using System;
using System.Collections.Generic;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Numerics;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using System.Security.Cryptography;
using System.Text;
using System.Xml.Serialization;

namespace StgSharp.Data.FileIO
{
    public class SSDraw
    {
        public const string FileType = "ssdraw";

        public const int SegmentCapacity = 16 * 16;
        private string _name;
        private SSDrawHead _head;
        private List<SSDSegment> segments;
        private SSDSegment currentSegment;
        private int previousHash;

        public SSDraw(string name)
        {
            _name = name;
            segments = new List<SSDSegment>();
        }

        public void WriteRaw(byte[] dataStream)
        {
            previousHash = BuildRawHead(0);
            currentSegment = new SSDSegment(previousHash);
            int t = 0;
            for (int i = 0; i < dataStream.Length; i++, t++)
            {
                if (t == SegmentCapacity)
                {
                    currentSegment.GetDataHash();
                    currentSegment.Head.Size = 256;
                    currentSegment.Head.globalID = i;
                    segments.Add(currentSegment);
                    previousHash = currentSegment.GetHashCode();
                    currentSegment = new SSDSegment(previousHash);
                    t = 0;
                }
                currentSegment[i] = dataStream[i];
            }
            currentSegment.FillRandomBytes(t);
            currentSegment.GetDataHash();
            currentSegment.Head.Size = t; 
            segments.Add(currentSegment);

        }
        
        public void CreateRawFile(string outputFolder, bool rewrite)
        {
            string route =
                (outputFolder == "" ? " " : $"{outputFolder}\\")
                + $"{_name}.{FileType}";
            if (File.Exists(route) && !rewrite)
            {
                throw new Exception("This SSDRAW has already existed.");
            }
            using (File.Create(route)) { }
            using (FileStream cf = File.Open(route, FileMode.Truncate)) { }
            FileStream f = File.Open(route, FileMode.Open);
            int size = 0;
            f.Write(_head.GetBytes(out size), 0, size);
            foreach (var _head in segments) 
            {
                f.Write(_head.GetBytes(), 0, 18 * 16);
            }
            f.Close();
        }

        private int BuildRawHead(int beginID)
        {
            SSDrawHead rawHead = new SSDrawHead(_name);
            _head = rawHead;
            return rawHead.GetHashCode();
        }

        public static SSDraw readRaw(string route)
        {
            string[] routeFolders = route.Split('\\');
            if (!routeFolders.Last().Contains($".{FileType}"))
            {
                throw new Exception($"File to open is not a {FileType} file.");
            }

            FileStream stream = File.Open(route, FileMode.Open);
            return new SSDraw("");
        }

    }

    [StructLayout(LayoutKind.Explicit)]
    public unsafe struct SSDSegment
    {
        [FieldOffset(0 * 16)] public SSDSegmentHead Head;
        [FieldOffset(12)] public int DataHash;
        [FieldOffset(8)] public int PreviousHash;
        [FieldOffset(16)] public fixed byte Data[16 * 16];

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

        public short Size
        {
            get { return Head.size; }
        }

        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 void FillRandomBytes(int begin)
        {
            if (begin > 255)
            {
                return;
            }
            for (int i = begin; i < 255; i++)
            {
                Data[i] = 0; //TODO: 使用STGSHARP内部随机数工具处理它
            }
        }

        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;
            }
        }

        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 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 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;
        }
    }

}