(Visual FoxPro) 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 ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

LOCAL loOauth2
LOCAL lnSuccess
LOCAL lcUrl
LOCAL loHttp
LOCAL lnNumMsWaited
LOCAL loJson
LOCAL loDtExpire
LOCAL loFac

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

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.OAuth2')
loOauth2 = CreateObject('Chilkat.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
loOauth2.ListenPort = 3017

loOauth2.AuthorizationEndpoint = "https://test-api.service.hmrc.gov.uk/oauth/authorize"
loOauth2.TokenEndpoint = "https://test-api.service.hmrc.gov.uk/oauth/token"

* Replace these with actual values.
loOauth2.ClientId = "HMRC-CLIENT-ID"
loOauth2.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.
loOauth2.Scope = "read:vat write:vat"

* Begin the OAuth2 three-legged flow.  This returns a URL that should be loaded in a browser.
lcUrl = loOauth2.StartAuth()
IF (loOauth2.LastMethodSuccess <> 1) THEN
    ? loOauth2.LastErrorText
    RELEASE loOauth2
    CANCEL
ENDIF

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.Http')
loHttp = CreateObject('Chilkat.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.
lnNumMsWaited = 0
DO WHILE (lnNumMsWaited < 120000) AND (loOauth2.AuthFlowState < 3)
    loOauth2.SleepMs(100)
    lnNumMsWaited = lnNumMsWaited + 100
ENDDO

* 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 (loOauth2.AuthFlowState < 3) THEN
    loOauth2.Cancel()
    ? "No response from the browser!"
    RELEASE loOauth2
    RELEASE loHttp
    CANCEL
ENDIF

* 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 (loOauth2.AuthFlowState = 5) THEN
    ? "OAuth2 failed to complete."
    ? loOauth2.FailureInfo
    RELEASE loOauth2
    RELEASE loHttp
    CANCEL
ENDIF

IF (loOauth2.AuthFlowState = 4) THEN
    ? "OAuth2 authorization was denied."
    ? loOauth2.AccessTokenResponse
    RELEASE loOauth2
    RELEASE loHttp
    CANCEL
ENDIF

IF (loOauth2.AuthFlowState <> 3) THEN
    ? "Unexpected AuthFlowState:" + STR(loOauth2.AuthFlowState)
    RELEASE loOauth2
    RELEASE loHttp
    CANCEL
ENDIF

? "OAuth2 authorization granted!"
? "Access Token = " + loOauth2.AccessToken

* Get the full JSON response:
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.JsonObject')
loJson = CreateObject('Chilkat.JsonObject')
loJson.Load(loOauth2.AccessTokenResponse)
loJson.EmitCompact = 0
? loJson.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 (loJson.HasMember("expires_on") <> 1) THEN
    * For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.CkDateTime')
    loDtExpire = CreateObject('Chilkat.CkDateTime')
    loDtExpire.SetFromCurrentSystemTime()
    loDtExpire.AddSeconds(loJson.IntOf("expires_in"))
    loJson.AppendString("expires_on",loDtExpire.GetAsUnixTimeStr(0))
ENDIF

? loJson.Emit()

* Save the JSON to a file for future requests.
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.FileAccess')
loFac = CreateObject('Chilkat.FileAccess')
loFac.WriteEntireTextFile("qa_data/tokens/hmrc.json",loJson.Emit(),"utf-8",0)

RELEASE loOauth2
RELEASE loHttp
RELEASE loJson
RELEASE loDtExpire
RELEASE loFac