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