//-----------------------------------------------------------------------
// -----------------------------------------------------------------------
// file="L4.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.Collections;
using StgSharp.Mathematics.Memory;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading.Tasks;
using System.Xml.Serialization;

namespace StgSharp.HighPerformance.Memory
{
    public unsafe partial class L4 : IDisposable
    {

        private const int CacheLineCount = 8192;

        private bool _disposed;
        private int _activeCount;
        private readonly nuint _baseAddress;

        private readonly SlabAllocator<CacheLineData> _cacheLineAllocator;

        private readonly SlabAllocator<CacheLineHead> _entryAllocator;

        private readonly SwissTable _map;

        public L4()
        {
            int cacheSize = Unsafe.SizeOf<CacheLineData>() * CacheLineCount;
            int entrySize = Unsafe.SizeOf<CacheLineHead>() * CacheLineCount;
            int mapSize = SwissTable.RequestedNativeMemorySize;
            _baseAddress = (nuint)NativeMemory.AlignedAlloc((nuint)(cacheSize + entrySize + mapSize), 16);
            nuint _buffer = _baseAddress;
            _cacheLineAllocator = SlabAllocator.FromBuffer<CacheLineData>(_buffer, CacheLineCount, _ => { });
            _entryAllocator = SlabAllocator.FromBuffer<CacheLineHead>(_buffer + (nuint)cacheSize, CacheLineCount, _ => { });
            _map = SwissTable.Create(_baseAddress + (nuint)(cacheSize + entrySize), _ => { });
        }

        [System.Diagnostics.CodeAnalysis.SuppressMessage(
                "Design",
                "CA1063:Implement IDisposable correctly",
                Justification = """
                    Only owns native memory via NativeMemory.AlignedFree();
                    no managed IDisposable fields.
                    Dispose(bool) pattern is unnecessary.
                    """)]
        public void Dispose()
        {
            if (_disposed) {
                return;
            }
            _disposed = true;
            NativeMemory.AlignedFree((void*)_baseAddress);
            GC.SuppressFinalize(this);
        }

        public CacheLine Map(nuint origin)
        {
            if (_map.TryGet(origin, out nuint entryHandle))
            {
                // cache hit
                CacheLineHead* entry = (CacheLineHead*)entryHandle;
                return new CacheLine(entry->_address, ref _activeCount, ref entry->_refCount);
            }

            // cache miss
            /*
             * post command
             * then wait for completion
             */
            return origin;   //error now
        }

        public ref struct CacheLine : IDisposable
        {

            private ref int _activeCount;
            private ref int _refCount;
            private nuint _handle;

            internal CacheLine(nuint handle, ref int activeCount, ref int cacheRefCount)
            {
                _handle = handle;
                _refCount = ref cacheRefCount;
                _activeCount = ref activeCount;
                _ = Interlocked.Increment(ref _activeCount);
                _ = Interlocked.Increment(ref _refCount);
            }

            public void Dispose()
            {
                if (_handle == 0) {
                    return;
                }
                _handle = 0;
                _ = Interlocked.Decrement(ref _activeCount);
                _ = Interlocked.Decrement(ref _refCount);
            }

        }

        private struct CacheLineData
        {

            private fixed byte Data[8192];

        }

    }
}