// Copyright (c) .NET Foundation and contributors. All rights reserved.
// Licensed under the MIT license. See LICENSE file in the project root for full license information.

using System;
using System.Collections.Generic;
using ILLink.Shared.TypeSystemProxy;
using Mono.Cecil;

namespace Mono.Linker
{
    sealed class TypeHierarchyCache
    {
        [Flags]
        private enum HierarchyFlags
        {
            IsSystemType = 0x01,
            IsSystemReflectionIReflect = 0x02,
        }

        readonly Dictionary<TypeDefinition, HierarchyFlags> _cache = new Dictionary<TypeDefinition, HierarchyFlags>();
        readonly LinkContext context;

        public TypeHierarchyCache(LinkContext context)
        {
            this.context = context;
        }

        private HierarchyFlags GetFlags(TypeDefinition resolvedType)
        {
            if (_cache.TryGetValue(resolvedType, out var flags))
            {
                return flags;
            }

            if (resolvedType.Name == "IReflect" && resolvedType.Namespace == "System.Reflection")
            {
                flags |= HierarchyFlags.IsSystemReflectionIReflect;
            }

            TypeDefinition? baseType = resolvedType;
            while (baseType != null)
            {
                if (baseType.IsTypeOf(WellKnownType.System_Type))
                {
                    flags |= HierarchyFlags.IsSystemType;
                }

                if (baseType.HasInterfaces)
                {
                    foreach (var iface in baseType.Interfaces)
                    {
                        if (iface.InterfaceType.Name == "IReflect" && iface.InterfaceType.Namespace == "System.Reflection")
                        {
                            flags |= HierarchyFlags.IsSystemReflectionIReflect;
                        }
                    }
                }

                baseType = context.TryResolve(baseType.BaseType);
            }

            if (resolvedType != null)
                _cache.Add(resolvedType, flags);

            return flags;
        }

        public bool IsSystemType(TypeDefinition type)
        {
            return (GetFlags(type) & HierarchyFlags.IsSystemType) != 0;
        }

        public bool IsSystemReflectionIReflect(TypeDefinition type)
        {
            return (GetFlags(type) & HierarchyFlags.IsSystemReflectionIReflect) != 0;
        }
    }
}