using StgSharp.Math;

using System;
using System.Collections.Generic;
using System.Linq;
using System.Numerics;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading.Tasks;

namespace StgSharp.Data
{
    [StructLayout(LayoutKind.Explicit)]
    public unsafe struct SSDSegment
    {

        [FieldOffset(16)] public fixed byte Data[16 * 16];
        [FieldOffset(12)] public int DataHash;
        [FieldOffset(0 * 16)] public SSDSegmentHead Head;
        [FieldOffset(8)] public int PreviousHash;

        public SSDSegment(int previousHash)
        {
            this.PreviousHash = previousHash;
        }

        public int ID
        {
            get { return Head.globalID; }
            set { Head.globalID = value; }
        }

        public byte this[int index]
        {
            get
            {
                if (index > (16 * 14) - 1)
                {
                    throw new IndexOutOfRangeException();
                }
                return Data[index];
            }

            set
            {
                if (index > (16 * 14) - 1)
                {
                    throw new IndexOutOfRangeException();
                }
                Data[index] = value;
            }
        }

        public short Size => Head.size;

        public void FillRandomBytes(int begin)
        {
            if (begin > 255)
            {
                return;
            }
            for (int i = begin; i < 255; i++)
            {
                Data[i] = Scaler.Random<byte>(); //TODO: 使用STGSHARP内部随机数工具处理它
            }
        }

        public byte[] GetBytes()
        {
            byte[] ret = new byte[16 * 18];
            fixed (M128* mptr = &Head.data)
            {
                fixed (byte* aptr = ret)
                {
                    Vector4* vsptr = (Vector4*)mptr;
                    Vector4* vtptr = (Vector4*)aptr;
                    for (int i = 0; i < 18; i++)
                    {
                        *(vtptr + i) = *(vsptr + i);
                    }
                }
            }

            return ret;
        }

        public int GetDataHash()
        {
            Vector4 v = Vector4.One;
            fixed (M128* mptr = &Head.data)
            {
                Vector4* vptr = (Vector4*)mptr;
                for (int i = 0; i < 16; i += 1)
                {
                    v += (*vptr) * 31;
                }
            }
            M128 m = new M128(v);
            DataHash = m.vec.GetHashCode();
            return DataHash;
        }

        public override int GetHashCode()
        {
            int ret = 17;
            fixed (M128* mptr = &Head.data)
            {
                Vector4* vptr = (Vector4*)mptr;
                for (int i = 0; i < 18; i++)
                {
                    ret = (ret + (*vptr).GetHashCode()) * 31;
                }
            }
            return ret;
        }

        public unsafe T ReadData<T>(int index) where T : struct
        {
            fixed (byte* bptr = Data)
            {
                T* tptr = (T*)bptr;
                return *(tptr + index);
            }
        }
        public unsafe void WriteData<T>(int index, T value) where T : struct
        {
            fixed (byte* bptr = Data)
            {
                T* tptr = (T*)bptr;
                *(tptr + index) = value;
            }
        }

    }

}