// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
 
using System.Collections;
using System.Collections.Generic;
using System.Diagnostics;
using System.Runtime;
using System.Runtime.CompilerServices;
using System.Security.Cryptography;
using System.Security.Principal;
using System.ServiceModel;
 
namespace System.IdentityModel.Claims
{
    internal class ClaimComparer : IEqualityComparer<Claim>
    {
        private static IEqualityComparer<Claim> s_defaultComparer;
        private static IEqualityComparer<Claim> s_hashComparer;
        private static IEqualityComparer<Claim> s_dnsComparer;
        private static IEqualityComparer<Claim> s_rsaComparer;
        private static IEqualityComparer<Claim> s_thumbprintComparer;
#if SUPPORTS_WINDOWSIDENTITY || !disabled
        private static IEqualityComparer<Claim> s_upnComparer;
#endif // SUPPORTS_WINDOWSIDENTITY
        private static IEqualityComparer<Claim> s_x500DistinguishedNameComparer;
        private IEqualityComparer _resourceComparer;
 
        private ClaimComparer(IEqualityComparer resourceComparer)
        {
            _resourceComparer = resourceComparer;
        }
 
        public static IEqualityComparer<Claim> GetComparer(string claimType)
        {
            if (claimType == null)
                throw DiagnosticUtility.ExceptionUtility.ThrowHelperArgumentNull("claimType");
            if (claimType == ClaimTypes.Dns)
                return Dns;
            if (claimType == ClaimTypes.Hash)
                return Hash;
            if (claimType == ClaimTypes.Rsa)
                return Rsa;
            if (claimType == ClaimTypes.Thumbprint)
                return Thumbprint;
#if SUPPORTS_WINDOWSIDENTITY || !disabled
            if (claimType == ClaimTypes.Upn)
                return Upn;
#endif // SUPPORTS_WINDOWSIDENTITY
            if (claimType == ClaimTypes.X500DistinguishedName)
                return X500DistinguishedName;
            return Default;
        }
 
        public static IEqualityComparer<Claim> Default
        {
            get
            {
                if (s_defaultComparer == null)
                {
                    s_defaultComparer = new ClaimComparer(new ObjectComparer());
                }
                return s_defaultComparer;
            }
        }
 
        public static IEqualityComparer<Claim> Dns
        {
            get
            {
                if (s_dnsComparer == null)
                {
                    s_dnsComparer = new ClaimComparer(StringComparer.OrdinalIgnoreCase);
                }
                return s_dnsComparer;
            }
        }
 
        public static IEqualityComparer<Claim> Hash
        {
            get
            {
                if (s_hashComparer == null)
                {
                    s_hashComparer = new ClaimComparer(new BinaryObjectComparer());
                }
                return s_hashComparer;
            }
        }
 
        public static IEqualityComparer<Claim> Rsa
        {
            get
            {
                if (s_rsaComparer == null)
                {
                    s_rsaComparer = new ClaimComparer(new RsaObjectComparer());
                }
                return s_rsaComparer;
            }
        }
 
        public static IEqualityComparer<Claim> Thumbprint
        {
            get
            {
                if (s_thumbprintComparer == null)
                {
                    s_thumbprintComparer = new ClaimComparer(new BinaryObjectComparer());
                }
                return s_thumbprintComparer;
            }
        }
 
#if SUPPORTS_WINDOWSIDENTITY || !disabled
        public static IEqualityComparer<Claim> Upn
        {
            get
            {
                if (s_upnComparer == null)
                {
                    s_upnComparer = new ClaimComparer(new UpnObjectComparer());
                }
                return s_upnComparer;
            }
        }
#endif // SUPPORTS_WINDOWSIDENTITY
 
        public static IEqualityComparer<Claim> X500DistinguishedName
        {
            get
            {
                if (s_x500DistinguishedNameComparer == null)
                {
                    s_x500DistinguishedNameComparer = new ClaimComparer(new X500DistinguishedNameObjectComparer());
                }
                return s_x500DistinguishedNameComparer;
            }
        }
 
        // we still need to review how the default equals works, this is not how Doug envisioned it.
        public bool Equals(Claim claim1, Claim claim2)
        {
            if (ReferenceEquals(claim1, claim2))
                return true;
 
            if (claim1 == null || claim2 == null)
                return false;
 
            if (claim1.ClaimType != claim2.ClaimType || claim1.Right != claim2.Right)
                return false;
 
            return _resourceComparer.Equals(claim1.Resource, claim2.Resource);
        }
 
        public int GetHashCode(Claim claim)
        {
            if (claim == null)
                throw DiagnosticUtility.ExceptionUtility.ThrowHelperArgumentNull("claim");
 
            return claim.ClaimType.GetHashCode() ^ claim.Right.GetHashCode()
                ^ ((claim.Resource == null) ? 0 : _resourceComparer.GetHashCode(claim.Resource));
        }
 
        private class ObjectComparer : IEqualityComparer
        {
            bool IEqualityComparer.Equals(object obj1, object obj2)
            {
                if (obj1 == null && obj2 == null)
                    return true;
                if (obj1 == null || obj2 == null)
                    return false;
                return obj1.Equals(obj2);
            }
 
            int IEqualityComparer.GetHashCode(object obj)
            {
                if (obj == null)
                    return 0;
                return obj.GetHashCode();
            }
        }
 
        private class BinaryObjectComparer : IEqualityComparer
        {
            bool IEqualityComparer.Equals(object obj1, object obj2)
            {
                if (ReferenceEquals(obj1, obj2))
                    return true;
 
                byte[] bytes1 = obj1 as byte[];
                byte[] bytes2 = obj2 as byte[];
                if (bytes1 == null || bytes2 == null)
                    return false;
 
                if (bytes1.Length != bytes2.Length)
                    return false;
 
                for (int i = 0; i < bytes1.Length; ++i)
                {
                    if (bytes1[i] != bytes2[i])
                        return false;
                }
 
                return true;
            }
 
            int IEqualityComparer.GetHashCode(object obj)
            {
                byte[] bytes = obj as byte[];
                if (bytes == null)
                    return 0;
 
                int hashCode = 0;
                for (int i = 0; i < bytes.Length && i < 4; ++i)
                {
                    hashCode = (hashCode << 8) | bytes[i];
                }
 
                return hashCode ^ bytes.Length;
            }
        }
 
        private class RsaObjectComparer : IEqualityComparer
        {
            bool IEqualityComparer.Equals(object obj1, object obj2)
            {
                if (ReferenceEquals(obj1, obj2))
                    return true;
                throw ExceptionHelper.PlatformNotSupported();
            }
 
            int IEqualityComparer.GetHashCode(object obj)
            {
                throw ExceptionHelper.PlatformNotSupported();
            }
        }
 
        private class X500DistinguishedNameObjectComparer : IEqualityComparer
        {
            private IEqualityComparer _binaryComparer;
            public X500DistinguishedNameObjectComparer()
            {
                _binaryComparer = new BinaryObjectComparer();
            }
 
            bool IEqualityComparer.Equals(object obj1, object obj2)
            {
                if (ReferenceEquals(obj1, obj2))
                    return true;
                throw ExceptionHelper.PlatformNotSupported();
            }
 
            int IEqualityComparer.GetHashCode(object obj)
            {
                throw ExceptionHelper.PlatformNotSupported();
            }
        }
 
#if SUPPORTS_WINDOWSIDENTITY || !disabled
        private class UpnObjectComparer : IEqualityComparer
        {
            bool IEqualityComparer.Equals(object obj1, object obj2)
            {
                throw ExceptionHelper.PlatformNotSupported();
            }
 
            int IEqualityComparer.GetHashCode(object obj)
            {
                throw new NotImplementedException();
            }
        }
#endif // SUPPORTS_WINDOWSIDENTITY
    }
}