VBScript
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.
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VBScript
Dim fso, outFile
Set fso = CreateObject("Scripting.FileSystemObject")
'Create a Unicode (utf-16) output text file.
Set outFile = fso.CreateTextFile("output.txt", True, True)

success = 0

' To further clarify, see OAuth 2.0 Authorization Flow

set oauth2 = 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
oauth2.ListenPort = 3017

oauth2.AuthorizationEndpoint = "https://test-api.service.hmrc.gov.uk/oauth/authorize"
oauth2.TokenEndpoint = "https://test-api.service.hmrc.gov.uk/oauth/token"

' Replace with your actual client ID
oauth2.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.
oauth2.Scope = "read:vat write:vat"

' Begin the OAuth2 Authorization code flow.  This returns a URL that should be loaded in a browser.
url = oauth2.StartAuth()
If (oauth2.LastMethodSuccess <> 1) Then
    outFile.WriteLine(oauth2.LastErrorText)
    WScript.Quit
End If

' Launch the default browser on the system and navigate to the url.
' The LaunchBrowser method was added in Chilkat v10.1.2.
success = oauth2.LaunchBrowser(url)
If (success = 0) Then
    outFile.WriteLine(oauth2.LastErrorText)
    WScript.Quit
End If

' Wait for the user to approve or deny authorization in the browser.
numMsWaited = 0
Do While (numMsWaited < 90000) And (oauth2.AuthFlowState < 3)
    oauth2.SleepMs 100
    numMsWaited = numMsWaited + 100
Loop

' 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 (oauth2.AuthFlowState < 3) Then
    success = oauth2.Cancel()
    outFile.WriteLine("No response from the browser!")
    WScript.Quit
End If

' 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 (oauth2.AuthFlowState = 5) Then
    outFile.WriteLine("OAuth2 failed to complete.")
    outFile.WriteLine(oauth2.FailureInfo)
    WScript.Quit
End If

If (oauth2.AuthFlowState = 4) Then
    outFile.WriteLine("OAuth2 authorization was denied.")
    outFile.WriteLine(oauth2.AccessTokenResponse)
    WScript.Quit
End If

If (oauth2.AuthFlowState <> 3) Then
    outFile.WriteLine("Unexpected AuthFlowState:" & oauth2.AuthFlowState)
    WScript.Quit
End If

outFile.WriteLine("OAuth2 authorization granted!")
outFile.WriteLine("Access Token = " & oauth2.AccessToken)

' Get the full JSON response:
set json = CreateObject("Chilkat.JsonObject")
success = json.Load(oauth2.AccessTokenResponse)
json.EmitCompact = 0
outFile.WriteLine(json.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 (json.HasMember("expires_on") <> 1) Then
    set dtExpire = CreateObject("Chilkat.CkDateTime")
    success = dtExpire.SetFromCurrentSystemTime()
    success = dtExpire.AddSeconds(json.IntOf("expires_in"))
    success = json.AppendString("expires_on",dtExpire.GetAsUnixTimeStr(0))
End If

outFile.WriteLine(json.Emit())

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

outFile.Close