void IThumbnailOp.Process(ThumbnailRequest request)
{
runStateMachine("download-start", request);
}
private bool runStateMachine(string state, ThumbnailRequest request, byte[] image = null, Exception error = null)
{
if (error != null)
{
return(handleError(state, request, error));
}
var trackingId = request.Srv.TrackingId;
var downloadKey = request.Url;
var thumbnailKey = request.Key;
switch (state)
{
case "download-start": {
var(download, firstTouch) = _cache.Get(downloadKey);
var cacheHit = download != null;
_log.info(trackingId, () => $"{state} firstTouch={firstTouch}, cacheHit={cacheHit}");
if (cacheHit)
{
return(runStateMachine("download-ready", request, download));
}
if (firstTouch)
{
_async.Start(downloadKey, downloadImage(request, request.Url));
}
_async.WhenReady(downloadKey,
(bytes, ex) => runStateMachine("download-ready", request, bytes, ex));
return(false);
}
case "download-ready": {
_cache.Put(downloadKey, image);
var(thumbnail, firstTouch) = _cache.Get(thumbnailKey);
var cacheHit = thumbnail != null;
_log.info(trackingId, () => $"{state} firstTouch={firstTouch}, cacheHit={cacheHit}");
if (cacheHit)
{
return(runStateMachine("thumbnail-ready", request, thumbnail));
}
if (firstTouch)
{
_async.Start(thumbnailKey, resizeImage(request, image));
}
_async.WhenReady(thumbnailKey,
(bytes, ex) => runStateMachine("thumbnail-ready", request, bytes, ex));
return(false);
}
case "thumbnail-ready": {
_cache.Put(thumbnailKey, image);
request.Srv.EndWith(image);
_log.info(trackingId, () => $"{state}");
return(true);
}
default:
throw new Exception("Should not get here");
}
}