public static void HandleSubscribe(Message message, TextWriter log)
{
string feedUrl = message.Body.FeedUrl;
string imageUri = message.Body.ImageUri;
string hash = Convert.ToBase64String(message.Hash.Code);
Guid userGuid = message.ObjectId;
using (var context = new CommuterDbContext())
{
Podcast podcast = context.Podcasts
.FirstOrDefault(p => p.FeedUrl == feedUrl);
if (podcast == null)
{
podcast = context.Podcasts.Add(new Podcast
{
FeedUrl = feedUrl,
ImageUri = imageUri
});
log.WriteLine($"Adding new podcast {feedUrl}.");
}
else
{
log.WriteLine($"Adding subscription for existing podcast {feedUrl}.");
}
context.Subscriptions.Add(new Subscription
{
Podcast = podcast,
UserGuid = userGuid,
Hash = hash
});
context.SaveChanges();
}
}
public static async Task CheckFeeds(TextWriter log, HttpMessagePump pump)
{
var yesterday = DateTime.UtcNow.AddDays(-1.0);
var halfHourAgo = DateTime.UtcNow.AddHours(-0.5);
using (var context = new CommuterDbContext())
{
var podcastsToCheck = context.Podcasts
.Include("Episodes")
.Where(p => context.Subscriptions.Any(
s => s.Podcast == p))
.Where(p =>
p.LastUpdateDateTime == null ||
p.LastUpdateDateTime < yesterday)
.Where(p =>
p.LastAttemptDateTime == null ||
p.LastAttemptDateTime < halfHourAgo)
.ToImmutableList();
var messages = await Task.WhenAll(podcastsToCheck
.Select(p => CheckFeed(p, log)));
pump.SendAllMessages(messages
.SelectMany(m => m)
.ToImmutableList());
await pump.JoinAsync();
if (pump.Exception != null)
throw pump.Exception;
context.ValidateAndSaveChanges();
}
}
public static void HandleUnsubscribe(Message message, TextWriter log)
{
var hashes = message.GetPredecessors("Subscription")
.Select(p => Convert.ToBase64String(p.Code))
.ToList();
using (var context = new CommuterDbContext())
{
var predecessors = context.Subscriptions
.Where(s => hashes.Contains(s.Hash))
.ToList();
context.Subscriptions.RemoveRange(predecessors);
log.WriteLine($"Removing {predecessors.Count} podcast subscriptions");
context.SaveChanges();
}
}
public static async Task CheckQueues(TextWriter log, HttpMessagePump pump)
{
using (var context = new CommuterDbContext())
{
await context.Database.ExecuteSqlCommandAsync(@"
update Subscription
set StartAtEpisodeId = last.EpisodeId
from Subscription
join (
select s.SubscriptionId, max(e.EpisodeId) EpisodeId
from Subscription s
join Episode e
on e.PodcastId = s.PodcastId
where s.StartAtEpisodeId = 0
group by s.SubscriptionId
) last
on Subscription.SubscriptionId = last.SubscriptionId
");
var episodesToQueue = (
from s in context.Subscriptions
where s.StartAtEpisodeId > 0
from e in s.Podcast.Episodes
where e.EpisodeId >= s.StartAtEpisodeId
where !(
from q in s.Queues
where q.Episode == e
select q
).Any()
select new { Subscription = s, Episode = e })
.ToImmutableList();
var distinctEpisodes = episodesToQueue
.Select(e => e.Episode)
.Distinct()
.Count();
var distinctSubscriptions = episodesToQueue
.Select(e => e.Subscription)
.Distinct()
.Count();
log.WriteLine($"Found {distinctEpisodes} new episodes to queue for {distinctSubscriptions} subscriptions.");
pump.SendAllMessages(episodesToQueue.Select(e =>
QueueMessage(e.Subscription, e.Episode))
.ToImmutableList());
await pump.JoinAsync();
if (pump.Exception != null)
throw pump.Exception;
log.WriteLine($"Sent {episodesToQueue.Count} messages.");
foreach (var e in episodesToQueue)
{
e.Subscription.Queues.Add(new Queue
{
Episode = e.Episode
});
}
context.ValidateAndSaveChanges();
log.WriteLine($"Saved {episodesToQueue.Count} records.");
}
}
