(Objective-C) Egyptian eReceipt OAuth2 Client Credentials

See more Egypt eReceipt Examples

Get an OAuth2 access token for the Egyptian eReceipt REST API using client credentials (no interactivity with a web browser required).

For more information, see https://sdk.invoicing.eta.gov.eg/ereceiptapi/01-authenticate-pos/

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#import <CkoHttp.h>
#import <CkoHttpRequest.h>
#import <CkoHttpResponse.h>
#import <CkoStringBuilder.h>
#import <CkoJsonObject.h>
#import <NSString.h>

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

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

// Note: Any provider of a REST API, such as the Egyptian government in this case, can make life 
// much easier for developers by providing one or more of the following in the API documentation:
// 
// 1) A sample CURL statement for each API call.
// 2) A Postman collection, or Swagger/OpenAPI specification file.
// 3) A sample of a raw HTTP request and response for each API call.
// 
// The sample CURL statements or raw HTTP request/responses do not need to comprehensively show all 
// possible options.  Providing a sample allows one to quickly make a successful API call.
// It also allows for code generation directly from the CURL, Postman collection, or raw request/response,
// and it tends to answer all questions about the format/structure of a request that, suprisingly,
// remain ambiguous or not obvious in other forms of documentation.

CkoHttpRequest *req = [[CkoHttpRequest alloc] init];
[req AddParam: @"grant_type" value: @"client_credentials"];
// Use your actual client ID and client secret...
[req AddParam: @"client_id" value: @"d0394a9f-0607-40de-a978-2d3eb8375b04"];
[req AddParam: @"client_secret" value: @"6d62315e-d65a-4e41-9112-4195ea834edf"];

[req AddHeader: @"posserial" value: @"1234567899"];
[req AddHeader: @"pososversion" value: @"os"];
[req AddHeader: @"posmodelframework" value: @"1"];
[req AddHeader: @"presharedkey" value: @"03ac674216f3e1..."];

// When writing this example, the documentation at https://sdk.invoicing.eta.gov.eg/ereceiptapi/01-authenticate-pos/
// shows us the HTTP verb and path (POST /connect/token), however,
// we don't see the actual domain where the request is to be sent.
// What are the endpoints???
// It took some searching, but we found some endpoints here:  https://sdk.invoicing.eta.gov.eg/faq/
// It's not immediately apparent which endpoint is to be used with a given API call.
// Why not just include the endpoint in the documentation for each REST API call?
// Endpoints are literally the #1 thing that needs to be known.
// They can't just be buried in a FAQ.  They should be up-front and obvious.
// 
// So.. we're guessing the endpoint is likely "https://invoicing.eta.gov.eg/connect/token"
CkoHttpResponse *resp = [http PostUrlEncoded: @"https://invoicing.eta.gov.eg/connect/token" req: req];
if (http.LastMethodSuccess == NO) {
    NSLog(@"%@",http.LastErrorText);
    return;
}

CkoStringBuilder *sbResponseBody = [[CkoStringBuilder alloc] init];
[resp GetBodySb: sbResponseBody];

CkoJsonObject *jResp = [[CkoJsonObject alloc] init];
[jResp LoadSb: sbResponseBody];
jResp.EmitCompact = NO;

NSLog(@"%@",@"Response Body:");
NSLog(@"%@",[jResp Emit]);

int respStatusCode = [resp.StatusCode intValue];
NSLog(@"%@%d",@"Response Status Code = ",respStatusCode);
if (respStatusCode >= 400) {
    NSLog(@"%@",@"Response Header:");
    NSLog(@"%@",resp.Header);
    NSLog(@"%@",@"Failed.");

    return;
}

// If successful, the OAuth2 access token JSON looks like this:

// {
//   "token_type": "Bearer",
//   "access_token": "eyJraW......R2sbqrY",
//   "expires_in": "3600",
//   "scope": "..."
// }

NSString *token_type = [jResp StringOf: @"token_type"];
NSString *access_token = [jResp StringOf: @"access_token"];
NSString *expires_in = [jResp StringOf: @"expires_in"];
NSString *scope = [jResp StringOf: @"scope"];