(.NET Core C#) Refresh Access Token on 401 Unauthorized and Retry (Service Account)

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Demonstrates how to handle an expired access token error, refresh the token, and retry the request. (In this case, the request is to download an object from Google Cloud Storage.)

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

// This example uses a previously obtained access token having permission for the 
// scope "https://www.googleapis.com/auth/cloud-platform"

// In this example, Get Google Cloud Storage OAuth2 Access Token, 
// the service account access token was saved to a text file.  This example fetches the access token from the file..
Chilkat.StringBuilder sbToken = new Chilkat.StringBuilder();
bool success = sbToken.LoadFile("qa_data/tokens/googleCloudStorageAccessToken.txt","utf-8");
if (success == false) {
    Debug.WriteLine("Failed to load access token.");
    return;
}

Chilkat.Http http = new Chilkat.Http();

http.AuthToken = sbToken.GetAsString();

// Construct a URL to download an object named "starfish.jpg" from the "chilkat-ocean" bucket.
http.SetUrlVar("bucket_name","chilkat-ocean");
http.SetUrlVar("object_name","starfish.jpg");
string url = "https://www.googleapis.com/storage/v1/b/{$bucket_name}/o/{$object_name}?alt=media";

// If there is an error response, then we didn't actually download the file data,
// but instead we downloaded an error response..
Chilkat.BinData fileData = new Chilkat.BinData();
success = http.DownloadBd(url,fileData);
int responseCode = http.LastStatus;
if ((success == false) && (responseCode != 401)) {
    Debug.WriteLine(http.LastErrorText);
    return;
}

if (responseCode == 401) {
    Debug.WriteLine("Received 401 Unauthorized response. Attempting to refresh the access token...");

    // May be that the access token expired.
    // Load our JSON key and request a new access token, then retry the original request.
    Chilkat.FileAccess fac = new Chilkat.FileAccess();
    string jsonKey = fac.ReadEntireTextFile("qa_data/googleApi/ChilkatCloud-13a07a2e8b3f.json","utf-8");
    if (fac.LastMethodSuccess != true) {
        Debug.WriteLine(fac.LastErrorText);
        return;
    }

    Chilkat.AuthGoogle gAuth = new Chilkat.AuthGoogle();
    gAuth.JsonKey = jsonKey;
    gAuth.Scope = "https://www.googleapis.com/auth/cloud-platform";
    gAuth.ExpireNumSeconds = 3600;
    gAuth.SubEmailAddress = "";

    Chilkat.Socket tlsSock = new Chilkat.Socket();
    success = tlsSock.Connect("www.googleapis.com",443,true,5000);
    if (success != true) {
        Debug.WriteLine(tlsSock.LastErrorText);
        return;
    }

    success = gAuth.ObtainAccessToken(tlsSock);
    if (success != true) {
        Debug.WriteLine(gAuth.LastErrorText);
        return;
    }

    fac.WriteEntireTextFile("qa_data/tokens/googleCloudStorageAccessToken.txt",gAuth.AccessToken,"utf-8",false);

    // Retry the original request.
    http.AuthToken = gAuth.AccessToken;
    success = http.DownloadBd(url,fileData);
    if (success == false) {
        Debug.WriteLine(http.LastErrorText);
        return;
    }

}

if (responseCode != 200) {
    // Get the error response
    Chilkat.StringBuilder sbErrorResponse = new Chilkat.StringBuilder();
    sbErrorResponse.AppendBd(fileData,"utf-8",0,0);
    Debug.WriteLine("Error response code = " + Convert.ToString(responseCode));
    Debug.WriteLine("Error:");
    Debug.WriteLine(sbErrorResponse.GetAsString());
    return;
}

Debug.WriteLine("Success.");

// Save the downloaded data to a file.
success = fileData.WriteFile("qa_output/starfish.jpg");