(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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#include <CkHttp.h>
#include <CkHttpRequest.h>
#include <CkHttpResponse.h>
#include <CkStringBuilder.h>
#include <CkJsonObject.h>

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

    CkHttp http;
    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.

    CkHttpRequest req;
    req.AddParam("grant_type","client_credentials");
    // Use your actual client ID and client secret...
    req.AddParam("client_id","d0394a9f-0607-40de-a978-2d3eb8375b04");
    req.AddParam("client_secret","6d62315e-d65a-4e41-9112-4195ea834edf");

    req.AddHeader("posserial","1234567899");
    req.AddHeader("pososversion","os");
    req.AddHeader("posmodelframework","1");
    req.AddHeader("presharedkey","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"
    CkHttpResponse *resp = http.PostUrlEncoded("https://invoicing.eta.gov.eg/connect/token",req);
    if (http.get_LastMethodSuccess() == false) {
        std::cout << http.lastErrorText() << "\r\n";
        return;
    }

    CkStringBuilder sbResponseBody;
    resp->GetBodySb(sbResponseBody);

    CkJsonObject jResp;
    jResp.LoadSb(sbResponseBody);
    jResp.put_EmitCompact(false);

    std::cout << "Response Body:" << "\r\n";
    std::cout << jResp.emit() << "\r\n";

    int respStatusCode = resp->get_StatusCode();
    std::cout << "Response Status Code = " << respStatusCode << "\r\n";
    if (respStatusCode >= 400) {
        std::cout << "Response Header:" << "\r\n";
        std::cout << resp->header() << "\r\n";
        std::cout << "Failed." << "\r\n";
        delete resp;
        return;
    }

    delete resp;

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

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

    const char *token_type = jResp.stringOf("token_type");
    const char *access_token = jResp.stringOf("access_token");
    const char *expires_in = jResp.stringOf("expires_in");
    const char *scope = jResp.stringOf("scope");
    }