Unicode C++

HMRC OAuth2 Access Token

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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. Unicode C++

#include <CkOAuth2W.h>
#include <CkJsonObjectW.h>
#include <CkDateTimeW.h>
#include <CkFileAccessW.h>

void ChilkatSample(void)
    {
    bool success = false;

    // To further clarify, see OAuth 2.0 Authorization Flow

    CkOAuth2W oauth2;

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

    // Replace with your actual client ID
    oauth2.put_ClientId(L"HMRC-CLIENT-ID");

    // 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(L"read:vat write:vat");

    // Begin the OAuth2 Authorization code flow.  This returns a URL that should be loaded in a browser.
    const wchar_t *url = oauth2.startAuth();
    if (oauth2.get_LastMethodSuccess() != true) {
        wprintf(L"%s\n",oauth2.lastErrorText());
        return;
    }

    // Launch the default browser on the system and navigate to the url.
    // The LaunchBrowser method was added in Chilkat v10.1.2.
    success = oauth2.LaunchBrowser(url);
    if (success == false) {
        wprintf(L"%s\n",oauth2.lastErrorText());
        return;
    }

    // Wait for the user to approve or deny authorization in the browser.
    int numMsWaited = 0;
    while ((numMsWaited < 90000) && (oauth2.get_AuthFlowState() < 3)) {
        oauth2.SleepMs(100);
        numMsWaited = numMsWaited + 100;
    }

    // If the browser does not respond within the specified time, AuthFlowState will be:
    // 
    // 1: Waiting for Redirect – The OAuth2 background thread is waiting for the browser's redirect request.
    // 2: Waiting for Final Response – The thread is awaiting the final access token response.
    // In either case, cancel the background task initiated by StartAuth.

    if (oauth2.get_AuthFlowState() < 3) {
        oauth2.Cancel();
        wprintf(L"No response from the browser!\n");
        return;
    }

    // Check AuthFlowState to determine if authorization was granted, denied, or failed:
    // 
    // 3: Success – OAuth2 flow completed, the background thread exited, and the successful response is in AccessTokenResponse.
    // 4: Access Denied – OAuth2 flow completed, the background thread exited, and the error response is in AccessTokenResponse.
    // 5: Failure – OAuth2 flow failed before completion, the background thread exited, and error details are in FailureInfo.

    if (oauth2.get_AuthFlowState() == 5) {
        wprintf(L"OAuth2 failed to complete.\n");
        wprintf(L"%s\n",oauth2.failureInfo());
        return;
    }

    if (oauth2.get_AuthFlowState() == 4) {
        wprintf(L"OAuth2 authorization was denied.\n");
        wprintf(L"%s\n",oauth2.accessTokenResponse());
        return;
    }

    if (oauth2.get_AuthFlowState() != 3) {
        wprintf(L"Unexpected AuthFlowState:%d\n",oauth2.get_AuthFlowState());
        return;
    }

    wprintf(L"OAuth2 authorization granted!\n");
    wprintf(L"Access Token = %s\n",oauth2.accessToken());

    // Get the full JSON response:
    CkJsonObjectW json;
    json.Load(oauth2.accessTokenResponse());
    json.put_EmitCompact(false);
    wprintf(L"%s\n",json.emit());

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

    wprintf(L"%s\n",json.emit());

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