Lianja

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. Lianja

llSuccess = .F.

// To further clarify, see OAuth 2.0 Authorization Flow

loOauth2 = createobject("CkOAuth2")

// 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 <> .T.) then
    ? loOauth2.LastErrorText
    release loOauth2
    return
endif

// Launch the default browser on the system and navigate to the url.
// The LaunchBrowser method was added in Chilkat v10.1.2.
llSuccess = loOauth2.LaunchBrowser(lcUrl)
if (llSuccess = .F.) then
    ? loOauth2.LastErrorText
    release loOauth2
    return
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
    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 (loOauth2.AuthFlowState = 5) then
    ? "OAuth2 failed to complete."
    ? loOauth2.FailureInfo
    release loOauth2
    return
endif

if (loOauth2.AuthFlowState = 4) then
    ? "OAuth2 authorization was denied."
    ? loOauth2.AccessTokenResponse
    release loOauth2
    return
endif

if (loOauth2.AuthFlowState <> 3) then
    ? "Unexpected AuthFlowState:" + str(loOauth2.AuthFlowState)
    release loOauth2
    return
endif

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

// Get the full JSON response:
loJson = createobject("CkJsonObject")
loJson.Load(loOauth2.AccessTokenResponse)
loJson.EmitCompact = .F.
? 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") <> .T.) then
    loDtExpire = createobject("CkDateTime")
    loDtExpire.SetFromCurrentSystemTime()
    loDtExpire.AddSeconds(loJson.IntOf("expires_in"))
    loJson.AppendString("expires_on",loDtExpire.GetAsUnixTimeStr(.F.))
endif

? loJson.Emit()

// Save the JSON to a file for future requests.
loFac = createobject("CkFileAccess")
loFac.WriteEntireTextFile("qa_data/tokens/hmrc.json",loJson.Emit(),"utf-8",.F.)


release loOauth2
release loJson
release loDtExpire
release loFac