(Excel) Get a Google Drive Application Specific Data OAuth2 Access Token

Demonstrates how to get a Google Drive OAuth2 access token from a desktop application or script for the purpose of uploading and fetching only application-specific data.

"The application data folder is a special hidden folder that your app can use to store application-specific data, such as configuration files. The application data folder is automatically created when you attempt to create a file in it. Use this folder to store any files that the user shouldn't directly interact with. This folder is only accessible by your application and its contents are hidden from the user and from other Drive apps.

The application data folder is deleted when a user uninstalls your app from their MyDrive. Users can also delete your app's data folder manually."

For more information, see https://developers.google.com/drive/api/v3/appdata

Download Excel Class Modules Chilkat Excel Class Modules

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

Dim oauth2 As Chilkat.OAuth2
Set oauth2 = Chilkat.NewOAuth2

' 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.
oauth2.ListenPort = 55568

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

' Replace these with actual values.
oauth2.ClientId = "GOOGLE-CLIENT-ID"
oauth2.ClientSecret = "GOOGLE-CLIENT-SECRET"

oauth2.CodeChallenge = True
oauth2.CodeChallengeMethod = "S256"

' Specify the scope for application specific data only.
oauth2.Scope = "https://www.googleapis.com/auth/drive.appdata"

' Begin the OAuth2 three-legged flow.  This returns a URL that should be loaded in a browser.

url = oauth2.StartAuth()
If (oauth2.LastMethodSuccess <> True) Then
    Debug.Print oauth2.LastErrorText
    Exit Sub
End If

' 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 QuickBooks 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 30 seconds.

numMsWaited = 0
Do While (numMsWaited < 30000) And (oauth2.AuthFlowState < 3)
    oauth2.SleepMs 100
    numMsWaited = numMsWaited + 100
Loop

' 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 (oauth2.AuthFlowState < 3) Then
    Dim success As Boolean
    success = oauth2.Cancel()
    Debug.Print "No response from the browser!"
    Exit Sub
End If

' 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 (oauth2.AuthFlowState = 5) Then
    Debug.Print "OAuth2 failed to complete."
    Debug.Print oauth2.FailureInfo
    Exit Sub
End If

If (oauth2.AuthFlowState = 4) Then
    Debug.Print "OAuth2 authorization was denied."
    Debug.Print oauth2.AccessTokenResponse
    Exit Sub
End If

If (oauth2.AuthFlowState <> 3) Then
    Debug.Print "Unexpected AuthFlowState:"; oauth2.AuthFlowState
    Exit Sub
End If

' Save the full JSON access token response to a file.
Dim sbJson As Chilkat.StringBuilder
Set sbJson = Chilkat.NewStringBuilder
success = sbJson.Append(oauth2.AccessTokenResponse)
success = sbJson.WriteFile("qa_data/tokens/googleDriveAppData.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"
' 	}
' 
Debug.Print "OAuth2 authorization granted!"
Debug.Print "Access Token = "; oauth2.AccessToken