Chapter 11 - Chat App/ChatAppFinished/Pods/FirebaseAuth/Firebase/Auth/Source/AuthProvider/OAuth/FIROAuthProvider.m
/*
 * Copyright 2017 Google
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <CommonCrypto/CommonCrypto.h>
#import "FIROAuthProvider.h"

#import <FirebaseCore/FIRApp.h>
#import <FirebaseCore/FIROptions.h>

#import "FIRAuthBackend.h"
#import "FIRAuth_Internal.h"
#import "FIRAuthErrorUtils.h"
#import "FIRAuthGlobalWorkQueue.h"
#import "FIRAuthRequestConfiguration.h"
#import "FIRAuthWebUtils.h"
#import "FIROAuthCredential_Internal.h"
#import "FIROAuthCredential.h"

#if TARGET_OS_IOS
#import "FIRAuthURLPresenter.h"
#endif

NS_ASSUME_NONNULL_BEGIN

/** @typedef FIRHeadfulLiteURLCallBack
    @brief The callback invoked at the end of the flow to fetch a headful-lite URL.
    @param headfulLiteURL The headful lite URL.
    @param error The error that occurred while fetching the headful-lite, if any.
 */
typedef void (^FIRHeadfulLiteURLCallBack)(NSURL *_Nullable headfulLiteURL,
               NSError *_Nullable error);

/** @var kHeadfulLiteURLStringFormat
    @brief The format of the URL used to open the headful lite page during sign-in.
 */
NSString *const kHeadfulLiteURLStringFormat = @"https://%@/__/auth/handler?%@";

/** @var kauthTypeSignInWithRedirect
    @brief The auth type to be specified in the sign-in request with redirect request and response.
 */
static NSString *const kAuthTypeSignInWithRedirect = @"signInWithRedirect";

@implementation FIROAuthProvider {
  /** @var _auth
      @brief The auth instance used for launching the URL presenter.
   */
  FIRAuth *_auth;

  /** @var _callbackScheme
      @brief The callback URL scheme used for headful-lite sign-in.
   */
  NSString *_callbackScheme;
}

+ (FIROAuthCredential *)credentialWithProviderID:(NSString *)providerID
                                        IDToken:(NSString *)IDToken
                                    accessToken:(nullable NSString *)accessToken {
  return [[FIROAuthCredential alloc] initWithProviderID:providerID
                                                IDToken:IDToken
                                            accessToken:accessToken
                                                 secret:nil
                                           pendingToken:nil];
}

+ (FIROAuthCredential *)credentialWithProviderID:(NSString *)providerID
                                     accessToken:(NSString *)accessToken {
  return [[FIROAuthCredential alloc] initWithProviderID:providerID
                                                IDToken:nil
                                            accessToken:accessToken
                                                 secret:nil
                                           pendingToken:nil];
}

+ (instancetype)providerWithProviderID:(NSString *)providerID {
  return [[self alloc]initWithProviderID:providerID auth:[FIRAuth auth]];
}

+ (instancetype)providerWithProviderID:(NSString *)providerID auth:(FIRAuth *)auth {
  return [[self alloc] initWithProviderID:providerID auth:auth];
}

#if TARGET_OS_IOS
- (void)getCredentialWithUIDelegate:(nullable id<FIRAuthUIDelegate>)UIDelegate
                         completion:(nullable FIRAuthCredentialCallback)completion {
  if (![FIRAuthWebUtils isCallbackSchemeRegisteredForCustomURLScheme:self->_callbackScheme]) {
    [NSException raise:NSInternalInconsistencyException
                format:@"Please register custom URL scheme '%@' in the app's Info.plist file.",
                       self->_callbackScheme];
  }
  __weak __typeof__(self) weakSelf = self;
  __weak FIRAuth *weakAuth = _auth;
  __weak NSString *weakProviderID = _providerID;
  dispatch_async(FIRAuthGlobalWorkQueue(), ^{
    FIRAuthCredentialCallback callbackOnMainThread = ^(FIRAuthCredential *_Nullable credential,
                                                       NSError *_Nullable error) {
      if (completion) {
        dispatch_async(dispatch_get_main_queue(), ^{
          completion(credential, error);
        });
      }
    };
    NSString *eventID = [FIRAuthWebUtils randomStringWithLength:10];
    NSString *sessionID = [FIRAuthWebUtils randomStringWithLength:10];
    __strong __typeof__(self) strongSelf = weakSelf;
    [strongSelf getHeadFulLiteURLWithEventID:eventID
                             sessionID:sessionID
                            completion:^(NSURL *_Nullable headfulLiteURL,
                                         NSError *_Nullable error) {
      if (error) {
        callbackOnMainThread(nil, error);
        return;
      }
      FIRAuthURLCallbackMatcher callbackMatcher = ^BOOL(NSURL *_Nullable callbackURL) {
        return [FIRAuthWebUtils isExpectedCallbackURL:callbackURL
                                              eventID:eventID
                                             authType:kAuthTypeSignInWithRedirect
                                       callbackScheme:strongSelf->_callbackScheme];
      };
      __strong FIRAuth *strongAuth = weakAuth;
      [strongAuth.authURLPresenter presentURL:headfulLiteURL
                                   UIDelegate:UIDelegate
                              callbackMatcher:callbackMatcher
                                   completion:^(NSURL *_Nullable callbackURL,
                                                NSError *_Nullable error) {
        if (error) {
          callbackOnMainThread(nil, error);
          return;
        }
        NSString *OAuthResponseURLString =
            [strongSelf OAuthResponseForURL:callbackURL error:&error];
        if (error) {
          callbackOnMainThread(nil, error);
          return;
        }
        __strong NSString *strongProviderID = weakProviderID;
        FIROAuthCredential *credential =
            [[FIROAuthCredential alloc] initWithProviderID:strongProviderID
                                                 sessionID:sessionID
                                    OAuthResponseURLString:OAuthResponseURLString];
        callbackOnMainThread(credential, nil);
      }];
    }];
  });
}
#endif  // TARGET_OS_IOS

#pragma mark - Internal Methods

/** @fn initWithProviderID:auth:
    @brief returns an instance of @c FIROAuthProvider associated with the provided auth instance.
    @param auth The Auth instance to be associated with the OAuthProvider instance.
    @return An Instance of @c FIROAuthProvider.
  */
- (nullable instancetype)initWithProviderID:(NSString *)providerID auth:(FIRAuth *)auth {
  self = [super init];
  if (self) {
    _auth = auth;
    _providerID = providerID;
    _callbackScheme = [[[_auth.app.options.clientID componentsSeparatedByString:@"."]
        reverseObjectEnumerator].allObjects componentsJoinedByString:@"."];
  }
  return self;
}

/** @fn OAuthResponseForURL:error:
    @brief Parses the redirected URL and returns a string representation of the OAuth response URL.
    @param URL The url to be parsed for an OAuth response URL.
    @param error The error that occurred if any.
    @return The OAuth response if successful.
 */
- (nullable NSString *)OAuthResponseForURL:(NSURL *)URL error:(NSError *_Nullable *_Nullable)error {
  NSDictionary<NSString *, NSString *> *URLQueryItems =
      [FIRAuthWebUtils dictionaryWithHttpArgumentsString:URL.query];
  NSURL *deepLinkURL = [NSURL URLWithString:URLQueryItems[@"deep_link_id"]];
  URLQueryItems =
      [FIRAuthWebUtils dictionaryWithHttpArgumentsString:deepLinkURL.query];
  NSString *queryItemLink = URLQueryItems[@"link"];
  if (queryItemLink) {
    return queryItemLink;
  }
  if (!error) {
    return nil;
  }
  NSData *errorData = [URLQueryItems[@"firebaseError"] dataUsingEncoding:NSUTF8StringEncoding];
  NSError *jsonError;
  NSDictionary *errorDict = [NSJSONSerialization JSONObjectWithData:errorData
                                                            options:0
                                                              error:&jsonError];
  if (jsonError) {
    *error = [FIRAuthErrorUtils JSONSerializationErrorWithUnderlyingError:jsonError];
    return nil;
  }
  *error = [FIRAuthErrorUtils URLResponseErrorWithCode:errorDict[@"code"]
                                               message:errorDict[@"message"]];
  if (!*error) {
    NSString *reason;
    if(errorDict[@"code"] && errorDict[@"message"]) {
      reason = [NSString stringWithFormat:@"[%@] - %@",errorDict[@"code"], errorDict[@"message"]];
    }
    *error = [FIRAuthErrorUtils webSignInUserInteractionFailureWithReason:reason];
  }
  return nil;
}

/** @fn getHeadFulLiteURLWithEventID:completion:
    @brief Constructs a URL used for opening a headful-lite flow using a given event
        ID and session ID.
    @param eventID The event ID used for this purpose.
    @param sessionID The session ID used when completing the headful lite flow.
    @param completion The callback invoked after the URL has been constructed or an error
        has been encountered.
 */
- (void)getHeadFulLiteURLWithEventID:(NSString *)eventID
                           sessionID:(NSString *)sessionID
                          completion:(FIRHeadfulLiteURLCallBack)completion {
   __weak __typeof__(self) weakSelf = self;
  [FIRAuthWebUtils fetchAuthDomainWithRequestConfiguration:_auth.requestConfiguration
                                                completion:^(NSString *_Nullable authDomain,
                                                             NSError *_Nullable error) {
    if (error) {
      if (completion) {
        completion(nil, error);
      }
      return;
    }
     __strong __typeof__(self) strongSelf = weakSelf;
    NSString *bundleID = [NSBundle mainBundle].bundleIdentifier;
    NSString *clienID = strongSelf->_auth.app.options.clientID;
    NSString *apiKey = strongSelf->_auth.requestConfiguration.APIKey;
    NSMutableDictionary *urlArguments = [@{
      @"apiKey" : apiKey,
      @"authType" : @"signInWithRedirect",
      @"ibi" : bundleID ?: @"",
      @"clientId" : clienID,
      @"sessionId" : [strongSelf hashforString:sessionID],
      @"v" : [FIRAuthBackend authUserAgent],
      @"eventId" : eventID,
      @"providerId" : strongSelf->_providerID,
    } mutableCopy];
    if (strongSelf.scopes.count) {
      urlArguments[@"scopes"] = [strongSelf.scopes componentsJoinedByString:@","];
    }
    if (strongSelf.customParameters.count) {
      NSString *customParameters = [strongSelf customParametersStringWithError:&error];
      if (error) {
        completion(nil, error);
        return;
      }
      if (customParameters) {
        urlArguments[@"customParameters"] = customParameters;
      }
    }
    if (strongSelf->_auth.requestConfiguration.languageCode) {
      urlArguments[@"hl"] = strongSelf->_auth.requestConfiguration.languageCode;
    }
    NSString *argumentsString = [strongSelf httpArgumentsStringForArgsDictionary:urlArguments];
    NSString *URLString =
        [NSString stringWithFormat:kHeadfulLiteURLStringFormat, authDomain, argumentsString];
    if (completion) {
      NSCharacterSet *set = [NSCharacterSet URLFragmentAllowedCharacterSet];
      completion([NSURL URLWithString:
          [URLString stringByAddingPercentEncodingWithAllowedCharacters:set]], nil);
    }
  }];
}

/** @fn customParametersString
    @brief Returns a JSON string representation of the custom parameters dictionary corresponding
        to the OAuthProvider.
    @return The JSON string representation of the custom parameters dictionary corresponding
        to the OAuthProvider.
 */
- (nullable NSString *)customParametersStringWithError:(NSError *_Nullable *_Nullable)error {
  if (!_customParameters.count) {
    return nil;
  }

  if (!error) {
    return nil;
  }
  NSError *jsonError;
  NSData *customParametersJSONData =
      [NSJSONSerialization dataWithJSONObject:_customParameters
                                      options:0
                                        error:&jsonError];
  if (jsonError) {
    *error = [FIRAuthErrorUtils JSONSerializationErrorWithUnderlyingError:jsonError];
    return nil;
  }

  NSString *customParamsRawJSON =
      [[NSString alloc] initWithData:customParametersJSONData encoding:NSUTF8StringEncoding];
  return customParamsRawJSON;
}

/** @fn hashforString:
    @brief Returns the SHA256 hash representation of a given string object.
    @param string The string for which a SHA256 hash is desired.
    @return An hexadecimal string representation of the SHA256 hash.
 */
- (NSString *)hashforString:(NSString *)string {
  NSData *sessionIDData = [string dataUsingEncoding:NSUTF8StringEncoding];
  NSMutableData *hashOutputData = [NSMutableData dataWithLength:CC_SHA256_DIGEST_LENGTH];
  if (CC_SHA256(sessionIDData.bytes,
      (CC_LONG)[sessionIDData length],
      hashOutputData.mutableBytes)) {
  }
  return [self hexStringFromData:hashOutputData];;
}

/** @fn hexStringFromData:
    @brief Returns the hexadecimal string representation of an NSData object.
    @param data The NSData object for which a hexadecical string is desired.
    @return The hexadecimal string representation of the supplied NSData object.
 */
- (NSString *)hexStringFromData:(NSData *)data {
  const unsigned char *dataBuffer = (const unsigned char *)[data bytes];
  NSMutableString *string = [[NSMutableString alloc] init];
  for (unsigned int i = 0; i < data.length; i++){
    [string appendFormat:@"%02lx", (unsigned long)dataBuffer[i]];
  }
  return [string copy];
}

- (NSString *)httpArgumentsStringForArgsDictionary:(NSDictionary *)argsDictionary {
  NSMutableArray* arguments = [NSMutableArray arrayWithCapacity:argsDictionary.count];
  NSString* key;
  for (key in argsDictionary) {
    NSString *description = [argsDictionary[key] description];
    [arguments addObject:[NSString stringWithFormat:@"%@=%@",
                          [FIRAuthWebUtils stringByUnescapingFromURLArgument:key],
                          [FIRAuthWebUtils stringByUnescapingFromURLArgument:description]]] ;
  }
  return [arguments componentsJoinedByString:@"&"];
}

@end

NS_ASSUME_NONNULL_END
