sebastienros.jint/Jint/Runtime/Interop/TypeResolver.cs

using System.Diagnostics.CodeAnalysis;
using System.Dynamic;
using System.Reflection;
using System.Threading;
using Jint.Runtime.Interop.Reflection;

namespace Jint.Runtime.Interop
{
    /// <summary>
    /// Interop strategy for resolving types and members.
    /// </summary>
    public sealed class TypeResolver
    {
        public static readonly TypeResolver Default = new();

        /// <summary>
        /// Registers a filter that determines whether given member is wrapped to interop or returned as undefined.
        /// By default allows all but will also be limited by <see cref="InteropOptions.AllowGetType"/> configuration.
        /// </summary>
        /// <seealso cref="InteropOptions.AllowGetType"/>
        public Predicate<MemberInfo> MemberFilter { get; set; } = _ => true;

        internal bool Filter(Engine engine, MemberInfo m)
        {
            return (engine.Options.Interop.AllowGetType || m.Name != nameof(GetType)) && MemberFilter(m);
        }

        /// <summary>
        /// Gives the exposed names for a member. Allows to expose C# convention following member like IsSelected
        /// as more JS idiomatic "selected" for example. Defaults to returning the <see cref="MemberInfo.Name"/> as-is.
        /// </summary>
        public Func<MemberInfo, IEnumerable<string>> MemberNameCreator { get; set; } = NameCreator;

        private static IEnumerable<string> NameCreator(MemberInfo info)
        {
            yield return info.Name;
        }

        /// <summary>
        /// Sets member name comparison strategy when finding CLR objects members.
        /// By default member's first character casing is ignored and rest of the name is compared with strict equality.
        /// </summary>
        public StringComparer MemberNameComparer { get; set; } = DefaultMemberNameComparer.Instance;

        internal ReflectionAccessor GetAccessor(
            Engine engine,
            Type type,
            string member,
            Func<ReflectionAccessor?>? accessorFactory = null,
            bool forWrite = false)
        {
            var key = new Engine.ClrPropertyDescriptorFactoriesKey(type, member);

            var factories = engine._reflectionAccessors;
            if (factories.TryGetValue(key, out var accessor))
            {
                return accessor;
            }

            accessor = accessorFactory?.Invoke() ?? ResolvePropertyDescriptorFactory(engine, type, member, forWrite);

            // racy, we don't care, worst case we'll catch up later
            Interlocked.CompareExchange(ref engine._reflectionAccessors,
                new Dictionary<Engine.ClrPropertyDescriptorFactoriesKey, ReflectionAccessor>(factories)
                {
                    [key] = accessor
                }, factories);

            return accessor;
        }

        private ReflectionAccessor ResolvePropertyDescriptorFactory(
            Engine engine,
            Type type,
            string memberName,
            bool forWrite)
        {
            var isInteger = long.TryParse(memberName, out _);

            // we can always check indexer if there's one, and then fall back to properties if indexer returns null
            IndexerAccessor.TryFindIndexer(engine, type, memberName, out var indexerAccessor, out var indexer);

            const BindingFlags BindingFlags = BindingFlags.Static | BindingFlags.Instance | BindingFlags.Public;

            // properties and fields cannot be numbers
            if (!isInteger
                && TryFindMemberAccessor(engine, type, memberName, BindingFlags, indexer, out var temp)
                && (!forWrite || temp.Writable))
            {
                return temp;
            }

            if (typeof(DynamicObject).IsAssignableFrom(type))
            {
                return new DynamicObjectAccessor(type, memberName);
            }

            var typeResolverMemberNameComparer = MemberNameComparer;
            var typeResolverMemberNameCreator = MemberNameCreator;

            if (!isInteger)
            {
                // try to find a single explicit property implementation
                List<PropertyInfo>? list = null;
                foreach (var iface in type.GetInterfaces())
                {
                    foreach (var iprop in iface.GetProperties())
                    {
                        if (!Filter(engine, iprop))
                        {
                            continue;
                        }

                        if (iprop.Name == "Item" && iprop.GetIndexParameters().Length == 1)
                        {
                            // never take indexers, should use the actual indexer
                            continue;
                        }

                        foreach (var name in typeResolverMemberNameCreator(iprop))
                        {
                            if (typeResolverMemberNameComparer.Equals(name, memberName))
                            {
                                list ??= new List<PropertyInfo>();
                                list.Add(iprop);
                            }
                        }
                    }
                }

                if (list?.Count == 1)
                {
                    return new PropertyAccessor(memberName, list[0]);
                }

                // try to find explicit method implementations
                List<MethodInfo>? explicitMethods = null;
                foreach (var iface in type.GetInterfaces())
                {
                    foreach (var imethod in iface.GetMethods())
                    {
                        if (!Filter(engine, imethod))
                        {
                            continue;
                        }

                        foreach (var name in typeResolverMemberNameCreator(imethod))
                        {
                            if (typeResolverMemberNameComparer.Equals(name, memberName))
                            {
                                explicitMethods ??= new List<MethodInfo>();
                                explicitMethods.Add(imethod);
                            }
                        }
                    }
                }

                if (explicitMethods?.Count > 0)
                {
                    return new MethodAccessor(type, memberName, MethodDescriptor.Build(explicitMethods));
                }
            }

            // if no methods are found check if target implemented indexing
            var score = int.MaxValue;
            if (indexerAccessor != null)
            {
                var parameter = indexerAccessor._indexer.GetIndexParameters()[0];
                score = CalculateIndexerScore(parameter, isInteger);
            }

            if (score != 0)
            {
                // try to find explicit indexer implementations that has a better score than earlier
                foreach (var interfaceType in type.GetInterfaces())
                {
                    if (IndexerAccessor.TryFindIndexer(engine, interfaceType, memberName, out var accessor, out _))
                    {
                        var parameter = accessor._indexer.GetIndexParameters()[0];
                        var newScore = CalculateIndexerScore(parameter, isInteger);
                        if (newScore < score)
                        {
                            // found a better one
                            indexerAccessor = accessor;
                            score = newScore;
                        }
                    }
                }
            }

            // use the best indexer we were able to find
            if (indexerAccessor != null)
            {
                return indexerAccessor;
            }

            if (!isInteger && engine._extensionMethods.TryGetExtensionMethods(type, out var extensionMethods))
            {
                var matches = new List<MethodInfo>();
                foreach (var method in extensionMethods)
                {
                    if (!Filter(engine, method))
                    {
                        continue;
                    }

                    foreach (var name in typeResolverMemberNameCreator(method))
                    {
                        if (typeResolverMemberNameComparer.Equals(name, memberName))
                        {
                            matches.Add(method);
                        }
                    }
                }

                if (matches.Count > 0)
                {
                    return new MethodAccessor(type, memberName, MethodDescriptor.Build(matches));
                }
            }

            return ConstantValueAccessor.NullAccessor;
        }

        private static int CalculateIndexerScore(ParameterInfo parameter, bool isInteger)
        {
            var paramType = parameter.ParameterType;

            if (paramType == typeof(int))
            {
                return  isInteger ? 0 : 10;
            }

            if (paramType == typeof(string))
            {
                return 1;
            }

            return 5;
        }

        internal bool TryFindMemberAccessor(
            Engine engine,
            Type type,
            string memberName,
            BindingFlags bindingFlags,
            PropertyInfo? indexerToTry,
            [NotNullWhen(true)] out ReflectionAccessor? accessor)
        {
            // look for a property, bit be wary of indexers, we don't want indexers which have name "Item" to take precedence
            PropertyInfo? property = null;
            var memberNameComparer = MemberNameComparer;
            var typeResolverMemberNameCreator = MemberNameCreator;

            PropertyInfo? GetProperty(Type t)
            {
                foreach (var p in t.GetProperties(bindingFlags))
                {
                    if (!Filter(engine, p))
                    {
                        continue;
                    }

                    // only if it's not an indexer, we can do case-ignoring matches
                    var isStandardIndexer = p.GetIndexParameters().Length == 1 && p.Name == "Item";
                    if (!isStandardIndexer)
                    {
                        foreach (var name in typeResolverMemberNameCreator(p))
                        {
                            if (memberNameComparer.Equals(name, memberName))
                            {
                                property = p;
                                break;
                            }
                        }
                    }
                }

                return property;
            }

            property = GetProperty(type);

            if (property is null && type.IsInterface)
            {
                // check inherited interfaces
                foreach (var iface in type.GetInterfaces())
                {
                    property = GetProperty(iface);
                    if (property is not null)
                    {
                        break;
                    }
                }
            }

            if (property is not null)
            {
                accessor = new PropertyAccessor(memberName, property, indexerToTry);
                return true;
            }

            // look for a field
            FieldInfo? field = null;
            foreach (var f in type.GetFields(bindingFlags))
            {
                if (!Filter(engine, f))
                {
                    continue;
                }

                foreach (var name in typeResolverMemberNameCreator(f))
                {
                    if (memberNameComparer.Equals(name, memberName))
                    {
                        field = f;
                        break;
                    }
                }
            }

            if (field is not null)
            {
                accessor = new FieldAccessor(field, memberName, indexerToTry);
                return true;
            }

            // if no properties were found then look for a method
            List<MethodInfo>? methods = null;
            void AddMethod(MethodInfo m)
            {
                if (!Filter(engine, m))
                {
                    return;
                }

                foreach (var name in typeResolverMemberNameCreator(m))
                {
                    if (memberNameComparer.Equals(name, memberName))
                    {
                        methods ??= new List<MethodInfo>();
                        methods.Add(m);
                    }
                }
            }

            foreach (var m in type.GetMethods(bindingFlags))
            {
                AddMethod(m);
            }

            foreach (var iface in type.GetInterfaces())
            {
                foreach (var m in iface.GetMethods())
                {
                    AddMethod(m);
                }
            }

            // TPC: need to grab the extension methods here - for overloads
            if (engine._extensionMethods.TryGetExtensionMethods(type, out var extensionMethods))
            {
                foreach (var methodInfo in extensionMethods)
                {
                    AddMethod(methodInfo);
                }
            }

            // Add Object methods to interface
            if (type.IsInterface)
            {
                foreach (var m in typeof(object).GetMethods(bindingFlags))
                {
                    AddMethod(m);
                }
            }

            if (methods?.Count > 0)
            {
                accessor = new MethodAccessor(type, memberName, MethodDescriptor.Build(methods));
                return true;
            }

            // look for nested type
            var nestedType = type.GetNestedType(memberName, bindingFlags);
            if (nestedType != null)
            {
                var typeReference = TypeReference.CreateTypeReference(engine, nestedType);
                accessor = new NestedTypeAccessor(typeReference, memberName);
                return true;
            }

            accessor = default;
            return false;
        }

        private sealed class DefaultMemberNameComparer : StringComparer
        {
            public static readonly StringComparer Instance = new DefaultMemberNameComparer();

            public override int Compare(string? x, string? y)
            {
                throw new NotImplementedException();
            }

            public override bool Equals(string? x, string? y)
            {
                if (ReferenceEquals(x, y))
                {
                    return true;
                }

                if (x == null || y == null)
                {
                    return false;
                }

                if (x.Length != y.Length)
                {
                    return false;
                }

                var equals = false;
                if (x.Length > 0)
                {
                    equals = char.ToLowerInvariant(x[0]) == char.ToLowerInvariant(y[0]);
                }

                if (equals && x.Length > 1)
                {
#if SUPPORTS_SPAN_PARSE
                    equals = x.AsSpan(1).SequenceEqual(y.AsSpan(1));
#else
                    equals = x.Substring(1) == y.Substring(1);
#endif
                }

                return equals;
            }

            public override int GetHashCode(string obj)
            {
                throw new NotImplementedException();
            }
        }
    }
}