105 lines
2.8 KiB
C#
105 lines
2.8 KiB
C#
using ErsatzTV.Core.Domain;
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using ErsatzTV.Core.Interfaces.Scheduling;
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namespace ErsatzTV.Core.Scheduling;
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public class ShuffledScheduleItemsEnumerator : IScheduleItemsEnumerator
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{
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private readonly IList<ProgramScheduleItem> _scheduleItems;
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private readonly int _scheduleItemsCount;
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private CloneableRandom _random;
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private ProgramScheduleItem[] _shuffled;
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public ShuffledScheduleItemsEnumerator(
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IList<ProgramScheduleItem> scheduleItems,
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CollectionEnumeratorState state)
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{
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_scheduleItemsCount = scheduleItems.Count;
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_scheduleItems = scheduleItems;
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if (state.Index >= _scheduleItems.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(_scheduleItems, _random);
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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 CollectionEnumeratorState State { get; }
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public ProgramScheduleItem Current => _shuffled[State.Index % _scheduleItemsCount];
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public void MoveNext()
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{
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if ((State.Index + 1) % _scheduleItemsCount == 0)
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{
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ProgramScheduleItem 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(_scheduleItems, _random);
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} while (_scheduleItems.Count > 1 && Current == tail);
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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 %= _scheduleItemsCount;
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}
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public ProgramScheduleItem Peek(int offset)
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{
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if (offset == 0)
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{
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return Current;
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}
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if ((State.Index + offset) % _scheduleItemsCount == 0)
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{
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ProgramScheduleItem[] shuffled;
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ProgramScheduleItem tail = Current;
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// clone the random
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CloneableRandom randomCopy = _random.Clone();
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do
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{
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int newSeed = randomCopy.Next();
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randomCopy = new CloneableRandom(newSeed);
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shuffled = Shuffle(_scheduleItems, randomCopy);
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} while (_scheduleItems.Count > 1 && shuffled[0] == tail);
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return shuffled[0];
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}
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return _shuffled[(State.Index + offset) % _scheduleItemsCount];
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}
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private static ProgramScheduleItem[] Shuffle(IEnumerable<ProgramScheduleItem> list, CloneableRandom random)
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{
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ProgramScheduleItem[] 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 copy;
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}
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}
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