(Visual FoxPro) 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

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

LOCAL loHttp
LOCAL loCert
LOCAL lnSuccess
LOCAL lcIss
LOCAL lcScope
LOCAL lcOauth_sub
LOCAL lnNumSec
LOCAL lcAccessToken

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

loHttp = CreateObject('Chilkat.Http')

* --------------------------------------------------------------------------------
* 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)
loCert = CreateObject('Chilkat.Cert')
lnSuccess = loCert.LoadPfxFile("c:/someDirectory/keys/chilkat25-cbd7b42afbd8.p12","notasecret")
IF (lnSuccess <> 1) THEN
    ? loCert.LastErrorText
    RELEASE loHttp
    RELEASE loCert
    CANCEL
ENDIF

* The ISS is your service account email address ending in gserviceaccount.com.
lcIss = "chilkatsvc@chilkat25.iam.gserviceaccount.com"

* The scope is always the following string:
lcScope = "https://mail.google.com/"

* The sub is your company email address
lcOauth_sub = "bob@yourcompany.com"

* The access token is valid for this number of seconds.
lnNumSec = 3600

lcAccessToken = loHttp.G_SvcOauthAccessToken(lcIss,lcScope,lcOauth_sub,lnNumSec,loCert)
IF (loHttp.LastMethodSuccess <> 1) THEN
    ? loHttp.LastErrorText
    RELEASE loHttp
    RELEASE loCert
    CANCEL
ELSE
    ? "access token: " + lcAccessToken
ENDIF

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

RELEASE loHttp
RELEASE loCert