using ErsatzTV.Core.Domain;
using ErsatzTV.Core.Interfaces.Scheduling;
using ErsatzTV.Core.Scheduling.BlockScheduling;

namespace ErsatzTV.Core.Scheduling;

/// <summary>
///     Builds the stateless-index <see cref="IMediaCollectionEnumerator" /> for a single content entry from its
///     <see cref="PlaybackOrder" /> and flat item list.
///     <para>
///         Extracted (issue #395) so the Scripted engine (<c>SchedulingEngine.EnumeratorForContent</c>) and the
///         Sequential/YAML engine (<c>EnumeratorCache.GetEnumeratorForContent</c>) share ONE construction switch
///         instead of two byte-identical copies. Kept a <c>public static</c> helper with dependencies passed as
///         parameters, matching the sibling <see cref="ShuffleSourceBuilder" /> / <see cref="MultiPartEpisodeGrouper" />
///         seams (issue #380).
///     </para>
///     <para>
///         Deliberately per-family and narrow: only <see cref="PlaybackOrder.Chronological" /> and
///         <see cref="PlaybackOrder.Shuffle" /> are supported, and Shuffle maps to the <em>block</em> variant
///         <see cref="BlockPlayoutShuffledMediaCollectionEnumerator" /> — NOT Classic's
///         <see cref="ShuffledMediaCollectionEnumerator" />, which is a different algorithm. Every other order returns
///         <see cref="Option{A}" />.<c>None</c> so each caller logs its own engine-specific "not supported" warning
///         (#70); folding the warning in here would lose that per-engine message.
///     </para>
/// </summary>
public static class ContentEnumeratorBuilder
{
    public static Option<IMediaCollectionEnumerator> ForContent(
        List<MediaItem> items,
        CollectionEnumeratorState state,
        PlaybackOrder playbackOrder,
        bool multiPart)
    {
        switch (playbackOrder)
        {
            case PlaybackOrder.Chronological:
                return new ChronologicalMediaCollectionEnumerator(items, state);
            case PlaybackOrder.Shuffle:
                List<GroupedMediaItem> groupedMediaItems = multiPart
                    ? MultiPartEpisodeGrouper.GroupMediaItems(items, false)
                    : items.Map(mi => new GroupedMediaItem(mi, null)).ToList();
                return new BlockPlayoutShuffledMediaCollectionEnumerator(groupedMediaItems, state);
            default:
                return Option<IMediaCollectionEnumerator>.None;
        }
    }
}