public IObservable <Message> LoadMessages(
Aggregate feed,
AggregateLoadingState state)
{
return(LoadAggregateMessages(feed, state)
.SelectMany(MapToMessage));
}
private IObservable <TdApi.Message> LoadAggregateMessages(
Aggregate aggregate,
AggregateLoadingState state)
{
var actualLimit = _limit;
var list = aggregate.Chats.Select(f =>
{
var stackedCount = state.CountStackedMessages(f.ChatData.Id);
return(Enumerable.Range(0, stackedCount)
.Select(_ => state.PopMessageFromStack(f.ChatData.Id)) // get stacked messages for this chat
.ToObservable()
.Concat(stackedCount < _limit
? LoadChannelMessages(f, new ChatLoadingState // load messages from the server
{
LastMessageId = state.GetLastMessageId(f.ChatData.Id)
}, _limit, 0)
: Observable.Empty <TdApi.Message>())
.Aggregate(new List <TdApi.Message>(), (l, m) =>
{
l.Add(m);
return l;
})
.Do(l =>
{
// api has no guarantees about actual number of messages returned
// actual limit would be equal to min number of messages for all feeds
// unless it is zero
if (l.Count > 0 && l.Count < actualLimit)
{
actualLimit = l.Count;
}
})
.SelectMany(messages => messages));
});
return(list.Merge()
.Aggregate(new List <TdApi.Message>(), (l, m) =>
{
l.Add(m);
return l;
})
.SelectMany(l =>
{
// make sure all messages are unique
var all = l.GroupBy(m => m.Id)
.Select(g => g.First())
.OrderByDescending(m => m.Date)
.ToArray();
var toBeReturned = all.Take(actualLimit);
var toBeStacked = all.Skip(actualLimit);
// remember last message id
foreach (var message in all.Reverse())
{
state.SetLastMessageId(message.ChatId, message.Id);
}
// put into stack
foreach (var message in toBeStacked.Reverse())
{
state.PushMessageToStack(message.ChatId, message);
}
return toBeReturned;
}));
}