// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System.Buffers.Binary;
using System.Collections;
using System.Diagnostics;
using System.Diagnostics.CodeAnalysis;
using System.Globalization;
using System.IO;
using System.Reflection;
using System.Runtime.CompilerServices;
using System.Security.Cryptography;
using System.Text;

namespace System.Xml.Serialization
{
    internal sealed class Compiler
    {
        private readonly StringWriter _writer = new StringWriter(CultureInfo.InvariantCulture);

        // SxS: This method does not take any resource name and does not expose any resources to the caller.
        // It's OK to suppress the SxS warning.
        [RequiresUnreferencedCode("Reflects against input Type DeclaringType")]
        internal static void AddImport(Type? type, Hashtable types)
        {
            if (type == null)
                return;
            if (TypeScope.IsKnownType(type))
                return;
            if (types[type] != null)
                return;
            types[type] = type;
            Type? baseType = type.BaseType;
            if (baseType != null)
                AddImport(baseType, types);

            Type? declaringType = type.DeclaringType;
            if (declaringType != null)
                AddImport(declaringType, types);

            foreach (Type intf in type.GetInterfaces())
                AddImport(intf, types);

            ConstructorInfo[] ctors = type.GetConstructors();
            for (int i = 0; i < ctors.Length; i++)
            {
                ParameterInfo[] parms = ctors[i].GetParameters();
                for (int j = 0; j < parms.Length; j++)
                {
                    AddImport(parms[j].ParameterType, types);
                }
            }

            if (type.IsGenericType)
            {
                Type[] arguments = type.GetGenericArguments();
                for (int i = 0; i < arguments.Length; i++)
                {
                    AddImport(arguments[i], types);
                }
            }

            Module module = type.Module;
            Assembly assembly = module.Assembly;
            if (DynamicAssemblies.IsTypeDynamic(type))
            {
                DynamicAssemblies.Add(assembly);
                return;
            }

            object[] typeForwardedFromAttribute = type.GetCustomAttributes(typeof(TypeForwardedFromAttribute), false);
            if (typeForwardedFromAttribute.Length > 0)
            {
                TypeForwardedFromAttribute? originalAssemblyInfo = typeForwardedFromAttribute[0] as TypeForwardedFromAttribute;
                Debug.Assert(originalAssemblyInfo != null);
                Assembly.Load(new AssemblyName(originalAssemblyInfo.AssemblyFullName));
            }
        }

        internal TextWriter Source
        {
            get { return _writer; }
        }

        internal static string GetTempAssemblyName(AssemblyName parent, string? ns)
        {
            return string.IsNullOrEmpty(ns) ?
                $"{parent.Name}.XmlSerializers" :
                $"{parent.Name}.XmlSerializers.{GetPersistentHashCode(ns)}";
        }

        private static uint GetPersistentHashCode(string value)
        {
            byte[] valueBytes = Encoding.UTF8.GetBytes(value);
            byte[] hash = SHA512.HashData(valueBytes);
            return BinaryPrimitives.ReadUInt32BigEndian(hash);
        }
    }
}