using System;
using System.Runtime.CompilerServices;
using System.Text;

namespace AlicizaX
{
    public static partial class Utility
    {
        /// <summary>
        /// 哈希计算相关的实用函数。
        /// </summary>
        public static partial class Hash
        {
            /// <summary>
            /// xxHash
            /// </summary>
            public static class XXHash
            {
                public static uint Hash32(byte[] buffer)
                {
                    return XXHashHelper.Hash32(buffer);
                }

                public static uint Hash32(string text)
                {
                    return XXHashHelper.Hash32(text);
                }

                public static uint Hash32(Type type)
                {
                    return XXHashHelper.Hash32(type);
                }

                public static uint Hash32<T>()
                {
                    return XXHashHelper.Hash32<T>();
                }

                public static ulong Hash64(byte[] buffer)
                {
                    return XXHashHelper.Hash64(buffer);
                }

                public static ulong Hash64(string text)
                {
                    return XXHashHelper.Hash64(text);
                }

                public static ulong Hash64(Type type)
                {
                    return XXHashHelper.Hash64(type);
                }

                public static ulong Hash64<T>()
                {
                    return XXHashHelper.Hash64<T>();
                }
            }

            /// <summary>
            /// XX Hash 计算帮助类
            /// </summary>
            static class XXHashHelper
            {
                [MethodImpl(MethodImplOptions.AggressiveInlining)]
                static unsafe uint Hash32(byte* input, int length, uint seed = 0)
                {
                    unchecked
                    {
                        const uint prime1 = 2654435761u;
                        const uint prime2 = 2246822519u;
                        const uint prime3 = 3266489917u;
                        const uint prime4 = 0668265263u;
                        const uint prime5 = 0374761393u;

                        uint hash = seed + prime5;

                        if (length >= 16)
                        {
                            uint val0 = seed + prime1 + prime2;
                            uint val1 = seed + prime2;
                            uint val2 = seed + 0;
                            uint val3 = seed - prime1;

                            int count = length >> 4;
                            for (int i = 0; i < count; i++)
                            {
                                var pos0 = *(uint*) (input + 0);
                                var pos1 = *(uint*) (input + 4);
                                var pos2 = *(uint*) (input + 8);
                                var pos3 = *(uint*) (input + 12);

                                val0 += pos0 * prime2;
                                val0 = (val0 << 13) | (val0 >> (32 - 13));
                                val0 *= prime1;

                                val1 += pos1 * prime2;
                                val1 = (val1 << 13) | (val1 >> (32 - 13));
                                val1 *= prime1;

                                val2 += pos2 * prime2;
                                val2 = (val2 << 13) | (val2 >> (32 - 13));
                                val2 *= prime1;

                                val3 += pos3 * prime2;
                                val3 = (val3 << 13) | (val3 >> (32 - 13));
                                val3 *= prime1;

                                input += 16;
                            }

                            hash = ((val0 << 01) | (val0 >> (32 - 01))) +
                                   ((val1 << 07) | (val1 >> (32 - 07))) +
                                   ((val2 << 12) | (val2 >> (32 - 12))) +
                                   ((val3 << 18) | (val3 >> (32 - 18)));
                        }

                        hash += (uint) length;

                        length &= 15;
                        while (length >= 4)
                        {
                            hash += *(uint*) input * prime3;
                            hash = ((hash << 17) | (hash >> (32 - 17))) * prime4;
                            input += 4;
                            length -= 4;
                        }

                        while (length > 0)
                        {
                            hash += *input * prime5;
                            hash = ((hash << 11) | (hash >> (32 - 11))) * prime1;
                            ++input;
                            --length;
                        }

                        hash ^= hash >> 15;
                        hash *= prime2;
                        hash ^= hash >> 13;
                        hash *= prime3;
                        hash ^= hash >> 16;

                        return hash;
                    }
                }

                [MethodImpl(MethodImplOptions.AggressiveInlining)]
                static unsafe ulong Hash64(byte* input, int length, uint seed = 0)
                {
                    unchecked
                    {
                        const ulong prime1 = 11400714785074694791ul;
                        const ulong prime2 = 14029467366897019727ul;
                        const ulong prime3 = 01609587929392839161ul;
                        const ulong prime4 = 09650029242287828579ul;
                        const ulong prime5 = 02870177450012600261ul;

                        ulong hash = seed + prime5;

                        if (length >= 32)
                        {
                            ulong val0 = seed + prime1 + prime2;
                            ulong val1 = seed + prime2;
                            ulong val2 = seed + 0;
                            ulong val3 = seed - prime1;

                            int count = length >> 5;
                            for (int i = 0; i < count; i++)
                            {
                                var pos0 = *(ulong*) (input + 0);
                                var pos1 = *(ulong*) (input + 8);
                                var pos2 = *(ulong*) (input + 16);
                                var pos3 = *(ulong*) (input + 24);

                                val0 += pos0 * prime2;
                                val0 = (val0 << 31) | (val0 >> (64 - 31));
                                val0 *= prime1;

                                val1 += pos1 * prime2;
                                val1 = (val1 << 31) | (val1 >> (64 - 31));
                                val1 *= prime1;

                                val2 += pos2 * prime2;
                                val2 = (val2 << 31) | (val2 >> (64 - 31));
                                val2 *= prime1;

                                val3 += pos3 * prime2;
                                val3 = (val3 << 31) | (val3 >> (64 - 31));
                                val3 *= prime1;

                                input += 32;
                            }

                            hash = ((val0 << 01) | (val0 >> (64 - 01))) +
                                   ((val1 << 07) | (val1 >> (64 - 07))) +
                                   ((val2 << 12) | (val2 >> (64 - 12))) +
                                   ((val3 << 18) | (val3 >> (64 - 18)));

                            val0 *= prime2;
                            val0 = (val0 << 31) | (val0 >> (64 - 31));
                            val0 *= prime1;
                            hash ^= val0;
                            hash = hash * prime1 + prime4;

                            val1 *= prime2;
                            val1 = (val1 << 31) | (val1 >> (64 - 31));
                            val1 *= prime1;
                            hash ^= val1;
                            hash = hash * prime1 + prime4;

                            val2 *= prime2;
                            val2 = (val2 << 31) | (val2 >> (64 - 31));
                            val2 *= prime1;
                            hash ^= val2;
                            hash = hash * prime1 + prime4;

                            val3 *= prime2;
                            val3 = (val3 << 31) | (val3 >> (64 - 31));
                            val3 *= prime1;
                            hash ^= val3;
                            hash = hash * prime1 + prime4;
                        }

                        hash += (ulong) length;

                        length &= 31;
                        while (length >= 8)
                        {
                            ulong lane = *(ulong*) input * prime2;
                            lane = ((lane << 31) | (lane >> (64 - 31))) * prime1;
                            hash ^= lane;
                            hash = ((hash << 27) | (hash >> (64 - 27))) * prime1 + prime4;
                            input += 8;
                            length -= 8;
                        }

                        if (length >= 4)
                        {
                            hash ^= *(uint*) input * prime1;
                            hash = ((hash << 23) | (hash >> (64 - 23))) * prime2 + prime3;
                            input += 4;
                            length -= 4;
                        }

                        while (length > 0)
                        {
                            hash ^= *input * prime5;
                            hash = ((hash << 11) | (hash >> (64 - 11))) * prime1;
                            ++input;
                            --length;
                        }

                        hash ^= hash >> 33;
                        hash *= prime2;
                        hash ^= hash >> 29;
                        hash *= prime3;
                        hash ^= hash >> 32;

                        return hash;
                    }
                }

                [MethodImpl(MethodImplOptions.AggressiveInlining)]
                public static uint Hash32(byte[] buffer)
                {
                    int length = buffer.Length;
                    unsafe
                    {
                        fixed (byte* pointer = buffer)
                        {
                            return Hash32(pointer, length);
                        }
                    }
                }

                [MethodImpl(MethodImplOptions.AggressiveInlining)]
                public static uint Hash32(string text) => Hash32(Encoding.UTF8.GetBytes(text));

                [MethodImpl(MethodImplOptions.AggressiveInlining)]
                public static uint Hash32(Type type) => Hash32(type.FullName);

                [MethodImpl(MethodImplOptions.AggressiveInlining)]
                public static uint Hash32<T>() => Hash32(typeof(T));

                [MethodImpl(MethodImplOptions.AggressiveInlining)]
                public static ulong Hash64(byte[] buffer)
                {
                    int length = buffer.Length;
                    unsafe
                    {
                        fixed (byte* pointer = buffer)
                        {
                            return Hash64(pointer, length);
                        }
                    }
                }

                [MethodImpl(MethodImplOptions.AggressiveInlining)]
                public static ulong Hash64(string text) => Hash64(Encoding.UTF8.GetBytes(text));

                [MethodImpl(MethodImplOptions.AggressiveInlining)]
                public static ulong Hash64(Type type) => Hash64(type.FullName);

                [MethodImpl(MethodImplOptions.AggressiveInlining)]
                public static ulong Hash64<T>() => Hash64(typeof(T));
            }
        }
    }
}