1 files changed, 166 insertions, 0 deletions
diff --git a/src/Jellyfin.Database/Jellyfin.Database.Implementations/JellyfinQueryHelperExtensions.cs b/src/Jellyfin.Database/Jellyfin.Database.Implementations/JellyfinQueryHelperExtensions.cs
new file mode 100644
index 000000000..4d5cfb8c9
--- /dev/null
+++ b/src/Jellyfin.Database/Jellyfin.Database.Implementations/JellyfinQueryHelperExtensions.cs
@@ -0,0 +1,166 @@
+#pragma warning disable RS0030 // Do not use banned APIs
+
+using System;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
+using System.Linq;
+using System.Linq.Expressions;
+using System.Reflection;
+using Jellyfin.Database.Implementations.Entities;
+using Microsoft.EntityFrameworkCore;
+
+namespace Jellyfin.Database.Implementations;
+
+/// <summary>
+/// Contains a number of query related extensions.
+/// </summary>
+public static class JellyfinQueryHelperExtensions
+{
+    private static readonly MethodInfo _containsMethodGenericCache = typeof(Enumerable).GetMethods(BindingFlags.Public | BindingFlags.Static).First(m => m.Name == nameof(Enumerable.Contains) && m.GetParameters().Length == 2);
+    private static readonly MethodInfo _efParameterInstruction = typeof(EF).GetMethod(nameof(EF.Parameter), BindingFlags.Public | BindingFlags.Static)!;
+    private static readonly ConcurrentDictionary<Type, MethodInfo> _containsQueryCache = new();
+
+    /// <summary>
+    /// Builds an optimised query checking one property against a list of values while maintaining an optimal query.
+    /// </summary>
+    /// <typeparam name="TEntity">The entity.</typeparam>
+    /// <typeparam name="TProperty">The property type to compare.</typeparam>
+    /// <param name="query">The source query.</param>
+    /// <param name="oneOf">The list of items to check.</param>
+    /// <param name="property">Property expression.</param>
+    /// <returns>A Query.</returns>
+    public static IQueryable<TEntity> WhereOneOrMany<TEntity, TProperty>(this IQueryable<TEntity> query, IList<TProperty> oneOf, Expression<Func<TEntity, TProperty>> property)
+    {
+        return query.Where(OneOrManyExpressionBuilder(oneOf, property));
+    }
+
+    /// <summary>
+    /// Builds a query that checks referenced ItemValues for a cross BaseItem lookup.
+    /// </summary>
+    /// <param name="baseQuery">The source query.</param>
+    /// <param name="context">The database context.</param>
+    /// <param name="itemValueType">The type of item value to reference.</param>
+    /// <param name="referenceIds">The list of BaseItem ids to check matches.</param>
+    /// <param name="invert">If set an exclusion check is performed instead.</param>
+    /// <returns>A Query.</returns>
+    public static IQueryable<BaseItemEntity> WhereReferencedItem(
+        this IQueryable<BaseItemEntity> baseQuery,
+        JellyfinDbContext context,
+        ItemValueType itemValueType,
+        IList<Guid> referenceIds,
+        bool invert = false)
+    {
+        return baseQuery.Where(ReferencedItemFilterExpressionBuilder(context, itemValueType, referenceIds, invert));
+    }
+
+    /// <summary>
+    /// Builds a query expression that checks referenced ItemValues for a cross BaseItem lookup.
+    /// </summary>
+    /// <param name="context">The database context.</param>
+    /// <param name="itemValueType">The type of item value to reference.</param>
+    /// <param name="referenceIds">The list of BaseItem ids to check matches.</param>
+    /// <param name="invert">If set an exclusion check is performed instead.</param>
+    /// <returns>A Query.</returns>
+    public static Expression<Func<BaseItemEntity, bool>> ReferencedItemFilterExpressionBuilder(
+        this JellyfinDbContext context,
+        ItemValueType itemValueType,
+        IList<Guid> referenceIds,
+        bool invert = false)
+    {
+        // Well genre/artist/album etc items do not actually set the ItemValue of thier specitic types so we cannot match it that way.
+        /*
+        "(guid in (select itemid from ItemValues where CleanValue = (select CleanName from TypedBaseItems where guid=@GenreIds and Type=2)))"
+        */
+
+        var itemFilter = OneOrManyExpressionBuilder<BaseItemEntity, Guid>(referenceIds, f => f.Id);
+
+        return item =>
+          context.ItemValues
+              .Join(context.ItemValuesMap, e => e.ItemValueId, e => e.ItemValueId, (item, map) => new { item, map })
+              .Any(val =>
+                  val.item.Type == itemValueType
+                  && context.BaseItems.Where(itemFilter).Any(e => e.CleanName == val.item.CleanValue)
+                  && val.map.ItemId == item.Id) == EF.Constant(!invert);
+    }
+
+    /// <summary>
+    /// Builds an optimised query expression checking one property against a list of values while maintaining an optimal query.
+    /// </summary>
+    /// <typeparam name="TEntity">The entity.</typeparam>
+    /// <typeparam name="TProperty">The property type to compare.</typeparam>
+    /// <param name="oneOf">The list of items to check.</param>
+    /// <param name="property">Property expression.</param>
+    /// <returns>A Query.</returns>
+    public static Expression<Func<TEntity, bool>> OneOrManyExpressionBuilder<TEntity, TProperty>(this IList<TProperty> oneOf, Expression<Func<TEntity, TProperty>> property)
+    {
+        var parameter = Expression.Parameter(typeof(TEntity), "item");
+        property = ParameterReplacer.Replace<Func<TEntity, TProperty>, Func<TEntity, TProperty>>(property, property.Parameters[0], parameter);
+        if (oneOf.Count == 1)
+        {
+            var value = oneOf[0];
+            if (typeof(TProperty).IsValueType)
+            {
+                return Expression.Lambda<Func<TEntity, bool>>(Expression.Equal(property.Body, Expression.Constant(value)), parameter);
+            }
+            else
+            {
+                return Expression.Lambda<Func<TEntity, bool>>(Expression.ReferenceEqual(property.Body, Expression.Constant(value)), parameter);
+            }
+        }
+
+        var containsMethodInfo = _containsQueryCache.GetOrAdd(typeof(TProperty), static (key) => _containsMethodGenericCache.MakeGenericMethod(key));
+
+        if (oneOf.Count < 4) // arbitrary value choosen.
+        {
+            // if we have 3 or fewer values to check against its faster to do a IN(const,const,const) lookup
+            return Expression.Lambda<Func<TEntity, bool>>(Expression.Call(null, containsMethodInfo, Expression.Constant(oneOf), property.Body), parameter);
+        }
+
+        return Expression.Lambda<Func<TEntity, bool>>(Expression.Call(null, containsMethodInfo, Expression.Call(null, _efParameterInstruction.MakeGenericMethod(oneOf.GetType()), Expression.Constant(oneOf)), property.Body), parameter);
+    }
+
+    internal static class ParameterReplacer
+    {
+        // Produces an expression identical to 'expression'
+        // except with 'source' parameter replaced with 'target' expression.
+        internal static Expression<TOutput> Replace<TInput, TOutput>(
+                        Expression<TInput> expression,
+                        ParameterExpression source,
+                        ParameterExpression target)
+        {
+            return new ParameterReplacerVisitor<TOutput>(source, target)
+                        .VisitAndConvert(expression);
+        }
+
+        private sealed class ParameterReplacerVisitor<TOutput> : ExpressionVisitor
+        {
+            private readonly ParameterExpression _source;
+            private readonly ParameterExpression _target;
+
+            public ParameterReplacerVisitor(ParameterExpression source, ParameterExpression target)
+            {
+                _source = source;
+                _target = target;
+            }
+
+            internal Expression<TOutput> VisitAndConvert<T>(Expression<T> root)
+            {
+                return (Expression<TOutput>)VisitLambda(root);
+            }
+
+            protected override Expression VisitLambda<T>(Expression<T> node)
+            {
+                // Leave all parameters alone except the one we want to replace.
+                var parameters = node.Parameters.Select(p => p == _source ? _target : p);
+
+                return Expression.Lambda<TOutput>(Visit(node.Body), parameters);
+            }
+
+            protected override Expression VisitParameter(ParameterExpression node)
+            {
+                // Replace the source with the target, visit other params as usual.
+                return node == _source ? _target : base.VisitParameter(node);
+            }
+        }
+    }
+}