public async Task <QueryState> ReadState(QueryETag etag)
{
var stream = etag.Key.GetCheckpointStream();
var result = await _context.Connection.ReadEventAsync(stream, StreamPosition.End, resolveLinkTos : false);
switch (result.Status)
{
case EventReadStatus.NoStream:
case EventReadStatus.NotFound:
return(new QueryState(etag.WithoutCheckpoint(), GetDefaultData(etag)));
case EventReadStatus.Success:
var number = result.Event?.Event.EventNumber;
var data = result.Event?.Event.Data;
var checkpoint = new TimelinePosition(number);
return(checkpoint == etag.Checkpoint
? new QueryState(etag)
: new QueryState(etag.WithCheckpoint(checkpoint), new MemoryStream(data)));
default:
throw new Exception($"Unexpected result when reading {stream}: {result.Status}");
}
}
QueryContent GetCheckpointContent(QueryETag etag, ResolvedEvent e)
{
var metadata = _context.ReadCheckpointMetadata(e);
if (metadata.ErrorPosition.IsSome)
{
throw new Exception($"Query is stopped at {metadata.ErrorPosition} with the following error: {metadata.ErrorMessage}");
}
var checkpoint = new TimelinePosition(e.Event.EventNumber);
return(checkpoint == etag.Checkpoint
? new QueryContent(etag)
: new QueryContent(etag.WithCheckpoint(checkpoint), new MemoryStream(e.Event.Data)));
}
