(Objective-C) Get OAuth2 Access Token for Azure Registered App

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This example requires Chilkat v10.1.2 or greater.

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

// To further clarify, see OAuth 2.0 Authorization Flow

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

// This should be the port in the localhost callback URL for your app.  
// The callback URL would look like "http://localhost:3017/" if the port number is 3017.
oauth2.ListenPort = [NSNumber numberWithInt:3017];

// ----------------------------------------------------------------------------------------------------------
// The screenshot at the bottom of this page shows how we created the Azure App Registration for this example.
// ----------------------------------------------------------------------------------------------------------

// Note: The endpoint depends on the Azure App Registration.
// See How to Choose the Correct Endpoints for your Azure App Registration
oauth2.AuthorizationEndpoint = @"https://login.microsoftonline.com/common/oauth2/v2.0/authorize";
oauth2.TokenEndpoint = @"https://login.microsoftonline.com/common/oauth2/v2.0/token";

// Replace these with actual values.
oauth2.ClientId = @"CLIENT_ID";

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

// Provide a SPACE separated list of scopes.
// See https://developer.microsoft.com/en-us/graph/docs/authorization/permission_scopes 

// Important: To get a refresh token in the final response, ask for "offline_access" scope
oauth2.Scope = @"openid profile offline_access user.readwrite mail.readwrite mail.send files.readwrite";

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

// 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 < 90000) && ([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!");
NSLog(@"%@%@",@"Access Token = ",oauth2.AccessToken);

// When the token is near expiration, your app can refresh as shown here:
// Refresh Expiring OAuth2 Access Token for Azure Registered App

// Get the full JSON response:
CkoJsonObject *json = [[CkoJsonObject alloc] init];
[json Load: oauth2.AccessTokenResponse];
json.EmitCompact = NO;

// The JSON response looks like this:

// {
//   "token_type": "Bearer",
//   "scope": "User.Read Mail.ReadWrite Mail.Send",
//   "expires_in": 3600,
//   "ext_expires_in": 0,
//   "access_token": "EwBAA8l6B...",
//   "refresh_token": "MCRMdbe...",
//   "id_token": "eyJ0eXA..."
// }

// 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"] != YES) {
    CkoDateTime *dtExpire = [[CkoDateTime alloc] init];
    [dtExpire SetFromCurrentSystemTime];
    [dtExpire AddSeconds: [json IntOf: @"expires_in"]];
    [json AppendString: @"expires_on" value: [dtExpire GetAsUnixTimeStr: NO]];
}

NSLog(@"%@",[json Emit]);

// Save the JSON to a file for future requests.
CkoFileAccess *fac = [[CkoFileAccess alloc] init];
[fac WriteEntireTextFile: @"qa_data/tokens/_myAzureApp.json" fileData: [json Emit] charset: @"utf-8" includePreamble: NO];

// This is a screenshot of how we created the Azure App for this example:
//