Pascal (Lazarus/Delphi)

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). Pascal (Lazarus/Delphi)

program ChilkatDemo;

// Demonstrates using the Chilkat Pascal wrapper via the C bridge DLL.
// Builds as a console application under Lazarus (FPC) or Delphi.

{$IFDEF FPC}
  {$MODE DELPHI}
{$ENDIF}
{$APPTYPE CONSOLE}

uses
  {$IFDEF UNIX}
  cthreads,
  {$ENDIF}
  SysUtils,
  CkDllLoader,
  Chilkat.Http,
  Chilkat.HttpRequest,
  Chilkat.HttpResponse,
  Chilkat.StringBuilder,
  Chilkat.JsonObject;

// ---------------------------------------------------------------------------

procedure RunDemo;
var
  success: Boolean;
  http: THttp;
  req: THttpRequest;
  resp: THttpResponse;
  sbResponseBody: TStringBuilder;
  jResp: TJsonObject;
  respStatusCode: Integer;
  token_type: string;
  access_token: string;
  expires_in: string;
  scope: string;

begin
  success := False;

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

  http := THttp.Create;

  //  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.

  req := THttpRequest.Create;
  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"
  req.HttpVerb := 'POST';
  req.ContentType := 'application/x-www-form-urlencoded';

  resp := THttpResponse.Create;
  success := http.HttpReq('https://invoicing.eta.gov.eg/connect/token',req,resp);
  if (success = False) then
    begin
      WriteLn(http.LastErrorText);
      Exit;
    end;

  sbResponseBody := TStringBuilder.Create;
  resp.GetBodySb(sbResponseBody);

  jResp := TJsonObject.Create;
  jResp.LoadSb(sbResponseBody);
  jResp.EmitCompact := False;

  WriteLn('Response Body:');
  WriteLn(jResp.Emit());

  respStatusCode := resp.StatusCode;
  WriteLn('Response Status Code = ' + respStatusCode);
  if (respStatusCode >= 400) then
    begin
      WriteLn('Response Header:');
      WriteLn(resp.Header);
      WriteLn('Failed.');
      Exit;
    end;

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

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

  token_type := jResp.StringOf('token_type');
  access_token := jResp.StringOf('access_token');
  expires_in := jResp.StringOf('expires_in');
  scope := jResp.StringOf('scope');


  http.Free;
  req.Free;
  resp.Free;
  sbResponseBody.Free;
  jResp.Free;

end;

// ---------------------------------------------------------------------------

begin

  try
    RunDemo;
  except
    on E: Exception do
      WriteLn('Unhandled exception: ', E.ClassName, ': ', E.Message);
  end;

  WriteLn;
  {$IFDEF MSWINDOWS}
  WriteLn('Press Enter to exit...');
  ReadLn;
  {$ENDIF}
end.