//-----------------------------------------------------------------------
//-----------------------------------------------------------------------
//     file="DataSegment.cs"
//     Project: StgSharp
//     AuthorGroup: Nitload Space
//     Copyright (c) Nitload Space. All rights reserved.
//     
//     Permission is hereby granted, free of charge, to any person 
//     obtaining a copy of this software and associated documentation 
//     files (the “Software”), to deal in the Software without restriction, 
//     including without limitation the rights to use, copy, modify, merge,
//     publish, distribute, sublicense, and/or sell copies of the Software, 
//     and to permit persons to whom the Software is furnished to do so, 
//     subject to the following conditions:
//     
//     The above copyright notice and 
//     this permission notice shall be included in all copies 
//     or substantial portions of the Software.
//     
//     THE SOFTWARE IS PROVIDED “AS IS”, 
//     WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, 
//     INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
//     FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. 
//     IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, 
//     DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, 
//     ARISING FROM, OUT OF OR IN CONNECTION WITH 
//     THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//     
//-----------------------------------------------------------------------
//-----------------------------------------------------------------------
using StgSharp.HighPerformance;
using StgSharp.HighPerformance;
using StgSharp.Internal.Intrinsic;

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.Internal
{
    [StructLayout( LayoutKind.Explicit, Size = StgSharp.ssdSegmentLength * 16 )]
    public unsafe struct SSDSegment : IComparable<int>, IComparable<SSDSegment>
    {

        [FieldOffset( 16 )] public fixed byte Data[
            16 * ( StgSharp.ssdSegmentLength - 1 ) ];
        [FieldOffset( 12 )] public int DataHash;
        [FieldOffset( 8 )] public int PreviousHash;
        [FieldOffset( 0 * 16 )] public SSDSegmentHead Head;

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

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

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

        public int ID
        {
            get { return Head.globalID; }
            set { Head.globalID = 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>();
            }
        }

        public static SSDSegment FromStream( byte[] stream )
        {
            if( stream.Length != 16 * StgSharp.ssdSegmentLength ) {
                throw new ArgumentException();
            }
            SSDSegment ret = new SSDSegment();
            fixed( byte* bptr = stream ) {
                ret.Head.data = *( M128* )bptr;
                for( int i = 1; i < StgSharp.ssdSegmentLength; i++ ) {
                    ret.WriteData<M128>(
                        i - 1, *( M128* )( bptr + ( 16 * i ) ) );
                }
            }
            return ret;
        }

        public byte[] GetBytes()
        {
            byte[] ret = new byte[16 * StgSharp.ssdSegmentLength];
            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 < StgSharp.ssdSegmentLength - 1; 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 < StgSharp.ssdSegmentLength; 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;
            }
        }

        int IComparable<int>.CompareTo( int other )
        {
            return ID.CompareTo( other );
        }

        int IComparable<SSDSegment>.CompareTo( SSDSegment other )
        {
            return ID.CompareTo( other.ID );
        }

    }
}