(Objective-C) X.com OAuth 2.0 Authorization Code with PKCE

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Note: This example requires Chilkat v10.1.2 or greater.

For more information, see https://docs.x.com/resources/fundamentals/authentication/oauth-2-0/authorization-code

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#import <CkoOAuth2.h>
#import <NSString.h>
#import <CkoJsonObject.h>
#import <CkoDateTime.h>

// For more information about the OAuth2, see OAuth 2.0 Authorization Flow

CkoOAuth2 *oauth2 = [[CkoOAuth2 alloc] init];

// The port should match the Authorized Redirect URL in your X.com app, 
// which would look like "http://127.0.0.1:3017/"
// See the screenshot below of the App Settings in the X Developer Portal
oauth2.LocalHost = @"127.0.0.1";
oauth2.ListenPort = [NSNumber numberWithInt:3017];

oauth2.AuthorizationEndpoint = @"https://x.com/i/oauth2/authorize";
oauth2.TokenEndpoint = @"https://api.x.com/2/oauth2/token";

// Replace this with your actual X.com OAuth2 Client ID and Client Secret
oauth2.ClientId = @"OAUTH2_CLIENT_ID";
oauth2.ClientSecret = @"OAUTH2_CLIENT_SECRET";

// This is for Require Proof Key for Code Exchange (PKCE)
// See OAuth2 PKCE Explained
oauth2.CodeChallenge = YES;
oauth2.CodeChallengeMethod = @"S256";

// Space separated scopes...
oauth2.Scope = @"tweet.read tweet.write users.read follows.read follows.write offline.access like.read like.write block.read block.write";

// Begin the OAuth2 Authorization code flow.  This returns a URL that should be loaded in a browser.
NSString *url = [oauth2 StartAuth];
if (oauth2.LastMethodSuccess != YES) {
    NSLog(@"%@",oauth2.LastErrorText);
    return;
}

NSLog(@"%@%@",@"url = ",url);

// Launch the default browser on the system and navigate to the url.
// The LaunchBrowser method was added in Chilkat v10.1.2.
BOOL success = [oauth2 LaunchBrowser: url];
if (success == NO) {
    NSLog(@"%@",oauth2.LastErrorText);
    return;
}

// Wait for the user to approve or deny authorization in the browser.
int numMsWaited = 0;
while ((numMsWaited < 10000) && ([oauth2.AuthFlowState intValue] < 3)) {
    [oauth2 SleepMs: [NSNumber numberWithInt: 100]];
    numMsWaited = numMsWaited + 100;
}

// If the browser does not respond within the specified time, AuthFlowState will be:
// 
// 1: Waiting for Redirect - The OAuth2 background thread is waiting for the browser's redirect request.
// 2: Waiting for Final Response - The thread is awaiting the final access token response.
// In either case, cancel the background task initiated by StartAuth.

if ([oauth2.AuthFlowState intValue] < 3) {
    [oauth2 Cancel];
    NSLog(@"%@",@"No response from the browser!");
    return;
}

// Check AuthFlowState to determine if authorization was granted, denied, or failed:
// 
// 3: Success - OAuth2 flow completed, the background thread exited, and the successful response is in AccessTokenResponse.
// 4: Access Denied - OAuth2 flow completed, the background thread exited, and the error response is in AccessTokenResponse.
// 5: Failure - OAuth2 flow failed before completion, the background thread exited, and error details are in FailureInfo.

if ([oauth2.AuthFlowState intValue] == 5) {
    NSLog(@"%@",@"OAuth2 failed to complete.");
    NSLog(@"%@",oauth2.FailureInfo);
    return;
}

if ([oauth2.AuthFlowState intValue] == 4) {
    NSLog(@"%@",@"OAuth2 authorization was denied.");
    NSLog(@"%@",oauth2.AccessTokenResponse);
    return;
}

if ([oauth2.AuthFlowState intValue] != 3) {
    NSLog(@"%@%d",@"Unexpected AuthFlowState:",[oauth2.AuthFlowState intValue]);
    return;
}

NSLog(@"%@",@"OAuth2 authorization granted!");

CkoJsonObject *json = [[CkoJsonObject alloc] init];
[json Load: oauth2.AccessTokenResponse];
json.EmitCompact = NO;

// If an "expires_on" member does not exist, then add the JSON member by
// getting the current system date/time and adding the "expires_in" seconds.
// This way we'll know when the token expires.
if ([json HasMember: @"expires_on"] == NO) {
    CkoDateTime *dtExpire = [[CkoDateTime alloc] init];
    [dtExpire SetFromCurrentSystemTime];
    [dtExpire AddSeconds: [json IntOf: @"expires_in"]];
    [json AppendString: @"expires_on" value: [dtExpire GetAsUnixTimeStr: NO]];
}

NSLog(@"%@%@",@"Access Token Response = ",[json Emit]);

// A sample access token response:

// {
//   "token_type": "bearer",
//   "expires_in": 7200,
//   "access_token": "VmNDLVZiYUZwejY5Mkx3RblFTmo3ek1leTRGclMuZFVOUTVUTWpNbVZKb1N5OjE3NDAxNjk4MDVxNTE6MToxOaF0OjE",
//   "scope": "block.read follows.read offline.access tweet.write block.write like.write like.read users.read tweet.read follows.write",
//   "refresh_token": "eThOWVVFSTRqdVp3QTFndGsxM2ZGZmFyNWVrU0phM1JKbGdrbGNWRGJzb1loOjE3NDAwMjk4MDUxNTI6MTowOnJ0OjE"
// }

NSLog(@"%@%@",@"Access Token = ",oauth2.AccessToken);

// Save the JSON access token response to a file for subsequent use..
[json WriteFile: @"qa_data/tokens/x.json"];

//