(AutoIt) Get GMail SMTP OAuth2 Access Token for Desktop App

Demonstrates how to get a GMail SMTP OAuth2 access token from a desktop application or script, which can be used with the XOAUTH2 authentication method.

This example requires a browser window to be displayed to allow the GMail account owner to authorize the access. The code for displaying the web browser is omitted. Suggestions for a few programming languages are provided in code comments. You'll need to find out how to display a web browser and navigate to the URL returned by the call to oauth2.StartAuth.

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

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

$oOauth2 = ObjCreate("Chilkat.OAuth2")
Local $bSuccess

; For Google OAuth2, set the listen port equal to the port used
; in the Authorized Redirect URL for the Client ID.
; For example, in this case the Authorized Redirect URL would be http://localhost:55568/
; Your app should choose a port not likely not used by any other application.
$oOauth2.ListenPort = 55568

$oOauth2.AuthorizationEndpoint = "https://accounts.google.com/o/oauth2/v2/auth"
$oOauth2.TokenEndpoint = "https://www.googleapis.com/oauth2/v4/token"

; Replace these with actual values.
$oOauth2.ClientId = "GOOGLE-CLIENT-ID"
$oOauth2.ClientSecret = "GOOGLE-CLIENT-SECRET"

$oOauth2.CodeChallenge = True
$oOauth2.CodeChallengeMethod = "S256"

; This is the full-permissions scope for GMail.
; oauth2.Scope = "https://mail.google.com/";
$oOauth2.Scope = "https://www.googleapis.com/auth/gmail.send"

; -------------------------------------------------------------------------------------------------------
; Important: Google claims there is a send-only scope:  "https://www.googleapis.com/auth/gmail.send"
; However, it has been found to NOT work when sending email using the SMTP protocol.
; Perhaps it works for sending GMail using the GMail REST API, but it most certainly does not
; provide access/authentication for sending email by SMTP.  The full GMail scope is required.
; In any case, it may be much easier to avoid using OAuth2 altogether and instead use "App Passwords".
; See Send GMail with App Passwords.
; -------------------------------------------------------------------------------------------------------

; Begin the OAuth2 three-legged flow.  This returns a URL that should be loaded in a browser.
Local $sUrl = $oOauth2.StartAuth()
If ($oOauth2.LastMethodSuccess <> True) Then
    ConsoleWrite($oOauth2.LastErrorText & @CRLF)
    Exit
EndIf

; At this point, your application should load the URL in a browser.
; For example, 
; in C#: System.Diagnostics.Process.Start(url);
;  in Java: Desktop.getDesktop().browse(new URI(url));
;  in VBScript: Set wsh=WScript.CreateObject("WScript.Shell")
;              wsh.Run url
; in Xojo: ShowURL(url)  (see http://docs.xojo.com/index.php/ShowURL)
; in Dataflex: Runprogram Background "c:\Program Files\Internet Explorer\iexplore.exe" sUrl        
; The Google account owner would interactively accept or deny the authorization request.

; Add the code to load the url in a web browser here...
; Add the code to load the url in a web browser here...
; Add the code to load the url in a web browser here...

; Now wait for the authorization.
; We'll wait for a max of 60 seconds.
Local $iNumMsWaited = 0
While ($iNumMsWaited < 60000) And ($oOauth2.AuthFlowState < 3)
    $oOauth2.SleepMs 100
    $iNumMsWaited = $iNumMsWaited + 100
Wend

; If there was no response from the browser within 30 seconds, then 
; the AuthFlowState will be equal to 1 or 2.
; 1: Waiting for Redirect. The OAuth2 background thread is waiting to receive the redirect HTTP request from the browser.
; 2: Waiting for Final Response. The OAuth2 background thread is waiting for the final access token response.
; In that case, cancel the background task started in the call to StartAuth.
If ($oOauth2.AuthFlowState < 3) Then
    $oOauth2.Cancel()
    ConsoleWrite("No response from the browser!" & @CRLF)
    Exit
EndIf

; Check the AuthFlowState to see if authorization was granted, denied, or if some error occurred
; The possible AuthFlowState values are:
; 3: Completed with Success. The OAuth2 flow has completed, the background thread exited, and the successful JSON response is available in AccessTokenResponse property.
; 4: Completed with Access Denied. The OAuth2 flow has completed, the background thread exited, and the error JSON is available in AccessTokenResponse property.
; 5: Failed Prior to Completion. The OAuth2 flow failed to complete, the background thread exited, and the error information is available in the FailureInfo property.
If ($oOauth2.AuthFlowState = 5) Then
    ConsoleWrite("OAuth2 failed to complete." & @CRLF)
    ConsoleWrite($oOauth2.FailureInfo & @CRLF)
    Exit
EndIf

If ($oOauth2.AuthFlowState = 4) Then
    ConsoleWrite("OAuth2 authorization was denied." & @CRLF)
    ConsoleWrite($oOauth2.AccessTokenResponse & @CRLF)
    Exit
EndIf

If ($oOauth2.AuthFlowState <> 3) Then
    ConsoleWrite("Unexpected AuthFlowState:" & $oOauth2.AuthFlowState & @CRLF)
    Exit
EndIf

; Save the full JSON access token response to a file.
$oSbJson = ObjCreate("Chilkat.StringBuilder")
$oSbJson.Append($oOauth2.AccessTokenResponse)
$oSbJson.WriteFile("qa_data/tokens/_gmailSmtp.json","utf-8",False)

; The saved JSON response looks like this:

; 	{
; 	 "access_token": "ya39.Ci-XA_C5bGgRDC3UaD-h0_NeL-DVIQnI2gHtBBBHkZzrwlARkwX6R3O0PCDEzRlfaQ",
; 	 "token_type": "Bearer",
; 	 "expires_in": 3600,
; 	 "refresh_token": "1/r_2c_7jddspcdfesrrfKqfXtqo08D6Q-gUU0DsdfVMsx0c"
; 	}
; 
ConsoleWrite("OAuth2 authorization granted!" & @CRLF)
ConsoleWrite("Access Token = " & $oOauth2.AccessToken & @CRLF)