#if !BESTHTTP_DISABLE_ALTERNATE_SSL && (!UNITY_WEBGL || UNITY_EDITOR)
#pragma warning disable
using System;
using System.Diagnostics;
#if NETCOREAPP3_0_OR_GREATER
using System.Buffers.Binary;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using System.Runtime.Intrinsics;
using System.Runtime.Intrinsics.X86;
#endif

using Best.HTTP.SecureProtocol.Org.BouncyCastle.Crypto.Utilities;
using Best.HTTP.SecureProtocol.Org.BouncyCastle.Utilities;

namespace Best.HTTP.Shared.TLS.Crypto.Impl
{
    /// <summary>
    /// Implementation of Daniel J. Bernstein's ChaCha stream cipher.
    /// </summary>



    [Best.HTTP.Shared.PlatformSupport.IL2CPP.Il2CppEagerStaticClassConstructionAttribute]
    public sealed class FastChaChaEngine
        : FastSalsa20Engine
    {
        /// <summary>
        /// Creates a 20 rounds ChaCha engine.
        /// </summary>
        public FastChaChaEngine()
        {
        }

        /// <summary>
        /// Creates a ChaCha engine with a specific number of rounds.
        /// </summary>
        /// <param name="rounds">the number of rounds (must be an even number).</param>
        public FastChaChaEngine(int rounds)
            : base(rounds)
        {
        }

        public override string AlgorithmName
        {
            get { return "ChaCha" + rounds; }
        }

        protected override void AdvanceCounter()
        {
            if (++engineState[12] == 0)
            {
                ++engineState[13];
            }
        }

        protected override void ResetCounter()
        {
            engineState[12] = engineState[13] = 0;
        }

        protected override void SetKey(byte[] keyBytes, byte[] ivBytes)
        {
            if (keyBytes != null)
            {
                if ((keyBytes.Length != 16) && (keyBytes.Length != 32))
                    throw new ArgumentException(AlgorithmName + " requires 128 bit or 256 bit key");

                PackTauOrSigma(keyBytes.Length, engineState, 0);

                // Key
                Pack.LE_To_UInt32(keyBytes, 0, engineState, 4, 4);
                Pack.LE_To_UInt32(keyBytes, keyBytes.Length - 16, engineState, 8, 4);
            }

            // IV
            Pack.LE_To_UInt32(ivBytes, 0, engineState, 14, 2);
        }

        protected override void GenerateKeyStream(byte[] output)
        {
            //ChachaCore(rounds, engineState, output);
            FastChaChaEngineHelper.ChachaCore(rounds, engineState, output);
        }

        internal static void ChachaCore(int rounds, uint[] input, byte[] output)
        {
            Debug.Assert(rounds % 2 == 0);
            Debug.Assert(input.Length >= 16);
            Debug.Assert(output.Length >= 64);

#if NETCOREAPP3_0_OR_GREATER
			if (Sse2.IsSupported)
			{
				var x0 = Load128_UInt32(input.AsSpan());
				var x1 = Load128_UInt32(input.AsSpan(4));
				var x2 = Load128_UInt32(input.AsSpan(8));
				var x3 = Load128_UInt32(input.AsSpan(12));

				var v0 = x0;
				var v1 = x1;
				var v2 = x2;
				var v3 = x3;

                for (int i = rounds; i > 0; i -= 2)
                {
					v0 = Sse2.Add(v0, v1);
					v3 = Sse2.Xor(v3, v0);
					v3 = Sse2.Xor(Sse2.ShiftLeftLogical(v3, 16), Sse2.ShiftRightLogical(v3, 16));
					v2 = Sse2.Add(v2, v3);
					v1 = Sse2.Xor(v1, v2);
					v1 = Sse2.Xor(Sse2.ShiftLeftLogical(v1, 12), Sse2.ShiftRightLogical(v1, 20));
					v0 = Sse2.Add(v0, v1);
					v3 = Sse2.Xor(v3, v0);
					v3 = Sse2.Xor(Sse2.ShiftLeftLogical(v3, 8), Sse2.ShiftRightLogical(v3, 24));
					v2 = Sse2.Add(v2, v3);
					v1 = Sse2.Xor(v1, v2);
					v1 = Sse2.Xor(Sse2.ShiftLeftLogical(v1, 7), Sse2.ShiftRightLogical(v1, 25));

					v1 = Sse2.Shuffle(v1, 0x39);
					v2 = Sse2.Shuffle(v2, 0x4E);
					v3 = Sse2.Shuffle(v3, 0x93);

					v0 = Sse2.Add(v0, v1);
					v3 = Sse2.Xor(v3, v0);
					v3 = Sse2.Xor(Sse2.ShiftLeftLogical(v3, 16), Sse2.ShiftRightLogical(v3, 16));
					v2 = Sse2.Add(v2, v3);
					v1 = Sse2.Xor(v1, v2);
					v1 = Sse2.Xor(Sse2.ShiftLeftLogical(v1, 12), Sse2.ShiftRightLogical(v1, 20));
					v0 = Sse2.Add(v0, v1);
					v3 = Sse2.Xor(v3, v0);
					v3 = Sse2.Xor(Sse2.ShiftLeftLogical(v3, 8), Sse2.ShiftRightLogical(v3, 24));
					v2 = Sse2.Add(v2, v3);
					v1 = Sse2.Xor(v1, v2);
					v1 = Sse2.Xor(Sse2.ShiftLeftLogical(v1, 7), Sse2.ShiftRightLogical(v1, 25));

					v1 = Sse2.Shuffle(v1, 0x93);
					v2 = Sse2.Shuffle(v2, 0x4E);
					v3 = Sse2.Shuffle(v3, 0x39);
				}

				v0 = Sse2.Add(v0, x0);
				v1 = Sse2.Add(v1, x1);
				v2 = Sse2.Add(v2, x2);
				v3 = Sse2.Add(v3, x3);

				Store128_UInt32(v0, output.AsSpan());
				Store128_UInt32(v1, output.AsSpan(0x10));
				Store128_UInt32(v2, output.AsSpan(0x20));
				Store128_UInt32(v3, output.AsSpan(0x30));
				return;
        }
#endif

            {
                uint x00 = input[0], x01 = input[1], x02 = input[2], x03 = input[3];
                uint x04 = input[4], x05 = input[5], x06 = input[6], x07 = input[7];
                uint x08 = input[8], x09 = input[9], x10 = input[10], x11 = input[11];
                uint x12 = input[12], x13 = input[13], x14 = input[14], x15 = input[15];

                for (int i = rounds; i > 0; i -= 2)
                {
                    x00 += x04; x12 = Integers.RotateLeft(x12 ^ x00, 16);
                    x01 += x05; x13 = Integers.RotateLeft(x13 ^ x01, 16);
                    x02 += x06; x14 = Integers.RotateLeft(x14 ^ x02, 16);
                    x03 += x07; x15 = Integers.RotateLeft(x15 ^ x03, 16);

                    x08 += x12; x04 = Integers.RotateLeft(x04 ^ x08, 12);
                    x09 += x13; x05 = Integers.RotateLeft(x05 ^ x09, 12);
                    x10 += x14; x06 = Integers.RotateLeft(x06 ^ x10, 12);
                    x11 += x15; x07 = Integers.RotateLeft(x07 ^ x11, 12);

                    x00 += x04; x12 = Integers.RotateLeft(x12 ^ x00, 8);
                    x01 += x05; x13 = Integers.RotateLeft(x13 ^ x01, 8);
                    x02 += x06; x14 = Integers.RotateLeft(x14 ^ x02, 8);
                    x03 += x07; x15 = Integers.RotateLeft(x15 ^ x03, 8);

                    x08 += x12; x04 = Integers.RotateLeft(x04 ^ x08, 7);
                    x09 += x13; x05 = Integers.RotateLeft(x05 ^ x09, 7);
                    x10 += x14; x06 = Integers.RotateLeft(x06 ^ x10, 7);
                    x11 += x15; x07 = Integers.RotateLeft(x07 ^ x11, 7);
                    x00 += x05; x15 = Integers.RotateLeft(x15 ^ x00, 16);
                    x01 += x06; x12 = Integers.RotateLeft(x12 ^ x01, 16);
                    x02 += x07; x13 = Integers.RotateLeft(x13 ^ x02, 16);
                    x03 += x04; x14 = Integers.RotateLeft(x14 ^ x03, 16);

                    x10 += x15; x05 = Integers.RotateLeft(x05 ^ x10, 12);
                    x11 += x12; x06 = Integers.RotateLeft(x06 ^ x11, 12);
                    x08 += x13; x07 = Integers.RotateLeft(x07 ^ x08, 12);
                    x09 += x14; x04 = Integers.RotateLeft(x04 ^ x09, 12);

                    x00 += x05; x15 = Integers.RotateLeft(x15 ^ x00, 8);
                    x01 += x06; x12 = Integers.RotateLeft(x12 ^ x01, 8);
                    x02 += x07; x13 = Integers.RotateLeft(x13 ^ x02, 8);
                    x03 += x04; x14 = Integers.RotateLeft(x14 ^ x03, 8);

                    x10 += x15; x05 = Integers.RotateLeft(x05 ^ x10, 7);
                    x11 += x12; x06 = Integers.RotateLeft(x06 ^ x11, 7);
                    x08 += x13; x07 = Integers.RotateLeft(x07 ^ x08, 7);
                    x09 += x14; x04 = Integers.RotateLeft(x04 ^ x09, 7);
                }

                Pack.UInt32_To_LE(x00 + input[0], output, 0);
                Pack.UInt32_To_LE(x01 + input[1], output, 4);
                Pack.UInt32_To_LE(x02 + input[2], output, 8);
                Pack.UInt32_To_LE(x03 + input[3], output, 12);
                Pack.UInt32_To_LE(x04 + input[4], output, 16);
                Pack.UInt32_To_LE(x05 + input[5], output, 20);
                Pack.UInt32_To_LE(x06 + input[6], output, 24);
                Pack.UInt32_To_LE(x07 + input[7], output, 28);
                Pack.UInt32_To_LE(x08 + input[8], output, 32);
                Pack.UInt32_To_LE(x09 + input[9], output, 36);
                Pack.UInt32_To_LE(x10 + input[10], output, 40);
                Pack.UInt32_To_LE(x11 + input[11], output, 44);
                Pack.UInt32_To_LE(x12 + input[12], output, 48);
                Pack.UInt32_To_LE(x13 + input[13], output, 52);
                Pack.UInt32_To_LE(x14 + input[14], output, 56);
                Pack.UInt32_To_LE(x15 + input[15], output, 60);
            }
        }

#if NETCOREAPP3_0_OR_GREATER
		[MethodImpl(MethodImplOptions.AggressiveInlining)]
		private static Vector128<uint> Load128_UInt32(ReadOnlySpan<uint> t)
		{
            if (BitConverter.IsLittleEndian && Unsafe.SizeOf<Vector128<uint>>() == 16)
                return MemoryMarshal.Read<Vector128<uint>>(MemoryMarshal.AsBytes(t));

            return Vector128.Create(t[0], t[1], t[2], t[3]);
		}

		[MethodImpl(MethodImplOptions.AggressiveInlining)]
		private static void Store128_UInt32(Vector128<uint> s, Span<byte> t)
		{
			if (BitConverter.IsLittleEndian && Unsafe.SizeOf<Vector128<uint>>() == 16)
			{
				MemoryMarshal.Write(t, ref s);
				return;
			}

			var u = s.AsUInt64();
            BinaryPrimitives.WriteUInt64LittleEndian(t[..8], u.GetElement(0));
            BinaryPrimitives.WriteUInt64LittleEndian(t[8..], u.GetElement(1));
		}
#endif
    }
}
#pragma warning restore
#endif