(Visual FoxPro) Twitter API v2 - Get OAuth2 Access Token

Demonstrates how to get a Twitter API v2 OAuth2 access token from a desktop application or script.

This example is deprecated and no longer valid.

For more information, see https://developer.twitter.com/en/docs/authentication/oauth-2-0/user-access-token

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

LOCAL lnSuccess
LOCAL loOauth2
LOCAL lcUrl
LOCAL lnNumMsWaited
LOCAL loJson
LOCAL loFac

lnSuccess = 0

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

loOauth2 = CreateObject('Chilkat.OAuth2')

* This should be the port in the localhost callback URI for your App (defined in the Twitter Developer Portal)
* The Callback URI / Redirect URL should be "http://localhost:3017/" if the port number is 3017.
loOauth2.ListenPort = 3017

loOauth2.AuthorizationEndpoint = "https://twitter.com/i/oauth2/authorize"
loOauth2.TokenEndpoint = "https://api.twitter.com/2/oauth2/token"

* Replace these with actual values.
loOauth2.ClientId = "CLIENT_ID"
loOauth2.ClientSecret = "CLIENT_SECRET"

loOauth2.Scope = "tweet.read users.read follows.read follows.write"

loOauth2.AddAuthQueryParam("offline.access","")
loOauth2.AddAuthQueryParam("state","state")
loOauth2.CodeChallenge = 1
loOauth2.CodeChallengeMethod = "plain"
loOauth2.UseBasicAuth = 1

* Begin the OAuth2 three-legged flow.  This returns a URL that should be loaded in a browser.
lcUrl = loOauth2.StartAuth()
IF (loOauth2.LastMethodSuccess = 0) THEN
    ? loOauth2.LastErrorText
    RELEASE loOauth2
    CANCEL
ENDIF

? lcUrl

* Launch the system's default browser navigated to the URL.
lnSuccess = loOauth2.LaunchBrowser(lcUrl)
IF (lnSuccess = 0) THEN
    ? loOauth2.LastErrorText
    RELEASE loOauth2
    CANCEL
ENDIF

* Now wait for the authorization.
* We'll wait for a max of 60 seconds.
lnNumMsWaited = 0
DO WHILE (lnNumMsWaited < 60000) AND (loOauth2.AuthFlowState < 3)
    loOauth2.SleepMs(100)
    lnNumMsWaited = lnNumMsWaited + 100
ENDDO

* If there was no response from the browser within 60 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

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

* Get the full JSON response:
loJson = CreateObject('Chilkat.JsonObject')
loJson.Load(loOauth2.AccessTokenResponse)
loJson.EmitCompact = 0

* The JSON response looks like this:

* {
*   "token_type": "bearer",
*   "expires_in": 7200,
*   "access_token": "NnAfRUxCVWhLNDB3MFRvd25yQlNnelRZY1F1WkFlQqVfNXYwOEVobVNqR0VfOjf2NTg4NDk0MjMxnzE6MTowOmF2OjE",
*   "scope": "users.read follows.read tweet.read follows.write"
* }

? loJson.Emit()

* Save the JSON to a file for future requests.
loFac = CreateObject('Chilkat.FileAccess')
loFac.WriteEntireTextFile("qa_data/tokens/twitter_v2_oauth2.json",loJson.Emit(),"utf-8",0)

RELEASE loOauth2
RELEASE loJson
RELEASE loFac