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Get OAuth 2.0 Access Token using G_SvcOauthAccessToken2

Obtains an OAUTH2 access token from the Google OAuth 2.0 Authorization Server using the G_SvcOauthAccessToken2 method. 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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Local $bSuccess = False

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

;  --------------------------------------------------------------------------------
;  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
;  --------------------------------------------------------------------------------

$oHttp = ObjCreate("Chilkat.Http")

;  When a service account (Client ID) is created at https://code.google.com/apis/console/
;  Google will generate a P12 key.  This is a PKCS12 (PFX) file that you will download
;  and save.  The password to access the contents of this file is "notasecret".
;  NOTE: The Chilkat Pfx API provides the ability to load a PFX/P12 and re-save
;  with a different password.

;  Begin by loading the downloaded .p12 into a Chilkat certificate object:
$oCert = ObjCreate("Chilkat.Cert")
$bSuccess = $oCert.LoadPfxFile("/myDir/API Project-1c43a291e2a1-notasecret.p12","notasecret")
If ($bSuccess <> True) Then
    ConsoleWrite($oCert.LastErrorText & @CRLF)
    Exit
EndIf

;  The next (and final) step is to request the access token.  Chilkat internally
;  does all the work of forming the JWT header and JWT claim set, encoding and
;  signing the JWT, and sending the access token request.
;  The application need only provide the inputs: The iss, scope(s), sub, and the
;  desired duration with a max of 3600 seconds (1 hour).
;  
;  Each of these inputs is defined as follows 
;  (see https://developers.google.com/accounts/docs/OAuth2ServiceAccount
;  iss: The email address of the service account.
;  scope: A space-delimited list of the permissions that the application requests.
;  sub: The email address of the user for which the application is requesting delegated access.
;  numSec: The number of seconds for which the access token will be valid (max 3600).

$oClaimParams = ObjCreate("Chilkat.Hashtable")

;  The required claim parameters that must be provided by the application are
;  the "iss" and "scope" params:
$bSuccess = $oClaimParams.AddStr("iss","761326798069-r5mljlln1rd4lrbhg75efgigp36m78j5@developer.gserviceaccount.com")
$bSuccess = $oClaimParams.AddStr("scope","https://mail.google.com/")

;  The "sub" param is required if there is an email address, such as for a
;  Google Apps domain—if you use Google Apps for Work, where the administrator of the Google Apps domain 
;  can authorize an application to access user data on behalf of users in the Google Apps domain.
;  
;  Comment out this line if there is no such email address.
$bSuccess = $oClaimParams.AddStr("sub","user@your-domain.com")

;  The "aud" parameter is optional.  If not set, it defaults to the value shown here:
$bSuccess = $oClaimParams.AddStr("aud","https://accounts.google.com/o/oauth2/token")

Local $iNumSec = 3600

Local $sAccessToken = $oHttp.G_SvcOauthAccessToken2($oClaimParams,$iNumSec,$oCert)
If ($oHttp.LastMethodSuccess <> True) Then
    ConsoleWrite($oHttp.LastErrorText & @CRLF)
Else
    ConsoleWrite("access token: " & $sAccessToken & @CRLF)
EndIf