public DatedFeedAsyncEnumerator(IDatedFeed datedFeed, FeedDate feedDate, bool cachePages = false)
: base(datedFeed, cachePages)
{
CurrentEarliest = feedDate.Date;
CurrentLatest = feedDate.Date;
DatedFeed = datedFeed;
}
public override async Task <PageReadResult> MoveNextAsync(CancellationToken cancellationToken)
{
PageReadResult?result = null;
Uri? pageUri = null;
FeedDate feedDate = default;
bool criticalFailure = false;
try
{
await _semaphore.WaitAsync(cancellationToken);
feedDate = new FeedDate(CurrentEarliest, DateDirection.Before);
pageUri = DatedFeed.GetUriForDate(feedDate);
if (pageUri == LastFetchedUri)
{
criticalFailure = true;
throw new FeedReaderException($"URL '{pageUri}' was previously read, aborting to avoid possible infinite loop.");
}
result = await DatedFeed.GetSongsAsync(pageUri, cancellationToken).ConfigureAwait(false);
LastFetchedUri = pageUri;
}
catch (OperationCanceledException ex)
{
result = PageReadResult.CancelledResult(pageUri, ex);
}
catch (Exception ex)
{
if (criticalFailure)
{
throw;
}
result = new PageReadResult(pageUri, null, null, null, 0, ex, PageErrorType.Unknown);
}
finally
{
ProcessResult(result, feedDate.Direction);
_semaphore.Release();
}
return(result);
}
public bool Equals(FeedDate other)
{
return(Date == other.Date && Direction == other.Direction);
}
