(Delphi DLL) Refresh HMRC OAuth2 Access Token

Demonstrates how to refresh an HMRC access token.

Chilkat for Delphi Downloads Chilkat non-ActiveX DLL for Delphi Chilkat ActiveX DLL for Delphi * The examples here use the non-ActiveX DLL.

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, OAuth2, StringBuilder, JsonObject, CkDateTime;

...

procedure TForm1.Button1Click(Sender: TObject);
var
jsonToken: HCkJsonObject;
success: Boolean;
oauth2: HCkOAuth2;
dtExpire: HCkDateTime;
sbJson: HCkStringBuilder;

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

// See Get HMRC Access Token 
// for sample code showing how to obtain a HMRC access token for desktop apps.

// It is assumed we previously obtained an OAuth2 access token for HMRC.

jsonToken := CkJsonObject_Create();
success := CkJsonObject_LoadFile(jsonToken,'qa_data/tokens/hmrc.json');
if (success <> True) then
  begin
    Memo1.Lines.Add('Failed to load hmrc.json');
    Exit;
  end;

// The access token JSON looks something 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": "..."
// }

oauth2 := CkOAuth2_Create();

CkOAuth2_putTokenEndpoint(oauth2,'https://test-api.service.hmrc.gov.uk/oauth/token');

// Replace these with actual values.
CkOAuth2_putClientId(oauth2,'HMRC-CLIENT-ID');
CkOAuth2_putClientSecret(oauth2,'HMRC-CLIENT-SECRET');

// Get the "refresh_token"
CkOAuth2_putRefreshToken(oauth2,CkJsonObject__stringOf(jsonToken,'refresh_token'));

// Send the HTTP POST to refresh the access token..
success := CkOAuth2_RefreshAccessToken(oauth2);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkOAuth2__lastErrorText(oauth2));
    Exit;
  end;

// Load the access token response into the json object 
CkJsonObject_Load(jsonToken,CkOAuth2__accessTokenResponse(oauth2));

// 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 (CkJsonObject_HasMember(jsonToken,'expires_on') = False) then
  begin
    dtExpire := CkDateTime_Create();
    CkDateTime_SetFromCurrentSystemTime(dtExpire);
    CkDateTime_AddSeconds(dtExpire,CkJsonObject_IntOf(jsonToken,'expires_in'));
    CkJsonObject_AppendString(jsonToken,'expires_on',CkDateTime__getAsUnixTimeStr(dtExpire,False));
  end;

// Save the new JSON access token response to a file.
// The access + refresh tokens contained in this JSON will be needed for the next refresh.
sbJson := CkStringBuilder_Create();
CkJsonObject_putEmitCompact(jsonToken,False);
CkJsonObject_EmitSb(jsonToken,sbJson);
CkStringBuilder_WriteFile(sbJson,'qa_data/tokens/hmrc.json','utf-8',False);

Memo1.Lines.Add('OAuth2 authorization granted!');
Memo1.Lines.Add('New Access Token = ' + CkOAuth2__accessToken(oauth2));

CkJsonObject_Dispose(jsonToken);
CkOAuth2_Dispose(oauth2);
    CkDateTime_Dispose(dtExpire);
CkStringBuilder_Dispose(sbJson);

end;