(PowerShell) Refresh HMRC OAuth2 Access Token

Demonstrates how to refresh an HMRC access token.

Chilkat .NET Downloads Chilkat .NET Assemblies

Add-Type -Path "C:\chilkat\ChilkatDotNet47-9.5.0-x64\ChilkatDotNet47.dll"

# 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.

$jsonToken = New-Object Chilkat.JsonObject
$success = $jsonToken.LoadFile("qa_data/tokens/hmrc.json")
if ($success -ne $true) {
    $("Failed to load hmrc.json")
    exit
}

# 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": "..."
# }

$oauth2 = New-Object Chilkat.OAuth2

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

# Replace these with actual values.
$oauth2.ClientId = "HMRC-CLIENT-ID"
$oauth2.ClientSecret = "HMRC-CLIENT-SECRET"

# Get the "refresh_token"
$oauth2.RefreshToken = $jsonToken.StringOf("refresh_token")

# Send the HTTP POST to refresh the access token..
$success = $oauth2.RefreshAccessToken()
if ($success -ne $true) {
    $($oauth2.LastErrorText)
    exit
}

# Load the access token response into the json object 
$jsonToken.Load($oauth2.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 ($jsonToken.HasMember("expires_on") -eq $false) {
    $dtExpire = New-Object Chilkat.CkDateTime
    $dtExpire.SetFromCurrentSystemTime()
    $dtExpire.AddSeconds($jsonToken.IntOf("expires_in"))
    $jsonToken.AppendString("expires_on",$dtExpire.GetAsUnixTimeStr($false))
}

# 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.
$sbJson = New-Object Chilkat.StringBuilder
$jsonToken.EmitCompact = $false
$jsonToken.EmitSb($sbJson)
$sbJson.WriteFile("qa_data/tokens/hmrc.json","utf-8",$false)

$("OAuth2 authorization granted!")
$("New Access Token = " + $oauth2.AccessToken)