(Delphi ActiveX) Refresh Expiring OAuth2 Access Token for Azure Registered App

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

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Chilkat_TLB;

...

procedure TForm1.Button1Click(Sender: TObject);
var
json: TChilkatJsonObject;
success: Integer;
dtExpire: TCkDateTime;
oauth2: TChilkatOAuth2;
fac: TCkFileAccess;

begin
// We previously obtained an access token and saved the JSON to a file using this example:
// Get OAuth2 Access Token for Azure Registered App

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

json := TChilkatJsonObject.Create(Self);
success := json.LoadFile('qa_data/tokens/_myAzureApp.json');
if (success <> 1) then
  begin
    Memo1.Lines.Add('Failed to load the access token.');
    Exit;
  end;

// The contents of the JSON look like this:
// {
//   "token_type": "Bearer",
//   "scope": "User.Read Mail.ReadWrite Mail.Send",
//   "expires_in": 3600,
//   "ext_expires_in": 0,
//   "access_token": "EwBAA8l6B...",
//   "refresh_token": "MCRMdbe6Cd...",
//   "id_token": "eyJ0eXAiOiJ...",
//   "expires_on": "1494112119"
// }

// The "expires_on" value is a Unix time.
dtExpire := TCkDateTime.Create(Self);
dtExpire.SetFromUnixTime(0,json.IntOf('expires_on'));

// If this date/time expires within 10 minutes of the current system time, refresh the token.
if (dtExpire.ExpiresWithin(10,'minutes') <> 1) then
  begin
    Memo1.Lines.Add('No need to refresh, the access token won''t expire within the next 10 minutes.');
    Exit;
  end;

// OK, we need to refresh the access token..
oauth2 := TChilkatOAuth2.Create(Self);

// Note: The endpoint depends on the Azure App Registration.
// See How to Choose the Correct Endpoints for your Azure App Registration
oauth2.TokenEndpoint := 'https://login.microsoftonline.com/common/oauth2/v2.0/token';

// Use your client ID.
oauth2.ClientId := 'CLIENT_ID';

// Get the existing refresh token.
oauth2.RefreshToken := json.StringOf('refresh_token');

// Send the HTTP POST to refresh the access token.
success := oauth2.RefreshAccessToken();
if (success = 0) then
  begin
    Memo1.Lines.Add(oauth2.LastErrorText);
    Exit;
  end;

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

// Get the full JSON response:
json.Load(oauth2.AccessTokenResponse);
json.EmitCompact := 0;

// 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') <> 1) then
  begin
    dtExpire.SetFromCurrentSystemTime();
    dtExpire.AddSeconds(json.IntOf('expires_in'));
    json.AppendString('expires_on',dtExpire.GetAsUnixTimeStr(0));
  end;

Memo1.Lines.Add(json.Emit());

// Save the new access token JSON to a file for future requests.
fac := TCkFileAccess.Create(Self);
fac.WriteEntireTextFile('qa_data/tokens/_myAzureApp.json',json.Emit(),'utf-8',0);
end;