(Unicode 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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#include <CkStringBuilderW.h>
#include <CkHttpW.h>
#include <CkBinDataW.h>
#include <CkFileAccessW.h>
#include <CkAuthGoogleW.h>
#include <CkSocketW.h>

void ChilkatSample(void)
    {
    // 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..
    CkStringBuilderW sbToken;
    bool success = sbToken.LoadFile(L"qa_data/tokens/googleCloudStorageAccessToken.txt",L"utf-8");
    if (success == false) {
        wprintf(L"Failed to load access token.\n");
        return;
    }

    CkHttpW http;

    http.put_AuthToken(sbToken.getAsString());

    // Construct a URL to download an object named "starfish.jpg" from the "chilkat-ocean" bucket.
    http.SetUrlVar(L"bucket_name",L"chilkat-ocean");
    http.SetUrlVar(L"object_name",L"starfish.jpg");
    const wchar_t *url = L"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..
    CkBinDataW fileData;
    success = http.DownloadBd(url,fileData);
    int responseCode = http.get_LastStatus();
    if ((success == false) && (responseCode != 401)) {
        wprintf(L"%s\n",http.lastErrorText());
        return;
    }

    if (responseCode == 401) {
        wprintf(L"Received 401 Unauthorized response. Attempting to refresh the access token...\n");

        // May be that the access token expired.
        // Load our JSON key and request a new access token, then retry the original request.
        CkFileAccessW fac;
        const wchar_t *jsonKey = fac.readEntireTextFile(L"qa_data/googleApi/ChilkatCloud-13a07a2e8b3f.json",L"utf-8");
        if (fac.get_LastMethodSuccess() != true) {
            wprintf(L"%s\n",fac.lastErrorText());
            return;
        }

        CkAuthGoogleW gAuth;
        gAuth.put_JsonKey(jsonKey);
        gAuth.put_Scope(L"https://www.googleapis.com/auth/cloud-platform");
        gAuth.put_ExpireNumSeconds(3600);
        gAuth.put_SubEmailAddress(L"");

        CkSocketW tlsSock;
        success = tlsSock.Connect(L"www.googleapis.com",443,true,5000);
        if (success != true) {
            wprintf(L"%s\n",tlsSock.lastErrorText());
            return;
        }

        success = gAuth.ObtainAccessToken(tlsSock);
        if (success != true) {
            wprintf(L"%s\n",gAuth.lastErrorText());
            return;
        }

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

        // Retry the original request.
        http.put_AuthToken(gAuth.accessToken());
        success = http.DownloadBd(url,fileData);
        if (success == false) {
            wprintf(L"%s\n",http.lastErrorText());
            return;
        }

    }

    if (responseCode != 200) {
        // Get the error response
        CkStringBuilderW sbErrorResponse;
        sbErrorResponse.AppendBd(fileData,L"utf-8",0,0);
        wprintf(L"Error response code = %d\n",responseCode);
        wprintf(L"Error:\n");
        wprintf(L"%s\n",sbErrorResponse.getAsString());
        return;
    }

    wprintf(L"Success.\n");

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