(Visual FoxPro) X.com OAuth 2.0 Authorization Code with PKCE

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

For more information, see https://docs.x.com/resources/fundamentals/authentication/oauth-2-0/authorization-code

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LOCAL loOauth2
LOCAL lcUrl
LOCAL lnSuccess
LOCAL lnNumMsWaited
LOCAL loJson
LOCAL loDtExpire

* For more information about the OAuth2, see OAuth 2.0 Authorization Flow

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

* The port should match the Authorized Redirect URL in your X.com app, 
* which would look like "http://127.0.0.1:3017/"
* See the screenshot below of the App Settings in the X Developer Portal
loOauth2.LocalHost = "127.0.0.1"
loOauth2.ListenPort = 3017

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

* Replace this with your actual X.com OAuth2 Client ID and Client Secret
loOauth2.ClientId = "OAUTH2_CLIENT_ID"
loOauth2.ClientSecret = "OAUTH2_CLIENT_SECRET"

* This is for Require Proof Key for Code Exchange (PKCE)
* See OAuth2 PKCE Explained
loOauth2.CodeChallenge = 1
loOauth2.CodeChallengeMethod = "S256"

* Space separated scopes...
loOauth2.Scope = "tweet.read tweet.write users.read follows.read follows.write offline.access like.read like.write block.read block.write"

* 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

? "url = " + lcUrl

* 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 user to approve or deny authorization in the browser.
lnNumMsWaited = 0
DO WHILE (lnNumMsWaited < 10000) AND (loOauth2.AuthFlowState < 3)
    loOauth2.SleepMs(100)
    lnNumMsWaited = lnNumMsWaited + 100
ENDDO

* If the browser does not respond within the specified time, AuthFlowState will be:
* 
* 1: Waiting for Redirect - The OAuth2 background thread is waiting for the browser's redirect request.
* 2: Waiting for Final Response - The thread is awaiting the final access token response.
* In either case, cancel the background task initiated by StartAuth.

IF (loOauth2.AuthFlowState < 3) THEN
    loOauth2.Cancel()
    ? "No response from the browser!"
    RELEASE loOauth2
    CANCEL
ENDIF

* Check AuthFlowState to determine if authorization was granted, denied, or failed:
* 
* 3: Success - OAuth2 flow completed, the background thread exited, and the successful response is in AccessTokenResponse.
* 4: Access Denied - OAuth2 flow completed, the background thread exited, and the error response is in AccessTokenResponse.
* 5: Failure - OAuth2 flow failed before completion, the background thread exited, and error details are in FailureInfo.

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!"

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.JsonObject')
loJson = CreateObject('Chilkat.JsonObject')
loJson.Load(loOauth2.AccessTokenResponse)
loJson.EmitCompact = 0

* If an "expires_on" member does not exist, then add the JSON member by
* getting the current system date/time and adding the "expires_in" seconds.
* This way we'll know when the token expires.
IF (loJson.HasMember("expires_on") = 0) THEN
    * For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.CkDateTime')
    loDtExpire = CreateObject('Chilkat.CkDateTime')
    loDtExpire.SetFromCurrentSystemTime()
    loDtExpire.AddSeconds(loJson.IntOf("expires_in"))
    loJson.AppendString("expires_on",loDtExpire.GetAsUnixTimeStr(0))
ENDIF

? "Access Token Response = " + loJson.Emit()

* A sample access token response:

* {
*   "token_type": "bearer",
*   "expires_in": 7200,
*   "access_token": "VmNDLVZiYUZwejY5Mkx3RblFTmo3ek1leTRGclMuZFVOUTVUTWpNbVZKb1N5OjE3NDAxNjk4MDVxNTE6MToxOaF0OjE",
*   "scope": "block.read follows.read offline.access tweet.write block.write like.write like.read users.read tweet.read follows.write",
*   "refresh_token": "eThOWVVFSTRqdVp3QTFndGsxM2ZGZmFyNWVrU0phM1JKbGdrbGNWRGJzb1loOjE3NDAwMjk4MDUxNTI6MTowOnJ0OjE"
* }

? "Access Token = " + loOauth2.AccessToken

* Save the JSON access token response to a file for subsequent use..
loJson.WriteFile("qa_data/tokens/x.json")

* 

RELEASE loOauth2
RELEASE loJson
RELEASE loDtExpire