(Swift) 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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func chilkatTest() {
    // For more information about the OAuth2, see OAuth 2.0 Authorization Flow

    let oauth2 = CkoOAuth2()!

    // 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
    oauth2.localHost = "127.0.0.1"
    oauth2.listenPort = 3017

    oauth2.authorizationEndpoint = "https://x.com/i/oauth2/authorize"
    oauth2.tokenEndpoint = "https://api.x.com/2/oauth2/token"

    // Replace this with your actual X.com OAuth2 Client ID and Client Secret
    oauth2.clientId = "OAUTH2_CLIENT_ID"
    oauth2.clientSecret = "OAUTH2_CLIENT_SECRET"

    // This is for Require Proof Key for Code Exchange (PKCE)
    // See OAuth2 PKCE Explained
    oauth2.codeChallenge = true
    oauth2.codeChallengeMethod = "S256"

    // Space separated scopes...
    oauth2.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.
    var url: String? = oauth2.start()
    if oauth2.lastMethodSuccess != true {
        print("\(oauth2.lastErrorText!)")
        return
    }

    print("url = \(url!)")

    // Launch the default browser on the system and navigate to the url.
    // The LaunchBrowser method was added in Chilkat v10.1.2.
    var success: Bool = oauth2.launchBrowser(url)
    if success == false {
        print("\(oauth2.lastErrorText!)")
        return
    }

    // Wait for the user to approve or deny authorization in the browser.
    var numMsWaited: Int = 0
    while (numMsWaited < 10000) && (oauth2.authFlowState.intValue < 3) {
        oauth2.sleepMs(100)
        numMsWaited = numMsWaited + 100
    }

    // 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 oauth2.authFlowState.intValue < 3 {
        oauth2.cancel()
        print("No response from the browser!")
        return
    }

    // 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 oauth2.authFlowState.intValue == 5 {
        print("OAuth2 failed to complete.")
        print("\(oauth2.failureInfo!)")
        return
    }

    if oauth2.authFlowState.intValue == 4 {
        print("OAuth2 authorization was denied.")
        print("\(oauth2.accessTokenResponse!)")
        return
    }

    if oauth2.authFlowState.intValue != 3 {
        print("Unexpected AuthFlowState:\(oauth2.authFlowState.intValue)")
        return
    }

    print("OAuth2 authorization granted!")

    let json = CkoJsonObject()!
    json.load(oauth2.accessTokenResponse)
    json.emitCompact = false

    // 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 json.hasMember("expires_on") == false {
        let dtExpire = CkoDateTime()!
        dtExpire.setFromCurrentSystemTime()
        dtExpire.addSeconds(json.int(of: "expires_in").intValue)
        json.append("expires_on", value: dtExpire.getAsUnixTimeStr(false))
    }

    print("Access Token Response = \(json.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"
    // }

    print("Access Token = \(oauth2.accessToken!)")

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

    // 

}