Xbase++ Requires Chilkat v10.1.2+

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. Xbase++

LOCAL nSuccess
LOCAL oOauth2
LOCAL cUrl
LOCAL nNumMsWaited
LOCAL oJson
LOCAL oDtExpire
LOCAL oFac

nSuccess := 0

//  To further clarify, see OAuth 2.0 Authorization Flow

oOauth2 := 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
oOauth2:ListenPort := 3017

oOauth2:AuthorizationEndpoint := "https://test-api.service.hmrc.gov.uk/oauth/authorize"
oOauth2:TokenEndpoint := "https://test-api.service.hmrc.gov.uk/oauth/token"

//  Replace with your actual client ID
oOauth2: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.
oOauth2:Scope := "read:vat write:vat"

//  Begin the OAuth2 Authorization code flow.  This returns a URL that should be loaded in a browser.
cUrl := oOauth2:StartAuth()
IF (oOauth2:LastMethodSuccess != 1)
    ? oOauth2:LastErrorText
    oOauth2:destroy()
    RETURN
ENDIF

//  Launch the default browser on the system and navigate to the url.
//  The LaunchBrowser method was added in Chilkat v10.1.2.
nSuccess := oOauth2:LaunchBrowser(cUrl)
IF (nSuccess == 0)
    ? oOauth2:LastErrorText
    oOauth2:destroy()
    RETURN
ENDIF

//  Wait for the user to approve or deny authorization in the browser.
nNumMsWaited := 0
DO WHILE (nNumMsWaited < 90000) .AND. (oOauth2:AuthFlowState < 3)
    oOauth2:SleepMs(100)
    nNumMsWaited := nNumMsWaited + 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 (oOauth2:AuthFlowState < 3)
    oOauth2:Cancel()
    ? "No response from the browser!"
    oOauth2:destroy()
    RETURN
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 (oOauth2:AuthFlowState == 5)
    ? "OAuth2 failed to complete."
    ? oOauth2:FailureInfo
    oOauth2:destroy()
    RETURN
ENDIF

IF (oOauth2:AuthFlowState == 4)
    ? "OAuth2 authorization was denied."
    ? oOauth2:AccessTokenResponse
    oOauth2:destroy()
    RETURN
ENDIF

IF (oOauth2:AuthFlowState != 3)
    ? "Unexpected AuthFlowState:" + Str(oOauth2:AuthFlowState)
    oOauth2:destroy()
    RETURN
ENDIF

? "OAuth2 authorization granted!"
? "Access Token = " + oOauth2:AccessToken

//  Get the full JSON response:
oJson := CreateObject("Chilkat.JsonObject")
oJson:Load(oOauth2:AccessTokenResponse)
oJson:EmitCompact := 0
? oJson: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 (oJson:HasMember("expires_on") != 1)
    oDtExpire := CreateObject("Chilkat.CkDateTime")
    oDtExpire:SetFromCurrentSystemTime()
    oDtExpire:AddSeconds(oJson:IntOf("expires_in"))
    oJson:AppendString("expires_on", oDtExpire:GetAsUnixTimeStr(0))
ENDIF

? oJson:Emit()

//  Save the JSON to a file for future requests.
oFac := CreateObject("Chilkat.FileAccess")
oFac:WriteEntireTextFile("qa_data/tokens/hmrc.json", oJson:Emit(), "utf-8", 0)

oOauth2:destroy()
oJson:destroy()
oDtExpire:destroy()
oFac:destroy()