1 files changed, 342 insertions, 0 deletions
diff --git a/Emby.Server.Implementations/Library/SimilarItems/MovieSimilarItemsProvider.cs b/Emby.Server.Implementations/Library/SimilarItems/MovieSimilarItemsProvider.cs
new file mode 100644
index 0000000000..57d1f7c770
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+++ b/Emby.Server.Implementations/Library/SimilarItems/MovieSimilarItemsProvider.cs
@@ -0,0 +1,342 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using Jellyfin.Data.Enums;
+using Jellyfin.Database.Implementations;
+using Jellyfin.Database.Implementations.Entities;
+using Jellyfin.Extensions;
+using MediaBrowser.Controller.Configuration;
+using MediaBrowser.Controller.Dto;
+using MediaBrowser.Controller.Entities;
+using MediaBrowser.Controller.Entities.Movies;
+using MediaBrowser.Controller.Library;
+using MediaBrowser.Controller.Persistence;
+using MediaBrowser.Model.Configuration;
+using Microsoft.EntityFrameworkCore;
+using BaseItemDto = MediaBrowser.Controller.Entities.BaseItem;
+
+namespace Emby.Server.Implementations.Library.SimilarItems;
+
+/// <summary>
+/// Provides similar items for movies and trailers using weighted scoring.
+/// </summary>
+public sealed class MovieSimilarItemsProvider : ILocalSimilarItemsProvider<Movie>, ILocalSimilarItemsProvider<Trailer>, IBatchLocalSimilarItemsProvider
+{
+    private const int GenreWeight = 10;
+    private const int TagWeight = 5;
+    private const int StudioWeight = 5;
+    private const int DirectorWeight = 50;
+    private const int ActorWeight = 15;
+
+    // Caps the batch fan-out so downstream IN-list sizes (per-source scores, accessible-id
+    // load, navigation includes) stay bounded regardless of caller input.
+    private const int MaxBatchSourceItems = 64;
+
+    private static readonly (ItemValueType Type, int Weight)[] _itemValueDimensions =
+    [
+        (ItemValueType.Genre, GenreWeight),
+        (ItemValueType.Tags, TagWeight),
+        (ItemValueType.Studios, StudioWeight)
+    ];
+
+    private static readonly Dictionary<string, int> _personTypeWeights = new(StringComparer.Ordinal)
+    {
+        [nameof(PersonKind.Director)] = DirectorWeight,
+        [nameof(PersonKind.Actor)] = ActorWeight,
+        [nameof(PersonKind.GuestStar)] = ActorWeight,
+    };
+
+    private static readonly string[] _scoredPersonTypes = [.. _personTypeWeights.Keys];
+
+    private readonly IDbContextFactory<JellyfinDbContext> _dbProvider;
+    private readonly IItemQueryHelpers _queryHelpers;
+    private readonly IServerConfigurationManager _serverConfigurationManager;
+    private readonly ILibraryManager _libraryManager;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="MovieSimilarItemsProvider"/> class.
+    /// </summary>
+    /// <param name="dbProvider">The database context factory.</param>
+    /// <param name="queryHelpers">The shared query helpers.</param>
+    /// <param name="serverConfigurationManager">The server configuration manager.</param>
+    /// <param name="libraryManager">The library manager.</param>
+    public MovieSimilarItemsProvider(
+        IDbContextFactory<JellyfinDbContext> dbProvider,
+        IItemQueryHelpers queryHelpers,
+        IServerConfigurationManager serverConfigurationManager,
+        ILibraryManager libraryManager)
+    {
+        _dbProvider = dbProvider;
+        _queryHelpers = queryHelpers;
+        _serverConfigurationManager = serverConfigurationManager;
+        _libraryManager = libraryManager;
+    }
+
+    /// <inheritdoc/>
+    public string Name => "Local Genre/Tag";
+
+    /// <inheritdoc/>
+    public MetadataPluginType Type => MetadataPluginType.LocalSimilarityProvider;
+
+    /// <inheritdoc/>
+    public async Task<IReadOnlyList<BaseItemDto>> GetSimilarItemsAsync(Movie item, SimilarItemsQuery query, CancellationToken cancellationToken)
+    {
+        var results = await GetBatchSimilarItemsAsync([item], query, cancellationToken).ConfigureAwait(false);
+        return results.TryGetValue(item.Id, out var items) ? items : [];
+    }
+
+    /// <inheritdoc/>
+    public async Task<IReadOnlyList<BaseItemDto>> GetSimilarItemsAsync(Trailer item, SimilarItemsQuery query, CancellationToken cancellationToken)
+    {
+        var results = await GetBatchSimilarItemsAsync([item], query, cancellationToken).ConfigureAwait(false);
+        return results.TryGetValue(item.Id, out var items) ? items : [];
+    }
+
+    bool ILocalSimilarItemsProvider.Supports(Type itemType)
+        => typeof(Movie).IsAssignableFrom(itemType) || typeof(Trailer).IsAssignableFrom(itemType);
+
+    Task<IReadOnlyList<BaseItem>> ILocalSimilarItemsProvider.GetSimilarItemsAsync(BaseItem item, SimilarItemsQuery query, CancellationToken cancellationToken)
+        => item switch
+        {
+            Movie movie => GetSimilarItemsAsync(movie, query, cancellationToken),
+            Trailer trailer => GetSimilarItemsAsync(trailer, query, cancellationToken),
+            _ => throw new ArgumentException($"Unsupported item type {item.GetType()}", nameof(item))
+        };
+
+    /// <inheritdoc/>
+    public async Task<Dictionary<Guid, IReadOnlyList<BaseItemDto>>> GetBatchSimilarItemsAsync(
+        IReadOnlyList<BaseItemDto> sourceItems,
+        SimilarItemsQuery query,
+        CancellationToken cancellationToken)
+    {
+        var includeItemTypes = new List<BaseItemKind> { BaseItemKind.Movie };
+        if (_serverConfigurationManager.Configuration.EnableExternalContentInSuggestions)
+        {
+            includeItemTypes.Add(BaseItemKind.Trailer);
+            includeItemTypes.Add(BaseItemKind.LiveTvProgram);
+        }
+
+        var limit = query.Limit ?? 50;
+        var dtoOptions = query.DtoOptions ?? new DtoOptions();
+
+        if (sourceItems.Count > MaxBatchSourceItems)
+        {
+            sourceItems = sourceItems.Take(MaxBatchSourceItems).ToList();
+        }
+
+        var context = await _dbProvider.CreateDbContextAsync(cancellationToken).ConfigureAwait(false);
+        await using (context.ConfigureAwait(false))
+        {
+            // Phase 1: Score all candidates per source item
+            var sourceIds = sourceItems.Select(i => i.Id).ToList();
+            var perSourceScores = await ComputeBatchScoresAsync(sourceIds, context, cancellationToken).ConfigureAwait(false);
+
+            var allCandidateIds = new HashSet<Guid>();
+            foreach (var (_, scores) in perSourceScores)
+            {
+                allCandidateIds.UnionWith(
+                    scores.OrderByDescending(kvp => kvp.Value)
+                        .Take(limit * 3)
+                        .Select(kvp => kvp.Key));
+            }
+
+            var result = new Dictionary<Guid, IReadOnlyList<BaseItemDto>>();
+            if (allCandidateIds.Count == 0)
+            {
+                return result;
+            }
+
+            // Phase 2: One access filter for all candidates
+            var filter = new InternalItemsQuery(query.User)
+            {
+                IncludeItemTypes = [.. includeItemTypes],
+                ExcludeItemIds = [.. query.ExcludeItemIds],
+                DtoOptions = dtoOptions,
+                EnableGroupByMetadataKey = true,
+                EnableTotalRecordCount = false,
+                IsMovie = true,
+                IsPlayed = false
+            };
+
+            if (query.User is not null)
+            {
+                _libraryManager.ConfigureUserAccess(filter, query.User);
+            }
+
+            _queryHelpers.PrepareFilterQuery(filter);
+            var baseQuery = _queryHelpers.PrepareItemQuery(context, filter);
+            baseQuery = _queryHelpers.TranslateQuery(baseQuery, context, filter);
+
+            var allCandidateIdsList = allCandidateIds.ToList();
+            var accessibleItems = await baseQuery
+                .WhereOneOrMany(allCandidateIdsList, e => e.Id)
+                .Select(e => new { e.Id, e.PresentationUniqueKey })
+                .ToListAsync(cancellationToken).ConfigureAwait(false);
+
+            // Phase 3: Pick top IDs per source, dedup by PresentationUniqueKey
+            var allOrderedIds = new HashSet<Guid>();
+            var perSourceOrderedIds = new Dictionary<Guid, List<Guid>>();
+
+            foreach (var item in sourceItems)
+            {
+                if (!perSourceScores.TryGetValue(item.Id, out var scores))
+                {
+                    continue;
+                }
+
+                var orderedIds = accessibleItems
+                    .Where(x => scores.ContainsKey(x.Id))
+                    .OrderByDescending(x => scores.GetValueOrDefault(x.Id))
+                    .DistinctBy(x => x.PresentationUniqueKey)
+                    .Take(limit)
+                    .Select(x => x.Id)
+                    .ToList();
+
+                if (orderedIds.Count > 0)
+                {
+                    perSourceOrderedIds[item.Id] = orderedIds;
+                    allOrderedIds.UnionWith(orderedIds);
+                }
+            }
+
+            if (allOrderedIds.Count == 0)
+            {
+                return result;
+            }
+
+            // Phase 4: One entity load for all results
+            var allOrderedIdsList = allOrderedIds.ToList();
+            var entities = await _queryHelpers.ApplyNavigations(
+                    context.BaseItems.AsNoTracking().WhereOneOrMany(allOrderedIdsList, e => e.Id),
+                    filter)
+                .AsSplitQuery()
+                .ToListAsync(cancellationToken).ConfigureAwait(false);
+
+            var entitiesById = entities
+                .Select(e => _queryHelpers.DeserializeBaseItem(e, filter.SkipDeserialization))
+                .Where(dto => dto is not null)
+                .ToDictionary(i => i!.Id);
+
+            // Phase 5: Split by source, preserving score order
+            foreach (var (sourceId, orderedIds) in perSourceOrderedIds)
+            {
+                var items = orderedIds
+                    .Where(entitiesById.ContainsKey)
+                    .Select(id => entitiesById[id]!)
+                    .ToList();
+
+                if (items.Count > 0)
+                {
+                    result[sourceId] = items;
+                }
+            }
+
+            return result;
+        }
+    }
+
+    private static async Task<Dictionary<Guid, Dictionary<Guid, int>>> ComputeBatchScoresAsync(List<Guid> sourceIds, JellyfinDbContext context, CancellationToken cancellationToken)
+    {
+        var result = new Dictionary<Guid, Dictionary<Guid, int>>();
+        foreach (var id in sourceIds)
+        {
+            result[id] = [];
+        }
+
+        foreach (var (valueType, weight) in _itemValueDimensions)
+        {
+            var sourceRows = await context.ItemValuesMap.AsNoTracking()
+                .Where(m => sourceIds.Contains(m.ItemId) && m.ItemValue.Type == valueType)
+                .Select(m => new { m.ItemId, Key = m.ItemValue.CleanValue })
+                .ToListAsync(cancellationToken).ConfigureAwait(false);
+
+            var sourceMap = sourceRows.GroupBy(r => r.ItemId).ToDictionary(g => g.Key, g => g.Select(x => x.Key).ToHashSet());
+            var allKeys = sourceMap.Values.SelectMany(v => v).Distinct().ToList();
+            if (allKeys.Count == 0)
+            {
+                continue;
+            }
+
+            var candidateRows = await context.ItemValuesMap.AsNoTracking()
+                .Where(m => m.ItemValue.Type == valueType && allKeys.Contains(m.ItemValue.CleanValue))
+                .Select(m => new { m.ItemId, Key = m.ItemValue.CleanValue })
+                .ToListAsync(cancellationToken).ConfigureAwait(false);
+
+            var keyToCandidates = candidateRows.GroupBy(r => r.Key).ToDictionary(g => g.Key, g => g.Select(x => x.ItemId).ToList());
+            ApplyDimensionScores(sourceIds, sourceMap, keyToCandidates, weight, result);
+        }
+
+        var personSourceRows = await context.PeopleBaseItemMap.AsNoTracking()
+            .Where(m => sourceIds.Contains(m.ItemId) && _scoredPersonTypes.Contains(m.People.PersonType))
+            .Select(m => new { m.ItemId, m.PeopleId, m.People.PersonType })
+            .ToListAsync(cancellationToken).ConfigureAwait(false);
+
+        if (personSourceRows.Count > 0)
+        {
+            var personCandidateRows = await context.PeopleBaseItemMap.AsNoTracking()
+                .Where(m => context.PeopleBaseItemMap
+                    .Where(s => sourceIds.Contains(s.ItemId) && _scoredPersonTypes.Contains(s.People.PersonType))
+                    .Select(s => s.PeopleId)
+                    .Contains(m.PeopleId))
+                .Select(m => new { m.ItemId, m.PeopleId })
+                .ToListAsync(cancellationToken).ConfigureAwait(false);
+
+            var personToCandidates = personCandidateRows
+                .GroupBy(r => r.PeopleId)
+                .ToDictionary(g => g.Key, g => g.Select(x => x.ItemId).ToList());
+
+            foreach (var weightGroup in personSourceRows.GroupBy(r => _personTypeWeights[r.PersonType!]))
+            {
+                var sourceMap = weightGroup
+                    .GroupBy(r => r.ItemId)
+                    .ToDictionary(g => g.Key, g => g.Select(x => x.PeopleId).ToHashSet());
+                ApplyDimensionScores(sourceIds, sourceMap, personToCandidates, weightGroup.Key, result);
+            }
+        }
+
+        foreach (var sourceId in sourceIds)
+        {
+            var scoreMap = result[sourceId];
+            scoreMap.Remove(sourceId);
+            if (scoreMap.Count == 0)
+            {
+                result.Remove(sourceId);
+            }
+        }
+
+        return result;
+    }
+
+    private static void ApplyDimensionScores<TKey>(
+        List<Guid> sourceIds,
+        Dictionary<Guid, HashSet<TKey>> sourceMap,
+        Dictionary<TKey, List<Guid>> keyToCandidates,
+        int weight,
+        Dictionary<Guid, Dictionary<Guid, int>> result)
+        where TKey : notnull
+    {
+        foreach (var sourceId in sourceIds)
+        {
+            if (!sourceMap.TryGetValue(sourceId, out var sourceKeys))
+            {
+                continue;
+            }
+
+            var scoreMap = result[sourceId];
+            foreach (var key in sourceKeys)
+            {
+                if (!keyToCandidates.TryGetValue(key, out var candidates))
+                {
+                    continue;
+                }
+
+                foreach (var candidateId in candidates)
+                {
+                    scoreMap[candidateId] = scoreMap.GetValueOrDefault(candidateId) + weight;
+                }
+            }
+        }
+    }
+}