(Lianja) Refresh HMRC OAuth2 Access Token

Demonstrates how to refresh an HMRC access token.

Chilkat Lianja Extension Download Chilkat Lianja Extension

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

// See Get HMRC Access Token 
// for sample code showing how to obtain a HMRC access token for desktop apps.

// It is assumed we previously obtained an OAuth2 access token for HMRC.

loJsonToken = createobject("CkJsonObject")
llSuccess = loJsonToken.LoadFile("qa_data/tokens/hmrc.json")
if (llSuccess <> .T.) then
    ? "Failed to load hmrc.json"
    release loJsonToken
    return
endif

// The access token JSON looks something 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": "..."
// }

loOauth2 = createobject("CkOAuth2")

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"

// Get the "refresh_token"
loOauth2.RefreshToken = loJsonToken.StringOf("refresh_token")

// Send the HTTP POST to refresh the access token..
llSuccess = loOauth2.RefreshAccessToken()
if (llSuccess <> .T.) then
    ? loOauth2.LastErrorText
    release loJsonToken
    release loOauth2
    return
endif

// Load the access token response into the json object 
loJsonToken.Load(loOauth2.AccessTokenResponse)

// 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 (loJsonToken.HasMember("expires_on") = .F.) then
    loDtExpire = createobject("CkDateTime")
    loDtExpire.SetFromCurrentSystemTime()
    loDtExpire.AddSeconds(loJsonToken.IntOf("expires_in"))
    loJsonToken.AppendString("expires_on",loDtExpire.GetAsUnixTimeStr(.F.))
endif

// Save the new JSON access token response to a file.
// The access + refresh tokens contained in this JSON will be needed for the next refresh.
loSbJson = createobject("CkStringBuilder")
loJsonToken.EmitCompact = .F.
loJsonToken.EmitSb(loSbJson)
loSbJson.WriteFile("qa_data/tokens/hmrc.json","utf-8",.F.)

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


release loJsonToken
release loOauth2
release loDtExpire
release loSbJson