ersatztv/ErsatzTV.Application/Channels/AutoTuneAxisMap.cs

using ErsatzTV.Core.Domain;

namespace ErsatzTV.Application.Channels;

public static class AutoTuneAxisMap
{
    // Server-owned Lucene smart-collection query for an axis value.
    public static string GenerateQuery(AutoTuneAxis axis, string value)
    {
        string escaped = EscapeLuceneValue(value);
        return axis switch
        {
            AutoTuneAxis.TvShow => $"type:episode AND show_title:\"{escaped}\"",
            AutoTuneAxis.TvGenre => $"type:episode AND genre:\"{escaped}\"",
            AutoTuneAxis.MovieGenre => $"type:movie AND genre:\"{escaped}\"",
            _ => throw new ArgumentOutOfRangeException(nameof(axis), axis, null)
        };
    }

    // Human-facing channel name. Movie-genre channels are suffixed so a genre that exists for
    // both TV and movies ("Comedy" vs "Comedy Movies") does not produce two identically-named channels.
    public static string GenerateName(AutoTuneAxis axis, string value) =>
        axis switch
        {
            AutoTuneAxis.TvShow => value,
            AutoTuneAxis.TvGenre => value,
            AutoTuneAxis.MovieGenre => $"{value} Movies",
            _ => throw new ArgumentOutOfRangeException(nameof(axis), axis, null)
        };

    // PseudoTV per-type defaults: single-show channels play in episode order; genre channels shuffle.
    public static PlaybackOrder PlaybackOrderFor(AutoTuneAxis axis) =>
        axis switch
        {
            AutoTuneAxis.TvShow => PlaybackOrder.SeasonEpisode,
            AutoTuneAxis.TvGenre => PlaybackOrder.Shuffle,
            AutoTuneAxis.MovieGenre => PlaybackOrder.Shuffle,
            _ => throw new ArgumentOutOfRangeException(nameof(axis), axis, null)
        };

    // Per-source member query for a weighted auto-tune channel (#425). The discriminator identifies ONE
    // content source within the channel's axis:
    //   * TV axes  -> the show title. Episodes carry no parent-show id in the search index (only show_title
    //     is denormalized onto them), so show_title is the only field that selects a show's episodes. It is
    //     the same discriminator the TvShow axis already uses, so this introduces no new fragility class;
    //     a post-create show rename empties the member (items fall through to the remainder) until re-tuned.
    //   * MovieGenre -> the movie's media-item id (the stable, rename-proof `id` field; a movie IS the
    //     played item, so its own id selects it exactly).
    // Deliberately discriminator-ONLY (no genre clause): membership is decided when the channel is tuned,
    // so a materialized show airs all its episodes and the remainder subtracts the whole source (below).
    public static string GenerateSourceQuery(AutoTuneAxis axis, string discriminator) =>
        axis switch
        {
            AutoTuneAxis.TvShow or AutoTuneAxis.TvGenre =>
                $"type:episode AND show_title:\"{EscapeLuceneValue(discriminator)}\"",
            AutoTuneAxis.MovieGenre => $"type:movie AND id:{discriminator}",
            _ => throw new ArgumentOutOfRangeException(nameof(axis), axis, null)
        };

    // The bare clause used to subtract a materialized/excluded source from the remainder query (below).
    // Mirrors GenerateSourceQuery's discriminator field, minus the type prefix.
    public static string SourceDiscriminatorClause(AutoTuneAxis axis, string discriminator) =>
        axis switch
        {
            AutoTuneAxis.TvShow or AutoTuneAxis.TvGenre =>
                $"show_title:\"{EscapeLuceneValue(discriminator)}\"",
            AutoTuneAxis.MovieGenre => $"id:{discriminator}",
            _ => throw new ArgumentOutOfRangeException(nameof(axis), axis, null)
        };

    // The catch-all remainder query: the base axis query minus every materialized/excluded source, so the
    // base set is partitioned across (member sources + remainder) with no item counted twice and none
    // dropped. Returns the plain base query when there is nothing to subtract. Emitted as valid classic
    // Lucene — `(base) AND NOT (d1 OR d2 ...)` — because a ParseException silently escapes the whole query
    // into a literal (SearchQueryParser.ParseQuery fallback).
    public static string GenerateRemainderQuery(
        AutoTuneAxis axis,
        string value,
        IReadOnlyCollection<string> subtractedDiscriminators)
    {
        string baseQuery = GenerateQuery(axis, value);
        if (subtractedDiscriminators is null || subtractedDiscriminators.Count == 0)
        {
            return baseQuery;
        }

        string negated = string.Join(
            " OR ",
            subtractedDiscriminators.Select(d => SourceDiscriminatorClause(axis, d)));
        return $"({baseQuery}) AND NOT ({negated})";
    }

    // Escape a value for a Lucene double-quoted phrase: backslash first, then double-quote.
    public static string EscapeLuceneValue(string value) =>
        (value ?? string.Empty).Replace("\\", "\\\\").Replace("\"", "\\\"");
}