Visual FoxPro

HMRC OAuth2 Access Token

See more OAuth2 Examples

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. Visual FoxPro

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

lnSuccess = 0

* To further clarify, see OAuth 2.0 Authorization Flow

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 with your actual client ID
loOauth2.ClientId = "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.
loOauth2.Scope = "read:vat write:vat"

* Begin the OAuth2 Authorization code 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

* Launch the default browser on the system and navigate to the url.
* The LaunchBrowser method was added in Chilkat v10.1.2.
lnSuccess = loOauth2.LaunchBrowser(lcUrl)
IF (lnSuccess = 0) THEN
    ? loOauth2.LastErrorText
    RELEASE loOauth2
    CANCEL
ENDIF

* Wait for the user to approve or deny authorization in the browser.
lnNumMsWaited = 0
DO WHILE (lnNumMsWaited < 90000) AND (loOauth2.AuthFlowState < 3)
    loOauth2.SleepMs(100)
    lnNumMsWaited = lnNumMsWaited + 100
ENDDO

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

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

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

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

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

* Get the full JSON response:
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
    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.
loFac = CreateObject('Chilkat.FileAccess')
loFac.WriteEntireTextFile("qa_data/tokens/hmrc.json",loJson.Emit(),"utf-8",0)

RELEASE loOauth2
RELEASE loJson
RELEASE loDtExpire
RELEASE loFac