the main thread.
 *  \param challenge The challenge to resolve. This must match the pendingChallenge property.
 *  \param credential The credential to use, or nil to continue without a credential.
 */

- (void)resolvePendingAuthenticationChallengeWithCredential:(nonnull NSURLCredential *)credential;
- (void)cancelPendingAuthenticationChallenge;

@end

/*! The delegate for the JAHPAuthenticatingHTTPProtocol class (not its instances).
 *  \details The delegate handles two different types of callbacks:
 *
 *  - authentication challenges
 *
 *  - logging
 *
 *  The latter is very simple.  The former is quite tricky.  The basic idea is that each JAHPAuthenticatingHTTPProtocol
 *  instance sends the delegate a serialised stream of authentication challenges, each of which it is
 *  expected to resolve.  The sequence is as follows:
 *
 *  -# It calls -authenticatingHTTPProtocol:canAuthenticateAgainstProtectionSpace: to determine if the delegate
 *     can handle the challenge.  This can be call on an arbitrary background thread.
 *
 *  -# If the delegate returns YES, it calls -authenticatingHTTPProtocol:didReceiveAuthenticationChallenge: to
 *     actually process the challenge.  This is always called on the main thread.  The delegate can resolve
 *     the challenge synchronously (that is, before returning from the call) or it can return from the call
 *     and then, later on, resolve the challenge.  Resolving the challenge involves calling
 *     -[JAHPAuthenticatingHTTPProtocol resolveAuthenticationChallenge:withCredential:], which also must be called
 *     on the main thread.  Between the calls to -authenticatingHTTPProtocol:didReceiveAuthenticationChallenge:
 *     and -[JAHPAuthenticatingHTTPProtocol resolveAuthenticationChallenge:withCredential:], the protocol's
 *     pendingChallenge property will contain the challenge.
 *
 *  -# While there is a pending challenge, the protocol may call -authenticatingHTTPProtocol:didCancelAuthenticationChallenge:
 *     to cancel the challenge.  This is always called on the main thread.
 *
 *  Note that this design follows the original NSURLConnection model, not the newer NSURLConnection model
 *  (introduced in OS X 10.7 / iOS 5) or the NSURLSession model, because of my concerns about performance.
 *  Specifically, -authenticatingHTTPProtocol:canAuthenticateAgainstProtectionSpace: can be called on any thread
 *  but -authenticatingHTTPProtocol:didReceiveAuthenticationChallenge: is called on the main thread.  If I unified
 *  them I'd end up calling the resulting single routine on the main thread, which meanings a lot more
 *  bouncing between threads, much of which would be pointless in the common case where you don't want to
 *  customise the default behaviour.  Alternatively I could call the unified routine on an arbitrary thread,
 *  but that would make it harder for clients and require a major rework of my implementation.
 */

typedef void (^JAHPDidCancelAuthenticationChallengeHandler)(JAHPAuthenticatingHTTPProtocol * __nonnull authenticatingHTTPProtocol, NSURLAuthenticationChallenge * __nonnull challenge);

@protocol JAHPAuthenticatingHTTPProtocolDelegate <NSObject>

@optional

/*! Called by an JAHPAuthenticatingHTTPProtocol instance to ask the delegate whether it's prepared to handle
 *  a particular authentication challenge.  Can be called on any thread.
 *  \param protocol The protocol instance itself; will not be nil.
 *  \param protectionSpace The protection space for the authentication challenge; will not be nil.
 *  \returns Return YES if you want the -authenticatingHTTPProtocol:didReceiveAuthenticationChallenge: delegate
 *  callback, or NO for the challenge to be handled in the default way.
 */

- (BOOL)authenticatingHTTPProtocol:(nonnull JAHPAuthenticatingHTTPProtocol *)authenticatingHTTPProtocol canAuthenticateAgainstProtectionSpace:(nonnull NSURLProtectionSpace *)protectionSpace;

/*! Called by an JAHPAuthenticatingHTTPProtocol instance to request that the delegate process on authentication
 *  challenge. Will be called on the main thread. Unless the challenge is cancelled (see below)
 *  the delegate must eventually resolve it by calling -resolveAuthenticationChallenge:withCredential:.
 *  \param protocol The protocol instance itself; will not be nil.
 *  \param challenge The authentication challenge; will not be nil.
 *  \returns an optional JAHPDidCancelAuthenticationChallengeHandler that will be called when the
 *  JAHPAuthenticatingHTTPProtocol instance cancels the authentication challenge. Just like
 *  -authenticatingHTTPProtocol:didCancelAuthenticationChallenge:. If this is returned, there is usually no need 
 *  to implement -authenticatingHTTPProtocol:didCancelAuthenticationChallenge:. This block will be called before
 *  -authenticatingHTTPProtocol:didCancelAuthenticationChallenge:.
 */

- (nullable JAHPDidCancelAuthenticationChallengeHandler)authenticatingHTTPProtocol:(nonnull JAHPAuthenticatingHTTPProtocol *)authenticatingHTTPProtocol didReceiveAuthenticationChallenge:(nonnull NSURLAuthenticationChallenge *)challenge;

/*! Called by an JAHPAuthenticatingHTTPProtocol instance to cancel an issued authentication challenge.
 *  Will be called on the main thread.
 *  \param protocol The protocol instance itself; will not be nil.
 *  \param challenge The authentication challenge; will not be nil; will match the challenge
 *  previously issued by -authenticatingHTTPProtocol:canAuthenticateAgainstProtectionSpace:.
 */

- (void)authenticatingHTTPProtocol:(nonnull JAHPAuthenticatingHTTPProtocol *)authenticatingHTTPProtocol didCancelAuthenticationChallenge:(nonnull NSURLAuthenticationChallenge *)challenge;

/*! Called by the JAHPAuthenticatingHTTPProtocol to log various bits of information.
 *  Can be called on any thread.
 *  \param protocol The protocol instance itself; nil to indicate log messages from the class itself.
 *  \param format A standard NSString-style format string; will not be nil.
 *  \param arguments Arguments for that format string.
 */

- (void)authenticatingHTTPProtocol:(nullable JAHPAuthenticatingHTTPProtocol *)authenticatingHTTPProtocol logWithFormat:(nonnull NSString *)format
// clang's static analyzer doesn't know that a va_list can't have an nullability annotation.
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wnullability-completeness"
                         arguments:(va_list)arguments;
#pragma clang diagnostic pop

/*! Called by the JAHPAuthenticatingHTTPProtocol to log various bits of information. Use this if implementing in Swift. Swift doesn't like
 * -authenticatingHTTPProtocol:logWithFormat:arguments: because 
 * `Method cannot be marked @objc because the type of the parameter 3 cannot be represented in Objective-C`
 *  I assume this is a problem with Swift not understanding that CVAListPointer should become va_list.
 *  Can be called on any thread.
 *  \param protocol The protocol instance itself; nil to indicate log messages from the class itself.
 *  \param message A message to log
 */

- (void)authenticatingHTTPProtocol:(nullable JAHPAuthenticatingHTTPProtocol *)authenticatingHTTPProtocol logMessage:(nonnull NSString *)message;

@end
