/// <summary>
/// Ultimately this is just the messenger, retrieving a file either in full or via ranges (bytes) from another service
/// What we had to do was pass the range request to the service and manage the content range and content lengths returned
/// Once we worked this out, the two services talked perfectly to each other and all browsers could stream content.
/// </summary>
/// <param name="BlobUri"></param>
/// <param name="headerfiletype"></param>
/// <param name="Response"></param>
/// <param name="filename"></param>
/// <param name="Cache"></param>
/// <param name="headers"></param>
/// <returns></returns>
public async Task<IActionResult> DownloadFileAsync(string BlobUri, string headerfiletype, HttpResponse Response, string filename, bool Cache = false, IDictionary<string, string> headers = null)
{
    //download entire file, then send file to client
    HttpClient xClient = httpClientFactory.CreateClient("DownloadFileAsync");

    string RangeHeader = "";
    // Pass through the range header if it exists (we are just the messenger)
    if (headers != null && headers.TryGetValue("Range", out var rangeHeader))
    {
        //lets ignore this request
        if (rangeHeader != "bytes=0-")
        {
            xClient.DefaultRequestHeaders.Add("Range", rangeHeader);                    
            RangeHeader = rangeHeader;
        }
    }



    
    //check the contentlength            
    var httpResponse = await xClient.GetAsync(BlobUri, HttpCompletionOption.ResponseHeadersRead);

    //Response.Headers.Append("Data-Test", RangeHeader);

    if (httpResponse.IsSuccessStatusCode)
    {
        //set headers on (need content type
        Response.Headers.Append("Content-Type", httpResponse.Content.Headers.ContentType.ToString());



        //Response.Headers.Append("Data-Test-StatusCode", httpResponse.StatusCode.ToString());

        //check if the source accepts ranges
        //Tell the client whether the source accepts ranges or not (dont ask us we are just the messenger)
        if (httpResponse.Content.Headers.TryGetValues("Accept-Ranges", out var acceptRanges))
        {
            Response.Headers.Append("Accept-Ranges", string.Join(",", acceptRanges));
            //Response.Headers.Append("Data-TestAccept-Ranges1", "bytes");

        }
        else
        {
            // Handle the case where the "Accept-Ranges" header is missing or null                        
            if (BlobUri.Contains("blob.core.windows.net"))
            {
                Response.Headers.Append("Accept-Ranges", "bytes");
                //Response.Headers.Append("Data-TestAccept-Ranges2", "bytes");
            }
        }


        
            //full file, allow caching - if you are Caching this at Azure front door, you have to set the age here


            if (httpResponse.Content.Headers != null && httpResponse.Content.Headers.ContentLength != null)
            {
                Response.Headers.Append("Content-Length", httpResponse.Content.Headers.ContentLength.ToString());
            }
            if (httpResponse.Content.Headers != null && httpResponse.Content.Headers.ContentRange != null)
            {
                Response.Headers.Append("Content-Range", httpResponse.Content.Headers.ContentRange.ToString());
            }
            if (httpResponse.Content.Headers != null && httpResponse.Content.Headers.ContentEncoding != null)
            {
                Response.Headers.Append("Content-Encoding", httpResponse.Content.Headers.ContentEncoding.ToString());
            }

            Response.StatusCode = (int)httpResponse.StatusCode;

        //if cache is requested, lets only cache status ok
        //in azure front door we cache all urls under /api/websiteCached/ but they only cache if the Cache-Control is set.
        if ((int)httpResponse.StatusCode == (int)HttpStatusCode.OK)
            {
                if (Cache)
                {
                    Response.Headers.Add("Cache-Control", "public, max-age=86400");
                }
                else
                {
                    Response.Headers.Add("Cache-Control", "no-cache");
                }
            }
            else
            {
                Response.Headers.Add("Cache-Control", "no-cache");
            }
        

        var stream = await httpResponse.Content.ReadAsStreamAsync();
        return new FileStreamResult(stream, httpResponse.Content.Headers.ContentType.ToString())
        {
            FileDownloadName = filename,
            EnableRangeProcessing = true
        };
    }
    else
    {
        Response.Headers.Append("Data-Test-Error", httpResponse.Content.ToString());
        Response.Headers.Append("Data-Test", RangeHeader);
        Response.Headers.Append("Data-StatusCode", httpResponse.StatusCode.ToString());
        Response.StatusCode = (int)httpResponse.StatusCode;
        return null;
    }

}