(Tcl) Get XOAUTH2 Access Token from Google OAuth 2.0 Authorization Server

Obtains an OAUTH2 access token from the Google OAuth 2.0 Authorization Server. This is for Server to server applications using Google API's that need an access token. See https://developers.google.com/accounts/docs/OAuth2ServiceAccount

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load ./chilkat.dll

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

set http [new_CkHttp]

# --------------------------------------------------------------------------------
# For a step-by-step guide for setting up your Google Workspace service account,
# see Setup Google Workspace Account for Sending SMTP GMail from a Service Account
# --------------------------------------------------------------------------------
# Begin by loading your Google service account key (.p12)
set cert [new_CkCert]

set success [CkCert_LoadPfxFile $cert "c:/someDirectory/keys/chilkat25-cbd7b42afbd8.p12" "notasecret"]
if {$success != 1} then {
    puts [CkCert_lastErrorText $cert]
    delete_CkHttp $http
    delete_CkCert $cert
    exit
}

# The ISS is your service account email address ending in gserviceaccount.com.
set iss "chilkatsvc@chilkat25.iam.gserviceaccount.com"

# The scope is always the following string:
set scope "https://mail.google.com/"

# The sub is your company email address
set oauth_sub "bob@yourcompany.com"

# The access token is valid for this number of seconds.
set numSec 3600

set accessToken [CkHttp_g_SvcOauthAccessToken $http $iss $scope $oauth_sub $numSec $cert]
if {[CkHttp_get_LastMethodSuccess $http] != 1} then {
    puts [CkHttp_lastErrorText $http]
    delete_CkHttp $http
    delete_CkCert $cert
    exit
} else {
    puts "access token: $accessToken"
}

# The access token allows us to send unlimited emails while it's valid. Once it expires, we must obtain and use a new one.

delete_CkHttp $http
delete_CkCert $cert