(MFC) HMRC OAuth2 Access Token

Demonstrates how to get an HMRC OAuth2 access token from a desktop (installed) application or script. This example gets an HMRC MTD VAT read/write access token.

Chilkat C/C++ Library Downloads MS Visual C/C++ Libs

See Also: Using MFC CString in Chilkat

#include <CkOAuth2.h>
#include <CkHttp.h>
#include <CkJsonObject.h>
#include <CkDateTime.h>
#include <CkFileAccess.h>

void ChilkatSample(void)
    {
    CkString strOut;

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

    CkOAuth2 oauth2;
    bool success;

    // This should be the port in the localhost callback URL for your app.
    // Important: Make sure the callback URI in your HMRC developer app 
    // is exactly "http://localhost:3017/".  Don't forget the ending "/" char.
    // The callback URL would look like "http://localhost:3017/" if the port number is 3017.

    // IMPORTANT: Don't forget to setup your HMRC application to use the Redirect URI "http://localhost:3017/" as shown
    // here: Configure Redirect URI for HMRC application
    oauth2.put_ListenPort(3017);

    oauth2.put_AuthorizationEndpoint("https://test-api.service.hmrc.gov.uk/oauth/authorize");
    oauth2.put_TokenEndpoint("https://test-api.service.hmrc.gov.uk/oauth/token");

    // Replace these with actual values.
    oauth2.put_ClientId("HMRC-CLIENT-ID");
    oauth2.put_ClientSecret("HMRC-CLIENT-SECRET");

    // The scopes are documented in the HMRC reference documentation for each API.
    // This example gets a read/write access token for the HMRC MTD VAT API.
    oauth2.put_Scope("read:vat write:vat");

    // Begin the OAuth2 three-legged flow.  This returns a URL that should be loaded in a browser.
    const char *url = oauth2.startAuth();
    if (oauth2.get_LastMethodSuccess() != true) {
        strOut.append(oauth2.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    CkHttp http;

    // At this point, your application should load the URL in a browser.
    // For example, 
    // in C#: System.Diagnostics.Process.Start(url);
    // in Java: Desktop.getDesktop().browse(new URI(url));
    // in VBScript: Set wsh=WScript.CreateObject("WScript.Shell")
    //              wsh.Run url
    // in Xojo: ShowURL(url)  (see http://docs.xojo.com/index.php/ShowURL)
    // in Dataflex: Runprogram Background "c:\Program Files\Internet Explorer\iexplore.exe" sUrl        
    // The GitHub account owner would interactively accept or deny the authorization request.

    // Add the code to load the url in a web browser here...
    // Add the code to load the url in a web browser here...
    // Add the code to load the url in a web browser here...

    // Now wait for the authorization.
    // We'll wait for a max of 120 seconds.
    int numMsWaited = 0;
    while ((numMsWaited < 120000) && (oauth2.get_AuthFlowState() < 3)) {
        oauth2.SleepMs(100);
        numMsWaited = numMsWaited + 100;
    }

    // If there was no response from the browser within 30 seconds, then 
    // the AuthFlowState will be equal to 1 or 2.
    // 1: Waiting for Redirect. The OAuth2 background thread is waiting to receive the redirect HTTP request from the browser.
    // 2: Waiting for Final Response. The OAuth2 background thread is waiting for the final access token response.
    // In that case, cancel the background task started in the call to StartAuth.
    if (oauth2.get_AuthFlowState() < 3) {
        oauth2.Cancel();
        strOut.append("No response from the browser!");
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // Check the AuthFlowState to see if authorization was granted, denied, or if some error occurred
    // The possible AuthFlowState values are:
    // 3: Completed with Success. The OAuth2 flow has completed, the background thread exited, and the successful JSON response is available in AccessTokenResponse property.
    // 4: Completed with Access Denied. The OAuth2 flow has completed, the background thread exited, and the error JSON is available in AccessTokenResponse property.
    // 5: Failed Prior to Completion. The OAuth2 flow failed to complete, the background thread exited, and the error information is available in the FailureInfo property.
    if (oauth2.get_AuthFlowState() == 5) {
        strOut.append("OAuth2 failed to complete.");
        strOut.append("\r\n");
        strOut.append(oauth2.failureInfo());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    if (oauth2.get_AuthFlowState() == 4) {
        strOut.append("OAuth2 authorization was denied.");
        strOut.append("\r\n");
        strOut.append(oauth2.accessTokenResponse());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    if (oauth2.get_AuthFlowState() != 3) {
        strOut.append("Unexpected AuthFlowState:");
        strOut.appendInt(oauth2.get_AuthFlowState());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    strOut.append("OAuth2 authorization granted!");
    strOut.append("\r\n");
    strOut.append("Access Token = ");
    strOut.append(oauth2.accessToken());
    strOut.append("\r\n");

    // Get the full JSON response:
    CkJsonObject json;
    json.Load(oauth2.accessTokenResponse());
    json.put_EmitCompact(false);
    strOut.append(json.emit());
    strOut.append("\r\n");

    // The JSON response looks 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": "..."
    // }

    // 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") != true) {
        CkDateTime dtExpire;
        dtExpire.SetFromCurrentSystemTime();
        dtExpire.AddSeconds(json.IntOf("expires_in"));
        json.AppendString("expires_on",dtExpire.getAsUnixTimeStr(false));
    }

    strOut.append(json.emit());
    strOut.append("\r\n");

    // Save the JSON to a file for future requests.
    CkFileAccess fac;
    fac.WriteEntireTextFile("qa_data/tokens/hmrc.json",json.emit(),"utf-8",false);


    SetDlgItemText(IDC_EDIT1,strOut.getUnicode());

    }