(Visual FoxPro) Google OAuth2 Access Token

Demonstrates how to get a Google OAuth2 access token from a desktop application or script.

Note: This example requires Chilkat v10.1.2 or later.

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

LOCAL loOauth2
LOCAL lcUrl
LOCAL lnSuccess
LOCAL lnNumMsWaited
LOCAL loSbJson

* To further clarify, see OAuth 2.0 Authorization Flow

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.OAuth2')
loOauth2 = CreateObject('Chilkat.OAuth2')

* 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 another application.
loOauth2.ListenPort = 55568

loOauth2.AuthorizationEndpoint = "https://accounts.google.com/o/oauth2/v2/auth"
loOauth2.TokenEndpoint = "https://www.googleapis.com/oauth2/v4/token"

* Replace this with your actual client ID.
loOauth2.ClientId = "GOOGLE-CLIENT-ID"

* This is the scope for Google Drive.
* See https://developers.google.com/identity/protocols/googlescopes
* Add the scopes that you need.
loOauth2.Scope = "https://www.googleapis.com/auth/drive"

* Begin the OAuth2 authorization code flow.  This returns a URL that should be loaded in a browser.
lcUrl = loOauth2.StartAuth()
IF (loOauth2.LastMethodSuccess <> 1) THEN
    ? loOauth2.LastErrorText
    RELEASE loOauth2
    CANCEL
ENDIF

* Launch the default browser on the system and navigate to the url.
* The LaunchBrowser method was added in Chilkat v10.1.2.
lnSuccess = loOauth2.LaunchBrowser(lcUrl)
IF (lnSuccess = 0) THEN
    ? loOauth2.LastErrorText
    RELEASE loOauth2
    CANCEL
ENDIF

* Wait for the interactive user to grant permission in the interactive browser session.
* We'll wait for a max of 90 seconds.
lnNumMsWaited = 0
DO WHILE (lnNumMsWaited < 90000) AND (loOauth2.AuthFlowState < 3)
    loOauth2.SleepMs(100)
    lnNumMsWaited = lnNumMsWaited + 100
ENDDO

* If there was no response from the browser within 90 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 (loOauth2.AuthFlowState < 3) THEN
    loOauth2.Cancel()
    ? "No response from the browser!"
    RELEASE loOauth2
    CANCEL
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 (loOauth2.AuthFlowState = 5) THEN
    ? "OAuth2 failed to complete."
    ? loOauth2.FailureInfo
    RELEASE loOauth2
    CANCEL
ENDIF

IF (loOauth2.AuthFlowState = 4) THEN
    ? "OAuth2 authorization was denied."
    ? loOauth2.AccessTokenResponse
    RELEASE loOauth2
    CANCEL
ENDIF

IF (loOauth2.AuthFlowState <> 3) THEN
    ? "Unexpected AuthFlowState:" + STR(loOauth2.AuthFlowState)
    RELEASE loOauth2
    CANCEL
ENDIF

* Save the full JSON access token response to a file.
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.StringBuilder')
loSbJson = CreateObject('Chilkat.StringBuilder')
loSbJson.Append(loOauth2.AccessTokenResponse)
loSbJson.WriteFile("qa_data/tokens/_googleDrive.json","utf-8",0)

* 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"
* 	}
* 
? "OAuth2 authorization granted!"
? "Access Token = " + loOauth2.AccessToken

* Here is an example showing how to define your OAuth 2.0 Credential in the Google Cloud Console
* Note: Even though your application is technically not a web app, you should still select "Web Application"
* because the Redirect URI is going to http://localhost:55568/ where Chilkat will receive it in a background thread.

* 

RELEASE loOauth2
RELEASE loSbJson