(Tcl) Refresh HMRC OAuth2 Access Token

Demonstrates how to refresh an HMRC access token.

Chilkat Tcl Extension Downloads Chilkat Tcl Extension Downloads

load ./chilkat.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.

set jsonToken [new_CkJsonObject]

set success [CkJsonObject_LoadFile $jsonToken "qa_data/tokens/hmrc.json"]
if {$success != 1} then {
    puts "Failed to load hmrc.json"
    delete_CkJsonObject $jsonToken
    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": "..."
# }

set oauth2 [new_CkOAuth2]

CkOAuth2_put_TokenEndpoint $oauth2 "https://test-api.service.hmrc.gov.uk/oauth/token"

# Replace these with actual values.
CkOAuth2_put_ClientId $oauth2 "HMRC-CLIENT-ID"
CkOAuth2_put_ClientSecret $oauth2 "HMRC-CLIENT-SECRET"

# Get the "refresh_token"
CkOAuth2_put_RefreshToken $oauth2 [CkJsonObject_stringOf $jsonToken "refresh_token"]

# Send the HTTP POST to refresh the access token..
set success [CkOAuth2_RefreshAccessToken $oauth2]
if {$success != 1} then {
    puts [CkOAuth2_lastErrorText $oauth2]
    delete_CkJsonObject $jsonToken
    delete_CkOAuth2 $oauth2
    exit
}

# Load the access token response into the json object 
CkJsonObject_Load $jsonToken [CkOAuth2_accessTokenResponse $oauth2]

# 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 {[CkJsonObject_HasMember $jsonToken "expires_on"] == 0} then {
    set dtExpire [new_CkDateTime]

    CkDateTime_SetFromCurrentSystemTime $dtExpire
    CkDateTime_AddSeconds $dtExpire [CkJsonObject_IntOf $jsonToken "expires_in"]
    CkJsonObject_AppendString $jsonToken "expires_on" [CkDateTime_getAsUnixTimeStr $dtExpire 0]
}

# 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.
set sbJson [new_CkStringBuilder]

CkJsonObject_put_EmitCompact $jsonToken 0
CkJsonObject_EmitSb $jsonToken $sbJson
CkStringBuilder_WriteFile $sbJson "qa_data/tokens/hmrc.json" "utf-8" 0

puts "OAuth2 authorization granted!"
puts "New Access Token = [CkOAuth2_accessToken $oauth2]"

delete_CkJsonObject $jsonToken
delete_CkOAuth2 $oauth2
delete_CkDateTime $dtExpire
delete_CkStringBuilder $sbJson