Stream custom live channels using your own media
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using ErsatzTV.Core.Domain;
using ErsatzTV.Core.Extensions;
using ErsatzTV.Core.Interfaces.Scheduling;
namespace ErsatzTV.Core.Scheduling;
public class ShuffledMediaCollectionEnumerator : IMediaCollectionEnumerator
{
private readonly CancellationToken _cancellationToken;
private readonly Lazy<Option<TimeSpan>> _lazyMinimumDuration;
private readonly int _mediaItemCount;
private readonly IList<GroupedMediaItem> _mediaItems;
private CloneableRandom _random;
private IList<MediaItem> _shuffled;
public ShuffledMediaCollectionEnumerator(
IList<GroupedMediaItem> mediaItems,
CollectionEnumeratorState state,
CancellationToken cancellationToken)
{
_mediaItemCount = mediaItems.Sum(i => 1 + Optional(i.Additional).Flatten().Count());
_mediaItems = mediaItems;
_cancellationToken = cancellationToken;
if (state.Index >= _mediaItems.Count)
{
state.Index = 0;
state.Seed = new Random(state.Seed).Next();
}
_random = new CloneableRandom(state.Seed);
_shuffled = Shuffle(_mediaItems, _random);
_lazyMinimumDuration =
new Lazy<Option<TimeSpan>>(
() => _shuffled.Bind(i => i.GetNonZeroDuration()).OrderBy(identity).HeadOrNone());
State = new CollectionEnumeratorState { Seed = state.Seed };
while (State.Index < state.Index)
{
MoveNext();
}
}
public void ResetState(CollectionEnumeratorState state)
{
// only re-shuffle if needed
if (State.Seed != state.Seed)
{
_random = new CloneableRandom(state.Seed);
_shuffled = Shuffle(_mediaItems, _random);
}
State.Index = state.Index;
}
public CollectionEnumeratorState State { get; }
public Option<MediaItem> Current => _shuffled.Any() ? _shuffled[State.Index % _mediaItemCount] : None;
public void MoveNext()
{
if ((State.Index + 1) % _mediaItemCount == 0)
{
Option<MediaItem> tail = Current;
State.Index = 0;
do
{
State.Seed = _random.Next();
_random = new CloneableRandom(State.Seed);
_shuffled = Shuffle(_mediaItems, _random);
} while (!_cancellationToken.IsCancellationRequested && _mediaItems.Count > 1 &&
Current.Map(x => x.Id) == tail.Map(x => x.Id));
}
else
{
State.Index++;
}
State.Index %= _mediaItemCount;
}
public Option<TimeSpan> MinimumDuration => _lazyMinimumDuration.Value;
public int Count => _shuffled.Count;
private IList<MediaItem> Shuffle(IEnumerable<GroupedMediaItem> list, CloneableRandom random)
{
GroupedMediaItem[] copy = list.ToArray();
int n = copy.Length;
while (n > 1)
{
n--;
int k = random.Next(n + 1);
(copy[k], copy[n]) = (copy[n], copy[k]);
}
return GroupedMediaItem.FlattenGroups(copy, _mediaItemCount);
}
}