(Objective-C) Refresh a Dynamics CRM OAuth2 Access Token

Demonstrates how to refresh an expiring Dynamics CRM access token using the refresh token. endpoint.

(If a REST API call fails with a 401 unauthorized error, an application can auto-recover by refreshing the access token, and then re-send the request using the new token.)

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#import <CkoJsonObject.h>
#import <CkoDateTime.h>
#import <CkoHttpRequest.h>
#import <CkoHttp.h>
#import <CkoHttpResponse.h>
#import <CkoFileAccess.h>

// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

// We previously obtained an access token and saved the JSON to a file using this example:
// Get Dynamics CRM OAuth2 Access Token

// This example will examine the JSON and expiration date, and if near expiration will
// refresh the access token.

CkoJsonObject *json = [[CkoJsonObject alloc] init];
BOOL success = [json LoadFile: @"qa_data/tokens/dynamicsCrm.json"];
if (success != YES) {
    return;
}

// The contents of the JSON look like this:
// {
//   "token_type": "Bearer",
//   "scope": "user_impersonation",
//   "expires_in": "3599",
//   "ext_expires_in": "0",
//   "expires_on": "1524783438",
//   "not_before": "1524779538",
//   "resource": "https://mydomain.api.crm.dynamics.com",
//   "access_token": "...",
//   "refresh_token": "...",
//   "id_token": "..."
// }

// The "expires_on" value is a Unix time.
CkoDateTime *dtExpire = [[CkoDateTime alloc] init];
[dtExpire SetFromUnixTime: NO t: [[json IntOf: @"expires_on"] intValue]];

// If this date/time expires within 10 minutes of the current system time, refresh the token.

// OK, we need to refresh the access token by sending a POST...
// 

CkoHttpRequest *req = [[CkoHttpRequest alloc] init];
[req AddParam: @"grant_type" value: @"refresh_token"];
[req AddParam: @"redirect_uri" value: @"http://localhost:3017/"];
[req AddParam: @"client_id" value: @"DYNAMICS-CRM-CLIENT-ID"];
[req AddParam: @"client_secret" value: @"DYNAMICS-CRM-SECRET-KEY"];
[req AddParam: @"refresh_token" value: [json StringOf: @"refresh_token"]];
[req AddParam: @"resource" value: @"https://mydynamicsdomain.api.crm.dynamics.com"];

CkoHttp *http = [[CkoHttp alloc] init];

CkoHttpResponse *resp = [http PostUrlEncoded: @"https://login.microsoftonline.com/DYNAMICS-ENDPOINT-GUID/oauth2/token" req: req];
if (http.LastMethodSuccess != YES) {
    NSLog(@"%@",http.LastErrorText);
    return;
}

// Load the JSON response.
[json Load: resp.BodyStr];
json.EmitCompact = NO;

// Show the JSON response.
NSLog(@"%@",[json Emit]);

NSLog(@"%@%d",@"Response status code: ",[resp.StatusCode intValue]);

// If the response status code is not 200, then it's an error.
if ([resp.StatusCode intValue] != 200) {
    return;
}

// 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) {
    [dtExpire SetFromCurrentSystemTime];
    [dtExpire AddSeconds: [json IntOf: @"expires_in"]];
    [json AppendString: @"expires_on" value: [dtExpire GetAsUnixTimeStr: NO]];
}

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